This synopsis includes experimental tests of organic farming only. Comparative studies of existing organic systems are not included.
Parasitism and mortality (caused by natural enemies):One of five studies (three replicated, controlled tests and two also randomised) from Europe, North America, Asia and Australasia found that organic farming increased parasitism or natural enemy-induced mortality of pests. Two studies found mixed effects of organic farming and two randomised, replicated, controlled studies found no effect. Natural enemies:Eight of 12 studies (including six randomised, replicated, controlled tests) from Europe, North America Asia and Australasia found more natural enemies under organic farming, although seven of these found effects varied over time or between natural enemy species or groups and/or crops or management practices. Three studies (one randomised, replicated, controlled) found no or inconsistent effects on natural enemies and one study found a negative effect. Pests and diseases:One of eight studies (including five randomised, replicated, controlled tests) found that organic farming reduced pests or disease, but two studies found more pests. Three studies found mixed effects and two studies found no effect. Crop damage: One of seven studies (including five randomised, replicated, controlled tests) found less crop damage in organic fields but two studies found more. One study found a mixed response and three studies found no or inconsistent effects. Weed seed predation and weed abundance: One randomised, replicated, controlled study from the USA found mixed effects of organic farming on weed seed predation by natural enemies. Three randomised, replicated, controlled studies from the USA found more weeds in organically farmed fields, but in one of these studies this effect varied between crops and years. One study found no effect. Yield and profit: Six randomised, replicated, controlled studies measured yields and found one positive effect, one negative effect and one mixed effect, plus no or inconsistent effects in three studies. One study found net profit increased if produce received a premium, but otherwise profit decreased. Another study found a negative or no effect on profit.
Biodiversity: Four studies in Asia, Europe, and the USA (including two site comparison studies and three replicated trials) found higher numbers, diversity, functional diversity (see background) or activity of soil organisms under organic management.
Soil organic carbon: Two replicated trials in Italy and the USA showed that organically managed orchards had higher soil carbon levels compared to conventionally managed orchards. One randomized, replicated trial in the USA found soil carbon was lower under organic management compared to alley cropping.
Soil organic matter: One replicated trial in Canada found that soil nutrients were lower in organically managed soils.
A small UK study found that a site with beetle banks had increasing populations of rare or declining species, although several other interventions were used on this site. A literature review from the UK found that grey partridge Perdix perdix populations were far larger on sites with beetle banks and other interventions than on other farms. Two replicated studies from the UK also investigated population-level effects: one found that no bird species were strongly associated with beetle banks; the second found no relationship between beetle banks and grey partridge population density trends.
A UK literature review found that two bird species nested in beetle banks and that some species were more likely to forage in them than others. A study in the UK found that one of two species used beetle banks more than expected. The other used them less than other agri-environment options.
Fourteen reports from eight studies out of a total 24 reports from 12 individual studies (including eight replicated studies of which three controlled and four literature reviews) from Denmark and the UK found that beetle banks provide some benefits to farmland biodiversity.
Natural enemies in fields: Six studies from Canada, the UK and USA (three replicated, controlled, of which two were also randomised) examined the effects on predator numbers in adjacent crops. A review found that predators increased in adjacent crops, but one study found effects varied with time and another found no effect. Two studies found small or slow movements of predators from banks to crops. One study found greater beetle activity in fields but this did not improve pest predation. Natural enemies on banks:Four studies and a review found more invertebrate predators on beetle banks than in surrounding crops, but one of these found that effects varied with time. Eight studies from the UK and USA (including two randomised, replicated, controlled trials and two reviews) compared numbers of predatory invertebrates on beetle banks with other refuge habitats. Two studies found more natural enemies on beetle banks, but one of these found only seasonal effects. One review found similar or higher numbers of predators on beetle banks and four studies found similar or lower numbers. Pests: A replicated, randomised study and a review found the largest pest reductions in areas closest to a beetle bank or on the beetle bank itself. One review found fewer pests in fields with than without a beetle bank. Economics: One replicated, randomised, controlled trial and a review showed that beetle banks could make economic savings if they prevented pests from reaching a spray threshold or causing 5% yield loss. Beetle bank design:Two studies from the UK found certain grass species held higher numbers of predatory invertebrates than others.
We have captured no evidence for the effects of creating corn bunting plots on farmland wildlife.
'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.
A randomised, replicated and controlled study from the UK found that more Eurasian skylarks used fields with open strips in, but that variations in skylark numbers were too great to draw conclusions from this finding.
Two studies (both randomized, replicated and controlled) investigated the effects of creating open strips in permanent grassland. One trial from the UK found that more Eurasian skylarks used fields containing open strips, but variations in skylark numbers were too great to draw conclusions from this finding. One trial from Scotland found insect numbers in grassy headlands initially dropped when strips were cleared.
A controlled study in Finland found that creating clover leys resulted in higher spider abundance and fewer pest insects than a barley control plot. A study in the UK found that one-year ley plots had significantly lower earthworm species richness and abundance than three-and-a-half-year leys.