Wild megafauna play a key role in maintaining ecological balance

An international team of researchers led by Aarhus University has recently highlighted the critical ecological roles played by large herbivores throughout history. 

The study, published in the journal Nature Ecology & Evolution, emphasizes the profound effects these megafauna have on terrestrial ecosystems, effects that have been significantly altered by human-induced extinctions. 

Ecological void

The research investigates the ecological void left by the disappearance of species such as European elephants, Australian giant wombats, and South American ground sloths, examining how their decline has led to shifts in ecosystem dynamics that are not fully understood.

This comprehensive study synthesizes data from various individual case studies to illustrate the widespread impacts of large animals on ecosystems, impacts that are largely absent in modern environments. 

Large herbivores 

The research points out that large herbivores are instrumental in nutrient cycling, maintaining open habitats, and controlling smaller animal populations. A pivotal discovery is the role of these animals in enhancing ecosystem diversity by creating more structurally varied vegetation.

“The positive impact on variability in vegetation structure is particularly noteworthy, given that environmental heterogeneity is known as a universal driver of biodiversity. While our study mostly looked at the impact of megafauna on small scales, our findings suggest that they promote biodiversity even on the landscape level,” said lead author Jonas Trepel, a PhD student at Aarhus.

The study explores how large herbivores, through their interactions with vegetation, such as consumption of biomass, breaking of woody plants, and trampling, influence ecosystem structure, an effect that varies with the animal’s size. 

Local plant diversity 

The research, covering a broad range of body sizes (45-4500 kg), provides insights into how the presence of larger herbivores tends to enhance local plant diversity, whereas smaller species may have the opposite effect.

“Large herbivores can eat lower-quality food such as branches and stems, which may result in proportionally greater impacts on dominant plant species and thus give less competitive plants better odds in their struggle for sunlight and space,” explained senior author Erick Lundgren, an ecologist at Aarhus.

“These findings support the expectation that many small herbivores cannot fully compensate for the loss of a few large ones,” added Elizabeth le Roux, also a senior author of the study and expert in megafauna ecology and restoration.

Ecosystem restoration

This meta-analysis, drawing from 297 studies and 5,990 data points, leverages a wide dataset to identify overarching patterns in how megafauna influence ecosystems, particularly through exclosure studies that compare fenced areas excluding large animals to unfenced ones.

The research underscores the necessity of integrating large herbivores into conservation and ecosystem restoration efforts, given their essential roles in promoting biodiversity and ecosystem resilience. Moreover, there are potential benefits of reintroducing large animals to protected areas, such as enhancing ecosystem dynamics and adaptability to global changes.

The study concludes with a call to not only protect the remaining megafauna species but also to actively work towards their restoration, emphasizing the critical importance of these animals in maintaining ecological balance and biodiversity, especially in the face of accelerating environmental changes.

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