Organic farming can increase the diversity of plants and animals, according to a recent analysis of more than 180 studies. The analysis showed that on average, the number of species increased about 30 percent in organic systems and the number of individual plants and animals was 50 percent greater on organic farms.
These results were obtained using a meta-analysis, which looks at many individual studies that ask the same question and finds trends or patterns in the data. Studies comparing biodiversity of organic and conventional farming used species richness and abundance as measures of diversity. Species richness looks at the number of different species present while abundance is the total number of individuals per unit area.
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This study shows organic farms tend to have a greater species richness and abundance. Clear increases were seen in plants, birds, insect predators and soil organisms. There was little evidence that other insects and pests were more abundant on organic farms.
The factors influencing the number of individuals and species present on farms aren’t limited to organic production. All farmers could increase biodiversity with environmentally friendly practices.
There’s been a definite decline in the variety and quantity of many species and that decline is associated with farming.
Land converted to farming loses biodiversity relative to native areas. Is there a difference between the effects that organic and conventional farming have on that variety and quantity?
Organic farming excludes synthetic chemicals in crop and livestock production. It also relies on longer, more diverse crop rotations, cover cropping, compost applications, intercropping, biological pest control and nutrient recycling. These practices, recommended for organic farming, result in a more diverse habitat for organisms.
Different organisms react differently to organic farming. Weeds were more common in organic systems and predatory insect densities were usually higher, but non-predatory insects were not higher, possibly because the predatory insects were eating the non-predatory insects. As well, the number of soil organisms was usually higher with organic farming.
Biodiversity and abundance are affected by factors other than the type of farming system, such as non-cropped areas. Field margins, wetlands, hedgerows, ditches and ponds are important habitats that increase biodiversity.
Other factors such as decreasing tillage and increasing organic matter inputs in the soil also affect biodiversity, which can vary from farm to farm.
Producers can increase biodiversity by using pesticides sparingly, using farm manure instead of chemical fertilizers and incorporating more diverse crop rotations.
Variations in landscape such as ditches, hedgerows and ponds could be preserved on farms. As a result, biodiversity can vary greatly based on the choices the individual farmer makes.
Overall, choices made by individual farmers have the biggest impact on biodiversity, such as reducing pesticide and herbicide applications, increasing crop rotation diversity and maintaining natural habitats on farms such as shelterbelts and ponds.
Biodiversity is important because a diverse landscape with a variety of plants and animals is more stable than having few species present. Producers are directly involved in biodiversity on their farms and helping preserve biodiversity is beneficial to us all.
Alison Burton is a MSc candidate in the Department of Plant Sciences at the University of Saskatchewan. Please send your comments to alison.burton@usask.ca or to Brenda Frick at 306-966-4975 or via e-mail at brenda.frick@usask.ca. OACC newspaper articles are archived at www.oacc.info.
