A new paper published in journal Nature reveals that human land use activity has begun to change the regional water and energy cycles - the interplay of air coming in from the Atlantic Ocean, water transpiration by the forest, and solar radiation - of parts of the Amazon basin. In addition, it shows that ongoing interactions between deforestation, fire, and climate change have the potential to alter carbon storage, rainfall patterns and river discharge on an even larger basin-wide scale.

The research was led by the Woods Hole Research Center (WHRC). Lead scientist Eric Davidson (WHRC) and 13 Brazilian and US colleagues from universities, government and the NGOs, all of whom participated in the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA), produced a framework by which the connections among climate change, agricultural expansion, logging, and fire risk can be evaluated. The framework considers changes in greenhouse-gas emissions, and energy and water cycles. Using it they found signs of transition to a disturbance-dominated regime in the southern and eastern portions of the Amazon basin.

The combination of deforestation, forest degradation, and the effects of climate change are weakening the resilience of the Amazon rainforest ecosystem, potentially leading to loss of carbon storage and changes in rainfall patterns and river discharge, finds a comprehensive review published in the journal Nature.

An international team of researchers examined 100 studies looking at the effects of disturbance and climate change on the functioning of the Amazon Basin. The found that while the Amazon may be resilient to individual disturbances, multiple interacting disturbances - including fire, logging, deforestation, fragmentation, and global and regional climate change - undermines its resilience.
Co-author Jennifer K. Balch says: "One strong sign of a new disturbance regime is the high number of recent large-scale wildfires, which are a by-product of intentional fires in Brazil's "arc of deforestation." These fires are frequent, occurring every few years, compared with every couple centuries in the past. Humans have been part of the Amazon basin forest-river system for thousands of years, but the expansion and intensification of agriculture, logging and urban development, and their synergistic impacts are beginning to stress the natural integrity of the ecosystem.

Main figure, the hydrologic Amazon basin is demarcated by a thick blue line; isopleths of mean daily precipitation during the three driest months of the year97 (in mm; white lines) are overlain onto four land-cover classes.

The researchers warn that events like the droughts that affected vast areas of Amazon rainforest in 2005 and 2010 could worsen if deforestation, forest degradation, and climate change worsen. Both deforestation and forest degradation from fire and logging reduce forest transpiration, which accounts for roughly a third of the moisture that forms precipitation over the Amazon basin. Meanwhile warmer temperatures in the Atlantic reduce the amount of moisture that reaches the basin. Drought exacerbates the risk of fire, which further degrades the forest and releases smoke which disrupts rainfall.

Protected areas and major planned infrastructure. b, The risk of fire by 205096 under business-as-usual deforestation and climate change scenario.

The authors note that current development plans will greatly increase the risk of deforestation and fragmentation across much of the Amazon. Meanwhile a spate of dams could affect the discharge of rivers already impacted by drought.

The researchers conclude will a call for further study to better understand "the trade-offs between land cover, carbon stocks, water resources, habitat conservation, human health and economic development in future scenarios of climate and land-use change."

"Brazil is poised to become one of the few countries to achieve the transition to a major economic power without destroying most of its forests," they write. "However, continued improvements in scientific and technological capacity and human resources will be required in the Amazon region to guide and manage both biophysical and socioeconomic transitions."

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