HUMAN societies have been degrading the land for more than 10 000 years. Change forest to grassland and you lose most of your soil. Plough up the grassland and you lose most of the rest. But we still feed the world 鈥� just.
Greens would call most of the changes 鈥渦nsustainable鈥�, but we must be doing something right. Land Degradation has an intriguing subtitle: 鈥淐reation and destruction鈥�. Throwing aside some of the cruder environmental presumptions, it offers the idea that land degradation can sometimes be a positive, intentional and 鈥渟ustainable鈥� process. We all know it is true, of course. Without the destructive/creative use of the axe and the land drain, there would be precious little dry and clear land for more than 55 million Britons to live on, but it sometimes seems politically incorrect to admit such a truth. The point is that some 鈥渄estruction鈥� works, and some does not.
This well-written, cogently argued book is rich in examples. It is important to see the distinction between, say, the ecological carnage caused by the draining of the Aral Sea for irrigation and the success story of draining wetlands to create the Netherlands. Or, in the rainforests of Borneo, between the largely sustainable practice of cutting down trees for shifting cultivation and the wreckage created by much mechanised forestry.
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The structure of the book reinforces the message. Most authors tackling this topic would work, chapter by chapter, from forests, through grasslands to deserts. But here the emphasis is on categorising the degradation, rather than the land. We have chapters on 鈥渦nintentional destructive change鈥� and 鈥渃reative destruction鈥�. It ends ambitiously with eight principles for successful land management. Everything is here: harbours and mining, deforestation and terraces, Chinese ponds and the Norfolk Broads, coral reefs and Chernobyl. The book effortlessly pans from the slow processes of geomorphology to the social organisation of primitive hunters and finally to modern irrigation technology.
We see the destruction of the fertile fields of ancient Mesopotamia from salt build-up. But we see the virtue of cutting terraces into hillsides 鈥� a destructive and intensive form of farming if ever there was, but productive and sustainable. The book analyses hard cases. Should we praise the Aswan Dam for increasing the potential for irrigation in Egypt, or mourn the fate of 100 000 Nubians flooded from their lands and fear for the future as the delta dies because it is deprived of silt? It is a shame that the index is lousy.
A much more limited stab at the same issue is provided in Changes in Land Use and Land Cover, a collection of reports from a workshop held in 1992. It is both grindingly workmanlike in its survey of the field, and in places, curiously lacking in rigour. Thus a 鈥渃ase study鈥� of Africa鈥檚 Sahel simply asserts that drought was not to blame for its desertification in the 1970s and 1980s. Social changes were the true cause, it says. Maybe, but it is hard to square this with its recovery in the 1990s. Did the social changes go away just as the rains returned?
Many parts are dull repetitions of current dogma. The livelier chapters are the ones least trapped in an academic rut. The chapter on technology by Arnulf Grubler, for instance, is fun, eye-opening and full of wild graphs. We learn from it that as early as 1600, Chinese agriculture 鈥渇ed 15 people per hectare of cultivated land, which far exceeds even present European land productivity levels鈥�. And that 鈥渁ctual manmade structures 鈥� the physical manifestations of our age 鈥� most likely do not cover more than 0.4 per cent of the land area鈥� of the planet. So plenty of room to go yet.
Watershed Management in India is a curious confection: good on traditional methods of 鈥渉arvesting鈥� water in the desert, trenchant in defence of the maligned eucalyptus tree, and plain batty in its espousal of a National Waterway Grid. It quotes Samuel Johnson and the Koran, and contains the alarming fact that floods carry away 12 billion tonnes of soil from India every year. In any language, that sounds like land degradation.
Land Degradation by Douglas L. Johnson and Laurence A. Lewis, Blackwell, pp 335, 拢19.99
Changes in Land Use and Land Cover by William B. Meyer and B. L. Turner II, Cambridge University Press, pp 537, 拢35
Watershed Management in India by J. V. S. Murty, Wiley Eastern, New Delhi, pp 197, Rupees 600