Weed control for the preservation of biological diversity

Invasions by non-native plants threaten the preservation of many plant and animal species and communities throughout North America. These pest species compete with and displace native plants and animals and may substantially alter ecosystem functions (e.g., fire occurrence and frequency, nutrient cycling). Awareness of these threats among wildland managers has greatly increased in the last decade. In a recent poll of National Park superintendents, 61% of 246 respondents indicated non-native plant invasions were moderate or major problems at their parks. Likewise, over 60% of Nature Conservancy stewards nationwide polled in 1992 indicated weeds were among their top 10 management problems, listing nearly 200 problem species. Over 12% indicated weeds were their worst problem. Weed control programs are now in place in wildlands across the continent, employing techniques ranging from manual removal, mechanical methods, prescribed fire, judicious use of herbicides, the release of biological control agents, and encouragement of native competitors. The most successful endeavors follow an adaptive management strategy in which plans based on the goals of the preserve are developed, weeds that interfere with those goals are identified and prioritized, and control measures are selected and implemented where appropriate. Emphasis is placed on preventing new weeds from becoming established and on early detection and elimination of incipient infestations. Managers must focus on the vegetation or community desired in place of the weeds and periodically re-evaluate whether their programs are moving them toward this objective. Control of weeds in wildlands poses unusual problems not ordinarily met in other systems which offer challenging research opportunities for weed scientists and ecologists.