Human land use of the Amazon basin has begun to change the regional water and energy cycles, says a new report, which also notes that continued interaction between deforestation, fire, and climate change have the potential to drastically alter carbon storage, rainfall patterns, and river discharge on an even larger basin-wide scale.
All of these changes are combining to create a “disturbance-dominated regime” in the southern and eastern portions of the Amazon basin.
In their book “Ecological Engineering Design: Restoring and Conserving Ecosystem Services”, Marty D. Matlock and Robert A. Morgan describe a “disturbance-dominated regime” thusly;
“Frequent disturbance events become defining characteristics, resulting in disturbance-dominated ecosystems, such that their primary species pool is dictated by the frequency and intensity of disturbance events.”
Co-author of the new study, published in the current edition of the journal Nature, Jennifer K. Balch notes that “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.’” She emphasizes that these fires “are extremely frequent, occurring every few years, compared with every couple centuries in the past.”
The research, led by the Woods Hole Research Center (WHRC), was the result of a framework produced by lead scientists 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).
The framework allowed the scientists to evaluate the connections among climate change, agricultural expansion, logging, and fire risk by considering changes in greenhouse-gas emissions, and energy and water cycles.
They found all the signs pointing towards a change to a disturbance-dominated regime.
Why is any of this important?
Because even though humans have been a part of the Amazon basin forest-river system for thousands of years, our expansion and intensification of agriculture, logging and urban development – as well as the interplay between them – are beginning to stress the natural integrity of the ecosystem.
Once again, why is this important?
Because the Amazon River produces approximately 20% of the world’s fresh water discharge and the Amazon Forest itself holds about 100 billion tonnes of carbon dioxide, which equals 10 years’ worth of global fossil fuel emissions.
Subsequently it is vitally important that the economic development in the region must play out along a sustainable path so that there is no further degradation of such a fragile and important ecosystem.
“The studies in this review, document changes in river flow, sedimentation in rivers, and lengthening of the dry season in the southern and eastern flanks of the Amazon Basin,” notes Dr. Davidson. “Whether similar changes are likely to occur in other parts of the basin will depend on the interplay of management decisions and the impacts of climate change during the next few years and decades.”
Resilient Only To a Point
The work shows that while the Amazon Forest is resilient to at times considerable climatic variation from year to year, it can only be pushed so far, and severe or prolonged drought can exceed this resiliency.
And while efforts in Brazil to curb deforestation have succeeded on the whole – reducing the clearing of forests in the Amazon basin from nearly 28,000 km2 per year in 2004 to less than 7,000 km2 in 2010 – the increase in wildfires has not decreased.
Source: Woods Hole Research Center