Ecological Integrity

Indicators of ecological integrity vary widely in their scale, complexity, and intent. For example, certain metabolic indicators can suggest the responses by individual organisms and populations to toxic stress, as is the case of assays of detoxifying enzyme systems that respond to exposure to persistent chlorinated hydrocarbons, such as DDT and PCBs. Indicators related to populations of endangered species are relevant to the viability of those species, as well as the integrity of their natural communities. There are also indicators relevant to processes occurring at the level of landscape. There are even global indicators, for example, relevant to climate change, depletion of stratospheric ozone, and deforestation.

Sometimes, relatively simple indicators can be used to integrate the ecological integrity of a large and complex ecosystem. In the western United States, for instance, the viability of populations of spotted owls (Strix occidentalis) is considered to be an indicator of the integrity of the types of old-growth forest in which this endangered bird breeds. If plans to harvest and manage those forests are judged to pose a threat to the viability of a population of spotted owls or the species, this would indicate a significant challenge to the integrity of the entire old-growth forest ecosystem.

Ecologists are also beginning to develop holistic indicators of ecological integrity. These are designed as composites of various indicators, analogous to certain economic indices such as the Dow-Jones Index of the stock market, the Consumer Price Index, and gross domestic product indices of economies. Composite economic indicators like these are relatively simple to design because all of the input data are measured in a common way, for example, in dollars. However, in ecology there is no common currency among the various indicators of ecological integrity, and it is therefore difficult to develop composite indicators that people will agree upon.

In spite of the difficulties, ecologists are making progress in their development of indicators of ecological integrity. This is an important activity for ecologists, because people and their larger society need objective information about changes in the integrity of species and ecosystems so that actions can be taken to prevent unacceptable degradations. It is being increasingly recognized that human economies can only be sustained over the longer term by ecosystems with integrity. These must be capable of supplying continuous flows of renewable resources, such as trees, fish, agricultural products, and clean air and water. There are also important concerns about the intrinsic value of native species and their natural ecosystems, all of which must be sustained along with humans. A truly sustainable economy can only be based on ecosystems with integrity.