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May 14, 2025

A new study co-authored by UVic Geography’s Dr. Noémie Boulanger-Lapointe sheds light on how Arctic plant communities are responding to accelerating climate change. Published in Nature, the research - put forward by the International Tundra Experiment (ITEX) and comprising 54 reasearchers from 50 different organizations - draws on four decades of in situ vegetation monitoring across 2,174 plots throughout the Arctic. The study finds that, contrary to any expectations of directional biodiversity loss, the reality is more nuanced: species richness has not consistently increased or decreased across the Arctic, even as local ecological changes intensify.

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Local Change Without a Clear Arctic-Wide Pattern

The Arctic is warming approximately four times faster than the global average. However, this study—built from more than 42,000 records representing 490 vascular plant species—found no overarching directional change in plant species richness over time. In other words, while some sites gained species and others lost them, the average number of species per plot has remained relatively stable.

What the study did observe, however, was widespread species turnover. Approximately 59% of plots showed species gains and/or losses between survey periods. In 99% of plots, researchers recorded changes in the relative abundance of species, indicating dynamic shifts in community composition even when species counts held steady.

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Warming and Shrub Expansion as Key Drivers

While no net trend in richness was detected, climate warming remains a key influence. Plots that experienced greater warming over time tended to show higher rates of both species gains and species losses. These opposing trends appear to balance one another at the Arctic scale, masking local shifts that could be ecologically significant.

Shrubification—the expansion of woody shrubs across tundra ecosystems—emerged as one of the most consistent drivers of biodiversity change. In particular, increases in erect shrubs were associated with decreasing species richness, reduced evenness, and higher rates of species loss. This is likely due to the shading, competition, and altered soil conditions that shrubs introduce, which can displace sun-loving or less competitive species.

Interestingly, while warming is often linked with shrub expansion, the study did not find a consistent relationship between the rate of temperature change and the degree of shrub cover increase. Instead, different shrub types responded differently to warming: erect shrubs tended to increase with temperature, while dwarf shrubs declined.

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No Evidence of Biotic Homogenization—Yet

One of the more surprising findings was the absence of biotic homogenization. Biotic homogenization refers to ecosystems becoming more similar to one another over time, typically as a result of widespread species invasions or extinctions. Despite high levels of species turnover, the study found no directional trend in plant community similarity across the Arctic. This suggests that plant communities are not converging toward a single dominant composition, but rather responding in diverse and locally specific ways.

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Implications for Biodiversity Monitoring and Arctic Futures

These findings highlight the complexity of ecological responses to climate change and emphasize the need for long-term, locally grounded monitoring.

Unfortunately, it was not possible to include non-vascular plants (bryophytes and lichens) in the analysis owing to inconsistent recording across plots, but the study's authors stress that non-vascular influence on vascular plant dynamics cannot be discounted. . A future priority will be to expand non-vascular plant surveys to obtain a comprehensive view of plant biodiversity changes and biotic interactions among functional groups. 

Read the full study at: