A tropical Sphagnum peatland ecosystem in lowland Belize.

Tropical peatlands are globally significant ecosystems for carbon cycling and storage,^1,2,3 hydrological regulation,^4,5 and unique biodiversity.^6,7 There is a diversity of tropical peatland types globally,⁸ but tropical peat-forming ecosystems are typically forested without the Sphagnum groundcover^3,9,10,11 that is often characteristic of high-latitude peatlands. Here, we report on a unique tropical peatland situated in Belize that challenges our understanding of both tropical and extra-tropical peatlands owing to the presence of Sphagnum in the undergrowth. We employed a suite of methods to investigate its composition, distribution, and history. The 2,175-ha peatland is comprised of a complex mosaic of open scrub and forested communities that are compositionally similar to northern temperate peatlands at higher taxonomic levels. Paleoecological data show that the peatland originated as a mangrove swamp beginning >7,700 years before present (BP) and Sphagnum spores and macrofossil remains suggest that this moss was locally established by c. 4,000 years BP. Drier conditions from 4,500 years BP impacted carbon accumulation rates and may have enabled burning, but the peatland remained intact despite these pressures. Floristics and structural affinities with coastal Panamanian peatlands^12,13 suggest the existence of a rare Central American peatland type that is underreported and may be already fragmented and threatened. This previously undocumented peatland highlights the knowledge gaps in tropical biodiversity¹⁴ that conceal important ecological and biogeographical insights. These floristic, paleoecological, and remote sensing datasets provide insights vital to understanding the functional diversity and climate resilience of globally important tropical peatland ecosystems.