Collected Evidence: Collected Evidence: Reduce the intensity of farmland meadow managementFour replicated trials in Europe have compared farmland meadows managed extensively with conventionally farmed meadows or silage fields. Two found enhanced numbers and diversity of wild bees on meadows with a delayed first cut and little agrochemical use. Two found no difference in bee diversity or abundance between conventional meadows and meadows with reduced fertilizer use or cutting intensity.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F22https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F22Thu, 20 May 2010 19:27:37 +0100Collected Evidence: Collected Evidence: Reduce tillageEvidence on whether reduced tillage or no tillage benefits ground-nesting bees is mixed. Two replicated trials on squash Cucurbita spp. farms in the USA had contrasting results. One showed no difference in the abundance of bees between tilled and untilled farms, the other found three times more squash bees Peponapis pruinosa on no-till farms than on conventional farms.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F11https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F11Thu, 20 May 2010 19:41:46 +0100Collected Evidence: Collected Evidence: Reduce tillage A total of 42 individual studies (including seven replicated, controlled and randomized studies and six reviews) from Belgium, Denmark, France, Germany, Hungary, Ireland, Lithuania, the Netherlands, Slovakia, Switzerland and the UK investigated the effects of reducing tillage on farmland wildlife. Thirty-four studies (of which 21 were replicated and controlled and seven also randomized, and five reviews) from nine European countries found some positive effects on earthworms, some invertebrates (other than earthworms), weeds or farmland birds, of reducing tillage compared to conventional management. Positive effects included increased biomass, species richness or abundance of earthworms, greater abundance of some invertebrates other than earthworms, increased numbers of some weeds and/or weed species, higher Eurasian skylark nest density, earlier laying date and shorter foraging distances on reduced tillage fields, and greater abundance of some birds - including Eurasian skylark, seed-eating songbirds and gamebirds in late winter on non-inversion or conservation tillage. A review found tillage had negative effects on invertebrate numbers and no-till systems had more invertebrate bird food resources. Twenty-six studies (of which 13 replicated and controlled and three also randomized, and five reviews) from nine European countries found reducing tillage had either negative, no effect or no consistent effects on abundance, biomass, or species richness of some invertebrates (other than earthworms), earthworm abundance, biomass, or species richness, number of different plant species found as seeds, number of some weed species, mammal abundance, some bird species, and one study found bird preferences for conservation tillage fields decreased over time. Two studies found that crop type affected the number of weeds under different tillage regimes. One small replicated trial in the UK compared bird numbers under two different forms of reduced tillage, and found more birds from species that make up the ‘Farmland Bird Index’ on broadcast than non-inversion tillage fields. Two studies looked at the long-term effects of reduced tillage on earthworms (after ten years). One study found higher earthworm biomass under reduced tillage, the other study found earthworm abundance was the same between conventional and reduced tillage plots. Three of the studies mentioned above did not distinguish between the effects of reducing tillage and reduced pesticide and/or fertilizer inputs.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F126https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F126Mon, 14 Nov 2011 18:00:22 +0000Collected Evidence: Collected Evidence: Reduce tillage Four replicated and controlled studies from North America and Canada and the UK and two literature reviews found that some or all bird groups had higher species richness or diversity on reduced-tillage fields, compared to conventional field in some areas. Two replicated and controlled studies from Canada and the UK and a review found that some measures of diversity were lower, or no different, on reduced-tillage fields, compared to conventional fields. Five replicated and controlled studies from the USA and Europe, a small study and two reviews all found that some bird species are found at higher densities on fields with reduced tillage than conventional fields. Five replicated and controlled studies from the USA, Canada and Europe, and a review found that some or all species were found at similar or lower densities on reduced-tillage fields compared to conventional fields, with one finding that preferences decreased over time (possibly due to extreme weather) and another finding that preferences were only found in spring. Two controlled studies (one replicated) and a review found evidence for higher productivity, nesting success or earlier laying on reduced tillage fields, compared to conventional fields. One controlled study found no evidence for greater success or larger chicks on reduced-tillage fields.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F211https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F211Mon, 16 Jul 2012 17:11:41 +0100Collected Evidence: Collected Evidence: Reduce seabird bycatch by releasing offal overboard when setting longlinesTwo replicated and controlled studies in the South Atlantic and sub-Antarctic Indian Ocean found significant reductions in the number of albatross and petrels attacking baits and being caught when offal was released overboard during line setting.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F299https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F299Tue, 24 Jul 2012 17:39:55 +0100Collected Evidence: Collected Evidence: Reduce visitor group size We found no intervention-based studies examining the effects of reducing visitor numbers on bird populations. However, a single, replicated study in forests in Spain in 2004 (Remacha et al. 2011) found that fewer birds, but not fewer species, were observed as visitor number increased. This effect was largely due to decreases in collared dove Streptopelia decaocto presence and serin Serinus serinus abundance. Remacha, C., Perez-Tris, J. & Antonio Delgado, J. (2011) Reducing visitors’ group size increases the number of birds during educational activities: Implications for management of nature-based recreation,Journal of Environmental Management, 92, 1564–1568. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.      Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F312https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F312Wed, 25 Jul 2012 17:36:40 +0100Collected Evidence: Collected Evidence: Reduce the intensity of lighthouse beams We found no evidence for the effects of reducing the intensity of lighthouse beams on bird mortality. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.    Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F468https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F468Wed, 29 Aug 2012 16:25:43 +0100Collected Evidence: Collected Evidence: Reduce tillage We found no evidence for the effects of reduced tillage on amphibian populations. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.    Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F789https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F789Thu, 22 Aug 2013 14:32:49 +0100Collected Evidence: Collected Evidence: Reduce the intensity of livestock grazing in forests One replicated study in the UK found that reducing grazing intensity increased the number of tree saplings. One replicated, randomized, controlled study in Greece found that reducing grazing intensity increased understory biomass.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1207https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1207Thu, 19 May 2016 14:24:40 +0100Collected Evidence: Collected Evidence: Reduce the size of forestry teams to include employees only (not family members) We found no evidence for the effects of reducing the size of forestry teams to include employees only and not family members on primate populations. 'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1499https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1499Tue, 17 Oct 2017 19:53:29 +0100Collected Evidence: Collected Evidence: Reduce the frequency of prescribed burning We found no studies that evaluated the effects of reducing the frequency of prescribed burning on shrublands. 'We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1614https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1614Sun, 22 Oct 2017 10:29:34 +0100Collected Evidence: Collected Evidence: Reduce water level of flooded peatlands We found no studies that evaluated the effects, on peatland vegetation, of reducing the water level in unnaturally flooded peatlands. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1757https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1757Mon, 27 Nov 2017 21:34:20 +0000Collected Evidence: Collected Evidence: Reduce ships/boats/vessels speed limits We found no studies that evaluated the effects of reducing ships/boats/vessels speed limits on subtidal benthic invertebrate populations.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2095https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2095Mon, 21 Oct 2019 15:24:31 +0100Collected Evidence: Collected Evidence: Reduce the number or modify the arrangement of tickler chains/chain mats on trawl nets Three studies examined the effects of reducing the number or modifying the arrangement of tickler chains/chain mats on subtidal benthic invertebrates. All studies were in the North Sea (Germany and Netherlands).   COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (3 STUDIES) Overall abundance (1 study): One replicated, paired, controlled study in the North Sea found that using a beam trawl with a chain mat caused lower mortality of benthic invertebrates in the trawl tracks compared to using a beam trawl with tickler chains. Unwanted catch abundance (2 studies): One of two replicated, paired, controlled studies in the North Sea found that all three modified parallel tickler chain arrangements reduced the combined amount of non-commercial unwanted invertebrate and fish catch compared to unmodified trawl nets, but the other found that none of three modified parabolic tickler chain arrangements reduced it. OTHER (2 STUDIES) Commercial catch abundance (2 studies): One of two replicated, paired, controlled studies in the North Sea found that three modified parabolic tickler chain arrangements caught similar amounts of commercial species to unmodified nets, but the other found that three modified parallel tickler chain arrangements caught lower amounts. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2140https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2140Tue, 22 Oct 2019 11:02:53 +0100Collected Evidence: Collected Evidence: Reduce the amount of pesticides used in aquaculture systems We found no studies that evaluated the effects of reducing the amount of pesticides used in aquaculture systems on subtidal benthic invertebrate populations.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2193https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2193Tue, 22 Oct 2019 13:05:17 +0100Collected Evidence: Collected Evidence: Reduce the amount of antibiotics used in aquaculture systems We found no studies that evaluated the effects of reducing the amount of antibiotics used in aquaculture systems on subtidal benthic invertebrate populations.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2194https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2194Tue, 22 Oct 2019 13:06:02 +0100Collected Evidence: Collected Evidence: Reduce underwater noise (other than sonar) We found no studies that evaluated the effects of reducing underwater noise on subtidal benthic invertebrate populations.   ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2209https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2209Tue, 22 Oct 2019 13:20:54 +0100Collected Evidence: Collected Evidence: Reduce the hauling speed of a trawl net We found no studies that evaluated the effects of reducing the hauling speed of a trawl net on marine fish populations.  ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2688https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2688Wed, 02 Dec 2020 10:47:28 +0000Collected Evidence: Collected Evidence: Reduce the duration of exposure to air of captured fish before release Three studies examined the effect of reducing the duration of exposure of fish to air on marine fish populations. One study was in each of the Bay of Biscay (Spain), Gulf of Alaska (Canada) and Coral Sea (Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (1 study): One replicated study in the Bay of Biscay found that reducing air exposure before release did not increase the survival of small-spotted catshark caught during commercial trawling. Condition (1 study): One replicated study in the Gulf of Alaska found that shorter durations of air exposure before release improved the physical condition and reduced the amount of injury to discarded chum salmon caught in purse seine nets.  BEHAVIOUR (1 STUDY) Behaviour change (1 study): One study in the Coral Sea found that minimal exposure to air and handling resulted in improved overall behaviour after release (activity and ability to return to reef) of reef fish, compared to fish exposed to air and handling for longer duration. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2690https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2690Wed, 02 Dec 2020 14:47:25 +0000Collected Evidence: Collected Evidence: Reduce shipping along inland waterways We found no studies that evaluated the effects of reducing shipping along inland waterways on freshwater mammal populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2763https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2763Tue, 02 Feb 2021 17:07:40 +0000Collected Evidence: Collected Evidence: Reduce the amount of pesticides used in aquaculture systems We found no studies that evaluated the effects of reducing the amount of pesticides used in aquaculture systems on marine and freshwater mammal populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2877https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2877Mon, 08 Feb 2021 11:42:45 +0000Collected Evidence: Collected Evidence: Reduce the amount of antibiotics used in aquaculture systems We found no studies that evaluated the effects of reducing the amount of antibiotics used in aquaculture systems on marine and freshwater mammal populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2878https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2878Mon, 08 Feb 2021 11:43:28 +0000Collected Evidence: Collected Evidence: Reduce the slope of subtidal artificial structures We found no studies that evaluated the effects of reducing the slope of subtidal artificial structures on the biodiversity of those structures. This means we did not find any studies that directly evaluated this intervention during our literature searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3442https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3442Fri, 20 Aug 2021 10:09:55 +0100Collected Evidence: Collected Evidence: Reduce the slope of intertidal artificial structures Two studies examined the effects of reducing the slope of intertidal artificial structures on the biodiversity of those structures. The studies were in an estuary in southeast Australia. COMMUNITY RESPONSE (1 STUDY) Overall richness/diversity (1 study): One before-and-after study in Australia reported that reducing the slope of an intertidal artificial structure, along with creating rock pools, increased the combined macroalgae, invertebrate and fish species richness on the structure. POPULATION RESPONSE (1 STUDY) Algal abundance (1 study): One replicated, controlled study in Australia found that reducing the slope of an intertidal artificial structure did not increase the macroalgal abundance on structure surfaces. Invertebrate abundance (1 study): One replicated, controlled study in Australia found that reducing the slope of an intertidal artificial structure did not increase the oyster or mobile invertebrate abundance on structure surfaces. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3461https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3461Tue, 14 Sep 2021 12:39:58 +0100Collected Evidence: Collected Evidence: Reduce the size of surface features when prospecting for or extracting underground products One study evaluated the effects on butterflies and moths of reducing the size of surface features when prospecting for or extracting underground products. This study was in Canada. COMMUNITY RESPONSE (1 STUDY) Richness/diversity (1 study): One replicated, site comparison study in Canada found that narrow corridors used for prospecting for oil had a lower species richness of butterflies than wide corridors, but were similar to undisturbed forest. POPULATION RESPONSE (1 STUDY) Abundance (1 study): One replicated, site comparison study in Canada found that narrow corridors used for prospecting for oil had a lower abundance of butterflies than wide corridors, but were similar to undisturbed forest. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3845https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3845Tue, 05 Jul 2022 11:09:11 +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.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust