The iconic beech tree, with its tall, slender trunk and lush dark green canopy, has long stood as a symbol of the temperate forests of Europe. These trees, which have thrived under the familiar climate conditions stretching from southern Sweden to central France, now face an uncertain future as climate change reshapes the environments they once dominated. A groundbreaking new study, spearheaded by researchers from Aarhus University in Denmark and Wageningen University in the Netherlands, reveals that by the turn of the century, the beech tree—and many other species—may no longer find suitable habitats in their long-established ranges.
Current climatic projections show that much of lowland Central Europe will experience summers that are hotter and drier, resembling the Mediterranean climate. This shift poses a grave challenge for the beech, which is adapted to cooler, more temperate conditions. The tree’s physiological sensitivity to increased heat and water stress limits its capacity to survive and regenerate under such altered circumstances. As the Mediterranean climate encroaches northwards, it threatens to displace these species, forcing an urgent reevaluation of forestry and conservation practices.
Professor Jens-Christian Svenning, director of the Danish National Research Foundation’s Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) at Aarhus University, highlights the importance of adaptive thinking in tree planting efforts. Svenning cautions against the continued reliance on species like beech and Norway spruce, which may become increasingly maladapted to the evolving climate. Instead, he advocates for a diversified approach, combining native species suitable to future conditions with those presently found in warmer southern regions, including sweet chestnut and Turkish hazel. This strategy, he argues, is not only prudent but necessary for ensuring resilient forest ecosystems.
The study’s implications extend beyond national borders and local forestry choices, tying directly into larger policy frameworks such as Denmark’s green tripartite agreement, which aims to transform significant tracts of agricultural land into forest. Svenning stresses that failing to integrate future climate projections into such reforestation plans risks planting trees doomed to decline. In this context, forestry must be informed by robust scientific insights about future habitats, ensuring tree populations can persist in an altered biosphere shaped by global warming.
One of the most striking elements of the research is its scope: analyzing over 32,000 tree species worldwide to assess their exposure to future climates that diverge markedly from current ones. Under realistic emission scenarios, nearly 70% of these species are expected to encounter significantly novel climatic conditions across at least 10% of their current natural ranges. This widespread exposure portends large-scale disruption in global forest biodiversity and ecosystem functioning, with many species facing the risk of local or even total extinction.
In European contexts such as Germany, these projections are already manifesting in intensifying tree mortality. The Norway spruce, long a staple species, is succumbing to increasing drought and heat stress. This physiological strain compromises tree defenses, making them more vulnerable to pests and pathogen outbreaks. This real-world example underscores a concerning trend: forests in ostensibly temperate zones are undergoing rapid ecological stress, driven by climate factors previously unseen in these regions.
Yet, there is a glimmer of hope amid the troubling forecasts. The research identifies potential climate refugia—geographically and climatically stable zones where species may find shelter from the most drastic warming trends. These refugia could serve as essential sanctuaries for tree species, preserving pockets of biodiversity in an otherwise rapidly transforming world. However, the protection and management of these refugia are critical; deforestation or degradation within these areas could eliminate some of the last bastions of suitable habitat.
While survival may be possible for individual tree species within these refugial patches, the broader outlook for forest ecosystems is less optimistic. The study highlights the threat not just to temperate zones but also to vast northern boreal forests and essential tropical systems like the Amazon rainforest. Increasingly frequent and intense heatwaves in these areas threaten large-scale die-offs, which could trigger cascades of ecological collapse. Such events carry profound consequences—not only for global biodiversity but also for climate regulation, since dying forests release significant quantities of carbon dioxide.
The compounded feedback loops between forest dieback and climate change are pivotal concerns. According to Svenning, the accelerated loss of forests due to climate stressors and fires—especially in vulnerable regions like southern Europe—could exacerbate global warming beyond current projections. Wildfires, fueled by hotter and drier conditions, devastate forest landscapes and impede natural regeneration. The study urges that biodiversity conservation must shift from static protection models toward dynamic strategies that encompass climate-driven species migration and assisted relocation.
Observing international responses, Svenning points to Austria’s pioneering efforts to introduce tree species such as Turkish hazel, native to warmer Balkan regions, into drought-stressed habitats further north. This form of “assisted migration” represents an adaptive management technique designed to maintain forest cover and function in a warming climate. Such interventions may become increasingly necessary worldwide as native species struggle under novel climatic regimes.
Coline C. F. Boonman, a key analyst behind the study’s computational modeling, emphasizes the identification of “exposure hotspots”—areas slated to experience the most dramatic shifts in tree species’ climatic envelopes. Equally important are the zones with the least exposure, which possess potential as future refugia. Preservation of such areas requires proactive measures to prevent deforestation and logging, securing these landscapes as safe havens for species facing the dire consequences of climate change.
This comprehensive modeling effort employs advanced computational simulations that integrate climate projections with detailed species distribution data. By quantifying the degree of climate novelty each species will encounter, the research provides an unprecedented global assessment of the risks and opportunities present in the next century’s forest dynamics. These findings underscore the urgency of integrating climate resilience into conservation and forestry policies for the preservation of global tree diversity.
Ultimately, the study presents a stark warning: without rapid, informed action, widespread forest degradation and biodiversity loss are likely. Yet, through strategic planning, diversity-focused planting, and the protection of climate refugia, humanity can foster ecosystems capable of adapting to rapidly shifting climates. This research marks a crucial step toward understanding the complex interplay between global warming and forest ecology, driving the needed transformation in how we grow, protect, and manage the world’s forests.
Subject of Research: Not applicable
Article Title: High tree diversity exposed to unprecedented macroclimatic conditions even under minimal anthropogenic climate change
News Publication Date: 23-Jun-2025
Web References:
References:
Jens-Christian Svenning et al., “High tree diversity exposed to unprecedented macroclimatic conditions even under minimal anthropogenic climate change,” Proceedings of the National Academy of Sciences, 23 June 2025.
Keywords: Beech tree, climate change, forestry, biodiversity, climate refugia, temperate forests, tree species extinction, drought stress, assisted migration, forest ecosystem collapse, computational modeling, global forest diversity
