However, impacts of wild fire decline on the subsequent ecosystem carbon cycling have not been well quantified, as prognostic fire models show large spreads in fire distribution and magnitude 10 and fire modules in the land surface models included in the GCP synthesis are not explicitly guided by the observed BA changes 13. In particular, deforestation fire and peatland burning are included in the land-use emission estimates 13, 19. Direct fire carbon emissions are often considered for global and regional carbon budgets 13, 17, 18. ![]() Instead of treating the land sink as a residual term between the anthropogenic emissions and the atmospheric and ocean uptakes as historically being done, the most recent report provides explicit land sink estimates using an ensemble of land models that account for climate warming, CO 2 fertilization, and land use change impacts, which result in a budget imbalance that requires an additional sink of ~0.6 PgC per year to explain the observed airborne fraction during the last decade 13. ![]() The Global Carbon Project (GCP) synthesizes observational and model-based flux estimates from multiple organizations and research groups around the world to report the Global Carbon Budget yearly 13. However, processes explaining the terrestrial component of this increase-likely related to CO 2 fertilization 12, 14, changing soil moisture and temperature regimes 15, and land use and land cover change 16-are still under debate. These declines are found to be correlated with agricultural expansion and landscape fragmentation 10, 11.Īt the same time, a decrease in the fraction of anthropogenic CO 2 emissions that remain in the atmosphere (airborne fraction, −2.2% per year) has been observed for the period 2002–2014 12, despite continued increases in anthropogenic CO 2 emissions 13. A 25% decline in the global burned area (BA) from 1997 to 2015 has been observed combining multiple satellite data sets, with the most significant decreases in the savannas of Africa 10. With the rapid increase in human population and agricultural production in the last decades, many regions have transited from natural to human-dominated fire regimes 9. ![]() However, human activities also affect fuel accumulation and fire risk and are responsible for most ignitions and all suppression efforts, thus they have a profound impact on the timing, frequency, extent, and intensity of fires 1, 3, 8. Climate plays a critical control on fire by regulating fuel load and conditions for fire ignition and spread 4, 5, 6, 7. Fire is an important disturbance agent in the terrestrial ecosystem, particularly in the dry tropics, tightly coupled with vegetation, climate, biogeochemical cycles, and human activities 1, 2, 3.
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