Ecology for Gardeners

Even a relatively small garden is a miniature ecosystem. It includes a surprising diversity of organisms that interact in a myriad of ways. Some are permanent residents, others come and go in search of a meal or a mate. An insect feeding on a garden plant is simultaneously hunted by predators and weakened by parasites; it competes with other herbivores for choice food plants; it is hindered in its feeding by the plants' chemical and physical defenses; and it challenges other members of its species for the best mates and locations for egg-laying. Ecologists Carroll and Salt argue that the more completely we understand these interactions, the better gardeners we become. The authors cite hundreds of examples drawn from personal experience and from literature on gardening and ecology.

Gardeners are faced with numerous difficult decisions: choosing which plants to grow, encouraging beneficial organisms and discouraging pests, caring for the soil and water, and so forth. Furthermore, even beneficial gardening activities often seem to compete for common resources or conflict with one another. Thus, it is important that a gardener evaluate the environmental impact of gardening practices holistically and globally. Holistic analysis means that all costs and benefits of practices and equipment should be taken into account, not just the immediately apparent aspects. For example, a gardener should consider the ultimate impacts of the production, packaging, transportation, application, use, and final disposal of all tools, equipment, and material used. Global analysis means that environmental costs or benefits that are remote to the garden and gardener in time or space should be identified and considered. For instance, the costs of obtaining raw materials and manufacturing a piece of equipment or supplying fuel or electric power may be remote to a particular garden, but they are just as consequential as are more immediate and obvious fuel consumption, noise, and local pollutant output. Out of sight, out of mind — but not out of existence! Failure to think and act both holistically and globally may result in a gardener (or anyone else, for that matter) short-sightedly adopting apparently good practices that are actually more harmful than others.

For example, a gardener might decide to replace a gasoline-powered piece of machinery with an electrical one with the goal of reducing the environmental impact. However, it should not be forgotten that the power plant generating the electricity might burn fossil fuels and release pollutants and that there are usually great losses of energy during long-distance transmission of electricity. Also to be considered are substantial inefficiencies both in the generation of electricity and its conversion into mechanical power. It is possible that a clean, quiet, electrical machine won't look so much better than a noisy, polluting, gasoline-powered one after a global and holistic analysis of all factors. Of course, human sweat-powered machines are much more energy efficient than any engine-powered ones, and the fuel that they burn may be potentially life-threatening fat deposits. So, a gardener may ultimately decide to use a hand tool instead of an engine-powered one and work out in the garden instead of at the health club.

Other cost-benefit analyses may focus on the extent of use (or nonuse) of pesticides and fertilizers. All substances applied in the garden — including organic ones — impose substantial environmental costs in their production, transportation, distribution, use, and disposal, yet few gardeners and virtually no farmers are willing to forswear their use. The ecologically astute gardener or farmer will, however, weigh the costs and benefits of all alternatives for pest control and plant nutrition and make decisions that optimize the trade-off between environmental costs and economic or aesthetic benefits.

Aesthetic benefits may impose other costs as well. No responsible person would knowingly turn loose a plague in his or her neighborhood, yet many gardeners frequently risk disrupting local ecosystems by planting beautiful but potentially invasive exotic ornamentals. Purple loosestrife entered this country as an ornamental and still is a beautiful ... plague. At the least, a wise gardener should seek information about the biological characteristics of a candidate garden plant that might make it an aggressive weed, such as spread by underground runners or rhizomes, production of wind-blown or bird-carried seeds, prolific self-reseeding, and so forth. This is not to say that all — or even most — exotic plants are environmentally hazardous, but an ecologically minded gardener would certainly want to identify those that likely are and avoid them, or at least take pains to prevent their spread.