BOOK REVIEW / The desert that bloomed with human invention: More People, Less Erosion - Mary Tiffen, Michael Mortimore and Francis Gichuki: John Wiley, pounds 22.50

THIS IS a book to make one whoop with joy with its tumbling insights, heaped anecdotes and nit-picking evidence that triumphantly give the lie to much modern misanthropic nonsense.

The book retails a 60-year history in which gloomy expectations went unfulfilled. In the Thirties there was general despair among the British colonial authorities that a district called Machakos, near Nairobi, was fast eroding. It was overgrazed by cattle, and the local people, the Akamba tribe, looked likely to face more or less continual famine on their leached soils. The officials took photographs of bare hillsides to prove their point, and these are the 'before' half of the book's many pairs of pictures. Miracle of miracles, the 'after' shots - taken in the early Nineties - show neat terraces, greenery, and trees. Its 200km by 60km is home to more than a million people, five times as many as in the Thirties, and the inhabitants are better and more securely fed than their forebears.

Nor, say the authors, is the Machakos' experience unique: other African peoples and hot, dry places have proved highly adaptive. As their population grew, human ingenuity responded by massively increasing the power of the land to grow food. Indeed, the book argues that population pressure can release in people the spirit of innovation which ensures that they are richer, not poorer, as the pressure mounts. The authors - researchers at the Overseas Development Institute and Nairobi University - find themselves quoting with approval the work of Julian Simon, who has for years controversially suggested that high and rising populations are a force for good.

This book surveys practically every factor anyone has ever considered in attacking Third World poverty. The authors remind us that native farmers are right to be cautious of innovations recommended by experts who got a good deal wrong before. Over and over, they suggest outsiders should remember to listen.

This is not new advice (Robert Chambers became famous by being eloquent on the theme), and part of the refreshing charm of this book is that it also suggests, a little unfashionably, that outsiders can be useful. Other factors that helped in Machakos were travel, which broadened many of the farmers' minds; that they got into cash-earning crops for export; that the Kenyan government didn't steal half their earnings in the name of socialism or anything else; that their land was near enough to the capital to allow people to go off and earn money in hard times; that the whole tribe and its members were secure in their landholdings.

The Akamba people remain poor. They need better roads and want electricity. They knew early on that education was the ticket to everything, not least because it allowed youngsters to gain the jobs that freed them from farming's uncertainties while enabling them to send money home to capitalise the farm improvements. The Akamba are learning fast that in the modern world having fewer children makes good sense.

I like this book so much because it says people are life-enhancers, and that, given half a chance, even dirt-poor people invest in their land. It does not decry capitalism. It celebrates decent government. It suggests that there are ways foreign aid can help poor countries. Above all, it gives us clues about how Africa can overcome its basket-case reputation. It does all this with low-key authority. It has 'classic' written all over it.