Global land use changes – including forest fragmentation, agricultural expansion and concentrated animal production – are creating favorable “hot spots” for bats carrying the coronavirus and where conditions are right for disease. pass from bats to humans, according to an analysis released this week by researchers at the University of California at Berkeley, Politecnico di Milano (Polytechnic University of Milan) and Massey University in New Zealand.
While the exact origins of the SARS-CoV-2 virus remain unclear, scientists believe the disease likely arose when a virus that infects horseshoe bats was able to pass to humans, either directly through contact between wildlife and humans, either indirectly through the first infecting an intermediate animal host, such as the pangolin, sometimes known as the scaly anteater.
Horseshoe bats are known to carry a variety of coronaviruses, including strains genetically similar to those that cause COVID-19 and severe acute respiratory syndrome (SARS).
The new study used remote sensing to analyze land use patterns across the horseshoe bat’s range, which stretches from Western Europe to Southeast Asia.
By identifying areas of forest fragmentation, human settlement, and agricultural and animal production, and comparing them to known horseshoe bat habitats, they identified potential hotspots where habitat is favorable for these bat species, and hence these so-called zoonotic viruses could potentially jump from bats to humans.
The analysis also identified locations that could easily become hot spots with changes in land use.
Land use changes can have a significant impact on human health, both because we change the environment, but also because they can increase our exposure to zoonotic diseases. “
Paolo D’Odorico, study co-author and professor, Environmental Science, Policy and Management, UC Berkeley
“Every formal land use change must be assessed not only for environmental and social impacts on resources such as carbon stocks, microclimate and water availability, but also for potential chain reactions that could have an impact on human health. “
Most of the current hot spots are clustered in China, where a growing demand for meat products has led to the expansion of large-scale factory farming. Concentrated animal production is of particular concern as the practice brings together large populations of genetically similar, often immunocompromised animals that are highly vulnerable to epidemics, the researchers said.
The analysis also found that parts of Japan, northern Philippines and China south of Shanghai are at risk of becoming hotspots with increased forest fragmentation, while parts of Indochina and Thailand could become hot spots with an increase in animal production.
“The analyzes aimed to identify the possible emergence of new hotspots in response to an increase in one of the three land use attributes, highlighting both areas that could become susceptible to fallout and the type of land use change that could induce hotspot activation, ”said study co-author Maria Cristina Rulli, professor of hydrology and water and food security at Politecnico di Milano in Italy.
“We hope these findings could be useful in identifying region-specific targeted interventions needed to increase resilience to coronavirus outbursts. “
Human encroachment into natural habitat can also indirectly increase exposure to zoonotic diseases by reducing valuable biodiversity. When forest lands become fragmented and natural habitats are destroyed, species that need very specific habitat to survive, called “specialists”, can decrease or even disappear. Without competition from specialists, “generalist” species, less picky about their habitat, can take over.
Horseshoes are a generalist species and have often been observed in areas characterized by human disturbance. Previous work by Rulli, D’Odorico and study co-author David Hayman has also linked forest fragmentation and habitat destruction in Africa to Ebola virus outbreaks.
“By creating disadvantageous conditions for specialized species, generalist species can thrive,” D’Odorico said. “While we are not able to directly trace the transmission of SARS-CoV-2 from wildlife to humans, we do know that the type of land use change that brings humans into the picture is generally associated with the presence of those bats known to carry the virus. “
While China has been a leader in tree planting and other greening efforts over the past two decades, many trees have been planted in discontinuous land areas or forest fragments. To tilt the ecological balance in favor of specialized species, the creation of continuous zones of forest cover and wildlife corridors is more important than increasing the total tree cover.
“Human health is closely linked to environmental health and animal health,” D’Odorico said. “Our study is one of the first to connect the dots and really explore geographic land use data to see how humans come into contact with species that could be carriers.”
Rulli, MC, et al. (2021) Land-use change and the livestock revolution increase the risk of transmission of the zoonotic coronavirus by rhinoophid bats. Natural food. doi.org/10.1038/s43016-021-00285-x.