Decreasing landscape carbon storage in western US forests with 2˚C of warming

Changing climate is altering the amount of carbon that can be sustained in
forest ecosystems. Increasing heat and drought are already causing
increased mortality and decreased regeneration in some locations. These
changes have implications for landscape carbon storage with ongoing
climate change. We used a climate analogs approach to project aboveground
forest carbon density under +2 °C warming above the pre-industrial climate
for western US forests. We calculated analogs for the current climate and
under +2 °C warming and associated carbon density for each time period. We
found that in most ecoregions, maximum carbon density values are projected
to decline, and the interquartile range of carbon density values is
projected to narrow. Using mean carbon density values, we project a 796 Tg
decline in landscape carbon storage across the western US. As tree
mortality increases, the transition from live to dead carbon will increase
fuel buildup and fire hazard in many ecosystems. Greater fire hazard and
increased susceptibility to insects from drought could cause carbon
density changes to occur more rapidly than our climate-only projections.
This may have substantial implications for forest-based carbon offset
projects.