• Over the past 57 years, the productivity of dryland forests in Canada has decreased by 1.3% per decade due to climate warming and drought.
• When comparing forests with the lowest tree trait diversity (monocultures) to those with the highest diversity, productivity in the forests with high diversity was maintained at levels 13% higher, despite the negative impacts of climate change.
• To maintain the long-term functioning of forests, it is important to consider tree trait diversity in forest management practices.

　Dryland biomes are among those most strongly affected by climate change. Nearly 35% of the world’s population resides in these areas, and dryland forests provide essential ecosystem services. Therefore, enhancing the resistance of forest functioning to climate change and developing sustainable management practices are important. This study examined the long-term impacts of climate change on forest productivity in the boreal forests of dryland western Canada and tested whether tree trait diversity can mitigate these impacts.

　We analyzed inventory data from Canadian provincial governments monitored between 1958 and 2015. We found that as temperatures increased and droughts became more intensified, forest productivity declined by 1.3% per decade. However, forests with higher tree trait diversity (such as variations in drought tolerance) were able to maintain 13% higher productivity compared to monoculture forests. In addition, forests dominated by species with better resource acquisition capabilities (deciduous broadleaves) may benefit from climate warming.

　These results suggest that tree trait diversity plays a crucial role in mitigating the long-term impacts of climate change and maintaining forests as sustainable carbon sinks. Furthermore, forest regeneration and afforestation efforts for climate change mitigation should not only focus on increasing plantation areas, but also on combining a variety of tree species with different traits, which could offer more effective Nature-based Solutions.

【DOI】https://doi.org/10.1126/sciadv.adn4152