Evolution Diary

A new study shows that although loss of tropical dry forests occurs in southern Madagascar, there are also large areas of forests regenerating. The return of forest cover was found to be substantial in the study area, with an overall net increase of 4 % during the period 1993-2000. These dry forests have the highest level of plant endemism (species found only in a particular region) in all of Madagascar and are listed as one of the 200 most important “ecoregions” of the world. The study also shows that the relationship between human population density and deforestation is much more complex than previously thought.

“We were surprised to find the highest deforestation rates in an area with low human population density and large distance to markets, while the area with highest population density had stable forest cover,” says Thomas Elmqvist, Professor at the Stockholm Resilience Centre, Sweden.

The results, based on analyses of satellite images and vegetation on the ground, surprised the team of scientists from Sweden and the University of Antananarivo in Madagascar. As a result, they went further and also made a social inventory based on interviews with local forest officials and villagers. This inventory revealed that loss of forest occurred mainly in areas with insecure property rights, while areas with well-defined local norms, rules and property rights for forest management showed either regenerating or stable forest cover.

“Regeneration of tropical forests has so far mostly been studied by ecologists trying to understand factors like seed dispersal and soil quality, our study clearly shows the importance of an increased understanding also of the social context behind forest regeneration,” says Elmqvist. The loss of tropical forests is a concern worldwide since these forests harbor more than 50 % of the terrestrial species richness in the world and have a large importance in global climate regulation. Estimates of tropical forest loss are still uncertain and a 50 % margin of error appears possible. However, scientists know even less about regeneration of tropical forests.

“We now know a fair amount about the human social context in which tropical forest loss is embedded, but very little is known about the role of social institutions in influencing regeneration of tropical forests,” says Maria Tengö from Stockholm university and one of the authors behind the new study.

The new study points to the large capacity of dry tropical forests to spontaneously regenerate if existing local rules and norms (including well-defined property rights) mitigate other drivers of deforestation and alternative land-use.

Citation: Elmqvist T, Pyykönen M, Tengö M, Rakotondrasoa F, Rabakonandrianina E, et al (2007) Patterns of Loss and Regeneration of Tropical Dry Forest in Madagascar: The Social Institutional Context. PLoS ONE 2(5): e402. doi:10.1371/journal.pone.0000402 http://www.plosone.org/doi/pone.0000402

Note: This story has been adapted from a news release issued by Public Library of Science.

Reposted from Science Daily