VEGETATION CHANGES

Each plant species or natural vegetation region (biome) occurs within a particular climatic range. Some of the climatic factors that limit plant distribution include rainfall amounts and seasonality, and minimum and maximum temperatures in summer and winter. The South African Country Study investigated the effects of climate change on 44 indigenous plant species and on the biomes as a whole. The researchers compared distribution maps of the plants and biomes with maps of various climatic factors. This enabled them to compile profiles of preferred climatic conditions for each biome and plant species. They then compared these profiles with maps of predicted climatic conditions in 2050 to construct future distribution maps for the biomes and plant species.

MORE THAN JUST CLIMATE

Although climate is important in determining where particular plants can grow, it is not the only factor. Soil types, fire, pests, grazing and competition from other plants all play a role. Furthermore, agriculture and urbanisation have fragmented many natural areas, reducing them to islands in a sea of development. Even without the above limitations, we do not know how quickly plants will be able to disperse into new areas, and whether they will be able to keep pace with shifting climates. Predictions based on climatic factors alone represent a first approximation of possible future plant distributions in South Africa. As the actual story unfolds, the patterns that emerge may be different, reflecting many of the interactions that influence where plants grow. What is of concern is that these other factors are likely to restrict plant distributions even further than the climate-based predictions in this report.