Collected Evidence: Collected Evidence: Retain/create habitat linkages in developed areasWe found no studies that evaluated the effects, on marsh/swamp vegetation, of retaining or creating habitat linkages in developed areas.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2947https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2947Mon, 01 Mar 2021 16:14:48 +0000Collected Evidence: Collected Evidence: Retain/create habitat linkages in farmed areasWe found no studies that evaluated the effects, on marsh/swamp vegetation, of retaining or creating habitat linkages in farmed areas.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2950https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2950Mon, 22 Mar 2021 13:40:33 +0000Collected Evidence: Collected Evidence: Retain/create habitat linkages in areas of energy production or miningWe found no studies that evaluated the effects, on marsh/swamp vegetation, of retaining or creating habitat linkages in areas of energy production or mining.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2986https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2986Thu, 25 Mar 2021 20:18:24 +0000Collected Evidence: Collected Evidence: Retain/create habitat linkages across service corridorsWe found no studies that evaluated the effects, on marsh/swamp vegetation, of retaining or creating habitat linkages across transportation or service corridors.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2996https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2996Mon, 29 Mar 2021 12:33:06 +0100Collected Evidence: Collected Evidence: Restrict vehicle useWe found no studies that evaluated the effects, on vegetation, of restricting vehicle use in or near marshes or swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3019https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3019Wed, 31 Mar 2021 14:39:31 +0100Collected Evidence: Collected Evidence: Restrict pedestrian accessWe found no studies that evaluated the effects, on vegetation, of restricting pedestrian access to marshes or swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3022https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3022Wed, 31 Mar 2021 14:42:11 +0100Collected Evidence: Collected Evidence: Slow down input water to allow more time for pollutants to be removedWe found no studies that evaluated the effects, on marsh or swamp vegetation, of slowing down input water to allow more time for pollutants to be removed.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3144https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3144Mon, 05 Apr 2021 15:14:35 +0100Collected Evidence: Collected Evidence: Retain/restore/create vegetation around freshwater marshes Four studies evaluated the effects, on vegetation in freshwater marshes, of retaining/restoring/creating vegetation around them. Three studies were in the USA and one was in China. Two studies were largely based on the same sites. VEGETATION COMMUNITY Community composition (2 studies): Two replicated, site comparison studies in the USA reported that freshwater marshes surrounded by restored upland vegetation contained a different overall plant community, after 1–20 years, to nearby marshes surrounded by natural vegetation. One of the studies also reported differences between marshes in restored vs degraded catchments. Overall richness/diversity (3 studies): One replicated, paired, site comparison study in the USA found that marshes surrounded by restored upland vegetation had greater overall plant species richness than marshes within cropland, and similar richness to marshes within natural grassland. One replicated, site comparison study in the USA reported that freshwater marshes surrounded by restored upland vegetation contained fewer wetland plant species, after 1–20 years, than nearby marshes surrounded by natural vegetation. One before-and-after study of a lakeshore marsh in China reported that after revegetating a polluted input river (along with planting directly into the marsh), overall plant species richness increased. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, paired, site comparison study in the USA found that marshes surrounded by restored upland vegetation contained more plant biomass than marshes within cropland, but also more plant biomass than marshes within natural grassland. Characteristic plant abundance (1 study): One replicated, paired, site comparison study in the USA found that marshes surrounded by restored upland vegetation typically had greater cover of wetland-characteristic plants than marshes within cropland, and similar cover of these species to marshes within natural grassland. Individual species abundance (1 study): One replicated, site comparison study of pothole wetlands the USA found that wetlands surrounded by restored upland vegetation had greater cover of hybrid cattail Typha x glauca, after 2–7 years, than nearby natural wetlands. VEGETATION STRUCTURE Visual obstruction (1 study): One replicated, site comparison study of pothole wetlands in the USA found that parts of wetlands surrounded by restored upland vegetation created more visual obstruction, after 2–7 years, than the corresponding zone of nearby natural wetlands. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3145https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3145Mon, 05 Apr 2021 15:14:57 +0100Collected Evidence: Collected Evidence: Retain/restore/create vegetation around brackish/salt marshesWe found no studies that evaluated the effects, on vegetation in brackish/salt marshes, of retaining/restoring/creating vegetation around them.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3146https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3146Mon, 05 Apr 2021 15:15:10 +0100Collected Evidence: Collected Evidence: Retain/restore/create vegetation around freshwater swampsWe found no studies that evaluated the effects, on vegetation in freshwater swamps, of retaining/restoring/creating vegetation around them.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3147https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3147Mon, 05 Apr 2021 15:15:21 +0100Collected Evidence: Collected Evidence: Retain/restore/create vegetation around brackish/saline swampsWe found no studies that evaluated the effects, on vegetation in brackish/saline swamps, of retaining/restoring/creating vegetation around them.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3148https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3148Mon, 05 Apr 2021 15:15:30 +0100Collected Evidence: Collected Evidence: Restore/create freshwater marshes in areas that will be climatically suitable in the futureWe found no studies that evaluated the effects, on vegetation, of restoring or creating freshwater marshes in areas expected to be climatically suitable in the future.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3186https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3186Tue, 06 Apr 2021 17:10:52 +0100Collected Evidence: Collected Evidence: Restore/create brackish/salt marshes in areas that will be climatically suitable in the futureWe found no studies that evaluated the effects, on vegetation, of restoring or creating brackish/salt marshes in areas expected to be climatically suitable in the future.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3187https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3187Tue, 06 Apr 2021 17:11:12 +0100Collected Evidence: Collected Evidence: Restore/create freshwater swamps in areas that will be climatically suitable in the futureWe found no studies that evaluated the effects, on vegetation, of restoring or creating freshwater swamps in areas expected to be climatically suitable in the future.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3188https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3188Tue, 06 Apr 2021 17:11:23 +0100Collected Evidence: Collected Evidence: Restore/create brackish/saline swamps in areas that will be climatically suitable in the future One study evaluated the effects, on vegetation, of restoring or creating brackish/saline swamps in areas expected to be climatically suitable in the future. The study was in South Africa. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study in an estuary in South Africa reported that over 42 years after planting mangrove trees just beyond their current range, the area of mangrove forests increased. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3189https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3189Tue, 06 Apr 2021 17:11:31 +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 brackish/saline marshes or swamps (specific action unclear) Seven studies evaluated the effects, on vegetation, of restoring/creating brackish/saline marshes or swamps using unclear or incompletely described actions. Four studies were in the USA. There was one study in each of Australia, Canada and Indonesia. VEGETATION COMMUNITY Community composition (4 studies): Three replicated, site comparison studies in the USA and Australia reported that the overall plant or algal community composition in restored/created marshes typically became more like natural reference marshes over time. One replicated, site comparison study of fresh/brackish wetlands in Canada reported that the overall plant community was lower quality in restored/created sites than natural sites, after ≥3 years. Overall richness/diversity (1 study): One replicated, site comparison study of salt marshes in the USA found that created marshes had similar overall plant diversity, after 1–14 years, to natural marshes. Created marshes had lower plant species richness than natural marshes on average, but richness became more similar to natural marshes with time since creation. Algae/phytoplankton richness/diversity (1 study): One replicated, paired, site comparison study of brackish/saline marshes in the USA reported that restored and natural marshes contained a similar number of algal species, and found that they had similar algal diversity, after 1–28 years. VEGETATION ABUNDANCE Overall abundance (2 studies): One replicated, site comparison study of salt marshes in the USA found that created marshes contained less overall plant biomass, after 1–14 years, than natural marshes – but that biomass increased with time since creation. One replicated, site comparison study of fresh/brackish/saline marshes in the USA found that created (but not restored) marshes had similar overall vegetation cover to natural marshes. Both created and restored marshes had similar cover of wetland vegetation to natural marshes. Herb abundance (2 studies): One replicated, paired, site comparison study of brackish/saline marshes in the USA reported that restored marshes contained a greater density of cordgrasses Spartina than natural marshes in six of eight comparisons. Vegetation was surveyed 1–28 years after restoration, which involved planting cordgrasses. One replicated, paired site comparison study in the USA reported that created intertidal wetlands contained more smooth cordgrass Spartina alterniflora than nearby natural mangrove forests for around 13 years. Tree/shrub abundance (2 studies): One replicated, paired site comparison study in the USA reported that created intertidal wetlands contained fewer adult mangrove trees than nearby natural mangrove forests for up to 20 years – but predicted equivalence within 55 years. One replicated study in Indonesia simply quantified the density of tree seedlings three years after restoration of former mangrove ponds. Algae/phytoplankton abundance (1 study): One paired, site comparison study of brackish/saline marshes in the USA reported that older restored marshes (≥26 years old) contained a similar or greater abundance of algae to natural marshes, whereas younger restored marshes (<13 years old) contained less algae than natural marshes. VEGETATION STRUCTURE Diameter/perimeter/area (1 study): One replicated, paired site comparison study in the USA reported that created intertidal wetlands contained thinner adult mangrove trees than nearby natural mangrove forests for up to 20 years – but predicted equivalence within 25 years. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3191https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3191Wed, 07 Apr 2021 07:28:08 +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: Restore/create brackish/saline marshes or swamps (multiple actions) Eight studies evaluated the effects, on vegetation, of using >3 combined actions to restore/create brackish/saline marshes or swamps. Six studies were in the USA. One was in Singapore. One was in Indonesia. Three studies were based on the same experimental set-up. VEGETATION COMMUNITY Overall extent (1 study): One study of a coastal site in the USA reported that the coverage of mangrove vegetation increased, and the coverage of herbaceous vegetation declined, over five years after intervention (intended to restore mangrove forest). Overall richness/diversity (3 studies): Three studies of one salt marsh restoration site in the USA simply quantified plant species richness for up to 13 growing seasons after intervention. Tree/shrub richness/diversity (1 study): One site comparison study in Indonesia reported that a restored aquaculture pond contained a similar number of mangrove species to nearby reference forests, just 6–7 months after intervention. Some trees may have been present before intervention. VEGETATION ABUNDANCE Overall abundance (4 studies): One replicated, paired, site comparison study of salt marshes in the USA found that restored marshes had similar overall vegetation cover to natural marshes after 9–20 years. Three studies of one salt marsh restoration site in the USA simply quantified overall vegetation abundance for up to 13 growing seasons after intervention. Tree/shrub abundance (3 studies): One replicated, paired, site comparison study of salt marshes in the USA found that restored marshes had similar, limited shrub cover to natural marshes after 9–20 years. One site comparison study of mangrove forests in Singapore reported that a created mangrove forest supported lower above-ground biomass than mature natural forests after ≥15 years. One study in Indonesia simply counted the number of mangrove trees present 6–7 months after intervention. Individual species abundance (4 studies): Four studies in estuaries in the USA simply quantified the abundance of individual plant species for up to 13 growing seasons after intervention. VEGETATION STRUCTURE Overall structure (1 study): One replicated, paired, site comparison study of salt marshes in the USA found that restored marshes had less cover of short vegetation and greater cover of medium-height vegetation than natural marshes after 9–20 years. Restored and natural marshes had similar cover of tall vegetation. Height (2 studies): One study of a created mangrove forest in Singapore reported that the average height of surviving mangrove saplings increased over five years. One study of a salt marsh restoration site in the USA reported that maximum vegetation height did not clearly increase between the third and twelfth/thirteenth growing seasons after intervention. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3193https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3193Wed, 07 Apr 2021 12:22:32 +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: Reprofile/relandscape: brackish/salt marshes Nine studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create brackish/salt marshes. Seven studies were in the USA. One was in Belgium. One was in Italy. Two of the studies were based on the same marsh. VEGETATION COMMUNITY Overall extent (2 studies): One paired, site comparison study in an estuary in the USA reported that vegetation coverage on reprofiled sediment, after 2–3 years, did not clearly differ from natural marsh areas in two of three comparisons. One replicated, paired, site comparison study in the USA reported that reprofiled coastal areas, where submerged sediment had been pushed into ridges, contained a smaller proportion of salt marsh habitat than nearby natural areas. Overall richness/diversity (2 studies): Two studies in Belgium and Italy simply quantified plant species richness in marshy areas that had been reprofiled or excavated (sometimes along with other interventions), for up to 23 years after intervention began. Characteristic plant richness/diversity (1 study): One study in an estuary in the USA simply reported the number of salt marsh plant species that colonized an area of reprofiled sediment over seven years. VEGETATION ABUNDANCE Overall abundance (2 studies): One site comparison study of salt marshes in the USA reported that a marsh created by reprofiling sediment (along with other interventions, including planting) had lower overall vegetation cover than a nearby natural marsh, after three growing seasons. One study in an estuary in Belgium simply quantified the cover of vegetation that colonized an area of reprofiled sediment over five years. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. Of four site comparison studies in the USA, three reported that the dominant herb species was typically less abundant – in terms of cover or biomass – in marshes that had been reprofiled (sometimes along with other interventions) than in natural areas, after 2–5 years. The other study reported that density of the dominant herb species in a reprofiled (and planted) marsh was within the range of nearby natural marshes, after five years. Two studies in the USA and Belgium simply quantified cover of individual plant species over five years after reprofiling (sometimes along with other interventions). VEGETATION STRUCTURE Overall structure (1 study): One replicated, paired, site comparison study in the USA found that the layout of salt marsh habitat (e.g. patch size and complexity) differed between reprofiled coastal areas, where submerged sediment had been pushed into ridges, and nearby natural areas. Height (1 study): One site comparison study in the USA reported that California cordgrass Spartina foliosa was shorter in a 5-year-old reprofiled marsh (also planted with cordgrass) than in nearby natural marshes. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3214https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3214Fri, 09 Apr 2021 09:10:21 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape: freshwater swamps Two studies evaluated the effects, on vegetation, of reprofiling or relandscaping to restore or create freshwater swamps. Both studies were in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study in the USA found that swamps created by reprofiling uplands (along with planting trees/shrubs) contained a similar proportion of tree species in different plant groups, after 7–11 years, to nearby swamps recovering naturally from logging. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in the USA found that swamps created by reprofiling uplands (along with planting trees/shrubs) had similar ground and canopy cover, after 7–11 years, to nearby swamps recovering naturally from logging. 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 reprofiling uplands (along with planting trees/shrubs) had less horizontal vegetation cover, after 7–11 years, than nearby swamps recovering naturally from logging. Height (1 study): The same study found that swamps created by reprofiling uplands (along with planting trees/shrubs) contained shorter woody vegetation, after 7–11 years, than nearby swamps recovering naturally from logging. Herbaceous vegetation, however, was of similar height in both created and naturally recovering swamps. Basal area (1 study): The same study found that swamps created by reprofiling uplands (along with planting trees/shrubs) had a lower vegetation basal area, after 7–11 years, than nearby swamps recovering naturally from logging. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3215https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3215Fri, 09 Apr 2021 09:10:34 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape: brackish/saline swamps Five studies evaluated the effects, on vegetation, of reprofiling/relandscaping to restore or create brackish/saline swamps. Three studies were in the USA. Two of these shared a study site. There was one study in Singapore and one in Thailand. VEGETATION COMMUNITY Overall extent (1 study): One study of a coastal site in the USA reported that the area of mangrove vegetation increased between 6 and 14 years after reprofiling (and planting propagules). Relative abundance (2 studies): Two site comparison studies in the USA and Singapore reported that areas of reprofiled coastal land (sometimes also planted with propagules) supported a different relative abundance of tree species to natural forests, after roughly 3–15 years. Overall richness/diversity (1 study): One site comparison study in Singapore reported that an area of reprofiled coastal land colonized by mangrove vegetation had higher plant species richness, after three and a half years, than an adjacent mature mangrove patch. Tree/shrub richness/diversity (3 studies): Two replicated, site comparison studies in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they contained a similar number of tree species to nearby mature forests after 7–30 years. One study in a former shrimp pond in Thailand simply reported the number of mangrove tree species that spontaneously colonized in the six years after reprofiling (along with other interventions). VEGETATION ABUNDANCE Overall abundance (1 study): One site comparison study in Singapore reported that an area of reprofiled coastal land colonized by mangrove vegetation had a higher density of individual plants, after three and a half years, than an adjacent mature mangrove patch. Tree/shrub abundance (3 studies): Two replicated, site comparison studies in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they contained a greater density of trees than nearby mature forests after 17–30 years. One study in a former shrimp pond in Thailand simply reported the number of mangrove trees that spontaneously colonized in the six years after reprofiling (along with other interventions). Individual species abundance (1 study): One study in a former shrimp pond in Thailand reported the number of mangrove trees, by species, that spontaneously colonized in the six years after reprofiling (along with other interventions). VEGETATION STRUCTURE Overall structure (1 study): One replicated, site comparison study in the USA reported that where mangrove forests developed on reprofiled (and planted) sites, they had a different overall structure to nearby mature forests after 17–30 years. Height (2 studies): One replicated, site comparison study in the USA, reported that where mangrove forests developed on reprofiled (and planted) sites, they had a shorter canopy than nearby mature forests after 17–30 years. One site comparison study in Singapore reported that in an area of reprofiled coastal land colonized by mangrove vegetation, most plants were in a similar height category to those in an adjacent mature mangrove patch, but that the maximum plant height was lower. Vegetation was surveyed three and a half years after reprofiling. Diameter/perimeter/area (2 studies): Two site comparison studies in the USA reported that mangrove forests that developed on reprofiled (and planted) coastal areas contained thinner trees, on average, than mature natural forests, after 7–18 years. Basal area (3 studies): Three site comparison studies in the USA compared mangrove forests that developed on reprofiled (and planted) coastal areas to mature natural forests. Two of the studies reported that restored forests had a smaller basal area than mature natural forests, after 7–18 years. The other study reported that restored forests had a similar basal area to mature natural forests, after 17–30 years. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3216https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3216Fri, 09 Apr 2021 09:10:45 +0100Collected Evidence: Collected Evidence: Soak non-woody plants before planting: brackish/saline wetlandsWe found no studies that evaluated the effects – on emergent, non-woody plants typical of brackish/saline wetlands – of soaking them before planting.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3360https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3360Sun, 11 Apr 2021 17:33:18 +0100Collected Evidence: Collected Evidence: Require mitigation of impacts to marshes or swamps Nine studies evaluated the overall effects – on vegetation or human behaviour – of requiring mitigation of impacts to marshes or swamps. All nine studies were in the USA. VEGETATION COMMUNITY Overall extent (6 studies): Four studies in the USA reported that requiring mitigation of impacts to wetlands did not prevent loss of wetland area: the total area restored/created was less than the area destroyed. One study in the USA reported that the total area of wetlands restored/created for mitigation was greater than the area destroyed. However, the area restored/created was smaller in most individual projects. Two of the studies reported that fewer individual wetlands were restored/created than destroyed. One before-and-after study in the USA found that wetland area declined after legislation to offset impacts came into force, but at a slower rate than before the legislation applied. Four of the studies reported discrepancies between the area of specific vegetation types restored/created vs destroyed. VEGETATION ABUNDANCE   VEGETATION STRUCTURE   OTHER Compliance (8 studies): Eight studies, all in the USA, provided information about compliance with required mitigation. Five of the studies reported that the total area of wetlands conserved was less than the area required in permits. Three of the studies reported that most mitigation projects failed to meet targets stipulated in permits. One of the studies reported that only one of seven vegetation targets was met in all mitigation sites. One of the studies reported that 64–74% of assessed mitigation areas met success criteria stipulated in permits. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3386https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3386Mon, 12 Apr 2021 11:47:00 +0100
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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