Urbanization, tropical deforestation and species extinction

Urbanization alleviates human pressure on forests. Rural-urban migrants abandon marginal agricultural lands allowing the return of forest. In a study just published in Biotropica, S. Joseph Wright and Helene C. Muller-Landau estimate tropical forest losses in the near future. To do so they combine information on rural and urban human population and forest area across countries, recent deforestation rates, human demographic projections, and urbanization trends. They report good news:

Current human demographic trends—slowing population growth and intense urbanization—give reason to hope that deforestation will slow, forest regeneration through secondary succession will accelerate, and a mass extinction of tropical forest species can be avoided. Our projections suggest that more than 33 percent of potential closed tropical forest will remain in forest in 2030. Tropical forests retracted to even smaller areas during repeated Pleistocene glacial events in Africa and more recently in selected areas that supported dense prehistoric human populations. Despite caveats—forest loss is particularly intense in selected endemicity hotspots, old growth forest is being replaced by secondary and logged forest, global change and technology will have unforeseen impacts—these projections and observations provide hope that many tropical forest species will be able to survive the current wave of deforestation and human population growth. The long time lags observed between habitat loss and species extinctions favor this possibility, providing time for secondary forests to mature and reestablish habitat suitable for forest residents.

Artificial attempts to provide a livelihood for the rural poor in situ make little sense. They take resources from urban dwellers and give them to rural dwellers. Among other undesirable consequences, these schemes retard urbanization and damage biological resources.