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Organic Agriculture and Biodiversity: Is there a link?

By Alison Burton

Organic farming can increase the diversity of plants and animals, according to a recent analysis of over 180 studies. The analysis showed that on average, the number of species increased about 30% in organic systems and the number of individual plants and animals was 50% greater on organic farms.

These results were obtained using a meta-analysis, which looks at many individual studies asking 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, whereas abundance is the total number of individuals per unit area.

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 both variety and quantity of many species associated with farming. Land converted to farming loses biodiversity relative to native areas. Is there a difference between the effects organic farming 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. Predatory insect densities were usually higher in organic systems, whereas non-predatory insects were not higher (possibly since the predatory insects were eating the non-predatory insects). As well, numbers of soil organism were 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 to the soil also affect biodiversity. All farmers can use practices that can increase biodiversity.

Biodiversity varies from farm to farm. Producers can increase biodiversity by choosing to use pesticides sparingly, use farm manure instead of chemical fertilizers, and have 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, the choices the individual farmer makes have the biggest impact on biodiversity. Producers can have a positive impact on biodiversity through practices such as reducing pesticide and herbicide applications, increasing their 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 very few species present. Producers are directly involved in biodiversity on their farms, and helping to preserve biodiversity is beneficial to us all.

Alison Burton is a M.Sc. candidate in the Department of Plant Sciences at the University of Saskatchewan. Please send your comments Alison at alison.burton@usask.ca or to Brenda Frick at 306-966-4975 or via email at brenda.frick@usask.ca.

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