Environmental Monitoring
Environmental monitoring detects changes in the health of an ecosystem and indicates whether conditions are improving, stable, or deteriorating. This quality, too large to gauge as a whole, is assessed by measuring indicators, which represent more complex characteristics. The concentration of sulfur dioxide, for example, is an indicator that reflects the presence of other air pollutants. The abundance of a predator indicates the health of the larger environment. Other indicators include metabolism, population, community, and landscape. All changes are compared to an ideal, pristine ecosystem. The SER (stressor-exposure-response) model, a simple but widely used tool in environmental monitoring, classifies indicators as one of three related types:
- Stressors, which are agents of change associated with physical, chemical, or biological constraints on environmental processes and integrity. Many stressors are caused by humans, such as air pollution, the use of pesticides and other toxic substances, or habitat change caused by forest clearing. Stressors can also be natural processes, such as wildfire, hurricanes, volcanoes, and climate change.
- Exposure indicators, which link a stressor's intensity at any point in time to the cumulative dose received. Concentrations or accumulations of toxic substances are exposure indicators; so are clear-cutting and urbanization.
- Response indicators, which shows how organisms, communities, processes, or ecosystems react when exposed to a stressor. These include changes in physiology, productivity, or mortality, as well as changes in species diversity within communities and in rates of nutrient cycling.
The SER model is useful because it links ecological change with exposure to environmental stress. Its effectiveness is limited, however. The model is a simple one, so it cannot be used for complex environmental situations. Even with smaller-scale problems, the connections between stressor, exposure, and response are not understood in many cases, and additional research is required.
Environmental monitoring programs are usually one of two types, extensive or intensive. Extensive monitoring occurs at permanent, widely spaced locations, sometimes using remote-sensing techniques. It provides an overview of changes in the ecological character of the landscape, often detecting regional trends. It measures the effects of human activities like farming, forestry, mining, and urbanization. Information from extensive monitoring is often collected by the government to determine such variables as water and air quality, to calculate allowable forest harvests, set bag limits for hunting and fishing, and establish the production of agricultural commodities.
Extensive monitoring usually measures stressors (such as emissions) or exposure indicators (concentration of pollutants in the air). Response indicators, if measured at all in these programs, almost always have some economic importance (damage to forest or agricultural crops). Distinct species or ecological processes do not have economic value and are not usually assessed in extensive-monitoring programs, even though these are the most relevant indicators of ecological integrity.
Intensive monitoring is used for detailed studies of structural and functional ecology. Unlike extensive monitoring, a relatively small number of sites provide information on stressors such as climate change and acid rain. Intensive monitoring is also used to conduct experiments in which stressors are manipulated and the responses studied, for example by acidifying or fertilizing lakes, or by conducting forestry over an entire watershed. This research, aimed at understanding the dynamics of ecosystems, helps develop ecological models that distinguish between natural and anthropogenic change.
Support for ecological monitoring of either kind has been weak, although more countries are beginning programs and establishing networks between monitoring sites. The United States has founded the Long-Term Ecological Research (LTER) network to study extensive ecosystem function, but little effort is directed toward understanding environmental change. The Environmental Monitoring and Assessment Program (EMAP) of the Environmental Protection Agency (EPA) studies intensive environmental change, but its activities are not integrated with LTER. In comparison, an ecological-monitoring network being designed by the government of Canada to study changes in the environment will integrate both extensive and intensive monitoring.
Communication between the two types of monitoring is important. Intensive information provides a deeper understanding of the meaning of extensive-monitoring indicators. For example, it is much easier to measure decreases in surface-water pH and alkalinity caused by acid rain than to monitor resulting changes in fish or other biological variables. These criteria can, however, be measured at intensive-monitoring sites, and their relationships to pH and alkalinity used to predict effects on fish and other fauna at extensive sites where only pH and alkalinity are monitored.
The ultimate goal of environmental monitoring is to measure, anticipate, and prevent the deterioration of ecological integrity. Healthy ecosystems are necessary for healthy societies and sustainable economic systems. Environmental monitoring programs can accomplish these goals, but they are expensive and require a substantial commitment by government. Much has yet to be accomplished.
Resources
Books
Freedman, B., C. Staicer, and N. Shackell. A Framework for a National Ecological-Monitoring Program for Canada. Ottawa: Environment Canada, 1992.
Periodicals
Franklin, J. F., C. S. Bledsoe, and J. T. Callahan. "Contributions of the Long-term Ecological Research Program." Bioscience 40 (1990): 509–524.
Odum, E. P. "Trends Expected in Stressed Ecosystems." Bioscience 35 (1985): 419–422.
Schindler, D. W. "Experimental Perturbations of Whole Lakes as Tests of Hypotheses Concerning Ecosystem Structure and Function." Oikos 57 (1990): 25–41.
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