ocr: Since most of Algeria is desert or semi-desert, over 90% ofthe population is torcedto live on the remaining 20% ofland. The desert is moving northward. Vegetation has been stripped for useas firewoodand animal fodder, leaving fragile soils exposed which then require expensive specialized care to conserve them. Water purification techniques are below standard and rivers are being increasingly contaminated by untreated sewage,industrial etluent and wastes from petroleum refining.
