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Independent of climate, forest cover in southern Amazon may fall to 20% by 2016

Independent of climate, forest cover in southern Amazon region may fall to 20% by 2016

Global warming aside, southern Amazon forest cover may fall to 20% by 2016

Rhett A. Butler,
September 3, 2008

Forest cover in the “Arc of Deforestation” of southern Amazonia will decline to around 20 percent 2016 due to continued logging and conversion of forests for cattle pasture and soy farms, report researchers writing in the journal Environmental Conservation. The results are independent of impacts resulting from climate change, which some researchers say could dry the Southern Amazon and turn it into a tinderbox.

Analyzing high resolution satellite data from 1984 through 2004 for the Alta Floresta region in northern Mato Grosso, Fernanda Michalski, Carlos Peres and Iain Lake of the University of East Anglia found that forest cover declined from from 91.1 percent to 41.7 percent between 1984 and 2004. They note that while the deforestation rate has slowed to around 2 percent per year since peaking at more than 8 percent annually in late 1980s to mid-1990s, renewed expansion of road networks will enable loggers to increasingly exploit remaining forests, leading to degradation and likely eventual conversion for agricultural use. Overall Michalski and colleagues forecast that forest cover in Alta Floresta will fall to 21 percent by 2016, a decline of 77 percent since 1984.

A series of land-use maps representing the evolution of the landscape structure in the Alta Floresta region at four-year intervals throughout through study period. Land-cover classes are represented by water (W), forest (F) and non-forest (NF). Courtesy of Michalski et al (2008)

The authors’ projections are based on a model that incorporates regional deforestation rates, changes in forest structure, and socioeconomic drivers of deforestation in the study area over the 20-year period. The results “indicate a critical threshold at 51% of forest cover in which landscape structure and connectivity changes abruptly.” Now that forest cover has dipped below this level the authors believe cover will trend downwards. To reserve course and maintain forest cover, Michalski and colleagues suggest that “environmental law enforcement, land-use planning and education programs” need to be effectively implemented.

“We suggest that the current proportion of forest cover should be maintained by ensuring the continuation of readily available data from satellite monitoring as well as in situ law enforcement of Brazilian forest legislation, especially during the dry season when most of the deforestation takes place,” they write.

Forest cover and predicted between 1984 and 2016 in the study area.

Drivers of deforestation in Alta Floresta

Counterintuitively the authors found a positive correlation between population density and forest cover during the early part of the study period. This occurrence stems from a gold rush which attracted large numbers of speculators and colonists. After easily accessible gold deposits were exhausted around 1994, the population of the area decreased significantly. The human population only began to rebound around 2000. In contrast, the Michalski and colleagues found a strong correlation between deforestation and distance to roads as well the number of head of cattle, indicating that cattle ranching is a significant driver of deforestation. Roads facilitate access for logging and subsequent conversion to pasture and agricultural land.

Failing to curtail deforestation in the region will have significant ecological impacts and may impair the Brazilian government’s plan to promote sustainable development, the authors warn.

“If observed deforestation probabilities remain unchanged, we predict that only 21% of the forest cover will remain in the study region by 2016, well below estimates of sustainable forest cover in the Amazon based on metrics of landscape structure, ecosystem services under future climate change scenarios, and current levels of bird and mammal species persistence,” Michalski and colleagues write. “If current rates of deforestation continue in this region, the region will reach a critical point where local extinctions of forest species will rapidly accelerate.”

“Aggressive colonization frontiers can rapidly reach critical landscape structure thresholds beyond which more benign land-use alternatives such as the creation of new protected areas are no longer available unless significant efforts in capital-intensive habitat restoration can be deployed,” the authors continue.

“A more cost-effective preventative approach should be followed based on greater enforcement to achieve wider compliance of private landholders with existing environmental laws. Additionally, the creation of protected areas in public land and environmental education of landowners in private areas can help maintain and conserve forests and biodiversity,” they conclude.

Fernanda Michalski, Carlos Peres and Iain Lake (2008). Deforestation dynamics in a fragmented region of southern Amazonia: evaluation and future scenarios. Environmental Conservation 35 (2): 93-103 doi:10.1017/S0376892908004864

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