Drought and fire change sink to source

Abstract

Aircraft have captured the 'breath' of the Amazon forest — carbon emissions over the Amazon basin. The findings raise concerns about the effects of future drought and call for a reassessment of how fire is used in the region. See Letter p.76 Amazonia stores large amounts of carbon, but our understanding of the sensitivity of the tropical terrestrial carbon budget to climate anomalies remains uncertain. An analysis of seasonal and annual carbon balances based on basin-wide atmospheric measurements of carbon dioxide and monoxide for anomalously dry and wet years together with forest plot data suggest that water availability has an important role in determining the carbon balance in the Amazon basin. Drought reduced plant production and limited the amount of carbon that could be stored in vegetation; at the same time large amounts of carbon were released by fire during the dry year. The region was carbon neutral during the wet year, because of reduced carbon loss through fires and increased carbon uptake by vegetation.