Agricultural expansion, human settlements, concentrated livestock production and forest fragmentation. These are just some of the global land-use changes, unsustainable for the environment, which have taken place in recent years. These changes are creating “hotspots”, that are areas where conditions are ripe for the transmission of coronaviruses from wild animals to humans.

This is what emerges from a study just published in Nature Food, by a team of researchers composed of Maria Cristina Rulli and Nikolas Galli of the Politecnico di Milano, Paolo D’Odorico of the University of California at Berkeley (USA) and David Hayman of Massey University (New Zealand).

While the exact origins of the SARS-CoV-2 virus remain unclear, scientists believe that the disease likely emerged when a virus that infects horseshoe bats was able to jump to humans, either directly through wildlife-human contact, or indirectly by first infecting an intermediate animal host. Horseshoe bats are known to carry a variety of coronaviruses, including strains that are genetically similar to ones that cause COVID-19 and Severe acute respiratory syndrome (SARS).

The result of about a year of work (which began during the lockdown of 2020), the study highlights how a change in land use unsustainable from an environmental point of view can trigger the spillover infection of new coronaviruses. In particular, the team of researchers, who in 2017 had already published a study on the link between the Ebola virus epidemic and forest fragmentation, used high-resolution satellite data to analyse land use patterns in regions populated by the horseshoebat.

Analysis of deforestation, fragmentation, distribution of cultivated land, density of animal farms, human settlements, and changes in land use in regions populated by horseshoe bats – a total area of more than 28.5 million square kilometres, stretching from Western Europe to East Asia – allowed authors to identify hotspot areas for coronavirus spillover from animals to humans.

Land use changes can have an important impact on human health, both because we are modifying the environment, but also because they can increase our exposure to zoonotic disease.

said Maria Cristina Rulli, Professor of Water and Food security at Politecnico di Milano.

“Every formal land use change should be evaluated not only for the environmental and social impacts on resources such as carbon stocks, microclimate and water availability, but also for the potential chain reactions that could impact human health”, adds study co-author Paolo D’Odorico, Professor of Environmental science, policy, and management at UC Berkeley.

Most of the current hotspots are clustered in China, where a growing demand for meat products has driven the expansion of large-scale, industrial livestock farming.

Concentrated livestock production is particularly concerning because the practice brings together large populations of genetically similar, often immune-suppressed animals that are highly vulnerable to disease outbreaks.

highlighted Maria Cristina Rulli.

The analysis also identified locations that could become easily become hotspots with changes in land use.

“The analyses aimed to identify the possible emergence of new hotspots in response to an increase in one of three land use attributes, highlighting both the areas that could become suitable for spillover and the type of land-use change that could induce hotspot activation”, said Maria Cristina Rulli.

We hope these results could be useful for identifying region-specific targeted interventions needed to increase resilience to coronavirus spillovers.

Understanding the circumstances in which coronaviruses can switch from wild animals to humans is crucial to try to avoid future epidemics or pandemics such as covid-19.

Human health is intertwined with environmental health and also animal health.

Our study is one of the first to associate unsustainable land use patterns with possible zoonoses spillovers, considering unsustainable land use as a means by which people come into contact with virus host species.

concludes Maria Cristina Rulli.