Effects of climatic change on soil processes

Effects of expected climate change on soil processes, especially in the Tropics and Subtropics. was the subject of a workshop organized by UNEP, CTA and the International Society of Soil Science (ISSS) in Nairobi from 12-14 February 1990. This was followed (15-17 February) by an ad hoc consultation meeting on 'Assessment of global desertification: status and methodologies.. Dr M K Tolba, Executive Director of UNEP gave an overview of the current situation and alternative future scenarios, stressing the determination of UNEP to help in the assessment of consequences by predictive analysis of the effect of expected climatic changes on soil processes and possible soil degradation. The workshop began with overviews on the historical development of climate and its relations to the smaller but more reactive biochemical cycle and the larger but strongly buffered geochemical cycle, which changes only slowly. There were also reports on the inputs of soils and agriculture to the greenhouse effect and to changing climate. This was followed by a geographical analysis of the expected changes of soil properties In various regions of the world (sub-polar, boreal, subboreal. Mediterranean/subtropical and tropical) with special emphasis on the African, Latin American and South-east Asian environments. Certain soil characteristics are bound to be affected by changing climate: soil moisture; texture, structure and erosion; secondary clay minerals; soil pH and Eh (redox potential); salinization and alkalinization; and soil organic matter content in response to changes in decomposition, recycling and biological activity. All these were discussed, as was the influence of changing climate on problem soils, especially those typical of the densely populated alluvial regions. The effect of climate changes on the yield potential of major cropping systems and soil vegetation interactions was also considered. Attention was also focussed on the interacting effect of man-made pollution and the physical effects of predicted sea level rises on global soil changes. Existing modelling systems were scrutinized and management possibilities for curtailing trace gas emissions by the creation of new sinks and by changing management from slash and bum to more sustainable agricultural land use systems. Three working groups on major problem areas considered research priorities. Among their conclusions were that climate changes are more likely to be apparent in cold and temperate regions than in the tropics but that exceptions will be coastal swamp and montaine regions in the tropics, irrigated areas, semi-arid regions, deforested areas and natural wetlands. Long-term monitoring to detect ecologically relevant changes related to climate change and modelling to derive predictions for management are vital for these zones that are most at risk. Data required from climatologists will include estimates of year to yearend month to month variability in mean and annual temperature and especially in rainfall. Also, the ecologists and crop production physiologists will need to measure effects of increased carbon dioxide levels on organic matter return to the soil and, in addition to quantity, qualitative aspects of the organic matter (possible changes in biodegradability) should be considered. One of the working groups emphasized in their conclusions that perhaps the essential overriding processes are those termed 'anthropogenic': the implications of man'. influence on soil processes and ecosystems are such that they tend to overshadow attempts to deal with natural ecosystem' and climate-induced changes. They have the potential to change the course of civilization if ignored. The full recommendations of the three working groups on major problem areas will appear in the proceedings of the workshop which will serve as an up-to-date reference for soil scientists and for governments.Effects of expected climate change on soil processes, a workshop organized by UNEP, CTA and the International Society of Soil Science (ISSS) in Nairobi from 12-14 February 1990. This was followed (15-17 February) by an ad hoc consultation meeting on 'Ass