The commercial wildlife trade and associated commercial wildlife markets for human consumption have been widely recognized as a major risk factor, and are the subject of a WCS policy brief focused specifically on that topic1. The current report looks at the broader issues of ecosystem integrity and ecosystem degradation. The degradation of ecosystems is often linked to the commercial wildlife trade but also results in various other processes that affect zoonotic disease transmission. The report contains an overview of the literature linking declines in the integrity of ecosystems to the risk of emerging infectious disease outbreaks that originate in wildlife, and also touches briefly on other impacts on human health.
Four key findings are identified, as follows:
1. Degradation has significantly altered ecological systems worldwide and continues to expand into new areas. 2. The majority of emerging infectious disease2 threats are zoonotic, originate from wildlife, and often cause major social and economic impacts. 3. Ecological degradation increases the overall risk of zoonotic disease outbreaks originating from wildlife. a. This relationship has been shown for multiple individual diseases, in regional and global multi-disease studies, and in theoretical models, although the proportion of cases of degradation that lead to substantially increased risk is not well understood. a. The increased risk results from multiple interacting pathways including increased human contact with pathogens and disruption in pathogen ecology. b. The key “ingredients” that accentuate the risk of an emerging infectious disease spillover event are activities (e.g., land conversion, creation of new habitat edges, wildlife trade and consumption, agricultural intensification) in or linked to areas of high biodiversity that elevate contact rates between humans and certain wildlife species. 4. Degradation of ecosystems also has complex effects, feedback loops, and some notable negative impacts on many other aspects of human health, including: the prevalence of endemic zoonotic diseases, the prevalence of vector-borne and water-borne diseases; air quality; nutrition; mental health; and access to traditional medicines; as well as effects on human health through the impacts of climate change. These all in turn can contribute to local and transnational conflicts over natural resources and undermine local and international security. Hence, avoiding ecosystem degradation (by keeping ecosystems as intact as possible and avoiding the creation of high-risk interface zones and high-risk activities that increase humanwildlife contact), combined with broader
One Health3 approaches that address the full range of 1 https://www.wcs.org/get-involved/updates/a-primer-on-the-coronavirus 2 ‘Emerging infectious diseases can be defined as infections that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range’ (Morse 1995). 3 www.wcs.org/one-planet-one-health-one-future; www.onehealthglobal.net/what-is-one-health/ 2 risk factors and are integrated into public health policies, will help to reduce the risk to humanity from emerging zoonoses and can have other beneficial health outcomes as well. Protecting ecological integrity should be a priority action within any comprehensive plan to avoid future zoonotic outbreaks, through actions such as spatial planning, the creation and management of effective protected areas, support to ecosystem management by Indigenous Peoples and local communities, and policies to minimize threats caused by particular economic sectors. Other critical measures in addition to protecting ecological integrity include: closing commercial wildlife markets and commercial wildlife trade for human consumption, especially of birds and mammals; building disease surveillance and response systems; providing global access to health care; and mitigating disease risks associated with domestic animals.
A One Health approach, optimizing human health and ecological integrity, can be used to find solutions for different landscape contexts (e.g. remote intact landscapes, mixed, partly natural landscapes, and heavily human-dominated landscapes). These conclusions are based on a range of evidence types including detailed case studies, global analyses, modelling, and broad expert consensus. Whilst the key conclusions are clear, it is important to acknowledge that the science is still somewhat incomplete and it is difficult to make predictions at the scale of individual ecosystems, locations or infectious agents, especially as major outbreaks are inherently rare events and the exact relationship between pathogen dynamics and ecosystem change is often context-specific and subject to interactions with many other environmental, socio-economic, political and cultural factors. In addition to lowering disease spillover risk, avoiding environmental degradation has many related benefits, including: climate change mitigation; climate change adaptation and environmental resilience; maintenance of watersheds and rainfall patterns; biodiversity conservation; enhancing food security, protection of the homelands, livelihoods and cultures of Indigenous Peoples and local communities; and conflict mitigation, stabilization and security. A separate WCS brief explores some of the issues relating to Indigenous Peoples and local communities in the context of the COVID-19 pandemic4.
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