How much does biodiversity loss contribute to the spread of new infectious diseases?

Researchers widely agree that loss of biodiversity due to factors such as human interference with ecosystems contributes to the transmission of pathogens from animals to humans, which is known as a zoonosis. But how large is this effect? Quantifying this phenomenon is the goal of an international team of researchers headed by Charité – Universitätsmedizin Berlin. The researchers hope their findings will contribute to identifying an elevated risk of emerging zoonoses early on. Their newly launched project, titled “Zoonosis Emergence across Degraded and Restored Forest Ecosystems” (ZOE), is receiving about four million euros in funding from the European Commission for a period of four years.

Zoonotic infectious diseases emerge where human and animal habitats overlap, in settings such as factory farming and the commercial wild animal trade or when people eat wild animals. The same process occurs in areas where humans intervene in natural ecosystems – for two major reasons. First, this brings people into contact with wildlife. And second, human interference upsets ecosystem health.

“When we intervene in natural spaces, it may increase the likelihood that populations of animals that are more successful under the new environmental conditions will grow at a greater rate,” explains Prof. Jan Felix Drexler, a virologist at Charité and the head of the new research project. “There are indications that when those populations grow, they also spread their pathogens, which can potentially pose a risk to people.”

This means loss of biodiversity affects the likelihood of zoonoses emerging. This effect is felt especially keenly where people use landscapes for the first time or in a different way than before, such as when forests are cleared to create pastureland for livestock or plantations, or where cities spread into the surrounding areas.

Interdisciplinary team charts biodiversity at the macro and micro levels

The exact connections between land use changes, loss of biodiversity, and the risk of zoonoses are still unclear. To better understand how these factors fit together, Drexler teamed up with Prof. Nadja Kabisch, a landscape ecologist at Leibniz University Hannover and the project’s co-coordinator, to assemble an interdisciplinary consortium with proven expertise in the fields of virology, geography, epidemiology, geobotany, ecology, immunology, sociology, psychology, anthropology, and dissemination of knowledge.

The researchers, who come from seven countries in Europe and four in the Americas, plan to assess biodiversity in detail in forested areas that have been subjected to different kinds of human intervention. To that end, the team will be investigating native forests as well as degraded and reforested areas in Guatemala, Costa Rica, Slovenia, and Slovakia.

To identify the land use and the various species living in these areas, the researchers plan to use both satellite imaging and on-site field studies to gather information on landscape characteristics and the flora and fauna present there. They also intend to determine how many potentially dangerous microorganisms are circulating in the ecosystem by using advanced sequencing methods to test rodents, ticks, and mosquitoes – all important vectors for zoonotic diseases – for various bacteria and viruses.

Blood samples from people living in the area should shed light on how many of these pathogens have already been transmitted. In addition to the biomedical studies, the team also plans to conduct systematic household surveys on aspects such as how people living in the areas studied perceive the environmental changes taking place there, how often illnesses emerge, and how they deal with the risk of infection.

Predictive models for early detection of zoonosis risk

“We plan to take this wide range of data and use it to develop statistical models,” Drexler says. “Our hope is that this information will tell us how much the risk of zoonotic infections increases, depending on the degree of land use changes and the loss of biodiversity. We also hope to gain insight into the effects of reforestation measures. We think it’s especially important to share this information with local people in the area and with the public at large, including environmental protection agencies, and jointly develop recommendations. Through our work, we aim to help with efforts to identify and limit the risk of new zoonoses right where they emerge, as one way to prevent future epidemics.”