Tropical carbon emissions are largely derived from direct forest clearing processes. Yet, emissions from drought-induced forest fires are, usually, not included in national-level carbon emission inventories. Here we examine Brazilian Amazon drought impacts on fire incidence and associated forest fire carbon emissions over the period 2003–2015. We show that despite a 76% decline in deforestation rates over the past 13 years, fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. The 2015 drought had the largest ever ratio of active fire counts to deforestation, with active fires occurring over an area of 799,293 km2. Gross emissions from forest fires (989 ± 504 Tg CO2 year−1) alone are more than half as great as those from old-growth forest deforestation during drought years. We conclude that carbon emission inventories intended for accounting and developing policies need to take account of substantial forest fire emissions not associated to the deforestation process.

27B razil has been unique worldwide in terms of land use. Although vast areas of forests and savannahs have been converted into farmland (Fig. 1) -placing the country as a leading global producer of agricultural commodities -it still safeguards the largest tracts of native tropical vegetation on Earth, with extremely high levels of biodiversity. Patterns of land use change, which until recently exhibited the highest worldwide absolute rates of tropical deforestation, largely resulted in low-productivity cattle pastures 2 . Moreover, climate change issues in Brazil are inextricably related to land use and land-use change (LUC) as approximately 80% of the country's total CO 2 -equivalent (CO 2 e) emissions in 2005 were sourced from agriculture and LUC 3 .Demand for farmland is the key immediate driver of LUC in Brazil, and there is little evidence that agricultural expansion is grinding to a halt 4-7 . In fact, Brazil holds the greatest potential for further agricultural expansion in the twenty-first century 8 . Understanding recent LUC patterns (Box 1) and visualizing a sustainable land-use pathway in Brazil have become highly strategic -not only for Brazilians, given that regional and global climate change, food and energy provision, and biodiversity conservation are all at stake. This Review presents an integrated analysis and provides new insights on recent trends in the Brazilian land-use system. In the first two sections we show how Brazil's agriculture is becoming both gradually decoupled from deforestation processes and increasingly intensified and oriented to large-scale farming of trade commodities throughout the country. Next we explain the economic and political factors driving those changes. The fourth section reveals the drawbacks of those changes in aggravating the long history of inequality in land ownership. We then explore repercussions for climate change, namely Agriculture, deforestation, greenhouse gas emissions and local/regional climate change have been closely intertwined in Brazil. Recent studies show that this relationship has been changing since the mid 2000s, with the burgeoning intensification and commoditization of Brazilian agriculture. On one hand, this accrues considerable environmental dividends including a pronounced reduction in deforestation (which is becoming decoupled from agricultural production), resulting in a decrease of ~40% in nationwide greenhouse gas emissions since 2005, and a potential cooling of the climate at the local scale. On the other hand, these changes in the land-use system further reinforce the long-established inequality in land ownership, contributing to rural-urban migration that ultimately fuels haphazard expansion of urban areas. We argue that strong enforcement of sector-oriented policies and solving long-standing land tenure problems, rather than simply waiting for market self-regulation, are key steps to buffer the detrimental effects of agricultural intensification at the forefront of a sustainable pathway for land use in Brazil.for the country's g...

Following an intense occupation process that was initiated in the 1960s, deforestation rates in the Brazilian Amazon have decreased significantly since 2004, stabilizing around 6000 km(2) yr(-1) in the last 5 years. A convergence of conditions contributed to this, including the creation of protected areas, the use of effective monitoring systems, and credit restriction mechanisms. Nevertheless, other threats remain, including the rapidly expanding global markets for agricultural commodities, large-scale transportation and energy infrastructure projects, and weak institutions. We propose three updated qualitative and quantitative land-use scenarios for the Brazilian Amazon, including a normative 'Sustainability' scenario in which we envision major socio-economic, institutional, and environmental achievements in the region. We developed an innovative spatially explicit modelling approach capable of representing alternative pathways of the clear-cut deforestation, secondary vegetation dynamics, and the old-growth forest degradation. We use the computational models to estimate net deforestation-driven carbon emissions for the different scenarios. The region would become a sink of carbon after 2020 in a scenario of residual deforestation (~1000 km(2) yr(-1)) and a change in the current dynamics of the secondary vegetation - in a forest transition scenario. However, our results also show that the continuation of the current situation of relatively low deforestation rates and short life cycle of the secondary vegetation would maintain the region as a source of CO2 - even if a large portion of the deforested area is covered by secondary vegetation. In relation to the old-growth forest degradation process, we estimated average gross emission corresponding to 47% of the clear-cut deforestation from 2007 to 2013 (using the DEGRAD system data), although the aggregate effects of the postdisturbance regeneration can partially offset these emissions. Both processes (secondary vegetation and forest degradation) need to be better understood as they potentially will play a decisive role in the future regional carbon balance.