A recent study found that both native and non-native large herbivores, like elephants and wild horses, have similar impacts on plant diversity. This research challenges the long-held belief that introduced species are more harmful to ecosystems than their native counterparts.1
The study suggests that an animal’s traits, such as body size and feeding habits, are more important than its origin in determining its ecological role. This finding has significant implications for conservation efforts, as millions of dollars are spent each year to control or eradicate non-native herbivores.
The Surprising Findings
A recent meta-analysis conducted by an international team of scientists from Aarhus University and the University of Oxford has revealed that both native and introduced large herbivores have similar effects on plant diversity and abundance. This finding contradicts the common belief that non-native species have stronger negative impacts on ecosystems.
The researchers analyzed 221 studies and found that animal communities with larger herbivores tend to have positive effects on local plant diversity, while those with smaller species (less than 100 kg) tend to decrease it. Surprisingly, the study found no significant differences between the ecological impacts of native and introduced megaherbivores.
Functional Traits Matter More Than Origin
The study highlights that an animal’s functional traits, such as body size and diet selectivity, are more important than its evolutionary origin in determining its impact on the landscape. For example, small-bodied picky-eaters like deer tend to suppress plant diversity, while larger, generalist bulk-feeders like horses or buffalo tend to increase it.
This finding supports the idea that introduced species can help fill ecological niches vacated by extinctions and extirpations in recent prehistory, often due to human activities. By focusing on re-establishing functions rather than concepts of belonging, conservation efforts like rewilding can be more effective in restoring ecosystems.
The Importance of Grazing Refuges
Rewilding with large herbivores can successfully create wood-pasture landscapes on abandoned agricultural land, as long as grazing refuges are present for sapling establishment.
These refuges provide protection for young trees and shrubs, allowing them to grow and contribute to the overall diversity of the ecosystem.
Using Functional Traits for Conservation Priorities
Identifying conservation priorities for the world’s large herbivores can be done using functional traits. Species with traits such as habitat specialism and lower reproductive investment are more vulnerable and should be prioritized for conservation efforts.
On the other hand, species that tolerate climate extremes are more likely to persist in the face of environmental changes.
The Bottom Line
The study’s findings suggest that we should reevaluate the practice of killing large non-native herbivores based on notions of “belonging.” Instead, we should study these animals’ ecological roles in ecosystems, regardless of their origin.
By focusing on functional ecology and the re-establishment of crucial ecosystem functions, we can develop more effective and adaptive conservation strategies.
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Davin is a jack-of-all-trades but has professional training and experience in various home and garden subjects. He leans on other experts when needed and edits and fact-checks all articles.