Collected Evidence: Collected Evidence: Remove residential or commercial developmentWe found no studies that evaluated the effects, on vegetation, of removing residential or commercial development to restore/create 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%2F2946https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F2946Mon, 01 Mar 2021 16:14:22 +0000Collected Evidence: Collected Evidence: Remove plant litter: freshwater marshes One study evaluated the effects, on vegetation, of removing plant litter from freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots cleared of plant litter contained a plant community characteristic of wetter conditions than uncleared plots after one growing season – but not after two. Overall richness/diversity (1 study): The same study found that plots cleared of plant litter contained a similar number of wetland plant species to uncleared plots, after 1–2 growing seasons. VEGETATION ABUNDANCE                                                          Overall abundance (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots cleared of plant litter had greater cover of wetland plants than uncleared plots after one growing season – but not after two. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3062https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3062Fri, 02 Apr 2021 12:40:27 +0100Collected Evidence: Collected Evidence: Remove plant litter: brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of removing plant litter from brackish/salt marshes.   ‘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%2F3063https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3063Fri, 02 Apr 2021 13:01:21 +0100Collected Evidence: Collected Evidence: Remove plant litter: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of removing plant litter from freshwater 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%2F3064https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3064Fri, 02 Apr 2021 13:01:38 +0100Collected Evidence: Collected Evidence: Remove plant litter: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of removing plant litter from brackish/saline 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%2F3065https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3065Fri, 02 Apr 2021 13:01:57 +0100Collected Evidence: Collected Evidence: Remove pollutants from waste gases before they enter the environmentWe found no studies that evaluated the effects, on vegetation in marshes or swamps, of removing pollutants from waste gases before releasing them into the environment.   ‘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%2F3179https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3179Tue, 06 Apr 2021 16:11:49 +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 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 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 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: Remove surface soil/sediment: freshwater marshes Six studies evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create freshwater marshes. Four studies were in the USA. One study was in the Netherlands. One study was in Japan. VEGETATION COMMUNITY                              Community composition (3 studies): Two replicated, site comparison studies in the USA reported that freshwater marshes being restored by removing excess soil/sediment (along with other interventions) typically contained a different overall plant community, after 1–12 years, to both degraded and natural marshes nearby. One replicated study of dune slacks in the Netherlands simply reported changes in the overall plant community composition over four years after stripping topsoil (along with other interventions). Overall richness/diversity (4 studies): One replicated, site comparison study of dune slacks in the Netherlands reported that overall plant species richness was greater in restored slacks (topsoil stripped five years previously, along with other interventions) than in mature unmanaged slacks. One replicated, site comparison study in the USA reported that freshwater marshes being restored by removing topsoil (along with other interventions) contained fewer wetland plant species, after 1–12 years, than nearby natural marshes. Two studies (including one site comparison) in freshwater marshes in the USA and Japan reported that the effect of removing topsoil on overall plant species richness depended on the amount removed. Characteristic plant richness/diversity (2 studies): One replicated, site comparison study of a floodplain marsh in Japan found that where stripped plots were colonized by plants within two growing seasons, they contained more wetland-characteristic species than an adjacent unstripped area. One replicated study of dune slacks in the Netherlands simply reported the number of characteristic plant species present over five years after stripping topsoil (along with other interventions). VEGETATION ABUNDANCE Overall abundance (3 studies): Three studies (two replicated) in the Netherlands, the USA and Japan simply quantified the overall abundance of vegetation that colonized – within five years – freshwater wetlands stripped of topsoil (sometimes along with other interventions). Characteristic plant abundance (2 studies): Two studies (one replicated) in freshwater marshes in the USA and Japan simply quantified the abundance of wetland-characteristic plant species that colonized – within five years – areas stripped of topsoil. Individual species abundance (5 studies): Five 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 pothole wetlands restored by removing excess sediment (sometimes along with planting herbs) had lower hybrid cattail Typha x glauca cover than unrestored wetlands after 2–7 years, and similar hybrid cattail cover to nearby natural wetlands. One replicated study of dune slacks in the Netherlands simply quantified the cover of individual species present over five years after stripping topsoil (along with other interventions). Only two species had >1% cover in any slack. VEGETATION STRUCTURE Overall structure (1 study): One study in a freshwater marsh in the USA reported that the effect of removing topsoil on the abundance of tall vegetation depended on the amount removed. Visual obstruction (1 study): One replicated, site comparison study of pothole wetlands in the USA found that the effect of removing excess sediment (sometimes along with planting herbs) on horizontal vegetation cover, 2–7 years later, depended on the elevation/vegetation zone. Height (1 study): One site comparison study in the USA reported that sedge tussocks were shorter in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Diameter/perimeter/area (1 study): One site comparison study in the USA reported that sedge tussocks had a smaller perimeter in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in natural meadows, after 11–14 years. Basal area (1 study): One site comparison study in the USA reported that the basal area of sedge tussocks was smaller in a wet meadow restored by removing excess sediment (along with other interventions, including planting sedges) than in nearby natural meadows, after 11–14 years. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3221https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3221Fri, 09 Apr 2021 13:07:41 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: brackish/salt marshes One study evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create brackish/salt marshes. The study was in the Netherlands. VEGETATION COMMUNITY                              Overall richness/diversity (1 study): One study in the Netherlands reported that 23 plant species colonized over two years after stripping topsoil from coastal farmland. VEGETATION ABUNDANCE Individual species abundance (1 study): One study in the Netherlands reported the frequency of plant species that colonized over two years after stripping topsoil from coastal farmland. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3222https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3222Fri, 09 Apr 2021 13:08:28 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create freshwater 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%2F3223https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3223Fri, 09 Apr 2021 13:08:44 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of removing surface soil/sediment to restore or create brackish/saline 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%2F3224https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3224Fri, 09 Apr 2021 13:08:54 +0100Collected Evidence: Collected Evidence: Reprofile/relandscape (before planting)We found no studies that evaluated the effects, on vegetation, of reprofiling/relandscaping before planting emergent marsh/swamp plants.   ‘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%2F3285https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3285Sat, 10 Apr 2021 17:30:50 +0100Collected Evidence: Collected Evidence: Remove surface soil/sediment (before planting)We found no studies that evaluated the effects, on vegetation, of removing surface soil/sediment before planting emergent marsh/swamp plants.   ‘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%2F3290https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3290Sat, 10 Apr 2021 20:04:01 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted non-woody plants: freshwater wetlands Three studies evaluated the effects, on emergent non-woody vegetation planted in freshwater wetlands, of removing competing plants. All three studies were in the USA. Two studies used the same experimental wet basins but planted different species. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, paired, controlled study in wet meadows in the USA found removing an invasive species with herbicide before sowing mixed grass and forb seeds increased the total biomass of sown species after 1–2 growing seasons, but that burning to remove the invasive species had no significant effect on sown species biomass. Individual species abundance (1 study): One replicated, paired, controlled study in wet basins in the USA found that the effect of weeding to remove competitors on lake sedge Carex lacustris biomass and density, in the three years after planting, depended on the year and water level. VEGETATION STRUCTURE Height (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the height of planted sedges. One of the studies found that weeding had no significant effect on the height of planted tussock sedge Carex stricta in three of three years. The other study found that weeding reduced the average height of lake sedge Carex lacustris in the first year after planting, but had no significant effect in the following two years. OTHER Survival (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the survival of planted sedges Carex spp. Both studies found that weeding had no significant effect on sedge survival in at least two of three years. One of the studies found that weeding affected tussock sedge Carex stricta survival in the second year after planting, but that the direction of the effect depended on plot elevation. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3332https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3332Sun, 11 Apr 2021 14:05:56 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted non-woody plants: brackish/saline wetlands One study evaluated the effects, on emergent non-woody vegetation planted in brackish/saline wetlands, of removing competing plants. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE   VEGETATION STRUCTURE   OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in an estuarine salt marsh in the USA found that thinning cover of the dominant plant before sowing dwarf saltwort Salicornia bigelovii seeds had no significant effect on saltwort seedling density, over the following two months. Survival (1 study): The same study found that thinning the dominant plant increased the survival rate of dwarf saltwort Salicornia bigelovii transplants over the first six months after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3333https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3333Sun, 11 Apr 2021 14:08:52 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted trees/shrubs: freshwater wetlands Five studies evaluated the effects, on trees/shrubs planted in freshwater wetlands, of removing competing plants. Four studies were in the USA. Two of these took place in the same swamp, but with different experimental set-ups. One study was in Australia. VEGETATION COMMUNITY   VEGETATION ABUNDANCE   VEGETATION STRUCTURE Height (3 studies): Three replicated, controlled studies (two also randomized, two also paired) in a wet meadow in Australia and a degraded swamp in the USA found that clearing vegetation before planting tree/shrub seedlings typically had no clear or significant effect on their height, after 1–4 growing seasons. However, one of the studies in the USA found that planted baldcypress Taxodium distichum seedlings were taller, after three growing seasons, when planted amongst cut woody vegetation than below an uncleared canopy. Diameter/perimeter/area (1 study): One replicated, randomized, paired, controlled study in a wet meadow in Australia found that clearing vegetation, before planting tree/shrub seedlings, typically had no significant effect on the diameter of these seedlings nine months later. OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in a wet meadow in Australia found that there were more seedlings in plots that had been cleared of vegetation before sowing tree/shrub seeds, than in plots that had not been cleared before sowing. Seedlings were counted two months after sowing. Survival (4 studies): Three replicated, controlled studies (two also randomized, two also paired) in a wet meadow in Australia and a degraded swamp in the USA found that clearing vegetation before planting tree/shrub seedlings typically had no clear or significant effect on their survival, after 1–4 growing seasons. However, one of the studies in the USA found that planted baldcypress Taxodium distichum seedlings had a lower survival rate, after three growing seasons, when planted amongst cut woody vegetation than below an uncleared canopy. One replicated, randomized, paired, controlled study in degraded swamps in the USA found that removing reed canarygrass Phalaris arundinacea before planting tree/shrub seedlings never significantly reduced their survival rate over 1–2 growing seasons, and often increased it. Growth (1 study): One replicated, randomized, controlled study in the USA found that baldcypress Taxodium distichum seedlings planted into a marsh grew more in diameter, but less in height, when planted into plots cleared of vines than when planted into uncleared plots. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3334https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3334Sun, 11 Apr 2021 14:09:05 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted trees/shrubs: brackish/saline wetlandsWe found no studies that evaluated the effects, on trees/shrubs planted in brackish/saline wetlands, of removing competing plants.   ‘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%2F3335https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3335Sun, 11 Apr 2021 14:09:29 +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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