Parts of Amazon on the verge of forest-to-grassland shift

Sep 03, 2013

The stability of the Amazon rainforest, and the ecosystem's resilience to widespread deforestation, may be much lower than previously thought. The replacement of stands of trees with grassland changes evapotranspiration rates and atmospheric moisture convergence, which in turn reduce regional rainfall, a feedback effect that could drive further deforestation. Previous research indicated that a dramatic shift from forest to grassland could overtake the Amazon when the total deforested area hits 40 to 50 percent of the forest's current size. New research by Pires and Costa, however, find that the deforestation needed to trigger this equilibrium shift is much lower, closer to just 10 percent.

Using a climate-biosphere model the authors calculated how different parts of the Amazon, such as the forest interior or the border regions, would stand up to deforestation-induced precipitation changes. They find that in different zones of the Amazon the precipitation responds to deforestation in different ways. In some places deforestation causes a linear decrease in precipitation. In some areas, it takes dramatic deforestation to induce a change in rainfall, while in others, slight deforestation results in sharp precipitation declines. The fact that the region's sensitivity to deforestation was found to be significantly higher than previously reported stems from the fact that in addition to the rainforest itself the authors also considered of nearby cerrado, a region of savanna-like vegetation in central Brazil.

The authors argue that to avoid an equilibrium shift, 90 percent of existing forest and 40 percent of cerrado land should be preserved. Presently, around 40 percent of the Amazon is protected area. They suggest that the forests of Bolivia and of Brazil's Pará state are most susceptible to such an equilibrium shift.

Explore further: El Nino-spawned dry spell to hit Philippine food production

More information: Pires, G. and Costa, M. Deforestation causes different subregional effects on the Amazon bioclimatic equilibrium, Geophysical Research Letters. DOI: 10.1002/grl.50570 , 2013 http://onlinelibrary.wiley.com/doi/10.1002/grl.50570/abstract

Related Stories

Brazil says Amazon deforestation at record low

Nov 27, 2012

Deforestation of Brazil's Amazon has slowed for a fourth consecutive year to its lowest rate since authorities began monitoring the world's largest rainforest, officials said Tuesday.

Brazil to do a biodiversity study of the Amazon

Jan 25, 2013

The Brazilian government says it's undertaking a four-year, $33 million study of its vast Amazon rainforest to compile a detailed inventory of the plants, animals and people that live there.

Recommended for you

Meeting to cover cleanup plan for former nuke missile site

2 hours ago

The U.S. Army Corps of Engineers plans to hold a public meeting about a proposal to use vegetable oil to stimulate the growth of naturally occurring bacteria that would clean up groundwater at a former nuclear missile site.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.