Large Reductions in Temperate Rainforest Biome Due to Unmitigated Climate Change

Abstract

Temperate rainforests are rare ecosystems globally; restricted to cool, moist conditions that are sensitive to a changing climate. Despite their crucial conservation importance, a global assessment of how temperate rainforests will be impacted by climate change is lacking. We calculated historical (1970–2000) climate conditions for the temperate rainforest biome using ERA5 reanalysis data for three key bioclimatic variables: warmest quarter temperature, annual precipitation and proportion of rainfall during warmest quarter. We used high‐spatial resolution climate projections for these variables to identify regions likely to become unsuitable for temperate rainforests under four future shared socioeconomic pathway (SSP) scenarios. We predict unmitigated climate change (SSP 5–8.5) would lead to a 68.3 (95% confidence interval (95 CI): 53.4–81.3)% loss in the existing temperate rainforest biome by 2100 at a global scale with some national‐level reductions exceeding 90%. Restricting global warming to <2°C (consistent with SSP 1–2.6), limits loss of global temperate rainforest biome to 9.7 (95 CI: 7.8–13.3)% by 2100 and is crucial to ensuring temperate rainforest persistence. Deforestation has resulted in loss of up to 43% of the current temperate rainforest biome with only 37% of primary forest remaining, and some regions like Europe with virtually none. Protection and restoration of the temperate rainforest biome, along with emissions reductions, are vital to its climate future.

Plain Language Summary

Temperate rainforests are rare ecosystems found only in wet and cool regions, making them vulnerable to a warming climate. They are important to conserve because they host unique species and can store high amounts of carbon. We use global maps of forest cover and condition to assess how much temperate rainforest remains, and how much it has been impacted by human activity. We find that only 37% of the temperate rainforest area is still covered by primary forest. We use a map of existing temperate rainforests along with records of past weather conditions to estimate what climate conditions are needed for its survival. We then use estimates of future climate under four different scenarios of greenhouse gas emissions to see which areas of temperate rainforest will maintain these conditions up to 2100. We find that under the most pessimistic scenario, 68% of temperate rainforest will be lost, while under the most optimistic scenario, only 9% will be lost. Our study can aid temperate rainforest conservation by identifying the areas of temperate rainforest that are least/most vulnerable to climate change, and where there is potential to restore forest.

Key Points

• Temperate rainforests rely on a cool and moist climate biome that globally rare and vulnerable to climate change

• Unmitigated climate change would lead to a loss of 68% of the temperate rainforest biome, but climate mitigation limits loss to 9%

• We identify historical, intact and potential temperate rainforest extent and climate change vulnerability to inform conservation efforts