Conservation Evidence: Evidence Data

Collected 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: 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: Facilitate tidal exchange to restore/create brackish/salt marshes from other land uses Fourteen studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore/create brackish/salt marshes from other land uses or habitat types. Seven studies were in the UK. Five studies were in the USA. There was one study in each of Australia and the Netherlands. There was overlap in the sites used in four of the studies. VEGETATION COMMUNITY Overall extent (3 studies): Three before-and-after studies in Australia, the UK and the Netherlands reported increases in the overall extent of salt marsh vegetation over 3–10 years after restoring tidal exchange. Community types (3 studies): One replicated, paired, site comparison study in the UK reported that restored marshes, developing after 2–13 years of tidal exchange, contained a different type of salt marsh plant community to natural marshes in four of four cases. Two before-and-after studies in the UK and the Netherlands reported increases in the frequency or coverage of salt marsh plant communities after restoring tidal exchange, reaching 93–100% after 9–10 years. Community composition (4 studies): Four site comparison studies (two replicated, one paired) in the UK and the USA reported that after facilitating tidal exchange on freshwater wetlands or farmland, the overall plant community composition remained somewhat different from natural brackish/salt marshes for up to 30 years. Three of the studies reported increasing community similarity to natural marshes over 11–30 years of tidal exchange. Overall richness/diversity (6 studies): Two site comparison studies of brackish/salt marshes in the USA and the UK reported that overall plant species richness was similar in marshes developing after 4–11 years of tidal exchange, and in nearby natural marshes. Two site comparison studies (one replicated) of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) had lower plant species richness or diversity than nearby natural marshes. Two before-and-after studies in the UK compared the number of plant/algae species present in salt marshes that developed over 1–9 years after restoring tidal exchange to the number of plant species present before intervention. In one study there were more species after intervention, but in the other study there were fewer. Characteristic plant richness/diversity (2 studies): One replicated, site comparison study of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange contained a similar number of salt-tolerant plant species to natural marshes. One before-and-after study in the Netherlands reported that all 23 target brackish/salt marsh species were present in the study site 10 years after restoring regular tidal exchange: more than were present before restoration. VEGETATION ABUNDANCE Overall abundance (6 studies): Two site comparison studies (one replicated) of salt marshes in the UK reported that marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) had lower overall vegetation cover than nearby natural marshes. One before-and-after study in the UK reported that 99% of salt marsh quadrats were vegetated nine years after restoring tidal exchange, compared to 100% in the freshwater wetland that previously occupied the site and 43% one summer after restoration. Three studies in the USA and the UK simply quantified the overall cover of vegetation present in sites for up to 15 years after facilitating tidal exchange (sometimes along with other interventions). Characteristic plant abundance (1 study): One site comparison study in the USA reported that some plant species diagnostic of natural brackish marshes were absent from a marsh that had developed over >30 years of restored tidal exchange. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. For example, three site comparison studies of salt marshes in the UK reported that cover of saltmarsh grass Puccinellia maritima was similar or lower in marshes developing after 1–14 years of tidal exchange (sometimes along with other interventions) than in nearby natural marshes. In contrast, in these studies, cover of glassworts Salicornia was higher in restored than natural marshes. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3207https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3207Fri, 09 Apr 2021 07:49:08 +0100Collected Evidence: Collected Evidence: Facilitate tidal exchange to restore/create brackish/saline swamps from other land uses Two studies evaluated the effects, on vegetation, of facilitating tidal exchange to restore/create brackish/saline swamps from other land uses or habitat types. One study was in Australia and one was in Thailand. VEGETATION COMMUNITY Overall extent (1 study): One before-and-after study in an estuary in Australia reported that the area of mangrove forest on an island was greater 3–9 years after restoring full tidal exchange than in the years before. Tree/shrub richness/diversity (1 study): One study in a former shrimp pond in Thailand reported the number of mangrove tree species that spontaneously colonized in the six years after restoring full tidal exchange (along with other interventions). VEGETATION ABUNDANCE 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 restoring full tidal exchange (along with other interventions). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3209https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3209Fri, 09 Apr 2021 07:49:33 +0100Collected Evidence: Collected Evidence: Excavate freshwater pools Seven studies evaluated the effects, on vegetation within pools or surrounding marshes/swamps, of excavating freshwater pools. Five studies were in the USA, one was in Guam and one was in Canada. Two of the studies in the USA were based on the same set of pools. VEGETATION COMMUNITY Relative abundance (2 studies): One replicated, paired, site comparison study in a freshwater marsh in Canada reported that a smaller proportion of individual plants around excavated pools were wetland-characteristic species, compared to the proportion around natural pools. The excavated pools were 1–3 years old. One replicated study in the USA reported that excavated pools became dominated by non-native plant species over eight years. Overall richness/diversity (3 studies): One replicated, paired, site comparison study in a freshwater marsh in Canada found that overall plant species richness and diversity were similar around excavated pools and natural pools, 1–3 years after excavation. Two studies involving freshwater marshes in Guam and the USA simply quantified plant species richness 12–18 months after excavation (along with other interventions). VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in the USA found that excavated and natural pools had similar cover of emergent vegetation, seven years after excavation. The same was true for submerged vegetation. Characteristic plant abundance (2 studies): Two replicated studies in the USA reported the abundance of native pool-characteristic species over 3–8 years after excavating pools. One of the studies was also a site comparison and reported that these species were less abundant in the excavated pools than nearby natural pools. Shrub abundance (2 studies): One replicated, site comparison study in the USA found that excavated and natural pools had similar cover of shrubby vegetation after seven years. One replicated study in the USA simply quantified shrub abundance over five years after excavating pools/potholes (along with other interventions). Algae/phytoplankton abundance (1 study): One replicated, site comparison study in the USA found that excavated and natural pools contained a similar biomass of surface-coating algae and phytoplankton, after seven years. The same was true for phytoplankton after eight years. 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 excavated and natural pools had similar cover of loosestrife Lythrum sp. seven years after excavation, but that excavated pools had greater cover of duckweed Lemna sp., cattails Typha spp. and common reed Phragmites australis. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3211https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3211Fri, 09 Apr 2021 08:47:38 +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%2Fwww.conservationevidence.com%2Factions%2F3213https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3214https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3215https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3216https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3216Fri, 09 Apr 2021 09:10:45 +0100Collected Evidence: Collected Evidence: Create mounds or hollows: brackish/saline swamps One study evaluated the effects, on vegetation, of creating mounds or hollows in brackish/saline swamps. The study was in Indonesia. VEGETATION COMMUNITY VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One study in Indonesia simply reported the number of mangrove tree seedlings that had colonized a pile of branches placed in a disused aquaculture pond, around seven months after depositing the branches (and releasing mangrove propagules). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3220https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3220Fri, 09 Apr 2021 12:55:02 +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%2Fwww.conservationevidence.com%2Factions%2F3221https%3A%2F%2Fwww.conservationevidence.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%2Fwww.conservationevidence.com%2Factions%2F3222https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3222Fri, 09 Apr 2021 13:08:28 +0100Collected Evidence: Collected Evidence: Disturb soil/sediment surface: freshwater marshes Two studies evaluated the effects, on vegetation, of disturbing the surface of freshwater marshes. Both studies were in the USA – in the same region but different sites. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that ploughed plots contained a plant community characteristic of wetter conditions than unploughed plots after one growing season – but not after two. Overall richness/diversity (2 studies): Two replicated, controlled studies in rewetted marshes in the USA found that ploughed plots typically contained more wetland plant species than unploughed plots after one growing season – but not after two. VEGETATION ABUNDANCE Overall abundance (2 studies): Two replicated, controlled studies in rewetted marshes in the USA found that ploughed plots had greater cover of wetland plants than unploughed plots after one growing season – but not after two. Individual species abundance (1 study): One replicated, controlled study in rewetted marshes in the USA found that ploughed plots had much greater cover of cattails Typha than unploughed plots after two growing seasons. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3226https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3226Fri, 09 Apr 2021 14:04:02 +0100Collected Evidence: Collected Evidence: Disturb soil/sediment surface: brackish/salt marshes One study evaluated the effects, on vegetation, of disturbing the surface of brackish/salt marshes. The study was in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, site comparison study of brackish/salt marshes in the USA reported that marshes disked every spring for at least six years (and drawn down during spring/autumn) shared only 24–34% of plant species with marshes that were not disked (or drawn down). Overall richness/diversity (1 study): The same study found that overall plant species richness and diversity were similar in managed marshes (disked every spring and drawn down during spring/autumn, for at least six years) and unmanaged marshes (neither disked nor drawn down). VEGETATION ABUNDANCE VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3227https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3227Fri, 09 Apr 2021 14:04:14 +0100Collected Evidence: Collected Evidence: Add sediment: freshwater marshes One study evaluated the effects, on vegetation, of adding sediment to existing freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, randomized, paired, controlled study in the USA reported that adding sediment to freshwater marshes typically reduced plant species richness after one growing season. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, randomized, paired, controlled study in the USA found that adding sediment to freshwater marshes had no significant effect on total live vegetation biomass after one growing season. Individual species abundance (1 study): The same study found that adding sediment to freshwater marshes had no significant effect on the biomass of most of the dominant herbaceous species after one growing season. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3230https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3230Fri, 09 Apr 2021 14:26:32 +0100Collected Evidence: Collected Evidence: Add sediment: brackish/salt marshes Five studies evaluated the effects, on vegetation, of adding sediment to existing brackish/salt marshes. All five studies were in the USA. Two studies were based on one experimental set-up and two studies were based on another. VEGETATION COMMUNITY Relative abundance (1 study): One replicated, site comparison study in the USA found that salt marshes amended with sediment typically supported a greater relative abundance of smooth cordgrass Spartina alterniflora than degraded marshes after two years, but that this typically remained lower than in natural marshes. Overall richness/diversity (1 study): The same study found that salt marshes amended with sediment typically had greater plant species richness than degraded marshes, and statistically similar richness to natural marshes, after two years. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in the USA found that salt marshes amended with sediment typically had greater total vegetation cover than degraded marshes, and statistically similar cover to natural marshes, after two years. Individual species abundance (4 studies): Four studies quantified the effect of this action on the abundance of individual plant species. For example, all four studies (including two replicated, randomized, paired, controlled) of salt marshes in the USA found that adding sediment typically increased the abundance of smooth cordgrass Spartina alterniflora, over approximately 1–5 years. This is based on total biomass, density and/or cover. One of the studies reported that adding sediment increased the cover of three other species after one year. VEGETATION STRUCTURE Height (1 study): One replicated, randomized, paired, controlled study in a salt marsh in the USA found that the height of the dominant plant species, smooth cordgrass Spartina alterniflora, did not significantly differ between plots amended with sediment and unamended plots. Height was measured 16 months after sediment amendment began. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3231https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3231Fri, 09 Apr 2021 14:26:47 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment to form physical structure of freshwater marshes Two studies evaluated the effects, on vegetation, of depositing soil/sediment to form the physical structure of freshwater marshes (without introducing vegetation). One study was in the USA and one was in the Netherlands. VEGETATION COMMUNITY Community types (1 study): One replicated, paired, site comparison study in the Netherlands reported that marshes created by depositing sand at lake margins contained fewer plant community types, after 8–16 years, than mature natural marshes. VEGETATION ABUNDANCE Overall abundance (2 studies): One site comparison study in the USA reported that plant stem density was similar, after 4–10 years, in marshes created by depositing sediment and in natural marshes, but that vegetation cover was lower in the created marshes. One replicated, paired, site comparison study in the Netherlands reported that marshes created by depositing sand at lake margins contained similar vegetation biomass to nearby natural marshes after 8–16 years. VEGETATION STRUCTURE Height (1 study): One site comparison study in the USA reported that a freshwater marsh created by depositing sediment contained vegetation of a similar height to nearby natural marshes after 4–10 years. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3235https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3235Fri, 09 Apr 2021 15:01:56 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment to form physical structure of brackish/salt marshes Four studies evaluated the effects, on vegetation, of depositing soil/sediment to form the physical structure of brackish/salt marshes (without introducing vegetation). Three studies were in the USA and one study was in Italy. Two studies took place in the same marsh, but in different areas. VEGETATION COMMUNITY Overall extent (1 study): One replicated study in a lagoon in Italy quantified the area of vegetation on sediment deposited up to 19 years previously (average six years four months, with 61% vegetation coverage). Community types (2 studies): Two replicated studies in coastal wetlands in the USA and Italy quantified the coverage of brackish or salt marsh plant communities on sediment deposited up to 19 years previously. Community composition (1 study): One replicated, site comparison study on the coast of the USA reported that the composition of the plant community that developed on deposited sediment depended on the time since deposition and the elevation of the sediment. Areas of sediment that were of a similar elevation to natural marshes (or slightly lower) developed (or were developing) a similar overall plant community composition to the natural marshes. Overall richness/diversity (1 study): One replicated study in an estuary in the USA reported that 1–2 plant species had colonized areas of deposited sediment after 4–8 years. VEGETATION ABUNDANCE VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3236https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3236Fri, 09 Apr 2021 15:02:12 +0100Collected Evidence: Collected Evidence: Add inorganic fertilizer: freshwater marshes One study evaluated the effects, on vegetation, of adding inorganic fertilizer to restore or create freshwater marshes. The study was in Germany. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that the effect of annual fertilization (for 20 years) on the average moisture preference of the vegetation varied between sites. Overall richness/diversity (1 study): The same study reported that the effect of annual fertilization (for 20 years) on total plant species richness varied between sites. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, paired, controlled study in wet grasslands in Germany reported that plots fertilized every spring contained more vegetation biomass, after 4–18 years, than unfertilized plots. Herb abundance (1 study): The same study reported that the effect of annual fertilization (for 20 years) on cover of herb groups (sedges, rushes, forbs, ferns, grasses and legumes) varied between sites. VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled, before-and-after study in wet grasslands in Germany reported that the effect of annual fertilization (for 20 years) on vegetation height varied between sites. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3239https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3239Sat, 10 Apr 2021 12:11:20 +0100Collected Evidence: Collected Evidence: Add inorganic fertilizer: brackish/salt marshes One study evaluated the effects, on vegetation, of adding inorganic fertilizer to restore or create brackish/salt marshes. The study was in Canada. VEGETATION COMMUNITY VEGETATION ABUNDANCE Characteristic plant abundance (1 study): One replicated, paired, controlled, before-and-after study in salt-contaminated bogs in Canada found that adding fertilizer had no significant effect on cover of salt marsh vegetation, in unplanted plots, after one year. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3240https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3240Sat, 10 Apr 2021 12:12:30 +0100Collected Evidence: Collected Evidence: Add below-ground organic matter: brackish/salt marshes One study evaluated the effects, on vegetation, of adding below-ground organic matter to restore or create brackish/salt marshes. The study was in the USA. VEGETATION COMMUNITY VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, randomized, controlled, before-and-after study in a salt marsh in the USA found that plots amended with alginate contained a greater density of smooth cordgrass Spartina alterniflora than unamended plots after 6–52 weeks. However, amended and unamended plots contained similar smooth cordgrass biomass when it was sampled after 52 weeks. VEGETATION STRUCTURE Height (1 study): One replicated, randomized, controlled, before-and-after study in a salt marsh in the USA found that amending plots with alginate had no significant effect on smooth cordgrass height in the first 16 weeks after intervention, but that amended plots contained taller smooth cordgrass than unamended plots after 28–52 weeks. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3244https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3244Sat, 10 Apr 2021 12:33:05 +0100Collected Evidence: Collected Evidence: Add surface mulch: brackish/salt marshes One study evaluated the effects, on vegetation, of using organic mulch to restore or create brackish/salt marshes. The study was in Australia. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, paired, controlled study on a sandflat in Australia found that mulched and unmulched plots had similar plant species richness over two years. VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, paired, controlled study on a sandflat in Australia found that mulched plots were more likely to contain glasswort Sarcocornia quinqueflora than unmulched plots, after 20 months. However, mulching had no significant effect on glasswort biomass after 20 months, and typically had no significant effect on glasswort cover over two years. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3248https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3248Sat, 10 Apr 2021 12:51:36 +0100Collected Evidence: Collected Evidence: Introduce nurse plants: brackish/saline swamps One study evaluated the effects, on naturally colonizing vegetation, of introducing nurse plants to restore or create brackish/saline swamps. The study was in India. VEGETATION COMMUNITY VEGETATION ABUNDANCE VEGETATION STRUCTURE Height (1 study): One study on an estuarine mudflat in India reported that the average height of mangrove propagules trapped by nurse grasses increased by 21–90% (depending on the species) over the first month after establishment. OTHER Germination/emergence (1 study): One study on an estuarine mudflat in India reported that 60–80% (depending on the species) of mangrove propagules trapped by nurse grasses developed into seedlings. Saltmarsh grasses trapped 1,200–1,372 mangrove propagules/m2/week, approximately 1–2 years after they were planted. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3255https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3255Sat, 10 Apr 2021 13:04:30 +0100