As climate change pushes Europe's native forests to their limits, the North American Douglas-fir (Pseudotsuga menziesii) is emerging as a potential climate-resilient candidate. But could this fast-growing newcomer harm local ecosystems? A sweeping new study recently published in Forest Ecosystems reveals unexpected answers.
Researchers from Technical University of Munich, University of Göttingen, and Centre of Biodiversity and Sustainable Land Use analyzed decades of data from across Europe, examining how Douglas-fir introduction affects biodiversity compared to native trees like spruce and beech. The results challenge common assumptions: in 78.6% of cases, Douglas-fir showed no significant impact on local species. Positive effects were rare (just 12% of observations), while negative impacts were even scarcer (only 9%).
The findings varied by species and habitat. Canopy spiders thrived in Douglas-fir's dense branches, while arthropod diversity is reduced due to the distinct bark structure. Birds faced mixed fortunes—some species found less food in Douglas-fir stands during winter, but mixed forests softened these effects. Soil organisms and fungi showed more complex responses, often tied to subtle changes in leaf litter and soil chemistry.
The key takeaway? Context matters. Pure Douglas-fir plantations sometimes altered ecosystems, but mixing them with native trees minimized disruptions. The study highlights important unknowns too, like impacts on bats and long-term soil health.
For forest managers, the message is clear: thoughtful integration beats wholesale replacement. Based on the limited studies retrieved by the review, it is reported that Douglas-fir inclusion has non-significant or neutral effects. The team calls for more studies to pinpoint safe thresholds for its use, ensuring this imported tree helps rather than harms Europe's struggling woodlands.
Funding: This study was supported by grant klifW018 of the Bavarian State Ministry for Food, Agriculture and Forestry for funding.
