Overstory #46 - Human Health and Agroecosystems

Editor's Note

During the past century, both the agricultural and health sciences have become compartmentalized, making great technical advances in relatively specialized technologies. These advances generated significant increases in food production and and reductions in human diseases. Although the primary purpose of agriculture is to maintain human health and human health depends on agriculture, there have been few efforts to integrate the two.

At a time when both health and agricultural workers are questioning the sustainability of their achievements, the concept is emerging that effective agroecosystem management may provide a cost-effective strategy to improve human health.

This edition of The Overstory is an extract from the new publication Environmental Health: A Sourcebook of Materials, published by the International Institute of Rural Reconstruction (IIRR), Cavite, Philippines. It is written by D. G. Peden of the International Development Research Centre, and explores some of the links between agricultural ecosystems and human health. Order information for this new publication is provided below.

Agriculture now faces the tasks of enhancing food production while simultaneously reversing soil degradation, replenishing soil capital and overcoming the harmful effects of agricultural chemicals. Degraded agricultural ecosystems (agroecosystems) are less resilient to stresses caused by global variation and climatic changes. Agricultural ecosystems are the focus of growing concern about how degraded agroecosystems are related to the projected increase in risks to human health.

Human health is directly linked to and dependent on the state of health of the ecosystems that support them. Because people are an integral component of agroecosystems, a range of socio-economic and biophysical factors affect their health. A few examples illustrate this point.

In subsistence agricultural systems, nutrition is a primary factor. Without food security, human health inevitably suffers. Although increased food production in terms of quantity has largely kept pace with the demands of a growing population, the quality of food available may be declining. Maintaining the high rate of production may be difficult.

Food shortages affect about 800 million people, but more than two billion people suffer from malnutrition. Although in some cases, nutrient deficiencies are simply characteristic of otherwise stable agroecosystems, land degradation aggravates the harmful effects that some factors in agroecosystems have on human nutrition. For example, iron deficiency alone affects 40 to 50% of women worldwide. Two hundred and fifty million children suffer from severe or moderate vitamin A deficiency with up to 500-1000 pre-schoolers becoming blind annually. There is a growing evidence that even in developed countries, deficiencies in fiber, folic acid, etc., threaten human health.

Apart from nutrition, naturally occurring heavy metals, vector-borne and non-vector-borne diseases, naturally occurring toxins, agricultural chemicals as well as imports and exports associated with a cash economy, contribute to the health risks faced by people within the context of their agroecosystem. In recent years, mercury contamination of fish in the Amazon basin and the consequent rise in toxicity symptoms in people who depend on fish has focused attention on the perceived negative impact of gold mining. However, new evidence suggests that gold mining is not the only source of this heavy metal. Rather, forest clearance followed by cultivation resulted in the leaching of mercury from exposed soil into adjacent aquatic ecosystems where it entered the food chain.

The introduction of agriculture initiated a process of soil degradation that directly threatened human health. With this knowledge, local people are in a position to modify their diets by shifting from the consumption of carnivorous to herbivorous fish, to establish vegetative buffer zones between the exposed soils and the rivers and to consider other community efforts to better manage vegetative cover of their crop lands. The solution to this health problem lies in the better management of the aquatic and terrestrial agricultural ecosystems.

Adoption of new or innovative agricultural technologies and policies often leads to unexpected or counterintuitive impacts. Understanding and responding to these often requires an agroecosystems perspective. Transformation from a subsistence to cash economy can generate a number of adverse health consequences. The move to cash economies can also result in new health risks. For example, chemical fertilizers, pesticides, herbicides and fungicides applied to food crops can be leached into ground water supplies, thus contaminating downstream and underground water.

Land degradation can adversely affect human health by changing the ecology of pathogenic and harmful organisms. One consequence of soil degradation is reduced water holding capacity and greater likelihood of drought-stressed crops. Peanuts subjected to drought develop high concentrations of pre-harvest aflatoxin. Aflatoxin is believed by many to cause acute liver damage and cancer. Although this connection has not been conclusively demonstrated in humans, the fear of its carcinogenic effect motivates a number of governments to regulate trade in potentially-contaminated food crops.

Not only do the condition and management of agroecosystems affect the health of people that depend on it for sustenance, human health also directly influences the ability of people to manage the system itself. For example, Acquired Immunodeficiency Syndrome (AIDS) causes major labor shortages and the diversion of family income to cover increased health care costs. Beyond AIDS, other aspects of poor health make effective management of agroecosystems more difficult.

The working hypothesis is that better management of agroecosystems is a cost-effective strategy to improve human health. This implies that agriculture must be viewed as ecosystem management, and that the principles of natural resource management are applied to it.

Reference

This excerpt originates from the 1999 publication "Agroecosystem Management for Improved Human Health: Applying the Principles of Integrated Pest Management" published by the International Institute of Rural Reconstruction.

IIRR Bookstore, Publications Unit International Institute of Rural Reconstruction Y. C. James Yen Center Silang, Cavite 4118, Philippines Tel (63-46) 414 2417, Fax (63-46) 414 2420 E-mail: pub-iirr@cav.pworld.net.ph.

Related Editions to The Overstory

• The Overstory #64--Tropical Homegardens
• The Overstory #44--Integrated Systems Approach
• The Overstory #34--Forest Islands, Kayapo Example
• The Overstory #24--Sustaining Physical Health