In a fairly optimistic paper published in Biotropica in 2006* Joseph Wright and Helene Muller-Landau suggested that declining rates of population growth in tropical countries, coupled with increased urbanisation “give reason to hope that deforestation will slow, natural forest regeneration through secondary succession will accelerate, and the widely anticipated mass extinction of tropical forest species will be avoided.” Their assertions have been controversial, and have attracted a fair bit of criticism.
In a forthcoming paper** in Biotropica Sean Sloan questions the assumption that declining rural populations is likely to correlate with increased forest cover. Looking at data from both Panama and Bolivia, Sloan questions Wright and Muller-Landau’s fundamental assumption that declining populations will lead to increased forest cover.
I find this issue really interesting. In Puerto Rico, declining rural populations was coupled with an increase in forest cover from about 7% to over 35% in the post-war period. However, this observation is in contrast with the “empty frontier model” of deforestation. The agricultural frontier advances as colonists move into a new area and clear forest land. As soil fertility declines, colonists clear additional land, but many move on as new lands are opened up along the agricultural frontier. Since increasing rural population was responsible for the initial deforestation, it would seem logical that a declining rural population would allow forests to recover. In reality (as Sloan documented) this process is often associated with increased rates of deforestation. Why is this? Primarily because declining populations (and declining soil fertility) often leads to a shift from labour-intensive smallholder operations to less labour-intensive agricultural operations including mechanised cropping or cattle pasture. The expansion of these operations drives both increased deforestation and increased emigration of colonists. Paradoxically, as Sloan noted, reforestation rates are often higher in more densely populated areas.
Large agricultural operations are often driven by government subsidies, which drive further declines in environmental quality. While the environmental kuznets curves observed in eastern North America and Puerto Rico are certainly possible, forces like this are unlikely to be able to override state subsidies which encourage deforestation.
* S. Joseph Wright, Helene C. Muller-Landau. 2006. The Future of Tropical Forest Species. Biotropica 38 (3), 287–301.doi:10.1111/j.1744-7429.2006.00154.x
**Sean Sloan. Fewer People May Not Mean More Forest for Latin American Forest Frontiers . Biotropica (OnlineEarly Articles). doi:10.1111/j.1744-7429.2007.00288.x