Appropriate Ecology: A Modest Stress-Strain Proposal

There is a worldwide need for straightforward scientific methods usable at a local political level for estimating the relative sensitivities and resiliencies of complex biological systems to human abuse. Such methods should give predictive quantitative advice to land-use decision-making.

It is possible to stress whole natural communities with a graded range of appropriate abuses, and to observe the resultant strain as a change of some key community function. I have used photosynthesis, community respiration, and plant-community cover to measure the response of benthic, planktonic, and salt-marsh communities to stresses including heavy metals, sewage treatment effluents, crude petroleum, induced siltation, and mechanical disturbance.

The stress-strain curves are mathematically simplified to yield two measures: (1) the half-effect, a value of stressor needed to reduce community function to half its natural value; and (2) the slope, the rate of change of function per unit (or In unit) stressor. These values characterize sensitivity, and the rates at which each changes through time give measures of resiliency of the community.