Ecosystem restoration and zoonotic disease risk in humans : an integrative literature review

Abstract

The objective of this thesis was to conduct a review of the literature to investigate the links between ecosystem restoration and zoonotic disease risk in humans. This topic is relevant, as zoonotic disease is an increasing problem, and the UN’s Decade of Ecosystem Restoration was launched in 2021.

The main results found that ecosystem restoration especially in the tropics and forested wildness areas can prevent emerging infectious zoonotic diseases. The mechanism through which this is hypothesized to work is through strengthening ecosystem regulation of disease though high biodiversity mediated dilution effect and through the prevention of zoonotic disease spillover. Large scale ecosystem restoration is seen as a protective measure against a future zoonotic pandemic disease. High priority target areas are fragmented tropical forest habitats and the periphery of remaining primary forests and intact wilderness areas.

However, ecosystem restoration can also lead to the increase and spread of already known and endemic zoonotic diseases through increased wildlife resulting in higher animals to human transmission risk. The most researched example being the spread of Lymes Disease in Europe and North America. The mechanisms through which these are hypothesized to work is through an increase of available habitat resulting in increased abundance of wildlife and subsequent increased risk of transmission of zoonotic disease in humans. This problem is compounded by human induced trophic changes such as reduction or extermination of large apex predators such as wolves and bears which would otherwise keep deer and other wildlife populations in check, free of such top-down restraint’s deer, and other animal numbers are higher than they would be otherwise, resulting in high incidence of zoonotic disease. High at-risk areas identified for an increase of zoonotic disease because of ecosystem restoration are peri-urban and urban areas where high wildlife population densities would increase the risk of transmission of zoonotic disease through increased human-animal interactions.

The results of this thesis could be beneficial in designing ecosystem restoration projects which acknowledge the complex interactions between ecosystems and zoonotic disease and human health.

Keywords: ecosystem restoration, zoonotic disease, vector-borne disease