Collected Evidence: Collected Evidence: Plant shrubs in clusters A randomized, controlled study in South Africa found that when shrubs were planted in clumps more of them died than when they were planted alone. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1715https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1715Mon, 23 Oct 2017 13:57:53 +0100Collected Evidence: Collected Evidence: Increase number of livestock and use prescribed burning to control trees One randomized, controlled, before-and-after study in Italy found that using prescribed burning and grazing to reduce tree cover reduced the cover of common heather and the basal area of trees. However, it did not alter the cover of purple moor grass. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1722https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1722Wed, 22 Nov 2017 14:37:45 +0000Collected Evidence: Collected Evidence: Cut and use prescribed burning to control grass One randomized, replicated, controlled, paired, before-and-after study in the UK found that burning and cutting to reduce the cover of purple moor grass reduced cover of common heather but did not reduce cover of purple moor grass. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1724https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1724Wed, 22 Nov 2017 16:30:40 +0000Collected Evidence: Collected Evidence: Use herbicide and prescribed burning to control grass One randomized, replicated, controlled, paired, before-and-after study in the UK found that burning and applying herbicide to reduce the cover of purple moor grass reduced cover of common heather but did not reduce cover of purple moor grass. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1725https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1725Wed, 22 Nov 2017 16:31:55 +0000Collected Evidence: Collected Evidence: Use ‘bracken bruiser’ to control bracken One randomized, replicated, controlled, before-and-after, paired study in the UK found that bracken bruising increased bracken cover, though bracken cover also increased in areas where bracken bruising was not done.There was no effect on the number of plant species or plant diversity. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1726https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1726Wed, 22 Nov 2017 17:04:59 +0000Collected Evidence: Collected Evidence: Disturb vegetation One randomized, replicated, controlled study in the UK found that vegetation disturbance did not increase the abundance or species richness of specialist plants but increased the abundance of generalist plants. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1727https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1727Thu, 23 Nov 2017 11:47:54 +0000Collected Evidence: Collected Evidence: Add topsoil (alongside planting/seeding) One randomized, replicated, paired, controlled study in the USA found that addition of topsoil alongside sowing of seed increased the biomass of grasses but reduced the biomass of forbs in comparison to addition of topsoil alone. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1857https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1857Fri, 01 Dec 2017 14:27:24 +0000Collected Evidence: Collected Evidence: Flood cropland when fallow to conserve freshwater marshes One study evaluated the effects, on freshwater marsh vegetation, of flooding cropland during fallow seasons or years. The study was in Brazil. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study in Brazil found that flooding rice fields during their fallow period affected the overall community composition of wetland plants, but that the nature of the effect depended on when fields were surveyed. Overall richness/diversity (1 study): The same study found that flooding rice fields during their fallow period had no significant effect on wetland plant species richness per site and per survey, although fewer species were recorded in the flooded fields over the year of the study. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2954https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2954Thu, 25 Mar 2021 13:44:32 +0000Collected Evidence: Collected Evidence: Cut/remove/thin forest plantations: freshwater marshes One study evaluated the effects, on vegetation, of cutting/removing/thinning forest plantations to restore freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Characteristic plant richness/diversity (1 study): One replicated, controlled study in the USA reported that the effect of thinning/clearing forest plantations on wetland-characteristic plant species richness depended on soil moisture. After three growing seasons, wetter thinned/cleared sites generally contained more wetland-characteristic plant species than drier thinned/cleared sites or sites that remained afforested. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2958https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2958Thu, 25 Mar 2021 13:56:32 +0000Collected Evidence: Collected Evidence: Use barriers to keep livestock off ungrazed brackish/salt marshes One study evaluated the effects, on vegetation, of using barriers to keep livestock off brackish/salt marshes that have never (or not recently) been grazed. The study was in the UK. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, controlled study in a salt marsh in the UK reported that plots fenced to exclude sheep contained more plant species, after four years, than plots that became grazed by sheep. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, controlled study in a salt marsh in the UK reported that plots fenced to exclude sheep contained more vegetation biomass, after two years, than plots that became grazed by sheep. Individual species abundance (1 study): The same study also quantified the effect of this action on the abundance of individual plant species. For example, plots fenced to exclude sheep contained more cordgrass Spartina and less saltbush Atriplex hastata, after four years, than plots that became grazed by sheep. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2963https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2963Thu, 25 Mar 2021 14:14:07 +0000Collected Evidence: Collected Evidence: Exclude or remove livestock from historically grazed brackish/saline swamps One study evaluated the effects, on vegetation, of excluding or removing livestock from historically grazed brackish/saline swamps. The study was in South Africa and the focal livestock were cattle. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, paired, controlled study in South Africa reported that more grey mangrove Avicennia marina seedlings appeared in plots fenced to exclude cattle for two years, than in plots left open to cattle. VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled study in South Africa reported that mangrove trees fenced off from cattle were taller, after two years, than trees accessible to cattle. OTHER Growth (1 study): One replicated, paired, controlled study in South Africa found that mangrove trees fenced off from cattle grew more over two years – in height, diameter and crown volume –than trees accessible to cattle. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2969https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2969Thu, 25 Mar 2021 14:15:41 +0000Collected Evidence: Collected Evidence: Abandon aquaculture facilities: allow brackish/saline marshes or swamps to recover without active intervention One study evaluated the effects, on vegetation, of abandoning aquaculture facilities with the expectation that brackish/saline marshes or swamps would recover spontaneously. The study was in Costa Rica. VEGETATION COMMUNITY Community composition (1 study): One site comparison study in Costa Rica reported that after 14 years, an abandoned shrimp pond contained the same four tree species as a nearby natural mangrove forest. VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One site comparison study in Costa Rica reported that after 14 years, an abandoned shrimp pond contained a greater density of trees than a nearby natural mangrove forest. VEGETATION STRUCTURE Height (1 study): One site comparison study in Costa Rica reported that after 14 years, an abandoned shrimp pond had a shorter tree canopy than a nearby natural mangrove forest. Basal area (1 study): The same study reported that the basal area of trees was smaller in an abandoned shrimp pond, after 14 years, than in a nearby natural mangrove forest. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2983https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2983Thu, 25 Mar 2021 15:27:56 +0000Collected Evidence: Collected Evidence: Abandon mined land: allow brackish/saline marshes or swamps to recover without active intervention One study evaluated the effects, on vegetation, of abandoning formerly mined land with the expectation that brackish/saline marshes or swamps would recover spontaneously. The study was in France. VEGETATION COMMUNITY Community types (1 study): One replicated study in France simply classified the plant community types that developed on abandoned salt pans. Areas flooded for at least part of the year developed salt marsh plant communities, with the exact community composition depending on the duration of flooding and soil salinity. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2985https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2985Thu, 25 Mar 2021 20:18:12 +0000Collected Evidence: Collected Evidence: Plug/dam canals or trenches: freshwater marshes One study evaluated the effects, on vegetation, of plugging/damming canals or trenches in freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Overall extent (1 study): One replicated, site comparison study of backfilled canals in freshwater marshes in the USA reported that emergent marsh vegetation coverage was greater within the channels of plugged than unplugged canals, after 6–60 months. However, coverage on former spoil areas did not significantly differ between plugged and unplugged canals. VEGETATION ABUNDANCE   VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2991https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2991Mon, 29 Mar 2021 12:08:23 +0100Collected Evidence: Collected Evidence: Reduce intensity of vegetation harvest: freshwater swamps One study evaluated the effects, on vegetation, of reducing the intensity of harvest in freshwater swamps (or harvesting at different intensities). The study was in China. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, controlled study in a freshwater swamp in China reported that overall herb biomass was statistically similar in plots logged at different intensities five years previously. Tree/shrub abundance (1 study): The same study reported that overall tree biomass was greatest in plots logged at the lowest intensity five years previously. In contrast, overall shrub biomass was greatest in plots logged at medium intensity. Individual species abundance (1 study): The same study reported that the density of the two most common tree species typically declined with increasing logging intensity. VEGETATION STRUCTURE Diameter/perimeter/area (1 study): One replicated, controlled study in a freshwater swamp in China reported that the diameter of the two most common tree species typically declined with increasing logging intensity. Basal area (1 study): The same study reported that the basal area of the two most common tree species typically declined with increasing logging intensity. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3003https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3003Wed, 31 Mar 2021 13:27:11 +0100Collected Evidence: Collected Evidence: Use low-impact methods to harvest vegetation: freshwater swamps One study evaluated the effects, on vegetation, of using supposedly low-impact methods to harvest vegetation in freshwater swamps. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One controlled study in a freshwater swamp in the USA reported that after seven years, a plot where logs had been extracted by helicopter only contained fewer plant species than a plot where logs had been extracted by helicopter and ground vehicles. VEGETATION ABUNDANCE Overall abundance (1 study): One controlled study in a freshwater swamp in the USA reported that after seven years, a plot where logs had been extracted by helicopter only contained less overall plant biomass than a plot where logs had been extracted by helicopter and ground vehicles. This was also true for the overstory and ground layers separately. However, overstory tree density did not significantly differ between helicopter-extracted and vehicle-extracted plots. Individual species abundance (1 study): The same study found that the abundance of some individual plant species – particularly swamp ash Fraxinus caroliniana and water tupelo Nyssa aquatica – significantly differed between helicopter-extracted and vehicle-extracted plots. VEGETATION STRUCTURE Height (1 study): One controlled study in a freshwater swamp in the USA found that after seven years, the average height of the overstory was similar in a plot where logs had been extracted by helicopter only and a plot where logs had been extracted by helicopter and ground vehicles. Diameter, perimeter, area (1 study): The same study found that after seven years, the average stem diameter of overstory trees was similar in helicopter-extracted and vehicle-extracted plots. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3011https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3011Wed, 31 Mar 2021 14:10:30 +0100Collected Evidence: Collected Evidence: Cut large trees/shrubs to maintain or restore disturbance: freshwater swamps One study evaluated the effects, on vegetation, of cutting large trees/shrubs to maintain or restore disturbance in freshwater swamps. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that cutting woody vegetation (and applying herbicide) had no significant effect on herbaceous ground cover one year later: there were similar changes in treated and untreated swamps. VEGETATION STRUCTURE Basal area (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that cutting woody vegetation (and applying herbicide) had no significant effect on the basal area of woody vegetation one year later: there were similar changes in treated and untreated swamps. Canopy cover (1 study): The same study found that cutting woody vegetation (and applying herbicide) reduced canopy cover – to similar levels as in high-quality swamps after one year. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3048https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3048Thu, 01 Apr 2021 19:10:54 +0100Collected Evidence: Collected Evidence: Use herbicide to maintain or restore disturbance: freshwater marshes One study evaluated the effects, on vegetation, of using herbicide to maintain or restore disturbance in freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, randomized, controlled, before-and-after study aiming to restore freshwater marshes in the USA found that applying herbicide to trees (along with other interventions) significantly affected the overall plant community composition over the following five years. VEGETATION ABUNDANCE Characteristic plant abundance (1 study): One replicated, randomized, controlled, before-and-after study aiming to restore freshwater marshes in the USA reported that of the 26 plant taxa that became more frequent after applying herbicide to trees (along with other interventions), 16 were obligate wetland taxa. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3058https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3058Fri, 02 Apr 2021 12:13:44 +0100Collected Evidence: Collected Evidence: Use herbicide to maintain or restore disturbance: freshwater swamps One study evaluated the effects, on vegetation, of using herbicide to maintain or restore disturbance in freshwater swamps. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that applying herbicide to woody vegetation (after cutting it) had no significant effect on herbaceous ground cover one year later: there were similar changes in treated and untreated swamps. VEGETATION STRUCTURE Basal area (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that applying herbicide to woody vegetation (after cutting it) had no significant effect on the basal area of woody vegetation one year later: there were similar changes in treated and untreated swamps. Canopy cover (1 study): The same study found that applying herbicide to woody vegetation (after cutting it) reduced canopy cover – to similar levels as in high-quality swamps after one year. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3060https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3060Fri, 02 Apr 2021 12:14:06 +0100Collected Evidence: Collected Evidence: Remove plant litter: freshwater marshes One study evaluated the effects, on vegetation, of removing plant litter from freshwater marshes. The study was in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots cleared of plant litter contained a plant community characteristic of wetter conditions than uncleared plots after one growing season – but not after two. Overall richness/diversity (1 study): The same study found that plots cleared of plant litter contained a similar number of wetland plant species to uncleared plots, after 1–2 growing seasons. VEGETATION ABUNDANCE                                                          Overall abundance (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots cleared of plant litter had greater cover of wetland plants than uncleared plots after one growing season – but not after two. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3062https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3062Fri, 02 Apr 2021 12:40:27 +0100Collected Evidence: Collected Evidence: Change season/timing of prescribed burning: freshwater marshes One study evaluated the effects, on vegetation, of burning freshwater marshes in different seasons or at different times. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, randomized, controlled study in a marsh in the USA found that spring-burned plots had greater plant species richness than summer-burned plots, at the end of the growing season. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, randomized, controlled study in a marsh in the USA found that spring-burned plots had greater overall vegetation cover than summer-burned plots, at the end of the growing season. Individual species abundance (1 study): The same study reported that the cover and frequency of some individual plant species responded differently to spring vs summer burning. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3074https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3074Fri, 02 Apr 2021 14:45:30 +0100Collected Evidence: Collected Evidence: Control problematic plants (specific intervention unclear): freshwater marshes or swamps One study evaluated the effects, on vegetation, of controlling problematic plants in freshwater marshes or swamps using unspecified or unclear methods. The study was in the USA. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated, site comparison study in the USA found that marshes in which non-native plants were actively controlled had higher overall plant richness and diversity, after three years, than marshes in which non-native plants were not controlled. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in the USA found that marshes in which non-native plants were actively controlled had similar overall vegetation cover, after three years, to marshes in which non-native plants were not controlled. Individual species abundance (1 study): One study quantified the effect of this action on the abundance of individual plant species, other than those being controlled. The replicated, site comparison study in the USA found, for example, that spikerush Eleocharis cover was greater in marshes where non-native plants were actively controlled than where they were not controlled. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3083https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3083Fri, 02 Apr 2021 17:04:16 +0100Collected Evidence: Collected Evidence: Control problematic plants (specific intervention unclear): brackish/saline marshes or swamps One study evaluated the effects, on vegetation, of controlling problematic plants in brackish/saline marshes or swamps using unspecified or unclear methods. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (1 study): One replicated, site comparison study in salt marshes in the USA found that plots in which common reed Phragmites australis had been controlled 4–10 years previously contained a similar density of plant stems to nearby natural marshes Individual species abundance (1 study): One study quantified the effect of this action on the abundance of individual plant species, other than those being controlled. The replicated, site comparison study in salt marshes in the USA found that plots in which common reed Phragmites australis had been controlled 4–10 years previously had similar cover of saltmarsh cordgrass Spartina patens to nearby natural marshes. VEGETATION STRUCTURE Height (1 study): One replicated, site comparison study in salt marshes in the USA found that plots in which common reed Phragmites australis had been controlled 4–10 years previously contained vegetation of similar height to nearby natural marshes. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3084https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3084Fri, 02 Apr 2021 17:04:33 +0100Collected Evidence: Collected Evidence: Control problematic plants (multiple interventions): freshwater marshes or swamps One study evaluated the effects, on vegetation, of controlling problematic plants in freshwater marshes or swamps using >3 combined interventions. The study was in Costa Rica. VEGETATION COMMUNITY Overall extent (1 study): One controlled study in a freshwater marsh in Costa Rica reported that coverage of live vegetation stands was lower in a plot where southern cattail Typha domingensis had been controlled for >15 years than in a plot where cattail had not been controlled. Overall richness/diversity (1 study): The same study reported that a plot in which southern cattail Typha domingensis had been controlled for >15 years had greater plant species richness than a plot where cattail had not been controlled. VEGETATION ABUNDANCE Overall abundance (1 study): One controlled study in a freshwater marsh in Costa Rica reported that a plot in which southern cattail Typha domingensis had been controlled for >15 years had less live vegetation cover than a plot where cattail had not been controlled. VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3087https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3087Sat, 03 Apr 2021 14:52:33 +0100Collected Evidence: Collected Evidence: Physically remove problematic plants: brackish/salt marshes One study evaluated the effects, on vegetation, of physically removing problematic plants from brackish/salt marshes. The study was in the USA. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Native/non-target abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in pepperweed invaded marshes in the USA found that physically removing pepperweed from plots sprayed with herbicide increased cover of native plants, over the following two years, compared to spraying with herbicide only. Individual species abundance (1 study): The same study quantified the effect of this action on the cover of individual plant species, other than the target of control (see original paper for data). VEGETATION STRUCTURECollected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3092https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3092Sat, 03 Apr 2021 14:59:44 +0100
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What Works in Conservation

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

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