Large herbivores naturally combat invasive plants in the ecosystem

Large herbivores play a crucial role in safeguarding local ecosystems by consuming and trampling invasive plant species that pose a threat to biodiversity.

You might question the logic behind this, as you may wonder if these large animals also consume and damage native plants. However, this is not the case. Native plants have evolved to withstand the impact of herbivores they have coexisted with for centuries, while invasive plants typically cannot.

Large Herbivores as Guardians Against Invasive Plants

This conclusion stems from a recent study conducted by Aarhus University and the Wildlife Institute of India, recently published in the scientific journal, Nature Ecology & Evolution. The research highlights the significant potential of using large herbivores as a natural defense against invasive plants, preventing them from outcompeting native species.

The study’s data was gathered from India, specifically from the world’s most extensive wildlife survey employing camera traps, conducted every four years, as well as India’s comprehensive plant monitoring program.

It’s worth noting that these findings are also applicable to regions without herbivores as large as those found in India, as we’ll discuss further.

The research focuses on mega-herbivores, which are animals weighing over one ton. In India, this category includes elephants, rhinos, wild water buffalo, and Indian bison (the world’s largest and heaviest bovine).

The study reveals a clear connection between the abundance of mega-herbivores and the equilibrium between native and invasive plant species: Regions with a high mega-herbivore population tend to have more native plants and fewer invasive ones. Conversely, areas dominated by invasive species typically lack or have very few mega-herbivores.

However, there are exceptions in certain Indian regions where invasive plants have grown so densely and tall that mega-herbivores are unable to access them. This situation is particularly concerning because the United Nations has identified invasive species as one of the top five major threats to global biodiversity.

Threats to Ecosystems and Economies

Invasive species encompass animals, plants, and fungi introduced to environments where they wouldn’t naturally occur, leading to adverse effects on native biodiversity. These biological invasions also incur significant societal costs, with over USD 120 billion spent worldwide in the past five decades on combating and managing them, often with limited success.

One challenge is that mega-herbivores, due to their large size and dietary needs, consume a wide variety of plant species, including those with lower nutritional value. Consequently, they are more likely to incorporate unfamiliar plants into their diet.

While the research team could have considered smaller herbivore species in their study, these animals have more complex roles in local ecosystems and are also prey for predators like tigers and leopards, unlike mega-herbivores such as elephants.

Bigger isn’t necessarily the determining factor, as we delve into how to apply the study’s findings in regions lacking elephants, rhinos, and similar mega-herbivores.

The presence of mega-herbivores is not a prerequisite for controlling invasive plant species. Smaller to medium-sized herbivores can yield comparable results.

For example, in Hungary, water buffalo have been shown to deter the invasive giant goldenrod, a species also problematic in Denmark. Similarly, Scottish Highland cattle are employed in Denmark to manage rosehip bushes, an Asian species often considered troublesome in Danish ecosystems, despite their smaller size compared to mega-herbivores.

Flexibility and Resilience in Conservation

According to Professor Jens-Christian Svenning from Aarhus University, the study’s lead author, the size of grazing animals isn’t the sole determining factor in combating invasive species. He emphasizes the effectiveness of employing a mix of large, medium, and small herbivores. Species like deer, buffalo, cattle, and horses can collaborate effectively in rewilding projects, addressing various invasive plant species. This approach enhances flexibility and resilience in conservation efforts.

Ninad Avinash Mungi, a postdoc at Aarhus University and the study’s lead author, underscores that a blend of herbivores of different sizes can be employed. This approach offers versatility and adaptability in addressing invasive species. He also suggests conducting a comprehensive European biodiversity survey akin to India’s Guinness World Record-holding initiative, given Europe’s greater resources for investing in nature and restoration.

Read the original article on: Phys

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