In recent decades, global efforts to conserve temperate forest ecosystems have intensified, yet an alarming paradox has emerged: plant diversity within these forests continues to decline despite the implementation of numerous conservation strategies. Central to this conundrum is a prevailing paradigm in forest ecology and management—the closed forest model—characterized by the assumption that dense, continuous canopy cover represents the optimal and natural forest state. This perspective has influenced silvicultural practices that prioritize uniform canopy closure, often with the intention of maximizing carbon sequestration and timber production. However, fresh evidence is challenging this orthodoxy, shedding light on a complex ecological narrative in which large herbivores have historically shaped semi-open forest environments that favor rich plant biodiversity.
This evolving understanding stems from a comprehensive study examining the light and herbivory preferences of nearly a thousand native temperate forest plant species across the biogeographical spans of central and western Europe. The research juxtaposes these preferences against conditions observed in two contrasting forest states: pristine closed-canopy forests and pasture woodlands—semi-open habitats modulated by grazing herbivores. With taxa spanning an evolutionary timescale from a mere hundred thousand to ten million years, the study leverages phylogenetic conservatism in plant niche affinities to infer long-term environmental adaptations and distributions, providing a temporal dimension rarely integrated into contemporary forest management discussions.
The findings illuminate a striking pattern: the majority of temperate forest plant species display a clear preference for heterogeneous, semi-open canopies that facilitate variable light regimes and are heavily influenced by large herbivory activity. This runs counter to the traditional closed-canopy model, emphasizing instead the ecological significance of disturbance regimes mediated by large herbivore populations that historically created diverse microhabitats. Such canopy heterogeneity not only supports a mosaic of light conditions but also promotes herbaceous layer dynamics critical to sustaining plant species richness.
Of particular concern is the link identified between plant species’ affinities for higher herbivory and reduced herbaceous biomass with their assessed extinction risks under current conditions. Plants adapted to these semi-open, dynamic habitats face heightened vulnerability, suggesting that the decline in large herbivore densities—driven primarily by human encroachment and hunting—has directly precipitated biodiversity loss within contemporary temperate forests. This insight reframes the role of herbivory, traditionally viewed through the lens of overgrazing and vegetation degradation, positioning large herbivores as keystone agents maintaining ecosystem complexity and resilience.
From a paleoecological perspective, these discoveries resonate with evidence pointing towards the prominence of open and semi-open woodlands in Europe’s recent geological past, shaped by the activity of megafauna such as deer, wild boar, and aurochs. As large herbivore populations dwindled following human expansion and land-use change, closed-canopy dominance emerged as a relatively recent ecological state rather than a longstanding natural baseline. This realization calls into question the current management frameworks heavily reliant on promoting canopy closure, often at the expense of understory diversity and forest structural heterogeneity.
Reconceptualizing temperate forests as ecosystems intrinsically shaped by large herbivores introduces transformative implications for conservation biology and forest restoration. Management practices must shift from simplistic canopy closure targets towards strategies that reintroduce or mimic natural disturbances via herbivory. Such approaches could reinstate the heterogeneity vital for accommodating a broader spectrum of plant species, particularly those historically adapted to intermittent canopy gaps and patchy vegetation structures.
Moreover, declines in large herbivore populations have cascading effects on ecosystem functions modeled around nutrient cycling, seed dispersal, and vegetation dynamics. Herbivores create and maintain light environments that influence competitive hierarchies among understory plants, mediate succession pathways, and promote coexistence. Reestablishing these dynamics holds promise not only for biodiversity preservation but also for enhancing forest resilience in the face of climate change and anthropogenic pressures.
The revelation that temperate forest plants retain evolutionary signatures tied to heterogeneous, herbivore-influenced habitats challenges the reductionist views underpinning many silvicultural regimes. It underscores the importance of integrating phylogenetic ecology, palaeoecology, and herbivore biology into forest management science to redesign conservation strategies that are not only ecologically sound but also historically informed.
This paradigm shift dovetails with broader ecological theories emphasizing disturbance and complexity as drivers of biodiversity. It highlights the risk of “shifting baselines” where management targets drift away from historically normed ecosystem states, inadvertently perpetuating simplified, biodiversity-poor environments. Recognizing large herbivores as architects of temperate forest heterogeneity could reverse such trends, promoting ecological restoration that honors evolutionary legacies.
However, implementing such prescriptions faces significant logistical, social, and ethical challenges. The reintroduction or augmentation of large herbivore populations in human-dominated landscapes demands careful consideration of animal welfare, human-wildlife conflict, and ecosystem capacity. Spatial planning must balance biodiversity objectives with agricultural practices, urban expansion, and recreation, requiring interdisciplinary collaboration and stakeholder engagement.
On a technical front, the study’s methodological approach leverages niche modeling coupled with phylogenetic frameworks to trace habitat affinities, integrating ecological niche optima as proxies for environmental preferences linked to evolutionary histories. Light availability was quantified in contrasting forest environments using remote sensing and ground-based assessments, while herbivory impacts were inferred through standardized biomass measurements and historical herbivore density reconstructions.
The comprehensive data set encompassing 917 species further strengthens the robustness of conclusions, spanning taxonomic breadth and evolutionary timescales. This extensive inventory supports the generalizability of findings across temperate Europe’s diverse forest types, making the argument compelling for a paradigm reorientation at continental scales.
Overall, this research offers a compelling narrative that reconceptualizes temperate forests not as static, closed-canopy realms but as dynamic, semi-open ecosystems sustained by large herbivore activity. As conservation science pivots to address accelerating biodiversity loss and ecosystem degradation, such insights are poised to inspire innovative management frameworks that bridge evolutionary ecology and practical forestry. Embracing the ecological roles of large herbivores may be pivotal in restoring the multiplicity of niches necessary to safeguard plant diversity in temperate forests into the future.
Subject of Research: Temperate forest plant diversity and its relationship with canopy structure and large herbivore activity.
Article Title: Temperate forest plants are associated with heterogeneous semi-open canopy conditions shaped by large herbivores.
Article References:
Czyżewski, S., Svenning, JC. Temperate forest plants are associated with heterogeneous semi-open canopy conditions shaped by large herbivores. Nat. Plants (2025). https://doi.org/10.1038/s41477-025-01981-3
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