human incidence of skin cancers and resistance to infectious disease, and the economic consequences of such changes. Such a research project ideally would use data such as the following:

Health Data at national level or in selected localities on deaths from skin cancer, incidence of skin cancer, and incidence of selected infectious diseases

Agriculture Productivity data on selected crops; vegetation density in forests

Economic Value of selected agricultural products in countries or selected localities; health care expenditures

Stratospheric ozone concentration Measured values from satellite observation for selected regions

UV-B incident radiation Measurements at ground level

Policy responses Enactment of policies to limit CFC releases; implementation of such policies; introduction of education campaigns for avoidance of direct exposure to sun; measures of resultant behavior change

Data on these variables are also uneven. A study of the effects of ozone depletion presents some of the same data problems illustrated by the study on the causes of greenhouse gas emissions, as well as others. For instance, data available summarizing political units (e.g., local or country-wide health data) must be compared with data available summarizing physical areas of map grids (e.g., satellite observations of ozone levels or color of vegetation) and with data collected at selected time points (e.g., incidents of UV-B radiation, surveys of individual beliefs or behaviors). Some data, such as satellite images, are available so frequently that techniques of time sampling must be used. Some data, such as that on human health effects or agricultural productivity, may not be available at the desired geographical level or on the precise effect of interest. Data from diverse methodologies, such as remote sensing, survey research, and health records, are generally not available from the same archives or in mutually intelligible form. And finally, some of the effects of interest are as yet unknown, so the monitoring process must leave room for adding other variables and reanalyzing the data.

ECONOMIC AND NONECONOMIC FORCES CAUSING LOSS OF BIOLOGICAL DIVERSITY

The activities most implicated in the loss of biological diversity are influenced by human demographics, technologies, political sys-



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