If we are to evaluate changes in natural ecosystems, we need to know more about the inherent stability of those ecosystems. One major difference between those who worry more about environmental damage and depletion and those who worry less is a difference in belief about the stability of the ecosystems within which we live. The worriers are more likely to fear that some man-made change will push over the edge and lead it inexorably away from the recent equilibrium. Economists believe that increased productivity of labour, of capital and of materials have contributed to the enormous increase in per capita income and wealth in the developed world.
Ecologists worry about increasing environmental pollution arising from economic growth.
These two themes come together in the question of the extent to which increases in productivity have arisen as a result of increased environmental pollution and damage. One would use the better developed model as the main model and attach the less developed model to it. We have macroeconomic models of the major developed countries that are detailed and robust. They capture important elements of our economies in significant detail and can describe the past with considerable accuracy while outlining possible future paths in significant detail. We do not have the ecological data, let alone the models, to claim that we could represent the main features of, for example, the Canadian or the US ecosystem in similar detail, with a similar historical base for comparison and estimation.