PNNL

Abstract

Tropical peatlands are among the most carbon-dense terrestrial ecosystems yet recorded. Collectively, they comprise a large but highly uncertain storage of the global carbon cycle, with wide-ranging estimates of their global area (441,025–1,700,000 km2) and below-ground carbon storage (105–288 Pg C). Substantial gaps remain in our understanding of peatland distribution in some key regions, including most of tropical South America. Here we compile 2,413 ground reference points in and around Amazonian peatlands and use them alongside a stack of remote sensing products in a random forest model to generate the first data-driven model of peatland distribution across the Amazon basin. Our model predicts a total Amazonian peatland extent of approximately 216,203 km2 (90th percentile interval: 115,072 - 317,334), greater than that of the Congo basin, but substantially less than some previous estimates of peatland extent in Amazonia. The model performs well against point observations but spatial gaps in the ground reference dataset mean that model uncertainty remains high, particularly in parts of Brazil and Bolivia. For example, we predict significant peatland areas in the Rio Negro basin and adjacent south-western Orinoco basin which have previously been predicted to hold Campinarana or white-sand forests. Similarly, we predict large areas of open peatlands in Bolivia, surprisingly given the strong climatic seasonality found over most of the country. Virtually no field data exists with which to quantitatively assess the accuracy of our map in these regions. Data gaps such as these should be a high priority for new field sampling. This new map can facilitate future research into the vulnerability of peatlands to climate change and anthropogenic impacts, which is likely to vary spatially across the Amazon basin.