Fires that emit massive amounts of CO 2 and particulate matter now burn with regularity in Southeast Asian tropical peatlands. Natural peatlands in Southeast Asia are waterlogged for most of the year and experience little or no fire, but networks of canals constructed for agriculture have drained vast areas of these peatlands, making the soil vulnerable to fire during periods of low rainfall. While soil moisture is the most direct measure of peat flammability, it has not been incorporated into fire studies due to an absence of regional observations. Here, we create the first remotely sensed soil moisture dataset for tropical peatlands in Sumatra, Borneo and Peninsular Malaysia by applying a new retrieval algorithm to satellite data from the Soil Moisture Active Passive (SMAP) mission with data spanning the 2015 El Niño burning event. Drier soil up to 30 days prior to fire correlates with larger burned area. The predictive information provided by soil moisture complements that of precipitation. Our remote sensing-derived results mirror those from a laboratory-based peat ignition study, suggesting that the dependence of fire on soil moisture exhibits scale independence within peatlands. Soil moisture measured from SMAP, a dataset spanning 2015-present, is a valuable resource for peat fire studies and warning systems.

In these wetland environments, persistent flooding and anoxic conditions suppress decomposition rates, allowing organic material to accumulate over time in deep peat deposits. This process, compounded over millennia, has made Southeast Asian (SEA) peatlands one of the world's largest terrestrial pools of organic carbon: an estimated 67 Gt of carbon are stored in peatlands in Indonesia, Malaysia, and Brunei (Page et al., 2011; Warren et al., 2017). In recent decades, this carbon sink has been

Over the past century, increased atmospheric CO2 concentrations have enhanced photosynthesis through CO2 fertilization across the globe. However, the increased growth has also led to greater respiration rates—both from vegetation (autotrophic respiration) and through the breakdown of plant litter and soil organic matter (heterotrophic respiration). The resulting change in carbon flux—and its spatial distribution—that can be attributed to increasing CO2 and climate change remains unknown. We used the Carbon Data Model Framework, a model‐data fusion system that assimilates global observations from satellites and other sources to create an ensemble of observationally constrained carbon cycle representations, to determine the photosynthesis and respiration fluxes that can be attributed to increased atmospheric CO2 and associated climate change from 1920 to 2015. Across the globe, the response of photosynthesis and respiration to atmospheric CO2 dominates their response to climate alone. The regional distribution of the carbon sink attributable to climate change and CO2 is strongly influenced by the 'loss ratio of carbon gained'—the fraction of enhanced photosynthesis that is lost to respiration. While the wet tropics' attributable photosynthesis flux is 1.4 times larger than that of the temperate region, the attributable flux of net carbon uptake is actually 1.25 larger in the temperate region, due to the wet tropics' greater heterotrophic respiration response to enhanced plant growth. At the global scale, the loss ratio of carbon gained is 83 ± 0.6%. Our results highlight the importance of the respiration responses to enhanced plant growth in regulating the land carbon sink.

No abstract

In these wetland environments, persistent flooding and anoxic conditions suppress decomposition rates, allowing organic material to accumulate over time in deep peat deposits. This process, compounded over millennia, has made Southeast Asian (SEA) peatlands one of the world's largest terrestrial pools of organic carbon: an estimated 67 Gt of carbon are stored in peatlands in Indonesia, Malaysia, and Brunei (Page et al., 2011;Warren et al., 2017). In recent decades, this carbon sink has been