The agricultural ecosystem

 An ecosystem is defined as all the organisms (animals, plants, microbes) in a certain habitat, plus also the environment that they live in (such as the soil, a pond, or a mountainside).  Natural ecosystems usually contain hundreds or thousands of species of organisms and are thus very complex in their functioning.  In contrast, an agricultural ecosystem (such as a corn field or an orchard) is relatively artificial, being modified and controlled by humans.  It contains fewer species and thus is simpler in its functioning.

But simpler is not really better.  A complex natural ecosystem, with its many species, operates with an intricate “web” of interrelationships among the species.  They can be pictured in a very simplified diagram:

These are the basic steps in a food chain.  Plants use soil nutrients, water and carbon dioxide from the air, and with the sun’s energy, they produce food that nourishes animals and humans.  But there are a few more vital steps:

In order to be sustainable, wastes and other organic matter are recycled and broken down by microbes (bacteria, fungi, protozoa) and some larger organisms (worms, insects) into soil humus and simple nutrients, which are then available for the plants to use.  It’s a beautiful, self-sustaining system, with each species doing its “job.”

Of course, within each of the large categories (“plants,” “animals,” “microbes”) are dozens or hundreds of species, each with slightly different activities.  For example, in a forest there are many types of trees, shrubs, vines, “wildflowers,” grasses, ferns, mosses, mushrooms, earthworms, roundworms, ants, beetles, flies, caterpillars, salamanders, birds, mice, squirrels, moles, raccoons, deer, coyotes . . . and so on.  Some eat certain other species, only to themselves be eaten by others in the food chain.

Because a natural ecosystem has so many interactions among its species, it is quite stable, able to withstand disturbances such as a damaging storm or a drought.  So, if one or several species are largely killed off, there are others that can take over their function in the system.  Thus a natural ecosystem is sustainable, able to continue indefinitely.  The variety of species in nature is often called “biological diversity,” or “biodiversity.”

Natural ecosystems also perform a number of functions that benefit humans, called ecosystem services.  These may include moderating the local weather (less extreme temperature and humidity), less severe flooding (by soaking up heavy rains), cleaning up polluted water, control of plant pests and diseases by their natural enemies, disposing of dead plants and animals, making the soil more fertile, and pollination of many plants.  In fact, we might say that human civilization would not exist without these free services of nature.

In contrast, the simplified agricultural ecosystems that humans create have relatively few species of plants and animals, primarily only the one type of crop plant or animal that the farmer wants to grow.  And, especially in conventional farming systems, just about any other species that dares to enter the field or barn is considered “the enemy” and liable to be exterminated by poisons.

Ecosystems with few species are easily disrupted by outside forces.  An invasion of a crop pest such as aphids or caterpillars will likely spread and ruin the crop rather than being controlled by predatory insects (ladybugs, wasps) or birds, as when the farmer leaves areas of natural ecosystem near his fields.

The soil on conventional farms has often been nearly sterilized by toxic chemicals or strong fertilizers, and is often very low in organic matter (humus).  Both humus and large numbers of soil organisms work to (1) make soil porous and well-aerated, (2) provide a good balance of soil nutrients to the growing crop, (3) protect  roots from soil-borne diseases and pests, and (4) reduce soil erosion.

Plants that grow in good, rich soil are likely to be healthy.  Healthy plants are able to resist or repel most pests and diseases, by means of  various processes analogous to the way our body’s immune system protects us from diseases.  And healthy plants also produce more nutritious food for animals and humans.  Eating a diet of healthful, nutritious food will help keep us healthy and reduce health-care expenses.  It’s a win-win system.

Considering the many benefits of healthy crops, good soil and a diverse ecosystem, it only makes sense for the farmer to do as much as possible (or feasible) to work with natural processes and receive the rewards of better soil, plants and animals.  Higher quality crops and animals can also command higher market prices, making farming more profitable.

Some ways a farm can be made to function in a more ecologically sound manner include:

1. Treat the soil as the valuable resource it is by improving its ability to grow healthy crops.  Recycle manure, crop residues and/or compost.  Avoid the use of strong fertilizers and toxic chemicals.
2. Encourage nearby natural ecosystems, such as grassy fence-row vegetation, field corners, and nearby meadows, woods and marshes.  Build bluebird and wren houses.
3. Plant more than one crop species at once (or consecutively).  Various cover crops and interplanted crops can smother weeds and supply nutrients to other crops (as with legumes supplying nitrogen), and if tilled into the soil, cover crops can supply humus and nutrients to the soil.  Crop rotations also provide similar benefits.
4. Diversify the farm by raising a variety of crops and animals.  Not only can diversity protect against bad weather and volatile markets, but a variety of species is a closer approximation of a natural ecosystem than is a monoculture of one or two crops and no animals.

A wise farmer should be an applied ecologist, aware of the variety and functions of both wild and domesticated plants and animals, and especially aware of the importance of good, “healthy” soil.  Don’t develop the profit-seeking, control-nature mindset that pervades high-tech agriculture.  Be a steward of the land.