To distinguish between these hypotheses, a group of Swedish and Malagasy researchers led by Thomas Elmqvist of Stockholm University decided to try to correlate changes in Madagascar’s forest cover with local population densities and customary laws. Their results have just been published in the Public Library of Science.

Dr Elmqvist and his colleagues collected their information on forest cover from space ...

Different parts of Androy exhibited different patterns. The west showed a continuous loss. The north showed continuous increase. The centre and the south appeared stable. Damagingly for the population-density theory, the western part of the region, the one area of serious deforestation, had a low population density.

This is not to say that a thin population is bad for forests; the north, where forest cover is increasing, is also sparsely populated. But what is clear is that lots of people do not necessarily harm the forest, since cover was stable in the most highly populated area, the south.