This vegetative growth, measured via the Normalized Difference Vegetation Index (NDVI), aligns with a 3.8°C rise in Arctic mean temperatures since 1979—nearly four times the global average. Crucially, moisture levels (assessed by the Normalized Difference Moisture Index, or NDMI) have remained stable or increased at most sites, a condition that supports the sustained growth of peat-forming plants.
Peatlands occupy over 3.5 million square kilometers and store approximately 415 gigatons of carbon, with nearly half embedded in permafrost zones. The Arctic subset plays a critical role in climate regulation due to the slow decomposition of organic material in cold, waterlogged soils. The new findings suggest that warmer temperatures and longer growing seasons are not just intensifying plant productivity but may be facilitating the lateral spread of peatland ecosystems into previously unvegetated or upland zones.
Field and satellite data across the Canadian and European Arctic—including sites in Svalbard, Bylot Island, and Lapland—show consistent trends. Sites with the most significant NDVI increases also recorded higher summer temperatures and, in some cases, increased summer moisture. While low Arctic sites showed some regional variability, particularly due to permafrost thaw and hydrological shifts, high Arctic zones showed more uniform gains in greening.
The expansion of peatlands, along with increased above-ground productivity, may signal a short-term negative feedback loop in the climate system: more carbon being drawn down and stored as plant biomass and eventually soil carbon. Radiocarbon dating of peat cores from multiple transects confirms that new peat accumulation has occurred since 1985—even at the expanding edges.
However, the long-term implications are uncertain. If future warming accelerates permafrost thaw, dries soil layers, or increases microbial decomposition, Arctic peatlands could eventually become carbon sources. While satellite NDVI and NDMI offer valuable insights into surface dynamics, they cannot alone confirm net soil carbon accumulation.
Current Earth system models do not dynamically account for peatland expansion or contraction, which limits predictive accuracy. As peatlands respond to complex variables including temperature, precipitation, permafrost stability, and vegetation shifts, researchers stress the importance of incorporating lateral peatland changes into land-surface models.
The study’s authors conclude that Arctic peatlands are likely to remain carbon sinks in the near term—particularly under scenarios where precipitation increases and warming is mitigated. But whether this trend offsets other losses, such as those due to wildfire, soil respiration, or infrastructure development, remains an open and urgent question.
