The many benefits of biodiversity - Organic Matters

Biodiversity is the variety of organisms living in an area. The more types of organisms, not just the number of individual creatures, means the greater the biodiversity.

Agricultural systems tend to limit biodiversity. As researchers take a broader view of farming systems, they discover advantages in biodiversity that go beyond simple explanations.

The International Federation of Organic Agriculture Movements includes among its principles “to maintain and encourage agricultural and natural biodiversity on the farm.” Conservation of biodiversity is an important role for organic farms, and reserving a portion of “wild” land on the farm is a component of certification for some groups.

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A recent study in Saskatchewan compared bird populations on different kinds of farms. The researchers found that organic farms had more upland and wetland birds than conventional farms, and included some species that were not found on conventional farms. The abundance of beneficial insects, such as carabid beetles and parasitic wasps, is often higher on organic farms. They are encouraged by the absence of insecticides and presence of weeds that provide habitat and food. Organic farms may play an important role in safeguarding biodiversity in agricultural landscapes.

Several recent studies show that biodiversity influences cropping systems in unexpected and beneficial ways. In Sweden, researchers have found that extracts of quackgrass, applied to barley plants, repel aphids. These extracts are exuded from quackgrass roots, and can be picked up by the barley from the soil. This suggests that the presence of quackgrass in a barley field may help protect it from aphid attack.

Researchers at Lethbridge found that soils had larger and more active microbial communities in the presence of earthworms. Crop yields were also higher in treatments that included earthworms. The earthworms altered the microbial community, and particularly the relative proportions of bacteria and fungi in ways that the researchers suspect may reduce plant diseases such as take-all in wheat.

Other Alberta researchers discovered that canola root maggots are less likely to lay eggs on canola plants in weedy fields. The authors of the study suggest several possible reasons: weeds might be a physical barrier; they may release volatile compounds that repel insects; or they may provide food or habitat for predators, parasites and pathogens of the pest insect.

In the case of the canola root maggot, the researchers suspect the problem, from the maggot’s perspective lies in the diversity of landing sites. The female makes several short flights before she lays her eggs. She must land on an acceptable plant each time to continue her egg laying sequence. If she lands on weeds instead, her egg laying flight is disrupted and egg laying is reduced.

Each study reminds us that cropping systems are complex and that all components interact, often in ways we have yet to understand. Fostering biodiversity, even leaving a small weed population, or seeding a mixture of crops, may have unexpected advantages.

Information about intercropping, or growing more than one crop in a field at a time, is still limited and difficult to access. Organic producers at recent consultation meetings in Alberta at Lethbridge, Lacombe and Beaverlodge, said they were interested in more research and information on this option.

Elmer Laird of the Back to the Farm Research Foundation is compiling farm-based information on the practice. He is asking producers who have experience with intercropping to contact him at Box 69, Davidson, Sask., S0G 1A0 with the following information: soil zone (ie. dark brown) and type (ie. Weyburn loam); and details of their experience, including varieties, time of planting, method of harvesting and weed management. He is asking for contact information (name, address, phone, fax and e-mail), and if the farmer is willing to accept phone calls or written questions from other farmers.

Laird will compile this farm-based research into a pamphlet on intercropping. The pamphlet will be free to all who supplied information, and sold to others to raise funds for the Organic Agriculture Protection Fund. For more information, see www.saskorganic.com/oapf.htm. This effort should provide a useful base for producers wishing to increase biodiversity on their own farms.

Frick is the Prairie co-ordinator for the Organic Agric-ulture Centre of Canada located at the University of Saskatchewan. Frick can be reached at 306-966-4975, at brenda.frick@usask.ca, or www.organicagcentre.ca.The opinions expressed in this column are not necessarily those of The Western Producer.