United Nations经济和社会事务部 可持续发展

World Meteorological Organization (WMO)

Thank you Mr Chairman,
One of the crosscutting issues at this thematic session on desertification is the impact of desertification on climate change. According to the WMO/UNEP Intergovernmental Panel Climate Change (IPCC) Fourth Assessment Report which was released in 2007, the warming of the climate system is unequivocal. Carbon dioxide-induced climate change and desertification remain inextricably linked because of feedbacks between land degradation and precipitation. Emissions due to land use change include those by deforestation, biomass burning, conversion of natural to agricultural ecosystems, drainage of wetlands and soil cultivation.
The impact of desertification on climate change can be described mainly through the land surface atmosphere interactions since land surface is an important part of the climate system. The interaction between land surface and the atmosphere involves multiple processes and feedbacks, all of which may vary simultaneously. Land use and land cover changes influence carbon fluxes and greenhouse gas emissions which directly alter atmospheric composition and radiative forcing properties.
Changes of vegetation type can modify the characteristics of the regional atmospheric circulation and the large-scale external moisture fluxes. Research results from the HAPEX-Sahel project suggested that a large-scale transformation of fallow savannah into arable crops like millet, may lead to a decrease in evaporation. Changes in forest cover in the Amazon basin affect the flux of moisture to the atmosphere, regional convection, and hence regional rainfall. More recent work shows that these changes in forest cover have consequences far beyond the Amazon basin.
In response to Decision 20 of COP-7 of UNCCD, WMO organized an International Workshop on Climate and Land Degradation in Arusha, United Republic of Tanzania in December 2006, jointly with UNCCD and the Tanzania Meteorological Agency. Among other issues, the workshop focused on the impact of desertification on climate change. Climate variability, climate change and land degradation are intimately linked and are generating unexpected effects such as an increased occurrence of fire-weather conditions in large parts of the globe. To address the impact of desertification on climate change, the workshop made three recommendations:
Monitoring of land degradation as well as climate at different spatial scales should be improved. Global assessments need to take into account the perceived reality of land degradation by local populations.
Innovative and adaptive land management responses to inherent climatic variability and natural hazards (droughts, floods, landslides, sand and dust storms, wildland fires etc.) must be identified and implemented for sustainable land management.
Land management practices in affected areas, particularly in Africa and other developing countries, should focus on improving the amount of rainfall that is used in biomass production. This can be facilitated by unlimited hydro-meteorological data and increased human and institutional capacity building.
Several programmes of WMO including the Agricultural Meteorology Programme, the World Climate Programme and the Hydrology and Water Resources Programme are taking follow-up actions to implement the above recommendations in collaboration with other organizations and institutions working on land degradation around the world.
Thank you.