Terrestrial ecosystems, increased solar ultraviolet radiation and interactions with other climatic change factors.

Based on research to date, we can state some expectations about terrestrial ecosystem response as several elements of global climate change develop in coming decades. Higher plant species will vary considerably in their response to elevated UV-B radiation, but the most common general effects are reductions in height of plants, decreased shoot mass if ozone reduction is severe, increased quantities of some phenolics in plant tissues and, perhaps, reductions in foliage area. In some cases, the common growth responses may be lessened by increasing CO2 concentrations. However, changes in chemistry of plant tissues will generally not be reversed by elevated CO2. Among other things, changes in plant tissue chemistry induced by enhanced UV-B may reduce consumption of plant tissues by insects and other herbivores, although occasionally consumption may be increased. Pathogen attack on plants may be increased or decreased as a consequence of elevated UV-B, in combination with other climatic changes. This may be affected both by alterations in plant chemistry and direct damage to some pathogens. Water limitation may decrease the sensitivity of some agricultural plants to UV-B, but for vegetation in other habitats, this may not apply. With global warming, the repair of some types of UV damage may be improved, but several other interactions between warming and enhanced UV-B may occur. For example, even though warming may lead to fewer killing frosts, with enhanced UV-B and elevated CO2 levels, some plant species may have increased sensitivity to frost damage.