Wetenschap - 9 mei 1996

Taking ecosystems to hospital

Taking ecosystems to hospital

Health indicators can be a good measure of the well-being of humans and animals. So why not apply the concept of health to agricultural ecosystems and adopt health jargon to analyze and indicate the condition of the systems? That is what a group of Canadian scientists had in mind when they started the Agroecosystem Health Project. One of them, John Van Leeuwen is doing his PhD research in Wageningen on water pollution.

In Costa Rica, there is a particular viral disease which can be pretty harmful to cows and to a lesser extent to human beings. If a cow is contaminated, its milk production decreases. Research has indicated that the disease is passed on by a sandfly. Spraying chemicals is one way of preventing the disease. This is, however, a very short term solution and has undesirable side effects. It may kill other, useful insects as well and can be harmful to human beings and the environment," says John VanLeeuwen, farm animal vet.

Farms where there are trees in the vicinity showed a higher incidence of the disease. Research shows that this fly is a night feeder and lives in trees. The furthest the insect can fly is a distance between 50 and 300 metres. Of course you can decide to cut down all trees within that range but another possibility is to adapt farm management practices. At night time you can either keep the animals indoors or put them in a field with no trees." Van Leeuwen is doing his PhD research within the Agroecosystem Health Project at the University of Guelph in Canada. This research programme has been designed and is being implemented by a group of researchers from various disciplines. The main goal is to develop a framework for evaluating and improving the health of agroecosystems and their components. The programme has developed a set of generic indicators to characterise the health of the systems. Individual research projects attempt to integrate a variety of dimensions in order to und
erstand the relationships and trade offs between the different components which go to make up the health of an agroecosystem.


VanLeeuwen discloses that the Agroecosystem Health Programme adopted the health concept for practical and strategic reasons: People have a pretty good idea of what health is and whether it is good or bad. It is a concept that appeals to people. If you were to use the term ecological integrity for the same kind of programme, nobody would know what you were talking about." However, according to VanLeeuwen, it is not purely a strategic choice. Being a veterinarian I do not think that any animal or human is 100% healthy. There are always little things that bother them from day to day."

The same applies to agroecosystems. To illustrate this, as part of the conceptual framework, VanLeeuwen designed the butterfly model. He feels that the concept of health goes beyond biomedical issues only. VanLeeuwen laughs: You can be in perfect shape physically but feel psychologically lousy. Or the other way around of course." In the model the health of an agroecosystem is compared to a butterfly. One wing of the butterfly stands for the biophysical environment: the air, soil, water, plants and so on. The other wing represents the psychological and socio-economic environment, including relationships and the political and economic situation.

Individual human beings within an agroecosystem, and the agroecosystem as a whole, are healthier when both wings are balanced in size, with neither dominating the other. If the insect is out of balance it will fly more slowly or crash.


Since his supervisors told him to narrow down his research VanLeeuwen has decided to focus the empirical part of his study on the relation between human health and pollution contamination due to agricultural chemicals in Ontario, Canada. The fact that he is looking into chemical contamination spread through water, was an important reason to come to The Netherlands. VanLeeuwen explains: This country definitely has a water contamination problem. I was interested in Dutch epidemiological research and the measures taken here to minimise contamination through surface water, for instance with regard to the manure surpluses in Dutch agriculture." VanLeeuwen soon discovered that the Dutch population obtains drinking water from a central water supply system and that there are virtually no private wells. Although he admits that his visit has been relatively fruitless in this respect, VanLeeuwen has not been wasting his time. He followed two extension courses of the MAKS programme and ha
s made a considerable effort to promote the programme. Networking among policy makers, researchers and other interest groups forms a part of the research objectives of the Agroecosystem Health Project. VanLeeuwen admits that the approach might seem a bit wishy-washy but he sees a point to a holistic approach to problem solving and policy initiatives.