I imagine most people would be hard put to place Burkina Faso on a map; it neatly fits that clich? of a faraway country of which we know nothing. It is a landlocked state in West africa, a bit bigger than Britain, once a French colony; it used to be called Upper Volta. Burkina is in the Sahel, that semi-arid belt of savannahs, grasslands and dry forest which runs across africa below the Sahara, the transitional zone between the desert to the north and the rainforest to the south.  There is a peculiarity about its economy, which is noticeable if you visit, as I did a few years ago: more than 90 per cent of its energy needs are supplied by wood. The vast majority of the people rely on wood fires to cook the daily meal of millet, and carts stacked high with firewood throng the roads leading to the capital, Ougadougou. They really do. Cart after cart.  This wood is gathered from the countryside, from the dry forest which covers it - or used to. For it has been so overexploited that much of Burkina is now a deforested wasteland, a dusty wrecked moonscape as shocking as anything in the amazon - it simply hasn't been publicised. In the villages I visited, the women who go out at dawn to gather wood were having to go further every year, four kilometres, then five, then six, as the area around each village became exhausted.  These people were visibly, and tragically, trashing their own natural resource base: not only was the forest gone, the soil itself was disappearing. Who could blame them? It was done out of need. They were only trying to survive. But they were consuming their own future. Many were aware of this, of course, and their attempts at reforestation - struggles might be a better word - were moving and inspiring, and I reported on them. But one specific factor means that these struggles will get much harder - population increase.  When I visited Burkina in 2003, its population was just under 13 million. Now it is closer to 17 million. By 2015, it will have doubled - in just 20 years - to about 20 million. (You can find all these figures in the UN's 2010 Revision of World Population Prospects). Then it really takes off. By 2050, according to the UN's central estimate, it will be 46.7 million. If you want to be optimistic, their low variant gives 41.8 million; if pessimistic, the high variant gives you 51.8 million. That's in less than 40 years.  Where on earth, where in God's name, are all these peop