Contrasting vulnerability of drained tropical and high-latitude peatlands to fluvial loss of stored carbon

Carbon sequestration and storage in peatlands rely on consistently highwater tables. Anthropogenic
pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause
loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can
shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also
export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We
analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast
Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to
increased release of older carbon from the peat profile but withmarked differences related to peat type. Very low
DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored
peat carbon. High-latitude peatlands appearmore resilient to drainage; 14Cmeasurements from UK blanket bogs
suggest that exported DOC remains young (<50 years) despite drainage. Boreal and temperate fens and raised
bogs in Finland and the Czech Republic showed intermediate sensitivity. We attribute observed differences
to physical and climatic differences between peatlands, in particular, hydraulic conductivity and temperature,
as well as the extent of disturbance associated with drainage, notably land use changes in the tropics. Data from
the UK Peak District, an area where air pollution and intensive land management have triggered Sphagnum
loss and peat erosion, suggest that additional anthropogenic pressures may trigger fluvial loss of much older
(>500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age.