Data from: Consequences of climatic thresholds for projecting fire activity and ecological change

Aim: Ecological properties governed by threshold relationships can exhibit
heightened sensitivity to climate, creating an inherent source of
uncertainty when anticipating future change. We investigated the impact of
threshold relationships on our ability to project ecological change
outside the observational record (e.g., the 21st century), using the
challenge of predicting late‐Holocene fire regimes in boreal forest and
tundra ecosystems. Location: Boreal forest and tundra ecosystems of
Alaska. Time period: 850–2100 CE. Major taxa studied: Not applicable.
Methods: We informed a set of published statistical models, designed to
predict the 30‐year probability of fire occurrence based on climatological
normals, with downscaled global climate model data for 850–1850 CE. To
evaluate model performance outside the observational record and the
implications of threshold relationships, we compared modelled estimates
with mean fire return intervals estimated from 29 published lake‐sediment
palaeofire reconstructions. To place our results in the context of future
change, we evaluate changes in the location of threshold to burning under
21st‐century climate projections. Results: Model–palaeodata comparisons
highlight spatially varying accuracy across boreal forest and tundra
regions, with variability strongly related to the summer temperature
threshold to burning: sites closer to this threshold exhibited larger
prediction errors than sites further away from this threshold. Modifying
the modern (i.e., 1950–2009) fire–climate relationship also resulted in
significant changes in modelled estimates. Under 21st‐century climate
projections, increasing proportions of Alaskan tundra and boreal forest
will approach and surpass the temperature threshold to burning, with
> 50% exceeding this threshold by > 2 °C by 2070–2099. Main
conclusions: Our results highlight a high sensitivity of statistical
projections to changing threshold relationships and data uncertainty,
implying that projections of future ecosystem change in threshold‐governed
ecosystems will be accompanied by notable uncertainty. This work also
suggests that ecological responses to climate change will exhibit high
spatio‐temporal variability as different regions approach and surpass
climatic thresholds over the 21st century.