Collected Evidence: Collected Evidence: Plant parks and gardens with appropriate flowersTwo replicated trials in the USA and Canada have found more wild bees (either more species or more individuals) in gardens planted with bee forage or native plants, relative to conventionally managed gardens. Another USA trial found more bee species after the addition of bee forage plants to a community garden. Three trials in the UK or USA have shown that native flowering plants or bee forage plants are well used by wild bees when planted in gardens. A UK trial demonstrated that some popular non-native or horticulturally modified garden flowers are not frequently visited by insects, despite providing nectar in some cases.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1Tue, 18 May 2010 15:19:40 +0100Collected Evidence: Collected Evidence: Translocate bumblebee colonies in nest boxesWe have captured three small trials in the 1950s and early 1960s testing the effect of translocating bumblebee colonies in nest boxes. Two trials in Canada provided evidence of queen death and one of these showed lower colony productivity following translocation. Just one, a UK trial, concluded that early bumblebee Bombus pratorum colonies adapt well to being moved.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F53https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F53Thu, 20 May 2010 01:34:59 +0100Collected Evidence: Collected Evidence: Provide artificial nest sites for bumblebees We have captured 11 replicated trials of bumblebee nest boxes. Several different types of nest box have been shown to be acceptable to bumblebees, including wooden or brick and tile boxes at the ground surface, underground tin, wooden or terracotta boxes and boxes attached to trees.   Three replicated trials since 1989 in the UK have shown very low uptake rates (0-2.5%) of various nest box designs (not including underground nest boxes), while seven trials in previous decades in the UK, USA or Canada, and one recent trial in the USA, showed overall uptake rates between 10% and 48%.   Wooden surface or above ground nest boxes of the kind currently marketed for wildlife gardening are not the most effective design. Eight studies test this type of nest box. Five (pre-1978, USA or Canada) find 10-40% occupancy. Three (post-1989, UK) find very low occupancy of 0-1.5%. The four replicated trials that have directly compared wooden surface nest boxes with other types all report that underground, false underground or aerial boxes are more readily occupied.   Nest boxes entirely buried 5-10 cm underground, with a 30-80 cm long entrance pipe, are generally the most effective. Seven replicated trials in the USA, Canada or the UK have tested underground nest boxes and found between 6% and 58% occupancy.   We have captured no evidence for the effects of providing nest boxes on bumblebee populations.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F48https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F48Thu, 20 May 2010 02:19:20 +0100Collected Evidence: Collected Evidence: Reintroduce laboratory-reared bumblebee colonies to the wildSeven replicated trials have monitored the success of laboratory-reared colonies of bumblebees introduced to the environment. In four of the trials (three in the UK, one in Canada) colonies were left to develop until new queens were produced or the founding queen died. In two of these (both in the UK), the numbers of queens/colony were very low or zero. In two trials, good numbers of new queens were produced. Rates of social parasitism by cuckoo bees Bombus [Psithyrus] spp. in colonies released to the wild are variable. Two replicated trials in Canada and the UK found high rates (25-66% and 79% respectively). The UK trial showed that parasitism was reduced by placing colonies in landscapes with intermediate rather than very high nectar and pollen availability, late, rather than early in the season. Five other replicated trials reported no social parasites. We have not found evidence to compare rates of parasitism in artificial nest boxes with the rate in natural nests. Two replicated trials examined the effects of supplementary feeding for bumblebee colonies placed in the field. One, in Canada, found supplementary feeding improved the reproductive success of captive-reared colonies, but did not reduce their parasite load. The other trial, in the USA, found supplementary feeding did not increase colony productivity. One small scale trial in Norway showed that colonies of the buff-tailed bumblebee B. terrestris prefer to forage more than 100 m from their nest sites.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F52https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F52Thu, 20 May 2010 02:59:51 +0100Collected Evidence: Collected Evidence: Restore heathlandOne small trial of early-stage lowland heath restoration activity did not have an adverse effect on bumblebee diversity at one site in southeast England. Two replicated trials in Dorset indicated that long-term restoration of dry lowland heath can restore a bee community similar to that on ancient heaths. One of these studies showed that the community of conopid flies parasitizing bumblebees remained impoverished 15 years after heathland restoration began. We found no evidence on interventions to conserve bees on upland heath or moorland.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F9https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F9Thu, 20 May 2010 03:20:44 +0100Collected Evidence: Collected Evidence: Eradicate existing populations of invasive non-native speciesOne replicated trial in Louisiana, USA, demonstrated that colonies of invasive Africanized honey bees Apis mellifera can be killed by providing insecticide (acephate)-laced syrup for 30 minutes. One replicated controlled before-and-after trial attempted to eradicate European buff-tailed bumblebees Bombus terrestris from trial sites in Japan by catching and killing foraging bees. The treatment led to an increase in numbers of two native bumblebee species, but did not eradicate B. terrestris.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F38https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F38Thu, 20 May 2010 04:54:57 +0100Collected Evidence: Collected Evidence: Replace honey-hunting with apiculture  One study reported that a programme to enhance take-up of stingless beekeeping in southern Mexico increased the number of managed colonies in the area. Five trials contributed to scientific improvement of stingless beekeeping methods. Two controlled trials showed that either brewer's yeast (one trial) or a mix with 25% pollen collected by honey bees Apis mellifera (one trial) can be used as a pollen substitute to feed Scaptotrigona postica in times of pollen scarcity. A study on the island of Tobago found a wooden hive design with separate, different-shaped honey and brood chambers allowed honey to be extracted without damaging the brood. One trial showed that 50 g of comb with mature pupae is enough to start a new daughter colony of S. mexicana. One trial found brood growth was higher in traditional log hives than in box hives with internal volumes exceeding 14 litres, and recommended smaller box hives. We have captured no clear evidence about whether these activities help conserve bees or enhance native bee populations.    Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F33https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F33Thu, 20 May 2010 06:29:24 +0100Collected Evidence: Collected Evidence: Convert to organic farmingEvidence on the impact of organic farming on wild bees is equivocal. Three replicated trials in Europe or Canada have shown that the abundance of wild bees is higher under organic arable farming than under conventional farming. One of these showed that bee diversity is higher in organically farmed wheat fields and in mown fallow strips adjacent to them. Three replicated trials in Europe or the USA have found no significant difference in the numbers of bumblebees (two trials), bumblebee species (one trial), or wild bees visiting flowering crops (one trial) between conventional and organic arable farms.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F25https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F25Thu, 20 May 2010 07:02:08 +0100Collected Evidence: Collected Evidence: Restore species-rich grassland vegetationOne replicated controlled trial in Scotland showed that species-rich grassland managed under agri-environment schemes attracted more nest-searching queen bumblebees but fewer foraging queens in the spring than unmanaged grassland. Three small trials, two in the UK and one in Germany, found that restored species-rich grasslands had similar flower-visiting insect communities (dominated by bees and/or flies) to paired ancient species-rich grasslands.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F8https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F8Thu, 20 May 2010 07:08:34 +0100Collected Evidence: Collected Evidence: Sow uncropped arable field margins with a native wild flower seed mixFive replicated trials in the UK showed that uncropped field margins sown with wild flowers and subsequently mown support a higher abundance (and in three trials higher species richness) of foraging bumblebees than cropped field edges (all five trials), grassy margins (four trials) or naturally regenerated uncropped margins (three trials). One small trial recorded the same number of bee species on wildflower sown and naturally regenerated strips. Two trials demonstrated that perennial leguminous herbs in the seed mixtures are important forage sources for bumblebees, particularly for long-tongued species. One small replicated trial showed that common long-tongued bumblebee species (Bombus pascuorum and B. hortorum) strongly preferred plots of perennial wildflower seed mix over a mix of annual forage plants. We have captured no evidence on the effects of field margin management on solitary bees.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F19https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F19Thu, 20 May 2010 07:11:24 +0100Collected Evidence: Collected Evidence: Provide artificial nest sites for solitary beesWe have captured 30 replicated trials of nest boxes for solitary bees in 10 countries, including Europe, North and South America and Asia. Twenty-nine of these trials showed occupancy by bees. Many species of solitary bee readily nest in the boxes, including some species considered endangered in a study on farmland in Germany, oil-collecting species of the genus Centris in South America and a recently discovered species in lowland tropical forest in Costa Rica. One trial in temperate forest in Canada recorded no bees using nest boxes. A set of replicated experiments in Germany estimated that four medium to large European species of solitary bee have a foraging range of 150 to 600 m, so nest boxes must be within this distance of foraging resources. Twenty-three replicated trials have shown nest boxes of cut hollow stems or tubes being occupied by solitary bees. Eleven trials demonstrated occupation of blocks of wood drilled with holes. Two trials in Neotropical secondary forest (one in Brazil, one in Mexico) showed that particular solitary bee species will nest in wooden boxes, without stems or confining walls inside. Two replicated trials have compared reproductive success in different nest box designs. One showed that reed stem and wooden grooved-board nest boxes produced more bees/nest than four other types. Nest boxes with plastic-lined holes, or plastic or paper tubes were much less productive, due to parasitism or mould. The other, a small trial, found nests of the oil-collecting bee Centris analis in Brazil were more productive in cardboard straws placed in drilled wooden holes than in grooved wooden boards stacked together. Three trials on agricultural land, one on a carpenter bee in India, one on a range of species in Germany and one on species of Osmia in the USA, have shown that the number of occupied solitary bee nests can double over three years with repeated nest box provision at a given site. One small replicated trial compared populations of solitary bees in blueberry fields in the USA with and without nest boxes over three years. The estimated number of foraging Osmia bees had increased in fields with nest boxes, compared to fields without nest boxes. Eleven replicated trials have recorded solitary bees in nest boxes being attacked by parasites or predators. Rates of mortality and parasitism have been measured in 10 studies. Mortality rates range from 13% mortality for cavity-nesting bees and wasps combined in Germany (2% were successfully parasitized), or 2% of bee brood cells attacked in shade coffee and cacao plantations in central Sulawesi, Indonesia, to 36% parasitism and 20% other mortality (56% mortality overall) for the subtropical carpenter bee Xylocopa fenestrata in India. Two replicated trials of the use of drilled wooden nest boxes by bees in California, USA, showed that introduced European earwigs Forficula auricularia and introduced European leafcutter bee species use the boxes. In one trial, these introduced species more commonly occupied the boxes than native bees. A small trial tested three soil-filled nest boxes for the mining bee Andrena flavipes in the UK, but they were not occupied.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F47https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F47Thu, 20 May 2010 07:16:20 +0100Collected Evidence: Collected Evidence: Increase the use of clover leys on farmlandWe have captured no evidence that increasing the use of clover leys can enhance wild bee populations. One replicated trial in Germany showed that fields planted with a white clover grass mixture do not attract solitary bees to nest preferentially on site. A trial in Switzerland showed that if white clover is mowed during flowering, injuries and mortality of bees can be reduced by avoiding the use of a processor attached to the mower.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F16https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F16Thu, 20 May 2010 08:48:02 +0100Collected Evidence: Collected Evidence: Provide grass strips at field margins for beesThree replicated controlled trials in the UK have monitored wild bees on uncropped grassy field margins. Evidence of the effects on bees is mixed. One trial showed that 6 m wide grassy field margins enhanced the abundance, but not diversity, of wild bees at the field boundary. One trial showed that 6 m wide grassy field margins enhanced the abundance and diversity of bumblebees within the margin. A third, smaller scale trial showed neither abundance nor diversity of bumblebees was higher on sown grassy margins than on cropped margins.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F14https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F14Thu, 20 May 2010 10:42:47 +0100Collected Evidence: Collected Evidence: Ensure commercial hives/nests are disease freeOne randomised controlled trial in Canada found that the antibiotic fumagillin is not effective against Nosema bombi infection in managed colonies of the western bumblebee Bombus occidentalis. One replicated controlled trial in South Korea found that Indian meal moth Plodia interpunctella in commercial bumblebee colonies can be controlled with the insect pathogen Bacillus thuringiensis (Bt) Aizawai strain, at a strength of 1 g Bt/litre of water.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F42https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F42Thu, 20 May 2010 11:17:19 +0100Collected Evidence: Collected Evidence: Leave field margins unsprayed within the crop (conservation headlands)Two replicated controlled trials in England showed that conservation headlands do not attract more foraging bumblebees than conventional crop fields. One replicated trial found fewer bees on conservation headlands than in naturally regenerated, uncropped field margins in England.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F29https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F29Thu, 20 May 2010 13:15:26 +0100Collected Evidence: Collected Evidence: Prevent escape of commercial bumblebees from greenhouses One small replicated trial in Canada showed that a plastic greenhouse covering that transmits ultraviolet light (so transmitted light is similar to daylight) reduced the numbers of bumblebees from managed colonies escaping through open gutter vents. One trial in Japan showed that externally mounted nets and zipped, netted entrances can keep commercial bumblebees inside greenhouses as long as they are regularly checked and maintained.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F40https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F40Thu, 20 May 2010 13:55:19 +0100Collected Evidence: Collected Evidence: Introduce agri-environment schemes to benefit wild beesFour replicated trials in Europe have shown enhanced diversity and/or abundance of foraging wild bees on land managed under various European agri-environment schemes, relative to conventionally-managed fields or field margins. These schemes were the Swiss Ecological Compensation Areas (one replicated trial), the German organic arable farming option (one replicated trial), the Dutch botanical and meadow bird agreements (one replicated trial, very low numbers of bee species) and the Scottish Rural Stewardship Scheme (one replicated trial, also included nest-searching queen bumblebees). Four replicated trials in Europe found that the number of bees and/or bee species is not enhanced on land managed under agri-environment schemes, including meadow bird agreements in wet grassland in the Netherlands, measures to protect steppe-living birds and compensation measures around a National Park in Spain, and 6 m wide grass field margin strips in England (one replicated trial for each). On a wider landscape scale, two replicated trials in the UK have found bumblebee populations were not enhanced on farmland managed under agri-environment schemes. One trial compared the reproductive success of colonies of the buff-tailed bumblebee Bombus terrestris, the other compared queen bumblebee numbers in spring in conventionally managed field margins, on farms with and without agri-environment schemes.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F24https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F24Thu, 20 May 2010 16:11:07 +0100Collected Evidence: Collected Evidence: Leave arable field margins uncropped with natural regenerationFour replicated trials in the UK have found more bumblebees (and more bee species in two trials) foraging on uncropped field margins than on cropped margins. One small unreplicated trial found similar bee species richness on a naturally regenerated margin as on margins sown with wildflowers. A small replicated trial found that neither abundance nor diversity of bumblebees were higher on naturally regenerated margins than on cropped margins. Two trials note that the value of naturally regenerated uncropped field margins is based on thistle species considered to be pernicious weeds requiring control. Two trials found that the value of naturally regenerated uncropped field margins for bees was not consistent from year to year. We have captured no evidence on the effects of field margin management on solitary bees.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F20https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F20Thu, 20 May 2010 16:57:57 +0100Collected Evidence: Collected Evidence: Rear and manage populations of solitary beesSeveral species of solitary bee in the family Megachilidae are reared and managed commercially as pollinators, mostly for the forage crop alfalfa, or fruit trees. These species readily nest in drilled wooden blocks, or stacked grooved boards of wood or polystyrene. Parasites and pathogens can be problematic and a number of control methods have been developed. Rearing methods have been investigated for two other species not yet commercially managed and one replicated trial shows that temperature regimes are important to survival. If rearing for conservation purposes is to be attempted, we would recommend a systematic review of these methods. Three management trials with megachilids not commercially managed in the USA or Poland, and a review of studies of managed species, found that local populations can increase up to six-fold in one year under management if conditions are good and plentiful floral resources are provided. Two replicated trials have reared solitary bees on artificial diets. One found high larval mortality in Osmia cornuta reared on artificial pollen-based diets, including honey bee-collected pollen. The other found Megachile rotundata could be reared on an artificial diet based on honey bee-collected pollen, but bees reared on synthetic pollen substitutes either died or had low pre-pupal weight.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F54https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F54Thu, 20 May 2010 18:24:45 +0100Collected 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: Create patches of bare ground for ground-nesting beesOne replicated controlled trial in Germany and four small trials (three replicated, one not) have shown that artificially exposed areas of bare soil can be successfully colonised by ground-nesting solitary bees and wasps in the first or second year. We have captured no evidence for the effect of creating areas of bare ground on bee populations or communities on a larger scale.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F13https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F13Thu, 20 May 2010 19:29:53 +0100Collected Evidence: Collected Evidence: Plant dedicated floral resources on farmlandFourteen trials in Europe and North America have recorded substantial numbers of wild bees foraging on perennial or annual sown flowering plants in the agricultural environment. Ten trials (eight replicated) have monitored bees foraging on patches sown with a high proportion of phacelia Phacelia tanacetifolia on farmland and all but one found substantial numbers of foraging wild (non-Apis) bees, particularly bumblebees Bombus spp. Six of these trials recorded the number of foraging bee species, which ranged from eight to 35. One replicated trial shows that phacelia is not very attractive to wild bees in Greece. One replicated controlled trial in the UK showed that planted perennial leguminous herbs, including clovers, were more attractive to bumblebees in landscapes with a greater proportion of arable farming. Four replicated trials have quantified the wider response of wild bee populations to planted flower patches by measuring reproductive success, numbers of nesting bees or numbers foraging in the surrounding landscape. One trial showed that planted patches of bigleaf lupine Lupinus polyphyllus in commercial apple orchards in Novia Scotia, Canada, significantly enhanced the reproductive success of blue orchard mason bees Osmia lignaria. One trial in the Netherlands showed that bee numbers and species richness are not higher in farmland 50-1,500 m away from planted flower patches. Two trials in Germany found no or relatively few species of solitary bee nesting on set-aside fields sown with phacelia or clover respectively.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F17https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F17Thu, 20 May 2010 20:02:31 +0100Collected Evidence: Collected Evidence: Rear declining bumblebees in captivityWe have captured 22 trials from 13 countries documenting captive rearing of bumblebee colonies by confining mated queens alone (eight trials), with one or more bumblebee workers (seven trials), honey bee workers (one trial), male bumblebee pupae (three trials) or following anaesthetisation with CO2 (four trials). One trial found that over four years of artificial rearing, Bombus terrestris queens gradually decreased in weight. Three trials have tried to rear North American bumblebees now declining or thought to be declining. Two induced spring queens of the half-black bumblebee B. vagans to rear adults in captivity, one trial induced queen yellow-banded bumblebees B. terricola (attempted in all three trials) and red-belted bumblebees B. rufocinctus (only attempted in one trial) to rear adults in captivity. All three trials tried to rear the yellow bumblebee B. fervidus and in all cases the queens laid eggs but the larvae died before becoming adults. One trial found the same pattern for the rusty-patched bumblebee and the American bumblebee B. pensylvanicus. One study reports rearing the large garden bumblebee B. ruderatus, a Biodiversity Action Plan species in the UK. Two trials have reported laboratory rearing of a pocket-making bumblebee, the Neotropical B. atratus. Three replicated trials demonstrated that the pollen diet of captively reared bumblebees influences reproductive success. In one trial, buff-tailed bumblebee B. terrestris colonies fed on freshly frozen pollen produced larger queens that survived better and produced larger colonies themselves than colonies fed on dried, frozen pollen. Two replicated trials demonstrated that B. terrestris workers can produce more offspring when fed types of pollen with a higher protein content. Two replicated experiments showed that an artificial light regime of eight hours light, 16 hours darkness, can reduce the time taken for artificially reared queen B. terrestris to lay eggs, relative to rearing in constant darkness. We have captured two replicated trials examining the effect of different artificial hibernation regimes in B. terrestris. One showed that hibernation of queens at 4-5°C for 45 days enhanced egg-laying and colony formation rates, but hibernated queens produced smaller colonies than non-hibernated queens. The second showed that queens should weigh more than 0.6 g (wet weight) and be hibernated for four months or less to have a good chance of surviving.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F50https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F50Thu, 20 May 2010 20:22:36 +0100Collected Evidence: Collected Evidence: Sow uncropped arable field margins with an agricultural nectar and pollen mixFive replicated trials in Europe (three controlled) have documented bumblebees foraging on field margins sown with an agricultural nectar and pollen seed mix. Four replicated trials showed that field margins sown with perennial leguminous flowering plants attract significantly more foraging bumblebees than naturally regenerated (two trials), grassy (four trials) or cropped (three trials) field margins. Three replicated trials showed that a mix of agricultural forage plants including legumes (all annual plants in one trial) attracts greater numbers of bumblebees than a perennial wildflower mix, at least in the first year. Three trials in the UK found evidence that margins sown with agricultural legume plants degrade in their value to bumblebees and would need to be re-sown every few years. We have captured no evidence on the effects of field margin management on solitary bees.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F18https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F18Thu, 20 May 2010 20:59:45 +0100Collected Evidence: Collected Evidence: Provide set-aside areas in farmland Two replicated trials showed that species richness of bees nesting (one study) or foraging (one study), is higher on set-aside that is annually mown and left to naturally regenerate for two years or more, relative to other set-aside management regimes or, in the nesting study, to arable crop fields.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F7https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F7Thu, 20 May 2010 21:22:12 +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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