The researchers found that the positive effect of organic farming has been stable throughout the 30-year period; the effect has not shown any signs of slowing as more studies are published.
– Our study shows that organic farming often has significant positive effects on especially the “ordinary”, common biodiversity, says Jan Bengtsson at SLU and Sean Tuck and Lindsay Turnbull from Oxford, who led the study.
– For many groups of organisms is organic farming one of several tools to reduce the loss of biodiversity in the industrialized agriculture, says Jan Bengtsson, Tuck Sean and Lindsay Turnbull
Pollinators and plants gain most from organic farming
The positive effect of organic production differ between groups of organisms. The variety of species of plants and pollinators like bumblebees and bees was, for example, more than 50 per cent higher in organic farming, while the diversity of soil organisms was not much affected. The positive effects were also greater in landscapes with contiguous fields compared with mosaic landscapes.
Studies from tropic areas are missing
The researchers also analysed how representative published studies are for agriculture globally. They found that different crops like cereals and vegetables were fairly well represented. However, virtually all studies were done in industrialized countries.
– It is surprising that there are no studies of large areas in tropic regions and developing countries, says Jan Bengtsson and Lindsay Turnbull.
– Why are no studies of, for example, cocoa and banana plantations where we know that they use large amounts of pesticides? It is products that are available in almost every grocery store in our countries, but we know nothing about how organic banana cultivation affect biodiversity. Here is a knowledge gap that needs to be filled, says Jan Bengtsson and Lindsay Turnbull
Organic farming positive for biodiversity
The benefits of organic production is often controversial. But when it comes to biodiversity, this study, like previous studies based on a smaller data set, shows that organic farming is largely positive and rarely have negative effects. The beneficial effects on the diversity of pollinators and natural enemies of pests moreover indicates that the ecosystem services that the farmer has advantages of, also benefits from organic agriculture. But that is another story, which is significantly less investigated.
The study is published this week in the prestigious English magazine Journal of Applied Ecology. The researchers reviewed the data on species diversity in organic and conventional farming, mainly comparisons between fields or farms of 94 studies published from 1989 and onwards. They also measured different dimensions of landscape, such as the share of agricultural land, with the help of satellite images. All data were then analysed using the so-called meta-analysis methodology, which has become increasingly common in areas such as evidence-based medicine and ecology. The work of the international research team was funded by the Research Council Formas, Ekhaga Foundation and NERC in the U