The last steppes : New perspectives on an old challenge

Proxy global assessment of land degradation using satellite AVHRR measurements of NDVI since 1981 reveals that about 22 per cent of the land surface has been degrading over the last thirty years. The areas hardest hit are sub-Equatorial Africa with outliers in the Ethiopian highlands and the Sahel; the Gran Chaco, Pampas, and Patagonia; the steppes from Moldova eastwards through Ukraine, Russia, and Kazakhstan; the Russian far east and northeast China; and swaths of high-latitude forest. All kinds of land use are afflicted. The data reveal both long-term trends and, also, many reversals; most parts of the world have experienced both greening and browning. Land degradation across the steppes corresponds with the best arable soil in the world-Chernozem, and its dryland cousin-Kastanozem. Both AVHRR and the more detailed MODIS data show that something dramatic happened in the mid-1990s which is not explained by rainfall variability but is probably related to the dismantling of the industrial-scale farming system of the former Soviet Union