Conservation Evidence: Evidence Data

Collected 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%2Fwww.conservationevidence.com%2Factions%2F3179https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3179Tue, 06 Apr 2021 16:11:49 +0100Collected Evidence: Collected Evidence: Add water to marshes or swamps to compensate for droughtWe found no studies that evaluated the effects, on vegetation, of adding water to marshes or swamps to compensate for drought. ‘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%2Fwww.conservationevidence.com%2Factions%2F3180https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3180Tue, 06 Apr 2021 16:13:02 +0100Collected Evidence: Collected Evidence: Build barriers to protect littoral freshwater marshes from rising water levels and severe weatherWe found no studies that evaluated the effects, on vegetation, of building barriers to protect littoral freshwater marshes from rising water levels and severe weather. ‘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%2Fwww.conservationevidence.com%2Factions%2F3181https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3181Tue, 06 Apr 2021 16:13:34 +0100Collected Evidence: Collected Evidence: Build barriers to protect littoral brackish/salt marshes from rising water levels and severe weather Five studies evaluated the effects, on vegetation, of building barriers to protect littoral brackish/salt marshes from rising water levels and severe weather. Three studies were in the USA, one was in Italy and one was in the Netherlands. VEGETATION COMMUNITY Overall extent (3 studies): Two controlled studies (one also replicated, randomized, paired) in Italy and the USA found that protecting salt marshes with offshore structures had no significant effect on the seaward limit of emergent vegetation, after 17–27 months. It was similar, or retreated at a similar rate, in protected and unprotected marshes. One replicated, randomized, paired, controlled study in the USA found that brackish marshes protected with oyster shell reefs receded less, over one year, than unprotected marshes. Community composition (1 study): One replicated, site comparison study in the Netherlands reported that marshes protected with low sea walls had a similar overall plant community composition to nearby natural salt marshes, 15–22 years after the walls were built. Overall richness/diversity (2 studies): One controlled study in Italy reported that a salt marsh protected with an offshore fence contained more plant species, after 17 months, than an unfenced marsh. One replicated, site comparison study in the Netherlands recorded 85 plant and algal species across two salt marshes that had developed behind low sea walls, over 15–22 years, compared to 155 species recorded across multiple natural marshes in the region. VEGETATION ABUNDANCE Overall abundance (2 studies): Two controlled studies (one also replicated, randomized, paired) in Italy and the USA found that brackish/salt marshes protected with offshore structures contained a similar total amount of vegetation to unprotected marshes. This was true for cover and biomass. Individual species abundance (2 studies): One replicated, paired, site comparison study in the USA found that salt marshes protected with offshore breakwaters (and planted with cordgrasses Spartina spp.) typically contained less smooth cordgrass S. alterniflora, after 2–3 growing seasons, than nearby natural marshes. One replicated, site comparison study in the Netherlands reported that in marshes protected with low sea walls for 15–22 years and nearby natural salt marshes, the same plant species were the most frequent. VEGETATION STRUCTURE Height (1 study): One replicated, paired, site comparison study in the USA found that salt marshes protected with offshore breakwaters (and planted with cordgrasses Spartina spp.) contained shorter smooth cordgrass S. alterniflora plants, after 2–3 growing seasons, than nearby natural marshes. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3182https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3182Tue, 06 Apr 2021 16:13:45 +0100Collected Evidence: Collected Evidence: Build barriers to protect littoral freshwater swamps from rising water levels and severe weatherWe found no studies that evaluated the effects, on vegetation, of building barriers to protect littoral freshwater swamps from rising water levels and severe weather. ‘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%2Fwww.conservationevidence.com%2Factions%2F3183https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3183Tue, 06 Apr 2021 16:13:55 +0100Collected Evidence: Collected Evidence: Build barriers to protect littoral brackish/saline swamps from rising water levels and severe weatherWe found no studies that evaluated the effects, on vegetation, of building barriers to protect littoral brackish/saline swamps from rising water levels and severe weather. ‘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%2Fwww.conservationevidence.com%2Factions%2F3184https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3184Tue, 06 Apr 2021 16:14:06 +0100Collected Evidence: Collected Evidence: Designate zones for migration of marshes or swamps as climate changesWe found no studies that evaluated the effects, on vegetation, of designating zones for migration of marshes or swamps under climate change. ‘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%2Fwww.conservationevidence.com%2Factions%2F3185https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3185Tue, 06 Apr 2021 17:10:15 +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%2Fwww.conservationevidence.com%2Factions%2F3186https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3187https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3188https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3189https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3190https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3191https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3192https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3193https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3193Wed, 07 Apr 2021 12:22:32 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment and introduce vegetation: freshwater marshesWe found no studies that evaluated the combined effects, on vegetation, of depositing soil/sediment to form the physical structure of freshwater marshes and introducing vegetation. ‘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%2Fwww.conservationevidence.com%2Factions%2F3194https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3194Wed, 07 Apr 2021 13:40:54 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment and introduce vegetation: brackish/salt marshes Six studies evaluated the combined effects, on vegetation, of depositing soil/sediment to form the physical structure of brackish/salt marshes and introducing vegetation. All six studies were in the USA. Several sites, and even the same data from some sites, were used in multiple studies. VEGETATION COMMUNITY Overall extent (2 studies): Two replicated, site comparison studies of salt marshes in the USA compared the overall area of emergent vegetation in marshes created by depositing sediment and planting vs natural marshes. One study found that created and natural marshes had similar vegetation coverage after 2–23 years. The other study reported that created marshes had slightly lower vegetation coverage than nearby natural marshes after 2–4 years. Community types (1 study): One replicated, site comparison study in the USA found that four of four plant community types had similar coverage in created and natural salt marshes after 3–15 years. For most marshes, creation involved depositing sediment and planting herbs. Community composition (1 study): One replicated, before-and-after, site comparison study in the USA reported that the overall plant community in salt marshes created by depositing sediment and planting herbs/shrubs was <36% similar to nearby natural salt marshes, after 2–4 years. VEGETATION ABUNDANCE Overall abundance (1 study): One paired, site comparison study in the USA found that salt marshes created by depositing sediment and planting/sowing herbs typically contained at least as much vegetation (biomass and density) as natural marshes, after 1–4 years. Individual species abundance (4 studies): Four studies quantified the effect of this action on the abundance of individual plant species. For example, two studies (one review, one site comparison) in the USA found that salt marshes created by depositing sediment and introducing vegetation typically contained a similar amount (density and/or biomass) of cordgrasses Spartina spp. to nearby natural marshes, after 1–9 years. Meanwhile, one paired, site comparison study in the USA reported that whether created marshes contained a higher, lower or similar cordgrass density to natural marshes depended on plot elevation. VEGETATION STRUCTURE Overall structure (2 studies): One replicated, site comparison study in the USA found that salt marshes created (mostly) by depositing sediment and planting herbs contained larger patches of vegetation with straighter edges than natural marshes, after 3–15 years. One replicated, paired, site comparison study in the USA reported that created salt marshes contained a similar proportion of edge habitat to nearby natural salt marshes, after 2–23 years. Height (2 studies): Two site comparison studies in the USA compared the height of cordgrasses Spartina sp. in created and nearby natural marshes. One study (also paired) found that created marshes typically contained cordgrass of similar height to natural marshes, after 1–4 growing seasons. The other study reported that cordgrass was shorter in created than natural marshes, after 7–9 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3195https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3195Wed, 07 Apr 2021 13:41:27 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment and introduce vegetation: freshwater swampsWe found no studies that evaluated the combined effects, on vegetation, of depositing soil/sediment to form the physical structure of freshwater swamps and introducing vegetation. ‘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%2Fwww.conservationevidence.com%2Factions%2F3196https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3196Wed, 07 Apr 2021 13:41:44 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment and introduce vegetation: brackish/saline swampsWe found no studies that evaluated the combined effects, on vegetation, of depositing soil/sediment to form the physical structure of brackish/saline swamps and introducing vegetation. ‘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%2Fwww.conservationevidence.com%2Factions%2F3197https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3197Wed, 07 Apr 2021 13:41:58 +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%2Fwww.conservationevidence.com%2Factions%2F3198https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3198Fri, 09 Apr 2021 07:44:56 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create brackish/salt marshes from other land uses Two studies evaluated the effects, on vegetation, of raising the water level to restore/create brackish/salt marshes from other land uses or habitat types. Both studies were in the same area of Iraq, but used different study sites. VEGETATION COMMUNITY Community types (1 study): One before-and-after study of a slightly brackish marsh in Iraq reported that fewer plant community types were present three years after reflooding than before drainage. Overall richness/diversity (2 studies): Two before-and-after studies of brackish marshes in Iraq reported that fewer plant species were present three years after reflooding than before drainage. One of these studies also reported that individual plant communities typically had lower diversity after reflooding than before drainage. VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after study of a slightly brackish marsh in Iraq reported that six of seven studied plant communities had lower spring and/or summer biomass three years after reflooding than before drainage. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3199https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3199Fri, 09 Apr 2021 07:45:05 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create freshwater swamps from other land uses Two studies evaluated the effects, on vegetation, of raising the water level to restore/create freshwater swamps from other land uses or habitat types. Both studies monitored the effects of one river dechannelization project in the USA. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study of a floodplain in the USA reported that after dechannelizing a river to raise the water level, the area of shrubby and forested wetlands increased – reaching greater coverage than before intervention, but also than before degradation. Community types (1 study): The same study broke down overall swamp coverage into specific community types. For example, most of the shrubby wetlands that developed after raising the water level were dominated by a non-native species – which was not present historically. VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after, site comparison study of historical shrubby wetlands on a floodplain in the USA reported that dechannelizing a river to raise the water level reduced overall vegetation cover in the following nine years. Characteristic plant abundance (1 study): The same study reported that after dechannelizing a river to raise the water level, only one of two sites became dominated by wetland-characteristic shrubs. The other site remained dominated by wetland-characteristic herb species. Individual species abundance (1 study): The same study reported that dechannelizing a river to raise the water level slightly increased cover of buttonbush Cephalanthus occidentalis in one of two sites (no data for other site). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3200https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3200Fri, 09 Apr 2021 07:45:18 +0100Collected Evidence: Collected Evidence: Raise water level to restore/create brackish/saline swamps from other land usesWe found no studies that evaluated the effects, on vegetation, of raising the water level to restore/create brackish/saline swamps from other land uses or habitat types. ‘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%2Fwww.conservationevidence.com%2Factions%2F3201https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3201Fri, 09 Apr 2021 07:45:30 +0100Collected Evidence: Collected Evidence: Lower water level to restore/create freshwater marshes from other land uses Two studies evaluated the effects, on vegetation, of lowering the water level to restore/create freshwater marshes from other land uses or habitat types. One study was in the USA and one was in the Netherlands. VEGETATION COMMUNITY Overall extent (1 study): One replicated, before-and-after study of a freshwater wetland in the USA reported that following a drawdown of water levels, emergent vegetation coverage increased in areas that were previously open water. VEGETATION ABUNDANCE Overall abundance (1 study): One before-and-after study at the edge of a freshwater lake in the Netherlands reported that following a drawdown of the lake water level, vegetation cover developed in areas that were previously open water. Cover varied between years and elevations. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3202https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3202Fri, 09 Apr 2021 07:46:42 +0100Collected Evidence: Collected Evidence: Lower water level to restore/create brackish/salt marshes from other land usesWe found no studies that evaluated the effects, on vegetation, of lowering the water level to restore/create brackish/salt marshes from other land uses or habitat types. ‘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%2Fwww.conservationevidence.com%2Factions%2F3203https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3203Fri, 09 Apr 2021 07:47:14 +0100