Biotic homogenization: Human impacts diminish biodiversity

Biotic homogenization occurs when human activity leads to the spread of non-native species, thereby diminishing global biodiversity. This phenomenon is at the core of a new study published in the journal Nature Communications.

Researchers from the University of Lausanne’s Department of Ecology and Evolution have unveiled the specific impact of this process on global ant populations. The findings demonstrate how biotic homogenization is reshaping the ecological landscape. This process is effectively blurring biogeographical boundaries that have stood for millions of years.

Through human trade and tourism, non-native ant species are transported across the globe, significantly impacting biodiversity. Consequently, this study illuminates the profound and unintended consequences of such dispersals. It underlines the urgent need for a deeper understanding of our ecological footprint.

Ants on the move: A global shift

Imagine lounging on a beach in northeast Bali, looking out towards Lombok. You’re unknowingly close to the Wallace Line, an invisible boundary shaped by ancient tectonic movements and evolutionary history. It separates the Indomalayan and Australasian biogeographic realms.

Discovered nearly 170 years ago by Alfred Russel Wallace, this line once marked a clear divide between distinct species on either side. Today, the relevance of these demarcations is questioned due to human activity’s pervasive influence on natural habitats.

The study by Cleo Bertelsmeier, Lucie Aulus-Giacosa, and Sébastien Ollier explores how 309 accidentally transported non-native ant species are breaking down natural barriers. This, a result of global trade and travel, is drastically homogenizing biodiversity – most notably in the tropics and on islands.

A small world: The homogenization of habitats

Lucie Aulus-Giacosa, the study’s lead author, points out that while previous research focused on gastropods, their study pioneers the investigation into insects, particularly ants, which comprise about 70% of the Earth’s terrestrial animal biomass.

Moreover, the implications of their findings extend beyond the examined species, suggesting a transformative effect on the entire biogeographical structure of ant biodiversity. This encompasses over 13,000 described species.

This homogenization is most apparent in the tropics, where territories below the Tropic of Cancer now host similar ant species.

Cleo Bertelsmeier, the project director, highlights the likelihood of finding the same ant species across continents like Australia, Africa, and South America. The study emphasizes the tropics’ unique diversity, prone to the accidental import and establishment of non-native species.

Bertelsmeier emphasized the significant human impact, highlighting how two centuries of human activity have altered biodiversity patterns. These patterns were formed over 120 million years.

Biotic homogenization on islands

The study also sheds light on the phenomenon of biotic homogenization on a global scale, with 52% of ant assemblages worldwide showing increased similarity.

“Strikingly, this trend was strongest on islands and in the tropics, which harbor some of the most vulnerable ecosystems,” wrote the researchers. “Overall, we show that the pervasive anthropogenic impacts on biodiversity override biogeographic patterns resulting from millions of years of evolution, and disproportionally affect particular regions.”

How does human activity affect island biodiversity?

Islands are known for their unique ecosystems and rich evolutionary history. The study raises concerns over the potential extinction of endemic species. Looking ahead, the experts aim to delve deeper into the effects of human activity on island biodiversity.

Lucie Aulus-Giacosa highlights the focus on islands, where tourists and imports bring non-native species that threaten fragile ecosystems. They aim to uncover why homogenization is more pronounced on some islands.

A delicate balance

In essence, the study urges us to consider the lasting impact of our actions on the planet’s biodiversity.

As we continue to blur the lines that nature has drawn over millennia, the question remains: can we find a balance between progress and preservation, or have we already crossed the point of no return?

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