Emerging Land-Cover Changes from Boreal-Tundra Greening Reveal Reduced Surface-warming Feedback Relevant to Boreal Afforestation Feasibility in Northern Canada.

Across Northern Canada’s boreal–tundra (CBT) ecozones, climate warming has driven rapid northward greening induced land-cover vegetation type changes that modifies the land–atmosphere energy exchanges. While classical vegetation-type-dependent albedo constrained models predict that high-stature vegetation expansion amplifies warming through surface darkening, our observations suggest contrary diverse climate responses.

Using Landsat-based NDVI and MODIS albedo trends (1986–2023), integrated with land-cover transitions, meteorological records, and surface-energy fluxes, we find that, rather than declining, vegetation increases across ecozones largely correspond to snow-free albedo increases of 0.2–0.8 % dec⁻¹. These albedo increases are spatially collocated with surface-energy trends ranging from −0.003 to −0.009 W m⁻² yr⁻¹, consistent with stronger surface-warming reduction tendencies reaching up to −0.028 °C yr⁻¹ across the majority of central and northern CBT ecozones, particularly where landcover shifts toward mixedwood, broadleaf, and treed-wetlands compared with ecozones regions dominated by highly conifers and shrubified assemblages.

Under classical albedo-constrained expectations, CBT afforestation has often been viewed as a warming risk. Here, by viewing CBT greening–induced increases in high-stature vegetation as natural afforestation analogs, our results show that near-surface warming can be dampened upon afforestation with specific vegetation types, indicating that CBT afforestation feasibility is highly conditional on vegetation structure, hydrological context, and ecozone setting. These findings provide empirical evidence for the possibilities of surface cooling–dominated boreal afforestation pathways in boreal–tundra regions, with implications for permafrost stability, land-based climate mitigation, adaptation, and ecosystem restoration.