SCOPE OF THIS REPORT

The most pronounced change in the atmosphere, and the one with greatest potential consequence, is the build-up of greenhouse gases. Hence, this report addresses in detail the amounts of greenhouse gas emission and possible ways of reducing them. We limit our discussions mainly to agricultural production itself and, except for ethanol, do not consider the fate of agricultural products once they leave the farm. Many of the findings presented were obtained from a national research program initiated by Agriculture and Agri-Food Canada in 1992.

Besides focusing on greenhouse gases, we also consider several other current atmospheric issues, though in less detail: ground-level O3, ammonia, ultraviolet (UV) radiation from the sun, aerosols, nitrogen oxides, pesticides, and farm-related odors. Wherever possible, our discussion is based on findings from Canadian studies but, where Canadian results are only just emerging, we have drawn on results from elsewhere.

Changes to the global environment may have pronounced effects on Canadian agriculture in the future: changing concentrations of CO₂ may affect plant growth; increasing temperature may allow greater diversity of crops but favor crop pests; changing patterns of precipitation may favor some areas but induce drought in others. Such changes remain hard to predict. Because of this uncertainty and the constraints of space in this report, how agriculture will adapt to future changes is only referred to indirectly; we await results of ongoing research to clarify this issue further.