Simulating fire regimes in the Amazon in response to climate change and deforestation

Abstract

Fires in tropical forests release globally significant amounts of carbon to the atmosphere and may increase in importance as a result of climate change. Despite the striking impacts of fire on tropical ecosystems, the paucity of robust spatial models of forest fire still hampers our ability to simulate tropical forest fire regimes today and in the future. Here we present a probabilistic model of human-induced fire occurrence for the Amazon that integrates the effects of a series of anthropogenic factors with climatic conditions described by vapor pressure deficit. The model was calibrated using NOAA-12 night satellite hot pixels for 2003 and validated for the years 2002, 2004, and 2005. Assessment of the fire risk map yielded fitness values > 85% for all months from 2002 to 2005. Simulated fires exhibited high overlap with NOAA-12 hot pixels regarding both spatial and temporal distributions, showing a spatial fit of 50% within a radius of 11 km and a maximum yearly frequency deviation of 15%. We applied this model to simulate fire regimes in the Amazon until 2050 using IPCC's A2 scenario climate data from the Hadley Centre model and a business-as-usual (BAU) scenario of deforestation and road expansion from SimAmazonia. Results show that the combination of these scenarios may double forest fire occurrence outside protected areas (PAs) in years of extreme drought, expanding the risk of fire even to the northwestern Amazon by midcentury. In particular, forest fires may increase substantially across southern and southwestern Amazon, especially along the highways slated for paving and in agricultural zones. Committed emissions from Amazon forest fires and deforestation under a scenario of global warming and uncurbed deforestation may amount to 21 +/- 4 Pg of carbon by 2050. BAU deforestation may increase fires occurrence outside PAs by 19% over the next four decades, while climate change alone may account for a 12% increase. In turn, the combination of climate change and deforestation would boost fire occurrence outside PAs by half during this period. Our modeling results, therefore, confirm the synergy between the two Ds of REDD (Reducing Emissions from Deforestation and Forest Degradation in Developing Countries).

Multi-year MODIS active fire type classification over the Brazilian Tropical Moist Forest Biome

“…The greatest and least number of fires occurred in 2005 and 2009, respectively. The large number of fires in 2005 has been observed by other researchers (Alencar, Nepstad, and Diaz 2006;Morton et al 2008;Silvestrini et al 2011) and is thought to be related to the extensive drought in that year (Espinoza et al 2011;Lewis et al 2011) when drier conditions increased the probability of escaped agricultural maintenance fires Nepstad et al 2001;Alencar, Solórzano, and Nepstad 2004;Alencar, Nepstad, and Diaz 2006) and opportunistic setting of fires to clear forested land (Araujo et al 2009(Araujo et al , 2010. From 2003 to 2010, deforestation decreased by almost 75% (Assunção, Gandour, and Rocha 2013;PRODES 2013;Souza et al 2013), likely associated with the promulgation of a 2008 government deforestation policy and the transparency offered by Brazilian satellite-based forest monitoring efforts (Nepstad et al 2009;Assunção, Gandour, and Rocha 2013).…”

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

“…Satellite observations over the last 40 years have confirmed the importance of these fireclimate-land use interactions (Alencar et al, 2015;Chen et al, 2013;Laurance, 1998), as have paleorecords of charcoal accumulation rates inferred from sedimentary cores (Bush et al, 2007;Cordeiro et al, 2014). Projections of Amazon fire activity also suggest strong synergies between climate change and anthropogenic expansion scenarios (Cardoso et al, 2003;Le Page et al, 2010;Silvestrini et al, 2011), but previous work focuses primarily on deforestation and agricultural burning. These types of fires are managed, burn different types of fuel, and are generally of short duration, thus providing few insights about the ecology of slow-moving, multiday understory fires.…”

Spatial Pattern of the Seasonal Drought/Burned Area Relationship across Brazilian Biomes: Sensitivity to Drought Metrics and Global Remote-Sensing Fire Products

“…In this ecosystem, fire occurrence is usually associated with extreme drought events, as induced by El Niño Southern Oscillation (ENSO) events and with an increasing number of human-induced ignitions due to deforestation, logging activities and expansion of the agriculture frontiers [34]. The climate is typically humid tropical with low seasonal temperature variability and annual precipitations ranging from 1000 to 2000 mm [35].…”