Multiple environmental changes will have consequences for global vegetation. To the
extent that crop yields and pasture and forest productivity are affected there can be
important economic consequences. We examine the combined effects of changes in
climate, increases in carbon dioxide, and changes in tropospheric ozone on crop, pasture,
and forest lands and the consequences for the global and regional economies. We
examine scenarios where there is limited or little effort to control these substances, and
policy scenarios that limit emissions of CO2 and ozone precursors. We find the effects of
climate and CO2 to be generally positive, and the effects of ozone to be very detrimental.
Unless ozone is strongly controlled damage could offset CO2 and climate benefits. We
find that resource allocation among sectors in the economy, and trade among countries,
can strongly affect the estimate of economic effect in a country.