Examining charcoal and fossil records from across the Amazon basin, Francis E. Mayle and Mitchell J. Power of the
…Many researchers have argued that while the Amazon has seen transition between tropical forest to savanna in the past, human activity — especially fire and deforestation — is creating unprecedented conditions, pushing it towards a "die-back" tipping point towards the end of the century. Mayle and Power counter by citing evidence of past human influence in the region, noting that charcoal records support the notion that pre-Colombian societies burned Amazon forests. While Mayle and Power concede that ancient burning was likely less extensive than it is today, they suggest that dire projections for the Amazon due to climate change alone may be overstated.
"Humans, rather than climate, may have been the key agents of disturbance of Holocene forests in many parts of the basin, especially if 'pre-Conquest'
"Our analysis shows that, notwithstanding floristic changes, the forest biome in most parts of
"A projected temperature increase of 3-8C over the twenty-first century... in combination with drying and forest fragmentation, would be expected to increase water stress and vulnerability to dieback, although this may be offset by higher CO2 concentrations. Of much greater cause for concern should be the unprecedented rates of deforestation, forest fragmentation... and uncontrolled burning, which are much more serious and immediate threats than climate change."
Francis E. Mayle and Mitchell J. Power (2008). Impact of a drier Early-Mid-Holocene climate upon Amazonian forests [FREE OPEN ACCESS]. Phil. Trans. R. Soc. B, DOI: 10.1098/rstb.2007.0026
Satellite photo of Amazon, above Manaus, by NASA, Wikimedia Commons