Benefits of Biodiversity

By Brenda Frick, Ph.D.

Biodiversity is the variety of living organisms in an area. It is greater if there are many types of organisms. 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 of organic farms, and reserving a portion of "wild" land on farm is a component of certification for some groups.

A recent study in Saskatchewan compared bird numbers 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 quack grass, applied to barley plants, repel aphids. These extracts are exuded from quack grass roots, and can be picked up by the barley from the soil. This suggests that the presence of quack grass 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, may release volatile compounds that repel insects, or 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 of these studies 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 residual 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 Lethbridge, Lacombe and Beaverlodge, Alberta indicated 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 intercropping. He is asking producers who have experience with intercropping to contact him at Box 69, Davidson, SK, S0G 1A0 with the following information: soil zone (eg. dark brown) and type (eg. 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 email), and if the farmer is willing to accept phone calls or written questions from other farmers. Elmer will compile this important 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 (click here for more information). This effort should provide a useful base for producers wishing to increase biodiversity on their own farms.

Click here for more information about organic agriculture.

References:
D. Shutler, A. Mullie and R.G.Clark, 2000 Bird communities of prairie uplands and wetlands in relation to farming practices in Saskatchewan Conservation Biology. 14(5): 1441-1451

IFOAM n.d. The Principles of Organic Agriculture. Retrieved 27 Nov 2003 from http://www.ifoam.org/

L. M. Dosdall, G.W. Clayton, K.N. Harker, J.T. O'Donovan and F.C. Stevenson. 2003. Weed control and root maggots: Making canola pest management strategies compatible. Weed Science 51: 576-585

M.J. Clapperton, N.O. Lee, F. Binet and R.L. Conner. 2001. Earthworms indirectly reduce the effects of take-all (Gaeumannomyces graminis var tritici) on soft white spring wheat (Triticum aestivum cv. Fielder). Soil Biology & Biochemistry 33: 1531-1538

R. Glinwood, J. Pettersson, E. Ahmed, V. Ninkovic, M. Birkett and J. Pickett. 2003. Change in acceptability of barley plants to aphids after exposure to allelochemicals from couch-grass (Elytrigia repens). Journal of Chemical Ecology 29 (2): 261-274


Brenda Frick, Ph.D., P.Ag., is the Prairie Coordinator for the Organic Agriculture Centre of Canada at the College of Agriculture, University of Saskatchewan. She welcomes your comments at 306-966-4975 or via email at brenda.frick@usask.ca.


This article first appeared in The Western Producer, and is published here on the OACC website with permission.


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Posted May 2006