This article by Jared Diamond in the Guardian asserts that the problems of many of the world's troubles are caused by environmental factors. It lists "environmentally stressed or overpopulated countries" as including Afghanistan, Bangladesh, Burundi, Haiti, Indonesia, Iraq, Rwanda, the Solomon Islands, and Somalia, plus others.
Let's examine a couple of these examples and compare them with countries that don't make the list:
Afghanistan (population density 43 people/sq km) is undoubtedly in a worse state than unlisted country Pakistan (204 p/sq km). They are similarly arid and have issues with water etc. Pakistan, however, has not been fought over by two superpowers and various crazed locals for the last 25 years.
Haiti (population 281/sq km) and Barbados (645/sq km) are similarly located in the Caribbean. Haiti should be better off than Barbados according to the "environmental stress" argument - it conspicuously isn't.
Come to think of it, there is a large country near here with a climate ranging from monsoon to arid, a variety of hostile wildlife, notably poor soil, a chronic water shortage, serious congestion and pollution problems in urban centres and regular bushfire damage caused by inappropriate development policies. You would expect an imminent descent into political anarchy by Mr Diamond's reckoning - actually the worst that's happened is the re-election of Howard.
(Update: I'll read the whole book before I totally condemn the theory - I suspect it may work out better in the long term than the short).