Health

The nexus between land use change and global pandemic

By - World Healthcare Journal

The nexus between land use change and global pandemic

Back in March 2020, the outbreak of Covid-19 took the world by shock. Medical researchers across the world have worked incessantly to find solutions to combat Covid-19.

While research on this pandemic tends to concentrate on strategies that may lead humanity out of the current crisis, there has been only limited work on the way pandemics can be prevented from happening in the first place.


The risk of zoonoses

There is growing evidence of the existence of a link between human encroachment into, and degradation of, the natural world and the risk of “zoonoses,” the transfer of animal diseases to humans. Researchers at the Politecnico di Milano, University of California, Berkeley and Massey University set out to quantitatively support this hypothesis.

Zoonotic spillover, which refers to the transmission of a pathogen from one species to another, may be more likely to occur in certain environmental conditions. Human intrusion into wildlife habitats enhances the interaction between people and wildlife species, as well as the likelihood of contact between the two, especially when livestock animals act as transmitters.

With most human diseases originating from animals, there are several ways in which environmental change can affect the development and transmission of infectious diseases through reshaping the interactions between animals, humans, and the environment.

Environmental change may also play a role in the emergence of infectious diseases in wildlife, and in enhancing the flow of pathogens across species. In addition, ecological degradation causes a loss of biodiversity, which can increase the prevalence of infectious diseases in host species. Human intrusion into wildlife habitats with domestic animals can shorten the distance between humans and pathogen hosts, thereby exposing humans to new infections.


SARSr-CoV-2 

Although the origin of SARSr-CoV-2 is unclear, it is known that Asian horseshoe bats host the greatest diversity of SARS-related coronaviruses. This is the reason we systematically collected published data on bat distributions and locations.

We generated a domain of almost 30 million square kilometres on which we mapped high resolution data (from 30m to 1000m) representing different land use patterns, including forest cover, croplands, human settlements, and data on the population density of livestock. From forest cover, we calculated forest fragmentation; a process through which human intrusion turns a once continuous forest habitat into multiple disconnected patches.

Our previous study on Ebola demonstrated that forest fragmentation represents a reliable indicator of the impact of environmental change on spillover risk. This can also be used as a proxy for the increased interface between anthropized land and wildlife habitat. We used multivariate hotspot analyses to study to what extent this indicator, along with human settlements and livestock density, may define the habitat of the Asian horseshoe bats.


Coronavirus hotspots 

This approach, allowed for the identification of actual and potential coronavirus spillover hotspots from horseshoe bats. Actual hotspots represent risk regions, in that they exhibit levels of forest fragmentation, human settlements, and livestock density comparable to those in the locations where the presence of horseshoe bats has been reported. Interestingly, these conditions tend to place wildlife and humans into closer contact, thereby facilitating the transmission of pathogens.

Potential hotspots are areas that cannot be classified as hotspots under current land use conditions, but where changes in only one of the indicators definiting hotspots, such as forest fragmentation, could induce transition to a hotspot.

Areas at risk of becoming a hotspot follow the same reasoning. For instance, some areas that are already fragmented may turn into a hotspot if human and livestock presence increase, while other areas may become at risk of spillover as the result of the expansion of a nearby hotspot.


Positive outcomes 

Environmental degradation can increase the risk of pathogen spillover from wildlife to humans. Strategies that mitigate this spillover risk can also contain biodiversity loss and reduce greenhouse gas emissions.

Likewise, there are a variety of policies with multisectoral potential positive outcomes such as habitat restoration, sustainable agriculture and livestock production, which would address several of the UN Sustainable Development Goals, such as “Ensure healthy lives and promote well-being for all at all ages” which includes the fight against communicable diseases.

The connection between problems and solutions, linked to the abiotic and biotic environment and human society, supports the implementation of the one health approach. This approach means that the health of humans is closely related to the health of animals and our shared environment. With this in mind, policy makers can work to mitigate the risks associated with human modification to the natural world and prevent future pandemics.


This article was authored by Professor Maria Cristina Rulli, Department of Civil and Environmental Engineering, Politecnico di Milano, Milan, Italy and Paolo D’Odorico, Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA.

Supported by:

Nikolas Galli, Department of Civil and Environmental Engineering, Politecnico di Milano, Milan, Italy.

David T. S. Hayman, Molecular Epidemiology and Public Health Laboratory, School of Veterinary Science, Massey University, Palmerston North, New Zealand.


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