Human impacts threaten billions of years of evolutionary history

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By ZSL Postdoctoral Research Scientist Rikki Gumbs – Edge of Existence Programme

Humanity’s relationship with biodiversity is complex. Our global social and economic systems are supported by the natural environment, yet our extraction of natural resources and changing land use is depleting the planet’s ability to support human life.

The loss of natural habitats to agriculture is the leading cause of biodiversity loss worldwide. More than 40% of Earth’s land surface has been converted and at least 75% changed by human activities to some extent. We recently set out, therefore, to determine how severely humans are damaging regions of the planet containing the world’s most irreplaceable biodiversity.

modified landscape
Agriculture and pasture threaten natural habitats around the world.

To do this we first mapped the tree of life for all terrestrial vertebrates—amphibians, birds, mammals and reptiles—to identify areas with the greatest unique evolutionary history: our measure of biodiversity. Focusing on reptiles, the least-studied yet most evolutionarily diverse group - we calculated the levels of human pressure across these key areas. Alarmingly, we found human pressures to be much greater across these areas than we expected: Almost 75% of the most important areas for reptilian evolutionary history are facing intense human pressure such as the Western Ghats of India, Sri Lanka, large swathes of Southeast Asia and the Caribbean. Just 5% are under little or no human pressure.

Mary river turtle
Reptiles comprise more unique evolutionary history than any other terrestrial vertebrate group. The Mary River Turtle (Elusor macrurus) is a priority EDGE Species.


We also identified evolutionarily unique species at the greatest risk from human activities as conservation priorities. Many of which have already been identified by our EDGE of Existence programme. These include the Purple Frog (Nasikabatrachus sahyadrensis) from the Western Ghats, which spends more than 360 days a year underground, and the Mary River Turtle (Elusor macrurus) of Australia, which can spend days underwater breathing through specialised gills – located in its genitals.

Purple frog
The Purple Frog (Nasikabatrachus sahyadrensis) is identified as a priority species due to its extreme evolutionary uniqueness and the levels of human pressure across its wider environment.

However, our EDGE prioritisations only include species with adequate conservation knowledge, thus we were particularly interested in unique species for which we lack adequate extinction risk data. Although our global knowledge of extinction risk for birds and mammals is relatively strong overall, data are currently lacking for around 8,000 species of amphibians and reptiles.

More than half of the twenty most unique snakes and lizards identified in our study lack sufficient extinction risk data, and these species alone represent more than 500 million years of evolutionary history. Even more concerning is the fact that, when we measured the impacts of human activities across all terrestrial vertebrates, more than 50 billion years of evolutionary history is at risk.

We are still learning the true extent to which human activities are encroaching on natural habitats, but our findings indicate that the magnitude is incomprehensibly large and appears to be overwhelmingly impacting the most irreplaceable areas and species. 

However, our research also shows us that it is not too late to change course: Local conservation efforts to protect some of the most unique and endangered species, such as those led by ZSL’s EDGE of Existence programme, are already underway and evidence suggests that even small increases in the global protected area network can have a big effect. If we all work together to reduce our impacts on the natural world and conserve natural habitats and biodiversity, we can avert the loss of billions of years of irreplaceable biodiversity. But we need to act now.

For more details on this research, see: www.edgeofexistence.org/blog/human-activities-threaten-billions-of-years-of-unique-evolutionary-history/

A lack of funding  - as a result of the current pandemic - has put ZSL’s world-leading expertise in serious jeopardy: as an international conservation charity, our work is only possible because of funds raised through our two zoos, ZSL London Zoo and ZSL Whipsnade Zoo – both of which are currently closed to the public.

Britain must continue its longstanding global leadership in zoological discovery and scientific endeavour – ZSL can help make sure that happens, but we need your help. Please give what you can to support ZSL at this crucial time: zsl.org/donate 

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