Updated: Jun 8
Deforestation (@Unsplash, Justin Menke)
Forests are critical in addressing the climate emergency. That is the central argument for REDD+, and the raison d’être for the UN-REDD Programme. But there is more. The world’s forests act as shields, keeping humans safe from new diseases.
As we are now collectively learning, halting and reversing deforestation is one of the most effective ways of preventing the spread of novel pathogens. It also costs substantially less than the economic and mortality costs of responding to a pandemic like the COVID 19 outbreak.
With that in mind, Emelyne Cheney has asked lead scientists Claire Lajaunie and Serge Morand to tell us more about the linkages between changes in forest cover and public health.
Q.: What do scientists know about the link between deforestation and zoonotic diseases like COVID-19?
Serge: This is an interesting question, often asked by journalists. The emergence of infectious diseases has been clearly and repeatedly linked to biodiversity loss, but there had been less evidence of the role of deforestation at the global level. Existing studies on this issue tend to be localized. For instance, they will look specifically at Brazil, Southeast Asia or North America. In contrast, our research looks at changes in forest cover globally, using and analyzing a global data set. It shows a clear pattern linking deforestation to the outbreaks of both vector-borne and zoonotic diseases, especially in tropical regions, over the last 30 years.
Q: Your research indicates that it is not just forest clearance that is responsible for the emergence of infectious diseases, but also reforestation and afforestation. Can you tell us more?
Serge: It was a bit of a surprise. When we collected the data on changes in forest cover, we decided to adopt the FAO definition of forest. Differentiating between types of forest among the land use and land cover data was a real challenge. But when we looked at the trends by forest type and country, we observed linkages between disease outbreaks and reforestation, mostly for the temperate zone, including China, India and Vietnam. We found evidence suggesting this could be related more specifically to large scale, mono-crop plantations and also to afforestation in the broad sense.
Q: Your paper looked specifically at the role of palm oil expansion in epidemics. What are your main findings?
Serge: We observed a very clear pattern linking palm oil expansion with vector-borne diseases like Zika, Chikungunya or Dengue fever and a correlation with zoonotic diseases in some countries. Our findings support a meta-analysis published a few years ago looking at infectious diseases in relation to land use change in Southeast Asia. This analysis did not find that agriculture at large, or even urbanization, had a significant effect on disease outbreaks, but it identified a clear impact from the introduction of new crops, commonly rubber, palm oil and teak. Our findings confirmed this.
Claire: Our findings point to the need to respond to environmental issues – forests, biodiversity, health – in a holistic and integrated manner. This is very difficult to do as public policies are often contradictory. There needs to be a common understanding that environmental law and public health are deeply connected. Environmental law can be integrated into international health regulations, as illustrated by the One Health approach.
Q: Continuing with the example of the palm oil sector, what would a holistic approach to environmental protection and public health look like?
Serge: As Claire said, it is about embracing the complexity and inter-connectedness of these issues. Policymakers should consider that palm oil cultivation occurs in a socio-ecological context shaped by local livelihoods, livestock production, economic development, etc. Disease transmission is a local process, so all these factors come into play. Until very recently, the health dimension was completely absent from academic and policy thinking on commodity plantations, like palm oil and rubber. Palm oil cultivation can, of course, offer economic benefits and alleviate poverty, but it also has an impact on public health which is not being considered in the economic costs of plantations. Public health costs are typically left to governments and local communities.
Claire: Yes, economic policies are significant in this context. We spoke about the effects of large-scale commodity plantations. We could perhaps think of incentives to reduce the size of plantations. And this is why we need environmental law to be reformed to reflect its inter-connectedness with public health, trade and development.
Serge: I agree and something that really needs to be discussed is the environmental and public health impact of global trade. For instance, in Thailand, the Ministry of Public Health is very concerned, and the Department of Disease Control contacted me to discuss the impact of rubber plantation on risks of diseases. But, ultimately, they should be talking to the Land Development Department.
Q: This leads to my last question. What recommendations can you offer to policymakers both at national and international levels?
Serge: There are a number of initiatives being launched such as One Health, PREZODE or Planetary Health. Now is the time to think jointly about human, animal and environmental health.
Claire: It would be helpful to have discussions with all UN agencies, to come up with joint solutions and get rid of the contradictions existing in international regulations. The debate on the protection of forests could be taken up in the CBD, for instance, as long as it is discussed in relation to health. It is also time to agree on how to operationalize the One Health approach so that it doesn’t remain a broad principle.
Serge: Our work with Claire is truly inter-disciplinary, at the junction between public health, ecology and environmental law. And the message to policymakers is that they should no longer work in silos but look at issues cross-sectorally. This is the only way to achieve a productive science-policy dialogue.
Serge Morand and Claire Lajaunie are the authors of the recently published paper entitled “Outbreaks of Vector-Borne and Zoonotic Diseases Are Associated With Changes in Forest Cover and Oil Palm Expansion at Global Scale”
Serge Morand is a disease ecologist at French CNRS and Cirad studying the impacts of land use and agriculture intensification on the interlinkages between biodiversity and health in collaboration with local communities, administrations and public health, based at Mahidol University (Bangkok, Thailand).
Claire Lajaunie investigates the inter-linkages between biodiversity and health and their evolution due to global changes through the study on Global Environmental Law, governance and the associated ethical issues. She works for the French National Institute of Health and Medical Research at the LPED – Population-Environment-Development Laboratory in Marseille, France. She is also Affiliate Researcher at the Strathclyde Centre for Environmental Law and Governance.
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