A total of 80 individual studies have in some way investigated the effects of flowering strips on biodiversity. Sixty-four individual studies show some benefits to one or more wildlife groups.
Sixty-five individual studies reported the effects of flower strips on invertebrates. Of these, fifty reported positive effects. Forty-one studies from eight European countries (including five reviews and twenty-three replicated controlled studies, of which one randomized and two site comparisons) found evidence that flower strips had a positive influence on invertebrate numbers with increased abundance, species richness/diversity, or both. Ten studies (nine replicated of which two controlled) found invertebrates visited or foraged on flower strips but did not specify increases/decreases in numbers. Two studies found effects on ground beetles other than changes in numbers. One replicated controlled study showed that ground beetles were more active or had enhanced feeding/reproductive conditions in flower strips. A review found flower strips supported ground beetle species that were rarely found in crops. Fifteen studies reported mixed or negative effects of flower strips on invertebrates. Six studies found no significant effects.
All five studies investigating the effects of wildflower strips on small mammals (four replicated studies from Switzerland and one review of studies from north-western Europe) found evidence that small mammals benefit from strips sown with wildflowers or flowers rich in pollen and nectar, with increases in abundance, density and species richness. One replicated study from Switzerland reported that most common vole home ranges and core regions of their territories were found within a wildflower strip.
We captured 40 studies (including 19 replicated and controlled studies of which six were also randomized, and six reviews) from nine European countries that found ten different techniques used alone or in combinations were effective for restoring species-rich grassland. Effective techniques included: grazing, introducing plant species, hay spreading and mowing.
We found 22 studies from seven European countries that included information on the length of time taken to restore grassland communities (including 16 replicated trials of which nine also controlled and three reviews). Six studies saw positive signs of restoration in less than five years, 11 studies within 10 years and two studies found restoration took more than 10 years. Six studies found limited or slow changes in plant communities following restoration. Two studies from Germany and the UK (one replicated controlled trial) found differences in vegetation between restored and existing species-rich grasslands nine or 60 years after restoration.
Nineteen studies from Finland, the Netherlands, Sweden and the UK (including seven replicated controlled studies of which two were randomized, and three reviews), found that planting grass buffer strips (some margins floristically-enhanced) increased arthropod abundance, species richness and diversity. A review found grass margins benefited bumblebees and some other invertebrates but did not distinguish between the effects of several different margin types.
Nine studies from the UK (including seven replicated studies of which two were controlled, and two reviews) found that planting grass buffer strips (some margins floristically-enhanced) benefits birds, resulting in increased numbers, densities, species richness and foraging time.
Seven studies from the Netherlands and the UK (all replicated of which four were controlled and two randomized), found that planting grass buffer strips (some margins floristically-enhanced) increased the cover and species richness of plants. A review found grass margins benefited plants but did not distinguish between the effects of several different margin types.
Twenty-two studies from 14 replicated, controlled experiments (of which two randomized) including two reviews, from a total of 32 studies from 20 experiments (of which 17 replicated, controlled) including three reviews from Finland, Germany, the Netherlands, Sweden and the UK that investigated species richness and diversity of farmland wildlife found that conservation headlands contained higher species richness or diversity of invertebrates or plants than other habitat types. Twelve studies (including a review) from ten replicated experiments (of which eight controlled and three controlled and randomized) found that some or all invertebrates or plants investigated did not have higher species richness or diversity on conservation headlands compared to other habitat types. This included both replicated, controlled studies investigating bee diversity. Two replicated studies from the UK found that unfertilized conservation headlands had more plant species than fertilized conservation headlands.
Positive effects of conservation headlands on abundances or behaviours of some or all species investigated were found by 27 studies from 15 replicated experiments (of which 13 controlled) including five reviews out of a total of 36 studies from 20 experiments (17 replicated, controlled) including five reviews from Finland, Germany, the Netherlands, Sweden and the UK that investigated birds (some studies looked at number of visits), mammals (some studies looked at number of visits), invertebrates and plant abundance/cover.One review from the UK found a positive effect on grey partridge populations but did not separate the effects of several other interventions including conservation headlands. Nineteen studies from 13 replicated (12 controlled) experiments and a review from Finland, Germany, the Netherlands and the UK found that some or all species of birds, invertebrates or plants investigated were at similar, or lower, abundances on conservation headlands compared to other management. One review from the UK and a study in Germany found conservation headlands had a positive effect on plants and some, but not all invertebrates, or rare arable weeds but did not specify how.
Biodiversity loss: Eleven studies from Canada, Europe, Mexico, or the USA measured effects of reduced tillage on soil animals or microbes. Of these, four (including three replicated trials (three also randomized and one also controlled)) found more microbes, more species of earthworm, or higher microbe activity under reduced tillage. One replicated trial found increased numbers of soil animals and earthworms under reduced tillage. One controlled, replicated trial found mixed effects on microbe diversity depending on time of sampling. Two, (including one controlled, replicated trial) found no effect of reduced tillage on earthworm activity or microbe activity.
Compaction: Five studies from Australia, Canada, and Europe measured the effect of controlled traffic and reduced tillage on compacted soils. Of these, two (including one before-and-after trial and one replicated trial) found reduced compaction and subsequent effects (reduced water runoff, for example) under controlled traffic, and one also found that crop yields increased under no-tillage. Three replicated trials, including one site comparison study, found higher compaction under reduced tillage.
Drought: Three replicated trials from Europe and India (one also randomized) found the size of soil cracks decreased, and ability of soil to absorb water and soil water content increased with conventional ploughing and sub-soiling.
Erosion: Nine replicated trials from Brazil, Europe, India, Nigeria and the USA, and one review showed mixed results of tillage on soil erosion. Seven trials (one also controlled and randomized) showed reduced soil loss and runoff under reduced tillage compared to conventional ploughing. One trial showed no differences between tillage systems, but demonstrated that across-slope cultivation reduced soil loss compared to up-and-downslope cultivation. Two trials showed that no-tillage increased soil loss in the absence of crop cover.
Soil organic carbon: Twelve studies from Australia, Canada, China, Europe, Japan and the USA compared the effect of no-tillage and conventionally tilled systems on soil organic carbon. All (including two randomized, five replicated, two randomized, replicated, and one controlled, randomized, replicated) found higher soil organic carbon in soils under a no-tillage or reduced tillage system compared to conventionally tilled soil. One review showed that no-tillage with cover cropping and manure application increases soil organic carbon. One randomized, replicated trial from Spain found greater soil organic carbon in conventionally tilled soil. One replicated trial from Canada found no effect of tillage on soil carbon.
Soil organic matter: Fifteen studies from Canada, China, Europe, Morocco, and the USA measured effects of reduced tillage on soil organic matter content and nutrient retention. Of these, eight studies (including four replicated (two also randomized), two site comparisons (one also replicated) and one controlled) found maintained or increased soil organic matter and improved soil structure under reduced tillage. Four trials (including two replicated and two site comparison studies) found higher nutrient retention under reduced tillage. One controlled, replicated trial found less carbon and nitrate in no-till compared to conventionally tilled soil, but conventionally tilled soil lost more carbon and nitrate. One controlled, randomized, replicated trial and one replicated trial found mixed effects of reduced tillage on soil nitrogen levels.
Yield:One replicated study from Canada found lower yields under minimum or no-tillage compared to conventional tillage, and one controlled, randomized, replicated study from the USA found higher yields when subsoiling was done. One randomized, replicated study from Portugal found no effect of tillage treatment on yield.
We found 34 studies comparing use of set-aside areas with control farmed fields. Two were reviews, none were randomized, replicated, controlled trials. Of these, 20 (from Austria, Finland, Germany and the UK) showed benefits to or higher use by all wildlife groups considered. Twelve (from Finland, Germany, Ireland, Sweden and the UK) found some species or groups used set-aside more than crops, others did not. Two studies (all from the UK) found no effect, one found an adverse effect of set-aside.
Three of the studies, all looking at skylarks, went beyond counting animal or plant numbers and measured reproductive success. Two from the UK found higher nest survival or productivity on set-aside than control fields. One from the UK found lower nest survival on set-aside.
Fifteen studies (from Belgium, Germany, Sweden and the UK) monitored wildlife on set-aside fields, or in landscapes with set-aside, without directly comparing with control fields or landscapes. Three looked at set-aside age and found more plants or insects on set-aside more than a year old. Two compared use of different non-crop habitats and found neither insects nor small mammals preferred set-aside. Two showed increased bird numbers on a landscape scale after set-aside was introduced, amongst other interventions. Eight looked at effects of set-aside management such as use of fertilizer and sowing or cutting regimes.
A systematic review from the UK found significantly higher densities of farmland birds on fields removed from production and under set-aside designation than on conventionally farmed fields in both winter and summer.
Thirty-nine studies (including 13 replicated controlled trials of which three also randomized and four reviews) from eight European countries compared wildlife on uncultivated margins with other margin options. Twenty-four found benefits to some wildlife groups (including 11 replicated controlled trials of which one also randomised, and four reviews). Nineteen studies (including one randomized, replicated, controlled trial) from Germany, Ireland, Lithuania, Norway, the Netherlands and the UK found uncultivated margins support more invertebrates (including bees) and/or higher plant diversity or species richness than conventionally managed field margins or other field margin options. One replicated, controlled study showed that uncultivated margins supported more small mammal species than meadows and farmed grasslands. Four studies (two replicated UK studies, two reviews) reported positive associations between birds and field margins including food provision. A review from the UK found grass margins (including naturally regenerated margins) benefited plants and some invertebrates.
Fifteen studies (including one randomized, replicated, controlled trial) from Germany, the Netherlands, Norway and the UK found that invertebrate and/or plant species richness or abundance were lower in naturally regenerated than conventionally managed fields or sown margins. Six studies (including one randomized, replicated, controlled trial) from Belgium, Germany and the UK found uncultivated margins did not have more plant or invertebrate species or individuals than cropped or sown margins. A review found grass margins (including naturally regenerated margins) did not benefit ground beetles.
Five studies (including three replicated controlled trials) from Ireland and the UK reported declines in plant species richness and invertebrate numbers in naturally regenerated margins over time. One replicated trial found that older naturally regenerated margins (6-years old) had more invertebrate predators (mainly spiders) than newly established (1-year old) naturally regenerated margins.
Five studies (including one replicated, randomized trial) from the Netherlands and the UK found that cutting margins had a negative impact on invertebrates or no impact on plant species. One replicated controlled study found cut margins were used more frequently by yellowhammers when surrounding vegetation was >60 cm tall.
Seven studies (including four replicated controlled trials and a review) from Ireland, the Netherlands, Norway and the UK reported increased abundance or biomass of weed species in naturally regenerated margins.
Thirty individual studies investigated the effects on birds of sowing wild bird seed or cover mixture, 21 studies found positive effects. Fourteen studies from the UK (including one systematic review and nine replicated controlled trials of which four randomized, and three reviews) found that fields sown with wild bird cover mix had higher abundance, density, species diversity and species richness of birds than other farmland habitats. Six studies from the UK (including one review and two replicated studies) found that birds showed a preference for wild bird cover and used it significantly more than other habitats. One review found the grey partridge population increased substantially on farms where conservation measures including cover crops were in place. Nine replicated studies from France and the UK reported mixed or negative effects of wild bird cover on birds compared to other farmland habitats. Six studies found that mixtures including kale or a mixture of kale and/or other species attracted the largest number of bird species or highest bird abundance.
Twelve studies from the UK looked at the effects of wild bird cover strips on invertebrates. Seven studies from the UK (including one review and four replicated controlled studies of which two were also randomized) found positive effects. Farmland habitats sown with wild bird cover mix were used more by butterflies, and had a higher abundance or species richness of butterflies and/or bees than other farmland habitats. One review found wild bird cover benefited invertebrates. Four studies (including one review and two replicated trials) reported mixed or negative effects of wild bird cover on invertebrate numbers compared with other farmland habitats. One study found that bees and butterflies showed preferences for particular plant species.
Eleven studies from five European countries (including three replicated paired site comparisons and two reviews) looked at the effects of agri-environment schemes on plants. Seven studies (including three replicated paired site comparisons and one European review) found agri-environment schemes maintained or had little or no effect on plants, plant diversity or species richness. Three studies found increases in plant species richness in areas with agri-environment schemes, two found decreases. A replicated site comparison study from Estonia found higher flower abundance on farms with agri-environment schemes in two out of four areas. A review found Environmentally Sensitive Areas in England had contributed to halting the loss of semi-natural grassland habitats but were less effective at enhancing or restoring grassland biodiversity.
Of 38 individual studies from Austria, the Czech Republic, Denmark, Finland, France, Germany, Ireland, the Netherlands, Sweden and the UK investigating the effects of reducing fertilizers, pesticides or herbicides, 34 studies (23 replicated, of which six also controlled and randomized, one review and one systematic review) found benefits to some invertebrates, plants, or farmland birds. Twenty-five studies (16 replicated, of which seven also randomized and controlled and one review) found negative, mixed, minimal or no effects on some invertebrates, farmland birds or plants.
Ten studies (six replicated, controlled studies of which two randomized) from three countries found positive effects of reducing or stopping pesticide applications on invertebrates, plants, or birds. Eight studies (two replicated controlled and randomized, one paired before-and-after trial) from four countries found inconsistent or no effects on some invertebrates or birds.
Ten studies (nine replicated, five also controlled and a European systematic review) from four countries found positive effects of reducing or stopping herbicide use on plants, invertebrates, and birds. Five replicated studies (two also controlled and randomized) from three countries found no or mixed effects on birds, invertebrates and plants.
Five studies (three replicated controlled of which two randomized) from four countries found positive effects of reducing or stopping fertilizer applications on invertebrates, Eurasian skylark, or plants. Four studies (three replicated, controlled and randomized) from two countries found reducing or stopping fertilizer inputs had no, or no consistent effects on some invertebrates and farmland birds. Two studies from the UK (one replicated) found plots where fertilizer inputs were not reduced tended to have higher earthworm biomass or abundance.
Fifteen studies (three replicated controlled of which one also randomized, five site comparisons and one review) from seven countries looked at the effects of reducing or stopping applications of two or more inputs: pesticides, herbicides, or fertilizers. Thirteen studies found positive effects of reducing two or more inputs on some or all invertebrates, plants, soil organisms, and birds studied. Seven studies found negative or no effects of reducing combinations of inputs on some invertebrates, plants or birds.