New Research Suggests Forest Restoration Can Decrease Zoonotic Spillover Risk, But Caution is Needed

JUNE 28, 2023 – Zoonotic diseases are transmitted from animals to humans, and more often than not, their emergence can be attributed to human-driven landscape changes. Since the onset of the COVID-19 pandemic, researchers and reporters have given greater import to the impact of human activity on zoonotic diseases, which represent 75% of emerging infectious diseases worldwide. Because not all species (or groups of species) are equally good hosts or vectors for pathogens, land use changes that benefit reservoir species (species which infectious pathogens depend on for survival), or bring humans into close contact with them, can drive an increase in the prevalence of zoonotic disease.

While the links between anthropogenic actions and these diseases are becoming better understood, very few studies have looked at the opposite question – if deforestation is a potential driver of zoonoses, does ecological restoration have the potential to repair the ecological damage and restore ecosystem degradation to the point of decreasing the incidence of these diseases, thus making landscapes healthier for humans?

In a recent paper, Prist and colleagues reviewed the existing evidence linking native vegetation restoration with zoonotic transmission risk, and proposed forest restoration strategies that could help in limiting the spread of zoonotic diseases. A large knowledge gap was identified, especially in tropical regions, confirming that there are few studies evaluating how forest restoration can affect zoonotic disease risk. The authors also identified that the studies addressing this topic do not consider important environmental aspects that can affect the outcomes of restoration on disease risk, such as land use history and landscape structural characteristics (i.e. the composition and configuration of native habitats).

Conceptual framework showing the expected results of forest restoration according to two different strategies in three landscapes with different amounts of forest cover (low, intermediate and high).

Based on the above, a conceptual framework to guide restoration initiatives was developed. This framework emphasizes two important points: (1) the effects of forest restoration may depend on the context of the existing landscape, especially the percentage of native vegetation existing at the beginning of the restoration; (2) these effects will also be dependent on the spatial arrangement of the restored area within the existing landscape.

Forest restoration activities happening in areas with a low amount of forest cover (~15%) may increase the transmission risk of zoonotic diseases. If performed in landscapes with 30 to 40% of forest cover, the spatial arrangement of restored areas is the factor that will determine zoonotic risk – with increased forest connectivity leading to increased risk. Therefore, care must be taken when carrying out restoration activities in tropical areas. If it is not possible to choose areas before implementing forest restoration in new areas, or to carry out spatial planning for them, preventative and control measures must be taken to avoid increasing the risk of transmission of zoonoses, in order to reduce exposure among people and animals.

Read more about the research at this link.

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