Biodiversity loss identified as biggest reason for emergence of infectious diseases

Changes in the environment have been linked to infectious diseases ranging from Ebola, Kyasanur forest disease, COVID-19 and even well known maladies like malaria and dengue. These diseases spread when a disease carrying host comes into contact with a susceptible population, usually through a vector.

Climate change has been blamed for most of these — for example, increase in temperature tends to increase the population of vectors.

A team of researchers in the United States looked at five global change drivers — biodiversity loss, climate change, chemical pollution, non-native species and habitat loss — in a bid to find the best management practices for controlling disease spread, in a new paper.

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For the analysis, published in the journal Nature on May 8, 2024, the team reviewed the existing literature and observed 2,938 cases of infectious disease responses to global change drivers across 1,497 host-parasite combinations.

They found that biodiversity loss was the biggest culprit, followed by climate change and invasive species. On the other hand, urbanisation reduced the spread of disease, largely due to improved environmental conditions.

The researchers also found that natural biodiversity gradients, deforestation and forest fragmentation played a relatively lower role in the spread. 

Links between biodiversity loss and infectious disease have been discussed earlier too. A study published in the journal The Lancet in November 2021 shows that COVID-19 pandemic, believed to have been spread by bats, has links to biodiversity loss. Other than bringing host and pathogen together, the pandemic also impacted efforts to conserve biodiversity.

The findings are crucial considering that drivers such as biodiversity loss and climate change are expected to worsen in the coming years and require the most policy attention. The Kunming Montreal Global Biodiversity Framework (KMGBF), adopted in December 2022, could help countries put such policies in place.

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The framework is part of global efforts to conserve biodiversity under the Convention on Biological Diversity. KMGBF has 23 targets that have to be met by 2030 and has synergies with the work being done under the United Nations Framework Convention on Climate Change and UN Convention to Combat Desertification. These three global pacts were made way back in 1992 at the Earth Summit in Brazil.

However, the new analysis does not indicate the true import of the situation, as the researchers looked at each stressor individually, a situation that does not exist in nature where these drivers are actually interconnected. For example, climate change and chemical pollution can cause habitat loss and change, which in turn can cause biodiversity loss and facilitate species introductions.

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