Conservation Evidence: Evidence Data

Collected Evidence: Collected Evidence: Exclude or remove livestock from historically grazed brackish/salt marshes Fifteen studies evaluated the effects, on vegetation, of excluding or removing livestock from historically grazed brackish/salt marshes. There were five studies in Germany. There were two studies in the UK, Denmark and the Netherlands. There was one study in each of the USA, Sweden, France and Argentina. Livestock were sheep, cattle, sheep and cattle, cattle and horses, or unspecified. There was overlap in the sites used in two studies. Two other studies took place in one marsh, but with different experimental set-ups. VEGETATION COMMUNITY Overall extent (1 study): One controlled study of a salt marsh in Germany reported that in a plot fenced to exclude cattle for eight years, the total vegetated area was greater than in a plot that remained grazed. Community types (1 study): One site comparison study of brackish and salt marshes in Germany reported that reducing (or stopping) grazing affected the nature of transitions between vegetation types over time, but that the precise effect varied with environmental conditions. Community composition (5 studies): Three paired studies (two also replicated and controlled) in brackish/salt marshes in France, Argentina and the Netherlands reported that the effect of excluding livestock for 5–30 years on the overall plant community composition depended on plot elevation/flooding regime. In one of these studies, the effect of livestock exclusion was not separated from the effect of general legal protection. Two studies in one salt marsh in Denmark reported that excluding livestock had little effect on the identity of plant species in the community after six years. Overall richness/diversity (6 studies): Two studies (one controlled, one before-and-after) in one salt marsh in Denmark reported that excluding sheep and cattle for 6–7 years had no effect on overall plant species richness. One replicated, paired, controlled study in a salt marsh in the Netherlands reported that plots fenced to exclude cattle for seven years had lower plant species richness than areas that remained grazed. Two controlled studies (one also replicated and paired) in salt marshes in Germany found that the effect of removing sheep on overall plant species richness depended on the scale of measurement and the grazing intensity used for comparison – with inconsistent results across these studies even for similar scales and intensities. One paired, site comparison study of salt marshes in Argentina found that the effect of excluding cattle (along with legal protection) increased plant species richness at lower elevations, but did not significantly affect plant diversity at any elevation. VEGETATION ABUNDANCE Overall abundance (4 studies): Three studies (two controlled, one before-and-after) in salt marshes in the UK and Denmark reported that excluding livestock for 2–6 years maintained or increased overall vegetation abundance (although in one study, only by a small amount). One controlled study in a salt marsh in Germany found that a paddock left ungrazed for 16–18 years had greater overall vegetation cover than lightly or heavily grazed paddocks, but lower cover than a moderately grazed paddock. Individual species abundance (11 studies): Eleven studies quantified the effect of this action on the abundance of individual plant species. For example, five studies (four controlled, one before-and-after) on salt marshes in the UK, Denmark, Germany and the Netherlands reported that excluding livestock for 2–8 years reduced (or prevented increases in) cover of saltmarsh grass Puccinellia maritima. However, two controlled studies (one also replicated and paired) on salt marshes in Denmark and Sweden reported greater saltmarsh grass cover in areas fenced to exclude livestock for 1–6 years than in areas that remained grazed. Four studies (three controlled, one before-and-after) on salt marshes in Denmark and Germany reported that excluding or removing livestock for 4–16 years increased cover of sea purslane Halimione portulacoides. VEGETATION STRUCTURE Height (5 studies): Five controlled studies (two also replicated and paired) in salt marshes in Sweden and Germany, and brackish wet grassland in the UK, found that ungrazed plots (livestock excluded or removed) contained taller vegetation than plots that remained grazed. Vegetation was surveyed after one month, 1–8 years or 16–22 years. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2967https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2967Thu, 25 Mar 2021 14:15:09 +0000Collected Evidence: Collected Evidence: Cut/mow herbaceous plants to maintain or restore disturbance: freshwater marshes Twenty studies evaluated the effects, on vegetation, of cutting/mowing to maintain or restore disturbance in freshwater marshes. There were four studies in Belgium, three of which took place in one wetland area so probably shared some experimental plots. There were two studies in each of the UK, the USA and Estonia. There was one study in each of seven other European countries, Japan, Mexico and Brazil. In 15 of the studies vegetation was measured at least six months after the last cut. VEGETATION COMMUNITY Community composition (6 studies): Four replicated, paired, controlled studies (two also randomized and before-and-after) of freshwater marshes and wet meadows in Belgium, Switzerland, Mexico and Estonia reported that the overall plant community composition differed between cut and uncut sites after 1–5 years, or typically diverged in cut and uncut areas over 3–10 years. One before-and-after study in a freshwater marsh in Belgium reported that the overall plant community composition changed over seven years after resuming annual mowing. One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that over 20 years, mowing increased the average moisture preference of the vegetation. Overall richness/diversity (11 studies): Seven studies (including two replicated, paired, controlled) in freshwater marshes in Belgium, the UK, Mexico and Estonia reported that cut marshes had higher plant species richness than uncut marshes. Two of these studies reported the same result for diversity. One before-and-after study in a freshwater marsh in Belgium reported that plant species richness increased over seven years after resuming annual mowing. Three replicated, paired, controlled studies in reedbeds in the UK and wet meadows in Germany and Estonia reported that cutting typically had no clear or significant effect on plant species richness, after 3–5 months or over 5–20 years. The two studies in the UK and Estonia found the same result for diversity. Characteristic plant richness/diversity (1 study): One replicated, paired, controlled, before-and-after study in a temporary marsh in France reported that two years of annual autumn cutting increased the number of habitat-characteristic plant species present. VEGETATION ABUNDANCE Overall abundance (3 studies): Two replicated, controlled studies (one also randomized, paired, before-and-after) in freshwater marshes in the USA found that cutting had no significant effect on overall vegetation cover over 72 days or three years. One replicated, paired, controlled study in wet grasslands in Belgium reported that plots mown annually for two years contained less above-ground biomass, just before mowing, than unmown plots. Herb abundance (1 study): One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that mowing increased sedge cover over 20 years, but had no clear effect on cover of rushes, forbs, ferns, grasses and legumes. Tree/shrub abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in a wet prairie in the USA found that cutting had no significant effect on woody plant cover: there were similar increases, over three years, in cut and uncut plots. Bryophyte abundance (1 study): One replicated study in a freshwater marsh in Belgium reported that total moss cover increased over five years after resuming annual mowing. Individual species abundance (15 studies): Fifteen studies quantified the effect of this action on the abundance of individual plant species. For example, five studies (including one replicated, randomized, paired, controlled) in freshwater marshes in Belgium, the UK and the Czech Republic reported that common reed Phragmites australis was more abundant in cut than uncut areas. Two studies (one site comparison, one before-and-after) in fresh/brackish marshes in Belgium and Denmark reported that cutting reduced common reed cover or density. The two studies in Belgium reported that cutting had no clear effect on common reed frequency. Four studies (including one replicated, randomized, paired, before-and-after) in freshwater marshes in the Netherlands, Switzerland, Japan and Italy found that the effect of cutting on common reed abundance depended on factors such as the year, plant community type, cutting season, cutting intensity and time since mowing. VEGETATION STRUCTURE Overall structure (1 study): One replicated, randomized, paired, controlled study in wet meadows in Switzerland reported that mown plots experienced a shift in vegetation cover towards lower vegetation layers, over 3–4 years, compared to a shift to upper layers in unmown plots. Visual obstruction (1 study): One replicated, controlled study in a freshwater marsh in Belgium reported that summer-cut plots had lower horizontal vegetation cover than uncut plots (or winter-cut plots) over six years after resuming annual mowing. Height (6 studies): Three replicated, controlled studies (one also randomized and paired) in freshwater marshes in Belgium, the UK and the USA reported that cut marshes had shorter vegetation than uncut marshes. This was true for vegetation overall, vegetation other than common reed Phragmites australis, and for common reed cut in winter or spring (but not summer). Two replicated, paired, controlled, before-and-after studies in a marsh in Mexico and wet grasslands in Germany reported that cutting/mowing had no significant or clear effect on vegetation height, after 12 months or over 20 years. One site comparison study in the Czech Republic found that common reed was taller, when measured in the summer, in a winter-mown reedbed than in an unmown reedbed. Diameter/perimeter/area (5 studies): Two studies (one site comparison, one before-and-after) in fresh/brackish marshes in Belgium and Denmark reported that cutting, or time since last cutting, had no significant or clear effect on the stem diameter of common reed Phragmites australis. Two studies (including one replicated, randomized, paired, controlled) of reedbeds in the UK and the Czech Republic found that cut areas contained thicker reed stems than uncut areas, after one growing season. One replicated, randomized, paired, controlled, before-and-after study in wet meadows in Switzerland found that the effect of cutting on common reed shoot diameter depended on the plant community type and season of mowing. Basal area (1 study): One site comparison study in a fresh/brackish marsh in Denmark found that the basal area of common reed Phragmites australis stems was smaller in a reedbed cut two years previously than in a reedbed cut seven years previously. Only “tall” stems were sampled. OTHER Survival (1 study): One replicated, randomized, paired, controlled study in a wet prairie in the USA found that mowing had no significant effect on woody plant survival over the following year. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3044https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3044Thu, 01 Apr 2021 15:18:37 +0100Collected Evidence: Collected Evidence: Use prescribed fire to maintain or restore disturbance: freshwater marshes Fifteen studies evaluated the effects, on vegetation, of using prescribed fire to maintain or restore disturbance in freshwater marshes. Ten studies were in the USA. Two studies, based on one experimental set-up, were in the Netherlands. There was one study in each of the UK, Romania and South Africa. VEGETATION COMMUNITY Community composition (4 studies): Of four replicated, controlled studies (three also before-and-after) in freshwater wetlands in the USA, two found that burning (sometimes along with other interventions) significantly affected the overall plant community composition in the following 2–5 years. The other two studies found that burning had no clear or significant effect on the overall plant community composition over the following two years. One of these studies also found that the plant community in burned marshes was less similar to pristine local marshes than the plant community in unburned marshes, after two years. Overall richness/diversity (8 studies): Four replicated, paired, controlled studies in freshwater marshes/wet meadows in the UK and the USA found that burning had no significant effect on overall plant species richness and/or diversity over 1–2 growing seasons. However, three replicated, paired, controlled studies in the UK and the USA reported that burning increased plant species richness or diversity after 1–3 growing seasons. Two replicated studies (including one paired, site comparison) in the USA and South Africa reported that burning reduced plant species richness or diversity after 1–3 growing seasons. However, the study in the USA also reported that burning increased richness after 4–8 growing seasons. VEGETATION ABUNDANCE Overall abundance (5 studies): Four studies (including two randomized, paired, controlled, before-and-after) in freshwater marshes/wet meadows in the USA found that prescribed burning had no significant effect on overall vegetation abundance (biomass or cover) after 1–3 growing seasons. One replicated, randomized, paired, controlled study in a freshwater marsh in the USA reported that burned plots contained less vegetation biomass, one year after the latest burn, than unburned plots. Characteristic plant abundance (1 study): One replicated, randomized, controlled, before-and-after study of overgrown freshwater marshes in the USA reported that of 26 plant taxa that became more frequent after burning (along with other interventions), 16 were obligate wetland taxa. Herb abundance (1 study): One replicated, paired, site comparison study of sedge meadows in the USA found that burned meadows typically contained similar cover of herbaceous plant groups (grasses, sedges/rushes and forbs) to unburned meadows, after 1–8 growing seasons. Tree/shrub abundance (2 studies): One replicated, randomized, paired, controlled, before-and-after study in a degraded, shrubby wet prairie the USA found that over three years, burning reduced woody plant cover. One replicated, before-and-after study of freshwater marshes within a forest plantation in South Africa reported that burning never increased overall tree density five months later, although the precise effect apparently depended on site wetness. Algae/phytoplankton abundance (1 study): One controlled study in a freshwater marsh in the USA found that burned plots contained a greater abundance (cover and biomass) of surface-encrusting algae, over the following 72 days, than unburned plots. Individual species abundance (9 studies): Nine studies quantified the effect of this action on the abundance of individual plant species. The nine studies (including eight controlled or site comparison) in the Netherlands, the UK, the USA, Romania and South Africa reported mixed effects of burning on dominant herbaceous species, depending on the species, metric, site conditions and/or time after burning. VEGETATION STRUCTURE Height (5 studies): Four studies (including one replicated, randomized, paired, controlled) – in reedbeds in the UK and Romania, a marsh in the USA and freshwater marshes within a forest plantation in South Africa – found that burned plots contained shorter vegetation than unburned plots in the subsequent growing season. One study in a marsh in the USA reported that over the 50 days after prescribed burning, the average height of sawgrass Cladium jamaicense increased. Diameter/perimeter/area (3 studies): Two replicated, paired, controlled studies in reedbeds in the Netherlands and the UK found that common reed Phragmites australis stems were typically thicker in spring-burned plots than unburned plots, in the subsequent growing season. However, one site comparison study of reedbeds in Romania found that common reed stems were thinner in winter-burned plots than unburned plots, in the following spring. OTHER Survival (1 study): One replicated, randomized, paired, controlled, before-and-after study in a degraded, shrubby wet prairie the USA found that woody plants had a lower survival rate, after one year, in burned plots than in unburned plots. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3054https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3054Fri, 02 Apr 2021 08:55:35 +0100Collected Evidence: Collected Evidence: Use herbicide to control problematic plants: freshwater marshes Seventeen studies evaluated the effects, on vegetation, of using herbicide to control problematic plants in freshwater marshes. Twelve studies were in the USA. Two studies were in Australia. There was one study in each of Canada, Mexico and the UK. There was overlap in the sites used in two studies. Two pairs of studies in Australia and the USA used the same general study area, but different plots or experimental set-ups. VEGETATION COMMUNITY Overall extent (3 studies): Two replicated, randomized, controlled, before-and-after studies in the USA found that marshes sprayed with herbicide had lower live vegetation coverage but greater dead vegetation coverage than unsprayed marshes, after 1–2 years. Overall vegetation coverage was lower in sprayed than unsprayed marshes in one study, but similar in sprayed and unsprayed marshes in the other. One study of a dune slack in the UK simply reported an increase in overall vegetation coverage between one and two years after clearing scrub (by cutting and applying herbicide). Overall richness/diversity (6 studies): Three studies (including one replicated, randomized, paired, controlled) in ephemeral marshes/wet meadows in the USA reported that spraying invaded vegetation with herbicide (sometimes along with other interventions) typically increased total plant species richness 1–5 growing seasons later. Two replicated, randomized, paired, controlled studies (one also before-and-after) in freshwater marshes/wet meadows in the USA and Mexico found that plots treated with herbicide (sometimes along with other interventions) had similar overall plant species richness and diversity to untreated plots, after 4–8 months or three years. One study of a dune slack in the UK simply reported a small increase in total plant richness between one and two years after clearing scrub (by cutting and applying herbicide). Characteristic plant richness/diversity (3 studies): Two before-and-after studies of floodplain marshes in the USA reported that cover of wet-prairie indicator species was higher 1–4 years after applying herbicide than before. However, one of these studies reported that the total cover of non-invasive, wetland-characteristic herbs was similar or lower 2–3 years after applying herbicide than before. One study of a dune slack in the UK simply reported an increase the number of slack-characteristic plant species present between one and two years after clearing scrub (by cutting and applying herbicide). Native/non-target richness/diversity (3 studies): One controlled, before-and-after study in a reed-dominated freshwater marsh in the USA found that applying herbicide (along with cutting/mowing) increased non-reed species richness three years later. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA reported that marshes sprayed with herbicide contained no living native plants one year later: fewer than were present before spraying and in unsprayed marshes. One study of a dune slack in the UK simply reported an increase in native plant richness between one and two years after clearing scrub (by cutting and applying herbicide). VEGETATION ABUNDANCE Overall abundance (4 studies): Three replicated studies (two also randomized, paired, controlled) in freshwater marshes/wet meadows in the USA and Mexico found that applying herbicide (sometimes along with other interventions) had no clear or significant effect on overall vegetation abundance four months to three years later. Cover and density were similar to untreated plots and/or pre-treatment levels. One replicated, randomized, paired, controlled study in the USA found that wet meadows sprayed with herbicide contained less total vegetation biomass than unsprayed marshes, 2–3 growing seasons later. Native/non-target abundance (7 studies): Four studies (including one replicated, randomized, paired, controlled, before-and-after) in marshes/wet meadows in the USA and Australia found that spraying invaded plots with herbicide (sometimes along with other interventions) did not reduce – and often increased – the abundance of native or non-target vegetation 1–3 growing seasons later. One replicated, controlled, before-and-after study in cattail-invaded marshes in the USA reported that marshes sprayed with herbicide contained no living native plants one year later: density and biomass were lower than before spraying and in unsprayed marshes. One replicated, randomized, paired, controlled study in an alligatorweed-invaded marsh in the USA found that spraying vegetation with herbicide had no significant effect on native plant biomass after 1–2 growing seasons. One study of a floodplain marsh in Australia simply reported non-target vegetation cover for up to four years after treating mimosa-invaded vegetation with herbicide (along with other interventions). Herb abundance (4 studies): Two replicated, randomized, paired, controlled studies in wet meadows in the USA found that treating a problematic plant species with herbicide (sometimes along with physical removal) had no significant effect on cover of forbs, grass-like plants or sedges after 2–3 growing seasons. One replicated, randomized, paired, controlled study in a loosestrife-invaded marsh in Canada found that the density of sedges and grasses was not lower in herbicide-sprayed plots, than in unsprayed plots, after 2–3 years. The precise effect depended on dose of herbicide used. One study of a floodplain marsh in Australia simply reported grass/sedge cover for up to four years after treating mimosa-invaded vegetation with herbicide (along with other interventions). Algae/phytoplankton abundance (1 study): One replicated, randomized, controlled study in a reed-invaded marsh in the USA reported that free-growing filamentous algae were more common in plots sprayed with herbicide than unsprayed plots, approximately one year later. However, spraying with herbicide had no significant effect on the density or biomass of biofilm algae. Individual species abundance (3 studies): Three studies quantified the effect of this action on the abundance of individual plant species, other than the species being controlled. For example, one replicated, randomized, paired, controlled study in a grass-invaded marsh in Mexico found that five of five monitored native species had similar cover in herbicide-sprayed and unsprayed plots after 4–8 months. Two of the studies do not distinguish between the effects of applying herbicide and other interventions. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3120https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3120Sun, 04 Apr 2021 17:19:04 +0100Collected Evidence: Collected Evidence: Exclude wild vertebrates: freshwater marshes Twelve studies evaluated the effects, on vegetation, of physically excluding wild vertebrates from freshwater marshes. Six studies were in the USA. Three studies were in the Netherlands, two were in Australia and one was in Canada. The problematic vertebrates were birds in five studies, mammals in four studies, fish in one study, and mixed taxa in two studies. Two studies were conducted in the same area, but with different experimental set-ups. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study in a freshwater marsh in Canada found that after two years of excluding common carp Cyprinus carpio, the area of emergent vegetation was similar to the area expected based on the water level and historical data (when carp were present). Community composition (1 study): One replicated, randomized, paired, controlled study in freshwater marshes in Australia found that areas fenced to exclude wild mammals typically had a similar overall plant community composition to open areas, over 14 years. Overall richness/diversity (4 studies): Three replicated, randomized, paired, controlled studies in freshwater marshes in the USA and Australia reported that fencing to exclude wild mammals had no clear or significant effect on total plant species richness. One replicated, paired, controlled study in freshwater marshes in the Netherlands found that fenced plots had higher emergent plant species richness than open plots, but similar diversity. VEGETATION ABUNDANCE Overall abundance (7 studies): Seven replicated, controlled studies (three also randomized and paired) involving freshwater marshes in the USA, the Netherlands and Australia found that areas fenced to exclude wild vertebrates contained at least as much vegetation as open areas – and typically more. This was true for biomass (fenced > open in six of six studies), cover (fenced > open in two of two studies) and stem density (fenced similar to open in one of one studies). Vegetation was monitored over the winter immediately after fencing, or after 1–4 growing seasons. Individual species abundance (8 studies): Eight studies quantified the effect of this action on the abundance of individual plant species. For example, seven replicated, controlled studies (four also paired, two also randomized) in freshwater marshes in the USA, the Netherlands and Australia found that dominant plant species had similar or greater abundance in areas fenced to exclude wild vertebrates, after 1–3 growing seasons, than in areas open to wild vertebrates. The dominant species included switchgrass Panicum virgatum, cordgrasses Spartina spp. and wild rice Zizania aquatica. VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled study in freshwater marshes in the USA found that plots fenced to exclude Canada geese Branta canadensis contained taller wild rice Zizania aquatica than open plots in two of three comparisons. In the other comparison, after two years of goose control, fenced and open plots contained wild rice of a similar height. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3132https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3132Mon, 05 Apr 2021 12:15:49 +0100Collected Evidence: Collected Evidence: Restore/create freshwater marshes or swamps (specific action unclear) Twenty-five studies evaluated the effects, on vegetation, of restoring/creating freshwater marshes or swamps using unclear or incompletely described actions. Twenty-three studies were in the USA. Two were in Canada. Two of the studies used the same set of wetlands. VEGETATION COMMUNITY Community types (1 study): One replicated, site comparison study in the USA reported that created wetlands had greater coverage of herbaceous vegetation after 7–8 years than natural wetlands, but lower coverage of forest and shrubby vegetation. Community composition (17 studies): Four replicated, site comparison studies in the USA found that the overall plant community composition in created freshwater wetlands differed from the community in natural wetlands, after 1–21 years. Two replicated, site comparison studies in the USA and Canada reported mixed effects of freshwater marsh restoration/creation on overall algal or plant community composition, depending on the habitat and use of mining waste during creation. Of four replicated, site comparison studies in the USA and Canada, three reported lower quality vegetation in restored/created wetlands than in natural wetlands, but one reported similar vegetation quality in created and natural wetlands. Two replicated, site comparison studies in the USA found that created marshes developed a plant community characteristic of similar wetness to natural marshes within 4–21 years – but in one study, this was only true for created marshes >10 years old. Seven replicated studies in the USA simply quantified the composition, quality or wetness of the plant community up to 22 years after wetland restoration/creation. Overall richness/diversity (17 studies): Eleven replicated studies, in the USA and Canada, compared overall plant richness/diversity in created/restored and natural/unmanaged freshwater wetlands. Five of the studies found that created/restored wetlands typically had similar plant taxonomic richness to natural/unmanaged wetlands. Three of the studies reported lower species richness in created than natural wetlands after 1–18 years. Two of the studies reported higher species richness in created than natural wetlands after 1–21 years. The final study reported mixed effects of marsh creation on plant species richness, depending on the vegetation zone and use of mining waste during creation. Two of the studies reported identical results for plant diversity as for richness (similar or greater in created vs natural wetlands) but one study found that the effect of management on plant diversity depended on the timing of drawdown. Six replicated studies in the USA simply quantified overall plant species richness and/or diversity over 1–16 years after wetland restoration/creation. Native richness/diversity (3 studies): Of two replicated, site comparison studies of freshwater wetlands in the USA, one found that restored/created wetlands contained more native plant species than natural wetlands after 1–11 years. The other found that restored wetlands contained fewer native plant species than natural wetlands after 2–8 years. One replicated study of swamp restoration sites in the USA simply quantified native plant richness over 1–8 years after intervention. VEGETATION ABUNDANCE Overall abundance (7 studies): Six replicated studies, all in the USA, compared overall vegetation abundance in created/restored and natural wetlands. Four of the studies found that created/restored freshwater wetlands contained less vegetation (cover or biomass) than natural wetlands after 1–18 years. Two of the studies found that created and natural fresh/brackish/saline wetlands contained a similar amount of vegetation (overall cover and density; wetland plant cover) after >1 year. One of these studies reported that restored wetlands had lower vegetation cover than natural marshes – but this reflected management goals. One replicated study in the USA simply quantified total vegetation cover and biomass 3–10 years after marsh creation. Herb abundance (2 studies): One replicated, site comparison study in the USA reported that created wetlands had greater overall cover of herb species, after 7–8 years, than natural wetlands. One replicated study in the USA simply quantified herb biomass in wetland restoration sites after 7–22 years. Tree/shrub abundance (1 study): One replicated study in the USA simply quantified the density of woody vegetation in wetland restoration sites after 7–22 years. Algae/phytoplankton abundance (1 study): One replicated, site comparison study in the USA found that ≤15-year-old restored freshwater marshes contained a similar phytoplankton biomass to natural marshes. Individual species abundance (9 studies): Nine studies quantified the effect of this action on the abundance of individual plant species. For example, one replicated, site comparison study in the USA found that created and natural freshwater marshes supported a similar abundance of pickerelweed Pontederia cordata after 1–11 years. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3190https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3190Wed, 07 Apr 2021 07:27:57 +0100Collected Evidence: Collected Evidence: Restore/create freshwater marshes or swamps (multiple actions) Seventeen studies evaluated the effects, on vegetation, of using >3 combined actions to restore/create freshwater marshes or swamps. Fourteen studies were in the USA. There was one study in each of Canada, the UK and East Africa. There was overlap in the sites used in three studies. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study in Canada reported that the area of emergent vegetation in a marsh was greater after 5–6 years of intervention than in the year before. Community composition (5 studies): Two replicated, site comparison studies in the USA found that restored/created freshwater wetlands contained different overall plant communities to natural or reference wetlands, after 1–8 years. Two site comparison studies in the USA reported similarity in species composition between restored/created and natural wetlands. Similarity ranged from 35% to 79% after 1–5 years. One study in the USA simply quantified the plant community composition of different pools within a marsh, two years after its creation. Overall richness/diversity (16 studies): Three studies (including one replicated, before-and-after, site comparison) of freshwater wetlands in the USA and Canada reported that multiple restoration actions increased overall or emergent plant species richness over 1–6 years. Another replicated, before-and-after, site comparison study in the USA reported that the effect of restoration on plant species richness varied between years. Two replicated, site comparison studies in the USA found that restored/created wetlands had similar plant species richness to natural or reference wetlands, after 1–8 years. One site comparison study in the USA reported that a created wetland contained fewer plant species than nearby natural marshes, after two years. Nine studies (four replicated, one before-and-after) in the USA and the UK simply quantified overall plant species richness and/or diversity approximately 1–10 years after intervention. Characteristic plant richness/diversity (6 studies): One replicated, before-and-after, site comparison study of freshwater wetlands in the USA reported that multiple restoration actions increased the richness of wetland-characteristic plant species over three subsequent years. Five studies (two replicated) in the USA simply quantified wetland-characteristic plant richness up to 10 years after intervention. VEGETATION ABUNDANCE Overall abundance (4 studies): Two replicated, before-and-after studies (one also a site comparison) of freshwater wetlands in the USA reported that multiple restoration actions reduced overall vegetation cover over the five subsequent years. Two replicated studies in the USA simply quantified overall vegetation cover for up to six years after intervention. Characteristic plant abundance (3 studies): Two replicated, before-and-after studies (one also a site comparison) of freshwater wetlands in the USA reported that multiple restoration actions did not increase the cover of wetland-characteristic vegetation over three subsequent years. One of the studies also monitored in the fifth (wetter) year after restoration, and reported greater cover of wetland-characteristic vegetation than before restoration. One replicated study on the same set of wetlands in the USA simply quantified wetland-characteristic vegetation cover for up to three years after intervention. Herb abundance (3 studies): One replicated, site comparison study in the USA found that restored wet prairies had similar grass and forb cover to remnant prairies after 3–8 years. Another replicated, site comparison study in the USA reported that created dune slacks had greater cover of annual herbs after three years than mature natural slacks, but similar cover of perennial herbs and floating aquatic herbs. One replicated, before-and-after study in the USA reported greater herb cover 1–5 years after restoration of freshwater wetlands than before. Tree/shrub abundance (3 studies): One replicated, site comparison study in the USA reported that created dune slacks had similar cover of trees and shrubs, after three years, to mature natural slacks. One replicated, before-and-after study in the USA reported lower cover of woody vegetation 1–5 years after restoration of freshwater wetlands than before. One replicated study in the USA simply quantified woody plant cover 1–2 years after intervention. Individual species abundance (10 studies): Ten studies quantified the effect of this action on the abundance of individual plant species. For example, the replicated, site comparison study in East Africa reported that the biomass of papyrus Cyperus papyrus in created marshes was within the range of natural marshes in the region after 18 months. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3192https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3192Wed, 07 Apr 2021 12:22:17 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create freshwater marshes from other land uses Twenty-six studies evaluated the effects, on vegetation, of raising the water level to restore/create freshwater marshes from other land uses or habitat types. Twenty-one studies were in the USA. There was one study in each of Israel, the UK, China, Luxembourg and Canada. Eight studies used sites from a common set of 62 restored prairie potholes in the Midwest USA. Five studies monitored the effects of one river dechannelization project in Florida. VEGETATION COMMUNITY Overall extent (5 studies): One replicated, paired, before-and-after, site comparison study in the USA reported that damming a stream reduced the area of emergent vegetation on the floodplain. Two before-and-after studies of a floodplain in the USA reported that after dechannelizing a river to raise the water level, the area of emergent herbaceous vegetation increased. Two studies in the USA and Luxembourg simply quantified coverage of wetland vegetation 1–6 years after raising the water table (sometimes along with other interventions). Community types (9 studies): Nine studies quantified the effect of this action on specific types of marsh vegetation. For example, one before-and-after study of a floodplain in the USA reported greatly increased coverage of wet prairie plant communities after dechannelizing a river to raise the water table, but only slightly increased coverage of mixed herbaceous/shrubby wetland communities. Five studies in the USA and Luxembourg simply quantified the number, abundance or extent of wetland plant communities present 1–6 years after raising the water table (typically along with other interventions). Community composition (8 studies): Three replicated, site comparison studies (two also paired) in the USA evaluated the effects of rewetting farmed depressions (along with planting cover crops in/around them). One of these studies reported that restored wetlands contained a different overall plant community to natural wetlands after 5–7 years. One study reported that the plant community composition differed more between restored and natural wetlands than amongst restored or natural wetlands. The final study found that restoration increased vegetation quality after ≥10 years, but not to the level of natural wetlands. Two site comparison studies in China and the USA reported that the plant community became more similar to natural wetlands over 6–15 years after raising the water level – in terms of species composition or overall wetness. Three replicated studies in the USA simply quantified the plant community composition for up to three years after rewetting farmland (sometimes along with other interventions). Overall richness/diversity (12 studies): Four replicated, site comparison studies (two also paired) of one set of historically farmed depressions in the USA reported that restored wetlands (rewetted, along with planting cover crops in/around the sites) had lower overall plant species richness than nearby natural wetlands, after 1–7 years. Two before-and-after, site comparison studies of historical wetlands on a floodplain in the USA reported that raising the water level reduced overall plant species richness in the following six years. One site comparison study of lakeshore marshes in China reported that the total plant species richness in former paddy fields with breached weirs was similar to a nearby natural marsh, after 2–15 years. Five studies (two replicated) in the USA and Israel simply quantified overall plant species richness and/or diversity between three months and 19 years after raising the water table (sometimes along with other interventions). Characteristic plant richness/diversity (1 study): One before-and-after, site-comparison study of a floodplain in the USA reported that dechannelizing a river to raise the water level had no clear effect on the richness of wetland-characteristic plant species in the following six years. VEGETATION ABUNDANCE Overall abundance (9 studies): Three before-and-after, site-comparison studies of historical wetlands on a floodplain in the USA reported that dechannelizing a river to raise the water level reduced overall vegetation cover in the following 6–9 years. One site comparison study in China reported that vegetation biomass in former paddy fields with breached weirs was similar to a nearby natural marsh, after 2–15 years. In contrast, one replicated, site comparison study in the USA found that vegetation cover in rewetted, formerly farmed depressions (also planted with cover crops) was lower than in nearby natural wetlands, after 5–7 years. Four studies (two replicated) in the USA and the UK simply quantified vegetation abundance between three months and six years after raising the water table (sometimes along with other interventions). Characteristic plant abundance (4 studies): Three before-and-after studies (two also site comparisons) of historical wetlands on a floodplain in the USA reported that dechannelizing a river to raise the water level increased the abundance of habitat- and/or wetland-characteristic plant species in the following 6–9 years. One study in the UK simply quantified the abundance of wet meadow plant species present 3–5 years after rewetting farmland (and introducing grazing). Bryophyte abundance (1 study): One replicated, site comparison study in the USA found that the frequency of bryophytes in (the wettest parts of) marshes rewetted 34 years previously was not significantly different from their frequency in (the wettest parts of) nearby natural marshes. Individual species abundance (11 studies): Eleven studies quantified the effect of this action on the abundance of individual plant species. For example, one replicated, site comparison study of freshwater marshes in the USA reported that Kneiff’s feathermoss Leptodictyum riparium was the most abundant plant species in marshes rewetted 34 years previously and nearby natural marshes. One before-and-after study of historical wetlands on a floodplain in the USA reported that after dechannelizing a river to raise the water level, some plots became dominated by a non-native grass species. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3198https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3198Fri, 09 Apr 2021 07:44:56 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore/create brackish/salt marshes from other land uses Fourteen studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore/create brackish/salt marshes from other land uses or habitat types. Seven studies were in the UK. Five studies were in the USA. There was one study in each of Australia and the Netherlands. There was overlap in the sites used in four of the studies. VEGETATION COMMUNITY Overall extent (3 studies): Three before-and-after studies in Australia, the UK and the Netherlands reported increases in the overall extent of salt marsh vegetation over 3–10 years after restoring tidal exchange. Community types (3 studies): One replicated, paired, site comparison study in the UK reported that restored marshes, developing after 2–13 years of tidal exchange, contained a different type of salt marsh plant community to natural marshes in four of four cases. Two before-and-after studies in the UK and the Netherlands reported increases in the frequency or coverage of salt marsh plant communities after restoring tidal exchange, reaching 93–100% after 9–10 years. Community composition (4 studies): Four site comparison studies (two replicated, one paired) in the UK and the USA reported that after facilitating tidal exchange on freshwater wetlands or farmland, the overall plant community composition remained somewhat different from natural brackish/salt marshes for up to 30 years. Three of the studies reported increasing community similarity to natural marshes over 11–30 years of tidal exchange. Overall richness/diversity (6 studies): Two site comparison studies of brackish/salt marshes in the USA and the UK reported that overall plant species richness was similar in marshes developing after 4–11 years of tidal exchange, and in nearby natural marshes. Two site comparison studies (one replicated) of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) had lower plant species richness or diversity than nearby natural marshes. Two before-and-after studies in the UK compared the number of plant/algae species present in salt marshes that developed over 1–9 years after restoring tidal exchange to the number of plant species present before intervention. In one study there were more species after intervention, but in the other study there were fewer. Characteristic plant richness/diversity (2 studies): One replicated, site comparison study of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange contained a similar number of salt-tolerant plant species to natural marshes. One before-and-after study in the Netherlands reported that all 23 target brackish/salt marsh species were present in the study site 10 years after restoring regular tidal exchange: more than were present before restoration. VEGETATION ABUNDANCE Overall abundance (6 studies): Two site comparison studies (one replicated) of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) had lower overall vegetation cover than nearby natural marshes. One before-and-after study in the UK reported that 99% of salt marsh quadrats were vegetated nine years after restoring tidal exchange, compared to 100% in the freshwater wetland that previously occupied the site and 43% one summer after restoration. Three studies in the USA and the UK simply quantified the overall cover of vegetation present in sites for up to 15 years after facilitating tidal exchange (sometimes along with other interventions). Characteristic plant abundance (1 study): One site comparison study in the USA reported that some plant species diagnostic of natural brackish marshes were absent from a marsh that had developed over >30 years of restored tidal exchange. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. For example, three site comparison studies of salt marshes in the UK reported that cover of saltmarsh grass Puccinellia maritima was similar or lower in marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) than in nearby natural marshes. In contrast, in these studies, cover of glassworts Salicornia was higher in restored than natural marshes. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3207https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3207Fri, 09 Apr 2021 07:49:08 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape: freshwater marshes Thirteen studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create freshwater marshes. Ten studies were in the USA. There was one study in each of France, the UK and Italy. Two pairs of studies used the same or similar sites in Connecticut and Nebraska. VEGETATION COMMUNITY Overall extent (1 study): One replicated, site comparison study in the USA reported that emergent vegetation stands covered a smaller area within excavated than natural marshes, 4–5 years after intervention. Community composition (3 studies): Two site comparison studies (one before-and-after, one replicated) in France and the USA reported that reprofiling affected the overall plant community composition. In the USA, the community differed from, but was not intermediate between, natural marshes and degraded marshes. One study in the USA simply quantified the wetness of the overall plant community in an excavated wetland, 1–2 growing seasons after intervention. Overall richness/diversity (9 studies): Three replicated, site comparison studies in the USA found that plant species richness (overall or wetland species) was similar in reprofiled and natural marshes, 1–13 years after intervention. One before-and-after, site comparison study in the UK reported that overall plant species richness was not higher in excavated (and planted) reedbeds, than in a nearby natural reedbed, after seven years. One before-and-after study in France reported that there were more plant species present in a marsh in the two summers after reprofiling than in the summer before. Four studies in the USA and Italy simply reported the number of plant species on wetlands that had been reprofiled or excavated (sometimes along with other interventions), after three months to 23 years. Characteristic plant richness/diversity (1 study): One study in the USA simply reported the number of wetland-characteristic plant species in excavated wetlands, for up to 18 years after intervention. VEGETATION ABUNDANCE Overall abundance (8 studies): Two replicated, site comparison studies in the USA reported that overall vegetation cover was similar in reprofiled and natural marshes, 2–13 years after intervention. One of the studies also found that vegetation cover was similar in reprofiled and degraded marshes. Another replicated, site comparison study in the USA reported that vegetation cover within emergent vegetation stands was lower in excavated than natural marshes, 4–5 years after intervention. Five studies in the USA simply quantified overall vegetation abundance on wetlands that had been reprofiled or excavated (sometimes along with other interventions), after three months to 18 years. One of these studies reported an absence of vegetation after two years. Characteristic plant abundance (1 study): One study in the USA simply quantified the abundance of wetland-characteristic plants in an excavated wetland, after 1–2 growing seasons. Bryophyte abundance (1 study): One replicated, site comparison study in the USA reported that excavated marshes contained a lower abundance (frequency and biomass) of bryophytes than natural marshes, 2–15 years after intervention. Trees/shrub abundance (1 study): One replicated, site comparison study in the USA reported that excavated marshes had lower woody plant cover than natural marshes, after 12–13 years. Individual species abundance (10 studies): Ten studies quantified the effect of this action on the abundance of individual plant species. Two of these studies were replicated site comparisons in the USA, and reported mixed responses. For example, broadleaf cattail Typha latifolia typically had lower cover in excavated than natural marshes in one study, but greater cover in excavated than natural marshes in the other study. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3213https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3213Fri, 09 Apr 2021 09:10:10 +0100Collected Evidence: Collected Evidence: Directly plant non-woody plants: freshwater wetlands Twenty-four studies evaluated the effects, on vegetation, of directly planting emergent, non-woody plants in freshwater wetlands. Sixteen studies were in the USA. There was one study in each of Guam, the Netherlands, Israel, Ireland, the UK, Italy, Australia and China. Two pairs of studies in Minnesota and South Dakota took place in the same area but used different experimental set-ups. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their near-shore plant community became more similar to that behind mature natural rush stands. Overall richness/diversity (9 studies): Two studies (including one replicated, randomized, controlled) in freshwater marshes in China and the USA reported that planting herbs increased plant species richness and/or diversity for up to five years. Two controlled studies in freshwater marshes in the USA reported that planted and unplanted sites had similar plant species richness after 2–3 years. Three studies in the USA, the UK and Australia compared plant species richness in marshes that had been planted with herbs (sometimes along with other interventions) and natural marshes, and reported that it was never higher in planted marshes. Three studies involving freshwater marshes in Guam, the USA and Italy simply quantified plant species richness for up to 13 years after planting herbs (along with other interventions). Characteristic plant richness/diversity (1 study): One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with wetland-characteristic herbs had a similar richness of wetland-characteristic plant species, after three years, to unplanted plots. VEGETATION ABUNDANCE Overall abundance (4 studies): One before-and-after study of a freshwater marsh and wet meadow in China found that vegetation cover was greater five years after planting herbs than in the year before planting. One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with herbs had similar overall vegetation cover, after three years, to unplanted plots. One replicated, site comparison study around fresh/brackish lakes in Australia found that as planted rush stands aged, the density of plants in adjacent near-shore vegetation became more similar to mature natural stands. One study in a freshwater marsh in the USA simply quantified vegetation cover and density over 1–9 years after planting herbs (along with other interventions). Characteristic plant abundance (1 study): One replicated, paired, controlled study in freshwater wetlands in the USA found that plots planted with wetland-characteristic herbs had greater cover of wetland-characteristic plants, after three years, than unplanted plots. Individual species abundance (13 studies): Thirteen studies quantified the effect of this action on the abundance of individual plant species. For example, one replicated, paired, controlled study in freshwater wetlands in the USA found that both planted herb species had greater cover in planted than unplanted plots, after three years. Three studies in the UK, the USA and Australia compared the abundance of herb species where they had been planted to their abundance in natural marshes: two found that the planted species was more dense in planted than natural areas after 5–14 years, and one found that planted rush stands became more dense (i.e. more like natural stands) as they aged. VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their width increased – becoming more like mature natural stands. Height (4 studies): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their maximum height increased – becoming more like mature natural stands. One before-and-after study of a freshwater marsh and wet meadow in China found that vegetation was taller five years after planting herbs than in the year before planting. One site comparison study of wet meadows in the USA reported that sedge tussocks in a restored meadow were shorter than sedge tussocks in natural meadows, 11–14 years after planting (along with other interventions). One replicated study in wet basins in the USA simply reported an increase in the average height of a herb species over three growing seasons after it was planted. Diameter/perimeter/area (1 study): One site comparison study of wet meadows in the USA reported that sedge tussocks in a restored meadow had a smaller perimeter than sedge tussocks in natural meadows, 11–14 years after planting (along with other interventions). Basal area (1 study): One site comparison study of wet meadows in the USA reported that the basal area of sedge tussocks was lower in a restored meadow than in natural meadows, 11–14 years after planting (along with other interventions). Individual plant size (2 studies): Two replicated studies in wet meadow restoration sites in the USA reported that the size of Carex stricta seedlings increased over two months or three growing seasons after planting. This was true for the average number of shoots/plant and biomass/plant. OTHER Survival (14 studies): Nine studies (eight replicated) in the USA and Israel quantified survival rates of individual herbs planted in freshwater wetlands. Survival rates ranged from 0% to 100% after 1–3 growing seasons. Eight studies (including five replicated and two before-and-after) in Guam, the USA, the Netherlands and Israel reported 0% survival or absence of planted (or sown) herb species, in at least some cases, after three months to seven years. Proposed factors affecting survival included elevation/water levels, herbivory, time of planting and plug type. Growth (2 studies): Two studies monitored true growth of individual herbs (rather than changes in average height of survivors). The two studies (one replicated) in Ireland and the USA reported that herbs grew over 1–2 growing seasons after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3256https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3256Sat, 10 Apr 2021 13:26:49 +0100Collected Evidence: Collected Evidence: Directly plant non-woody plants: brackish/saline wetlands Thirty studies evaluated the effects, on vegetation, of directly planting emergent, non-woody plants in brackish/saline wetlands. Twenty-four studies were in the USA. There was one study in each of Canada, New Zealand, Spain, Italy and Australia. One study was a global systematic review. Four of the studies monitored different outcomes of one planting experiment in California. Two other studies used the same marsh as each other. Two studies shared some plots with each other. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their near-shore plant community became more similar to that behind mature natural rush stands. Overall richness/diversity (3 studies): One controlled study on a brackish sandflat in the USA reported that an area planted with wetland herbs contained more plant species, after eight years, than an adjacent unplanted area. One replicated, site comparison study around fresh/brackish lakes in Australia found that the near-shore vegetation behind >8-year-old planted rush stands and mature natural stands contained a similar number of plant species. One study of a fresh/brackish/saline marsh in Italy simply quantified plant species richness for up to 13 years after planting herbs (along with other interventions). VEGETATION ABUNDANCE Overall abundance (4 studies): Two site comparison studies (one replicated) of brackish/saline marshes in the USA reported that areas planted with herbs (sometimes along with other interventions) contained less vegetation, after 2–3 growing seasons, than nearby natural marshes. This was true for biomass and cover. One replicated, site comparison study around fresh/brackish lakes in Australia found that the density of near-shore vegetation behind older planted rush stands was similar to that behind mature natural stands. One replicated, randomized, paired, controlled study in an estuary in the USA reported that plots planted with salt marsh vegetation contained more vegetation biomass than unplanted plots, after three growing seasons. Individual species abundance (18 studies): Eighteen studies quantified the effect of this action on the abundance of individual plant species. Four studies in the USA compared the abundance of plant species in planted and unplanted areas. Two replicated studies found that planted herb species were typically more abundant in planted than unplanted plots, after 2–4 growing seasons. One replicated, paired, controlled study reported that there were fewer common reed Phragmites australis stems in plots planted with other wetland herbs (and shrubs) than in unplanted plots, after 1–3 years. One replicated, randomized, controlled study reported species-specific effects of planted individuals on recruitment of conspecific seedlings. Nine studies in the USA and Australia compared the abundance of herb species where they had been planted to their abundance in natural brackish/saline marshes. Results varied between studies, species, metrics and time since planting. One before-and-after study of an intertidal site in the USA reported greater abundance of smooth cordgrass Spartina alterniflora over five years after planting (along with other interventions) than before. Seven studies (six replicated) in brackish/saline marshes in the USA and Canada simply quantified the abundance of individual species over 1–3 growing seasons after they were planted (sometimes along with other interventions). VEGETATION STRUCTURE Overall structure (2 studies): One replicated, randomized, paired, controlled, site comparison study in a salt marsh in the USA found that plots planted with herbs contained more canopy layers than unplanted plots after 2–4 growing seasons. One replicated, site comparison study around fresh/brackish lakes in Australia reported that as planted rush stands aged, their width increased – becoming more similar to mature natural stands. Height (11 studies): Three replicated studies in salt marshes in the USA found that vegetation in areas planted with herbs was at least as tall as vegetation in unplanted areas, 2–4 growing seasons after planting. Of six site comparison studies that compared vegetation height in planted and natural marshes (sometimes along with other interventions), three studies in the USA reported that vegetation was shorter in planted marshes after 2–5 growing seasons. Two studies in the USA and Australia found that vegetation was typically a similar height in planted and natural marshes after 2–11 years. One study in the USA found that vegetation was taller in planted marshes after three growing seasons. Four replicated studies in brackish/saline marshes in the USA simply quantified the height of herbs over 1–5 growing seasons after they were planted; in three of these studies, the average height increased over time. OTHER Survival (17 studies): Seventeen studies (including 13 replicated and one systematic review) in the USA, Canada, New Zealand, Spain and multiple countries quantified survival rates of individual herbs planted (or sown) in brackish/saline wetlands. Survival rates ranged from 0% to 100% after 20 days to 2 years. Four studies in the USA, New Zealand and multiple countries reported 0% survival or absence of planted herb species, in at least some cases, after nine months to eight years. Proposed factors affecting survival included elevation/water levels, age of planted individuals, treatment with root dip, planting date, soil pH, damage by waterbirds, salinity and sediment organic matter content. Growth (2 studies): Two studies monitored true growth of individual herbs (rather than changes in average height of survivors). One replicated study in a brackish marsh in the USA reported that in 8 of 10 cases, rushes/bulrushes grew in both height and circumference over the second year after planting. One replicated study in an estuary in Spain reported growth of planted small cordgrass Spartina maritima and glasswort Sarcocornia perennis over the year after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3257https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3257Sat, 10 Apr 2021 13:27:23 +0100Collected Evidence: Collected Evidence: Directly plant trees/shrubs: freshwater wetlands Seventeen studies evaluated the effects, on vegetation, of directly planting trees/shrubs in freshwater wetlands. Fifteen studies were in the USA. Two were in Australia. Two of the studies took place in the same site, but used different experimental set-ups. VEGETATION COMMUNITY Community composition (2 studies): Two replicated studies of freshwater wetlands in the USA found that planting trees/shrubs (sometimes along with other interventions) had no significant effect on aspects of plant community composition, after 1–11 years. Specifically, planted and unplanted wetlands had a similar proportion of species in different plant groups and relative abundance of different plant groups. Overall richness/diversity (1 study): One replicated, randomized, controlled, before-and-after study in depressional wetlands in the USA found that wetlands sparsely planted with tree seedlings contained a similar number of plant species, after 1–4 years, to unplanted wetlands. VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated studies (one site comparison; one randomized, controlled, before-and-after) of freshwater wetlands in the USA found that planting trees/shrubs (sometimes along with other interventions) had no significant effect on overall vegetation cover (both ground and canopy, separately or combined) after 1–11 years. Herb abundance (1 study): One study in a former firing range in the USA simply quantified herb cover approximately 1–2 years after reprofiling the site and planting trees/shrubs. Tree/shrub abundance (1 study): One study in a former firing range in the USA simply quantified woody plant cover approximately 1–2 years after reprofiling the site and planting trees/shrubs. VEGETATION STRUCTURE Visual obstruction (1 study): One replicated, site comparison study in the USA found that swamps created by planting trees/shrubs (after reprofiling) had less horizontal vegetation cover, after 7–11 years, than nearby swamps recovering naturally from logging. Height (6 studies): One replicated, site comparison study in the USA found that swamps created by planting trees/shrubs (after reprofiling) contained shorter woody vegetation, after 7–11 years, than nearby swamps recovering naturally from logging. Herbaceous vegetation, however, was of similar height. Five studies (four replicated) in freshwater wetlands in the USA simply quantified the height of trees and shrubs over 1–6 growing seasons after they were planted; in four of these studies, the average height typically increased over time. Diameter (1 study): One study in a freshwater wetland in the USA reported an increase in the diameter of surviving trees over the year after they were planted. Basal area (1 study): One replicated, site comparison study in the USA found that swamps created by planting trees/shrubs (after reprofiling) had a lower vegetation basal area, after 7–11 years, than nearby swamps recovering naturally from logging. OTHER Survival (15 studies): Fifteen studies (including eight replicated) in the USA and Australia quantified survival of individual trees/shrubs planted in freshwater wetlands. Survival rates ranged from 0% to 100% after 4–66 months. Seven of the studies (including six replicated) in the USA and Australia reported 0% survival of planted vegetation in at least some cases, after 1–6 growing seasons. Proposed factors affecting survival included elevation/water levels, the season of planting, protection from herbivores, root pruning, extreme weather, and if/how invasive vegetation was removed before planting. Growth (2 studies): Two studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). The two studies, in freshwater wetlands in the USA, reported that planted trees grew in diameter and/or height over their first 1–2 growing seasons. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3258https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3258Sat, 10 Apr 2021 13:27:32 +0100Collected Evidence: Collected Evidence: Directly plant trees/shrubs: brackish/saline wetlands Forty-seven studies evaluated the effects, on vegetation, of directly planting trees/shrubs in brackish/saline wetlands. Forty-four studies involved planting mangroves or other coastal swamp trees: 20 in Asia, seven in Central America, six in Africa, four in North America, four in South America, two in Oceania and one globally. Three studies involved planting shrubs in the USA or Spain. There was overlap in the sites used in two studies. One systematic review included several of the other summarized studies. VEGETATION COMMUNITY Overall extent (3 studies): Two before-and-after studies in India and South Africa reported that the area of mangrove forest was greater 6–42 years after planting mangrove trees (sometimes along with other interventions) than in the years before. One study in Sri Lanka simply quantified the area of mangrove vegetation present 8–10 years after planting seedlings (and propagules). Tree/shrub richness/diversity (6 studies): Three site comparison studies in the USA, Mexico and Brazil reported that where mangrove forests developed after planting trees (sometimes along with other interventions), they contained a similar number of tree species to mature and/or naturally regenerating forests after 10–30 years. One site comparison study in Vietnam reported that after 14–34 years, a planted mangrove forest contained more tree species than a (slightly older) naturally regenerated forest. One replicated, paired, before-and-after, site comparison study in Kenya reported that planted mangrove forest contained fewer adult tree species than mature natural forest after five years, but more species of seedling. One study in a former shrimp pond in Thailand simply reported the number of unplanted tree species that had colonized six years after planting (along with other interventions). VEGETATION ABUNDANCE Tree/shrub abundance (9 studies): Three replicated, site comparison studies of coastal sites in the Philippines, the USA and Brazil reported that where mangrove forests developed after planting trees (sometimes along with other interventions), woody vegetation was typically more dense than in mature natural forests and/or naturally regenerating forests. Two site comparison studies in Kenya and Vietnam found that tree abundance (density and biomass) was similar in planted and natural mangroves after 5–34 years. One site comparison study in Mexico reported that a planted mangrove forest contained fewer trees than pristine natural forests after 12 years. Two site comparison studies in the Philippines reported mixed results according to time since planting and site. One study in Thailand simply quantified the abundance of mangrove trees six years after planting (along with other interventions). Algae/phytoplankton abundance (1 study): One site comparison study in Kenya found that mangrove forests restored by planting contained a similar algal biomass, after eight years, to mature natural forests. However, mangrove forests created by planting into bare sediment contained less algal biomass than mature natural forests. Individual species abundance (7 studies): Seven studies quantified the effect of this action on the abundance of individual plant species. Four of the studies compared the abundance of woody vegetation or algae in planted mangrove forests and mature natural forests – and sometimes naturally regenerating forests (see original papers for data). One replicated, paired, controlled study in a brackish wetland in the USA reported that there were fewer common reed Phragmites australis stems in plots planted with wetland shrubs (and herbs) than in unplanted plots, after 1–3 years. One before-and-after study of an intertidal site in the USA reported greater abundance of red mangrove Rhizophora mangle over five years after planting (along with other interventions) than before. VEGETATION STRUCTURE Overall structure (3 studies): Three replicated, site comparison studies of coastal sites in the Kenya, the USA and the Philippines reported that where mangrove forests developed after planting trees (sometimes along with other interventions), their overall structure differed from mature natural forests for up to 50 years. Height (18 studies): Four site comparison studies (three replicated, three paired) of coastal sites in Kenya, the USA, Brazil and the Philippines reported that where mangrove forests developed after planting trees (sometimes along with other interventions), the vegetation was shorter than in mature and naturally regenerating forests after 5–30 years. One site comparison study in Mexico reported that planted mangrove forests contained taller trees than pristine natural forests after 12 years. Fourteen studies (four replicated) in Asia, Central/South America, Africa and North America simply quantified the height of mangrove trees for up to six years after they were planted; in 13 of these studies, the average height increased over time. Diameter (7 studies): Two site comparison studies in Mexio and Vietnam reported that tree diameters were similar in planted and natural mangroves after 12–34 years. In contrast, two site comparison studies in Brazil and the Philippines reported that planted mangroves contained thinner tree stems than mature natural mangroves after 7–12 years. The study in Brazil also reported that stem diameters were thinner than in naturally regenerating areas. Three studies in India and Nigeria simply quantified the diameter of mangrove trees for up to three years after they were planted; in all three studies, the average stem diameter increased over time. Basal area (3 studies): Two site comparison studies (one also replicated, paired, before-and-after) in Kenya and Mexico reported that planted mangrove forests had a smaller basal area than mature natural forests after 5–12 years. One replicated, site comparison study in the USA reported that where mangrove forests developed after planting trees (along with other interventions), their basal area was similar to mature natural forests after 17–30 years. OTHER Survival (37 studies): Thirty-six studies (including one review and one systematic review) quantified survival rates of individual trees/shrubs planted in brackish/saline wetlands. Survival rates ranged from 0% to 100% after 15 days to 21 years. The studies were of mangroves in North America, Central/South America, Asia, Africa, Oceania or globally, and of shrubs in the USA or Spain. Six studies reported 100% survival in some cases. Eleven studies reported 0% survival or absence of planted species in some cases. In six studies, survival of planted seedlings was not distinguished from survival of seeds or propagules. Proposed factors affecting survival included elevation/water levels, exposure to wind/waves, soil properties, sediment deposition, oyster/barnacle colonization, salinity, use of guidance and post-planting care. Growth (9 studies): Nine studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). The nine studies, in Colombia, the USA, the Philippines, Brazil and China, reported that planted trees/shrubs typically grew, over periods from 40 days to 50 years. One replicated study in the USA reported that planted seedlings grew less quickly than naturally colonizing seedlings. One replicated, site comparison study in the Philippines found that growth rates of trees in planted mangroves became more similar to those in mature natural mangroves over time. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3259https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3259Sat, 10 Apr 2021 13:27:43 +0100Collected Evidence: Collected Evidence: Introduce seeds of non-woody plants: freshwater wetlands Thirteen studies evaluated the effects, on vegetation, of introducing seeds of emergent, non-woody plants to freshwater wetlands. Eleven studies were in the USA. Two studies were in Australia. Two of the studies were based on exactly the same set of pools. Two sets of studies in the USA and Australia used the same general sites, but different experimental set-ups. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study of created wetlands in the USA reported that wetlands sown with herb (and some shrub) seeds contained a different overall plant community to unsown wetlands, after 1–2 years. Overall richness/diversity (1 study): The same study reported that wetlands sown with herb (and some shrub) seeds had higher plant diversity than unsown wetlands, after 1–2 years. VEGETATION ABUNDANCE Overall abundance (4 studies): Three replicated studies (two also randomized, paired, controlled, before-and-after) in wetlands in the USA and Australia found that plots sown with herb seeds (and in one study, some shrub seeds) had similar overall vegetation cover to unsown plots, after 1–3 years. One replicated, before-and-after study in the USA reported that vegetation biomass developed over 15 months after sowing mixed herb seeds. Biomass included all the sown species. Characteristic plant abundance (3 studies): Two replicated, controlled studies of recently excavated ephemeral pools in the USA found that native, pool-characteristic species were more common, over seven years, in pools where they were sown than where they were not sown. One of the studies found that this was true when a mixture of characteristic species were densely sown, but not when a single species was sparsely sown. One replicated, before-and-after study in experimental wet basins in the USA quantified the overall density of target sedge meadow species, in the vegetation that developed over 16 weeks after sowing. Herb abundance (2 studies): Two replicated, randomized, paired, controlled, before-and-after studies in a floodplain marsh in Australia found that plots sown with herb seeds had similar overall sedge/grass cover to unsown plots, after 1–3 years. Individual species abundance (8 studies): Eight studies quantified the effect of this action on the abundance of individual plant species. For example, four replicated, before-and-after studies in Australia and the USA reported that sown herb species were absent from plots in some cases, after 1–3 years. The two studies in Australia reported low abundance (<20% frequency and <2% cover) of wick grass Hymenachne acutigluma 1–3 years after sowing its seeds – although in one of the studies this was greater than in unsown plots. VEGETATION STRUCTURE Height (1 study): One replicated study in the USA reported data on cordgrass height, for up to three growing seasons after sowing. OTHER Germination/emergence (4 studies): Two replicated studies in the USA reported ≤1–61% germination of grass-like plants and forbs, after their seeds were sown onto wetlands. Another replicated study in the USA reported that seeds of six wetland herb species did not germinate when sown into a floodplain where an invasive plant was present (but being controlled). One replicated, randomized, paired, controlled study in a floodplain marsh in Australia found that sowing herb seeds had no significant effect on the number of invasive mimosa Mimosa pigra seedlings germinating, for up to three years. Survival (6 studies): Six studies in freshwater wetlands in Australia and the USA reported absence of sown (or planted) herb species, in at least some cases, after one month to seven years. It is not always clear whether this reflects death of seedlings or failure of seeds to germinate. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3264https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3264Sat, 10 Apr 2021 15:34:48 +0100Collected Evidence: Collected Evidence: Introduce tree/shrub seeds or propagules: brackish/saline wetlands Nineteen studies evaluated the effects, on vegetation, of introducing seeds or propagules of trees/shrubs to brackish/saline wetlands. All 19 studies involved planting mangrove propagules: seven in Asia, five in North America, three in Central America, two in Oceania, one in South America and one globally. Three studies in the USA shared some study sites. VEGETATION COMMUNITY Overall extent (2 studies): Two studies in the USA and Sri Lanka simply quantified the area of mangrove vegetation present 6–14 years after planting propagules (along with other interventions). Relative abundance (1 study): One replicated, paired, site comparison study in the USA reported that mangrove forests created by planting propagules (after reprofiling) supported a different relative abundance of tree species to natural forests, after 7–15 years. Tree/shrub richness/diversity (2 studies): Two replicated, site comparison studies in the USA reported that mangrove forests created by planting propagules (along with other interventions) contained a similar number of tree species to mature natural forests, after 7–30 years. VEGETATION ABUNDANCE Tree/shrub abundance (3 studies): Three replicated, site comparison studies of coastal sites in the USA and the Philippines reported that where mangrove forests developed after planting propagules (along with other interventions), trees were typically more dense than in mature natural forests. VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study in the USA reported that mangrove forests created by planting propagules (along with other interventions) had a different overall physical structure to mature natural forests, after 17–30 years. Height (4 studies): Four studies (three replicated) in Thailand, the USA, Mexico and the United Arab Emirates simply quantified the height of surviving mangrove trees for up to 16 years after sowing seeds or planting propagules; in all of these studies, the average height increased over time. Diameter/perimeter/area (3 studies): Two site comparison studies (one also replicated and paired) in the USA reported that mangrove forests created by planting propagules (after reprofiling) contained thinner trees, on average, than mature natural forests, after 7–18 years. One study in a coastal area planted with mangrove propagules in Thailand reported that the average diameter of surviving seedlings increased over time. Basal area (3 studies): Three site comparison studies (two also replicated, one also paired) in the USA compared mangrove forests created by planting propagules (along with other interventions) and mature natural forests. Two of the studies reported that planted forests had a smaller basal area than mature natural forests, after 7–18 years. The other study reported that planted forests had similar basal area to mature natural forests, after 17–30 years. OTHER Germination/emergence (2 studies): One replicated study in the United Arab Emirates reported 65–92% germination of sown grey mangrove Avicennia marina seeds, across five coastal sites. One replicated study in a brackish/saline estuary in China reported 38–100% germination of planted mangrove propagules, depending on the species and habitat. Survival (16 studies): Fifteen studies quantified survival of individual tree/shrub propagules planted in brackish/saline wetlands (or plants originating from them). All 15 studies were of mangroves: in Central/South America, Asia, North America, Oceania or gloablly. All reported survival in at least some cases, from 20 days to 30 years after planting. Five studies reported 100% survival in some cases. However, nine studies reported 0% survival or absence of planted species in some cases. In five studies, survival of seeds or propagules was not distinguished from survival of planted seedlings. Proposed factors affecting survival rates included elevation/water levels, substrate, invertebrate herbivory, use of tree shelters, mechanical stress, oyster colonization, use of guidance, post-planting care and repeated planting. Growth (5 studies): Five studies monitored true growth of individual trees/shrubs (rather than changes in average height of survivors). All five studies (three replicated) in Australia, the USA, Colombia and the Philippines reported that mangrove seedlings, originating from planted seeds or propagules, grew over time. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3267https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3267Sat, 10 Apr 2021 15:36:07 +0100

What Works in Conservation

The Conservation Evidence Journal

Discover more on our blog

Who uses Conservation Evidence?

Meet some of the evidence champions

For a full list of, and information about, our champions:

About our champions, why and how to become one:

What Works in Conservation

The Conservation Evidence Journal

Discover more on our blog

Who uses Conservation Evidence?

Meet some of the evidence champions

For a full list of, and information about, our champions:

About our champions, why and how to become one:

This website uses Cookies

1 Select a category

2 Refine category

3 View actions