21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions

TLDR

Tropical carbon emissions mainly arise from direct forest clearing, yet drought‑induced fires are often omitted from national inventories. The study examines how Amazon droughts affect fire incidence and associated forest fire carbon emissions from 2003 to 2015. We analyze fire incidence and carbon emission data over that period to assess drought impacts. Despite a 76 % decline in deforestation, fire incidence rose 36 % during the 2015 drought, with fire emissions (~989 Tg CO₂ yr⁻¹) exceeding half those from old‑growth deforestation, indicating that inventories must include fire emissions.

Abstract

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.