Strategies for Assessing the Health Impacts of Global Environmental Change

The meaning of the word “environment” is rather elastic. Today, there is an emerging recognition that we must differentiate two qualitatively distinct sources of environmental influence upon human health. One of these two domains is very familiar: there is a range of local physico-chemical and microbiological agents in the environment that are a source of direct-acting health hazard. These direct impacts arise via injury, toxicity, nutritional deficiency or infection. Less familiar, yet more fundamentally important, is the set of ecological and geophysical systems and processes that provide nature’s “goods and services”. These include climatic quasi-constancy, food yields, the supply of clean freshwater, and the healthy functioning of natural ecosystems. These are the foundational systems of the biosphere, and their disruption or depletion can affect health in ways that tend to be less direct, and sometimes less immediate, than the effects of specific “traditional” hazards.