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Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with

Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin., Humans have been part of the vast forest-river system of the Amazon basin for many thousands of years, but expansion and intensification of agriculture, logging and urban footprints during the [...]

Many researchers concerned about the enormous ecological impact of deforestation in the Amazon have turned their attention to this rich biome, which is the largest tropical forest in the world. [...]

Although still the largest expanse of tropical rainforests in the world, the Amazon is suffering a declining capacity to deliver ecosystem services, to which the widespread use of fire is one of the main contributing factors. Even if fires directly affect the timber sector, most current logging practices often tend to increase rather than mitigate the problem. We argue that in order to involve the timber sector in fire mitigation policies in the Amazon it is crucial to assess the economic impact of fire on the sector. This paper describes EcoFire (Economic Cost of Fire), a spatially explicit model for valuing the economic losses to sustainable timber harvest operations in the Brazilian Amazon as a result of fire. To conduct this analysis, we have integrated a set of models that simulate the synergy between logging and fire spread and intensity. Our results show that fire affects roughly 2% of the timber production areas that would be harvested between 2012 and 2041. In burnt areas, fire causes losses on average of US$39 ± 2 ha/year (equivalent annual annuity), which represents a loss of 0.8% of expected rents. Yet losses can reach up to US$183 ± 30 ha/year in areas hit by recurrent fires that are near milling centres. The results indicate that some of the municipalities that are likely to accumulate most economic losses due to fire do not yet have local‐level fire mitigation programmes. We therefore conclude that spatially explicit valuations of the economic impact of fire can pinpoint priorities to better target fire action plans as well as to engage local actors in integrated fire management practices. Although fires directly affect the timber sector in the Brazilian Amazon, most current logging practices often tend to increase rather than mitigate the problem. We argue that in order to involve the timber sector in fire mitigation policies in the biome it is crucial to assess the economic impact of fire on the sector. This paper describes EcoFire, a spatially‐explicit model for valuing the economic losses by fire to sustainable timber harvest operations in the Brazilian Amazon. [ABSTRACT FROM AUTHOR]

Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW·m-1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change. [ABSTRACT FROM AUTHOR]

The Pantanal biome integrates the lowlands of the Upper Paraguay Basin (UPB), which is hydrologically connected to the biomes of the Cerrado and Amazon (the highlands of the UPB). The effects of recent land-cover and land-use (LCLU) changes in the highlands, combined with climate change, are still poorly understood in this region. Here, we investigate the effects of soil erosion in the Brazilian Pantanal under climate and LCLU changes by combining different scenarios of projected rainfall erosivity and land-cover management. We compute the average annual soil erosion for the baseline (2012) and projected scenarios for 2020, 2035, and 2050. For the worst scenario, we noted an increase in soil loss of up to 100% from 2012 to 2050, associated with cropland expansion in some parts of the highlands. Furthermore, for the same period, our results indicated an increase of 20 to 40% in soil loss in parts of the Pantanal biome, which was associated with farmland increase (mainly for livestock) in the lowlands. Therefore, to ensure water, food, energy, and ecosystem service security over the next decades in the whole UPB, robust and comprehensive planning measures need to be developed, especially for the most impacted areas found in our study. [ABSTRACT FROM AUTHOR]