Collected 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%2Fconservationevidencejournal.com%2Factions%2F3211https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3211Fri, 09 Apr 2021 08:47:38 +0100Collected Evidence: Collected Evidence: Excavate brackish/saline poolsWe found no studies that evaluated the effects, on vegetation within pools or surrounding marshes/swamps, of excavating brackish/saline pools.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3212https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3212Fri, 09 Apr 2021 08:48:33 +0100Collected Evidence: Collected Evidence: Create mounds or hollows: freshwater marshesWe found no studies that evaluated the effects, on vegetation, of creating mounds or hollows in freshwater marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3217https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3217Fri, 09 Apr 2021 12:52:42 +0100Collected Evidence: Collected Evidence: Create mounds or hollows: brackish/salt marshesWe found no studies that evaluated the effects, on vegetation, of creating mounds or hollows in brackish/salt marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3218https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3218Fri, 09 Apr 2021 12:52:52 +0100Collected Evidence: Collected Evidence: Create mounds or hollows: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of creating mounds or hollows in freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3219https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3219Fri, 09 Apr 2021 12:53:02 +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%2Fconservationevidencejournal.com%2Factions%2F3220https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3220Fri, 09 Apr 2021 12:55:02 +0100Collected Evidence: Collected Evidence: Bury surface soil/sedimentWe found no studies that evaluated the effects, on vegetation, of burying surface soil/sediment to restore/create marshes or swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3225https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3225Fri, 09 Apr 2021 14:03:37 +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%2Fconservationevidencejournal.com%2Factions%2F3226https%3A%2F%2Fconservationevidencejournal.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%2Fconservationevidencejournal.com%2Factions%2F3227https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3227Fri, 09 Apr 2021 14:04:14 +0100Collected Evidence: Collected Evidence: Disturb soil/sediment surface: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of disturbing the surface of freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3228https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3228Fri, 09 Apr 2021 14:04:26 +0100Collected Evidence: Collected Evidence: Disturb soil/sediment surface: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of disturbing the surface of brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3229https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3229Fri, 09 Apr 2021 14:04:36 +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%2Fconservationevidencejournal.com%2Factions%2F3230https%3A%2F%2Fconservationevidencejournal.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%2Fconservationevidencejournal.com%2Factions%2F3231https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3231Fri, 09 Apr 2021 14:26:47 +0100Collected Evidence: Collected Evidence: Add sediment: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of adding sediment to existing freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3232https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3232Fri, 09 Apr 2021 14:27:03 +0100Collected Evidence: Collected Evidence: Add sediment: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of adding sediment to existing brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3233https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3233Fri, 09 Apr 2021 14:27:13 +0100Collected Evidence: Collected Evidence: Add upland topsoilWe found no studies that evaluated the effects, on vegetation, of adding upland topsoil to restore/create marshes or swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3234https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3234Fri, 09 Apr 2021 15:01:20 +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%2Fconservationevidencejournal.com%2Factions%2F3235https%3A%2F%2Fconservationevidencejournal.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%2Fconservationevidencejournal.com%2Factions%2F3236https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3236Fri, 09 Apr 2021 15:02:12 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment to form physical structure of freshwater swampsWe found no studies that evaluated the effects on vegetation, of depositing soil/sediment to form the physical structure of freshwater swamps (without 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%2Fconservationevidencejournal.com%2Factions%2F3237https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3237Fri, 09 Apr 2021 15:02:24 +0100Collected Evidence: Collected Evidence: Deposit soil/sediment to form physical structure of brackish/saline swampsWe found no studies that evaluated the effects on vegetation, of depositing soil/sediment to form the physical structure of brackish/saline swamps (without 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%2Fconservationevidencejournal.com%2Factions%2F3238https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3238Fri, 09 Apr 2021 15:02:32 +0100Collected Evidence: Collected Evidence: Add inorganic fertilizer: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of adding inorganic fertilizer to restore or create freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3241https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3241Sat, 10 Apr 2021 12:12:43 +0100Collected Evidence: Collected Evidence: Add surface mulch: freshwater marshesWe found no studies that evaluated the effects, on vegetation, of using organic mulch to restore or create freshwater marshes.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3247https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3247Sat, 10 Apr 2021 12:51:29 +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%2Fconservationevidencejournal.com%2Factions%2F3248https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3248Sat, 10 Apr 2021 12:51:36 +0100Collected Evidence: Collected Evidence: Add surface mulch: freshwater swampsWe found no studies that evaluated the effects, on vegetation, of using organic mulch to restore or create freshwater swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3249https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3249Sat, 10 Apr 2021 12:51:52 +0100Collected Evidence: Collected Evidence: Add surface mulch: brackish/saline swampsWe found no studies that evaluated the effects, on vegetation, of using organic mulch to restore or create brackish/saline swamps.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3250https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3250Sat, 10 Apr 2021 12:52:03 +0100
What Works 2021 cover

What Works in Conservation

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

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