Synergy between land use and climate change increases future fire risk in Amazon forests

Yannick Le Page,George Hurtt,Douglas Morton,Corinne Hartin,Ben Bond-Lamberty,José Miguel Cardoso Pereira,Ghassem Asrar

doi:10.5194/esd-8-1237-2017

Abstract

Abstract. Tropical forests have been a permanent feature of the Amazon basin for at least 55 million years, yet climate change and land use threaten the forest's future over the next century. Understory forest fires, which are common under the current climate in frontier forests, may accelerate Amazon forest losses from climate-driven dieback and deforestation. Far from land use frontiers, scarce fire ignitions and high moisture levels preclude significant burning, yet projected climate and land use changes may increase fire activity in these remote regions. Here, we used a fire model specifically parameterized for Amazon understory fires to examine the interactions between anthropogenic activities and climate under current and projected conditions. In a scenario of low mitigation efforts with substantial land use expansion and climate change – Representative Concentration Pathway (RCP) 8.5 – projected understory fires increase in frequency and duration, burning 4–28 times more forest in 2080–2100 than during 1990–2010. In contrast, active climate mitigation and land use contraction in RCP4.5 constrain the projected increase in fire activity to 0.9–5.4 times contemporary burned area. Importantly, if climate mitigation is not successful, land use contraction alone is very effective under low to moderate climate change, but does little to reduce fire activity under the most severe climate projections. These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change.

Highlights

Tropical forests face an unprecedented suite of environmental changes from regional and global human activities
HESFIRE captured the interannual variability in Amazon fire dynamics, such as the impacts of the 2005 and 2007 droughts (Fig. 2b, Fig. S4 in the Supplement), and the modeled fire size distribution was consistent with observations (Fig. 2c)
The model formulation is in line with key understory fire processes and its performance on a wide range of fire metrics provides a strong basis for evaluating future fire regimes in the Amazon

Summary

Introduction

Tropical forests face an unprecedented suite of environmental changes from regional and global human activities. Regional activities include forest conversion for agricultural land uses (Hansen et al, 2013), forest degradation from logging and fire (Asner et al, 2005; Morton et al, 2013), and fragmentation (Laurance and Williamson, 2001). Climate change is primarily driven by extra-regional activities, as rising greenhouse gas emissions from energy production and transport mostly originate outside of tropical forest regions (Quéré et al, 2016). Forest fires are one potential mechanism for a disturbance-driven dieback of Amazon forests (Balch et al, 2015; Barlow et al, 2016; Cochrane et al, 1999; Longo et al, 2017). Fires during the Amazon dry season result from human ignitions for large-scale deforestation (Morton et al, 2008), shifting cultivation (Thrupp et al, 1997), and agricultural

Methods

Results

Discussion

Conclusion