What’s the link between deforestation and public health/infectious diseases?

Infectious Diseases

We are thrilled to introduce Nerdy Guest Andrea Johnson to talk about deforestation and infectious disease.

1.) Tell me about your background and training.

I’m currently an Advisor to the Climate and Land Use Alliance, a philanthropic alliance that helps major foundations align their grantmaking end to fight deforestation and secure the rights and livelihoods of indigenous peoples and forest communities. I have degrees in environmental science and policy from Harvard and Yale, and have worked for 20 years on the technical, social and political aspects of conserving tropical ecosystems in three continents. For much of that time I’ve been living on forest frontiers in Indonesia, Peru, Central America, or the scariest jungle of all, Washington DC. I’ve conducted investigations of illegal timber and wildlife trade, government corruption, violence against activists, and pushed for policies on Capitol Hill and in international climate negotiations. Nowadays when I’m not helping to give away money to amazing organizations working for change, I’m restoring a degraded cattle pasture to native ecosystems in Costa Rica. And after bouts of malaria, cutaneous leishmaniasis and even a Malaysian sun bear attack, I consider myself something of an informal expert in the zoonotic risks of tropical forests!

2.) What’s the link between deforestation and public health/infectious diseases?

The first thing it’s critical to know is that deforestation, especially in the tropics, is a huge contributor to the climate change crisis – which is also a looming public health crisis. The Intergovernmental Panel on Climate Change’s estimates that 11% of annual global emissions come from land use change, mostly forest loss – and that destruction is often linked to fires, themselves a terrible public health problem nowadays in places like Brazil, Indonesia, and the US West Coast.
The combination of rising temperatures and increasing pressure on forests is a perfect storm for the emergence of zoonotic diseases. First, as habitats are disturbed, fragmented or lost to roads, mines, logging, hunting and industrial agriculture, we see that animals in general, and virus-carrying species like some rodents, insects or bats in particular, come into increasing contact with humans. Second, humans continue to push the forest frontier back, moving domesticated livestock into closer proximity with wild animals. So you have higher density of people, and peoples’ livestock and poultry farms; more roads and dams going deep into forests; increased temperatures from the loss of shade; more standing water; and increased bushmeat trade.

A recent Harvard task force confirmed that spillover of viruses from wildlife into people, either directly or via livestock, is the root cause of pandemic risk – and found that the spillover with greatest pandemic potential occurs from forest destruction. At least 50% of emerging infectious diseases originate in wildlife; The Global Virome Project says that hundreds of thousands of unknown viral species with zoonotic potential exist in animal reservoirs.

IPCC: Climate Change 2022: Mitigation of Climate Change

Harvard: Report on Preventing Pandemics

Nature: Global trends in emerging infectious diseases

3.) Can you give me an example of a recent outbreak (other than COVID) that was affected by deforestation?

Sure – unfortunately there are lots to draw from. In Africa, researchers found increased probability of Ebola outbreaks in human in sites linked to recent deforestation. In Central America, deforestation increased rodent reservoirs for Hantavirus Pulmonary Syndrome. The correlation between malaria incidence and deforestation rates in the Amazon is well documented. In your own backyards, forest fragmentation and ecosystem degradation has driven emergence of Lyme disease across huge new swaths of the eastern US.

Another compelling example is the Nipah virus, which has killed hundreds of people across Southeast Asia. Nipah was brought to Malaysian pig farms by fruit bats who were forced to leave Indonesian forests in search of food. Why wasn’t their own habitat producing fruit? It was covered in a giant cloud of smoke from other nearby rainforests being burned to establish vast oil palm plantations.

Habitat destruction is also a silent partner in many recent disease outbreaks, because we’re talking about highly interconnected ecological and social systems here. For example – wildlife trade. The data are clear that hunting and poaching increase along vectors of human disturbance like road building, which creates better access into more remote forest areas, inevitably leading to deforestation. And zoonotic disease emergence is strongly associated with wildlife trade: monkeypox and SARS coronavirus come to mind!

Meanwhile at the edge of degraded forest and wetland ecosystems, highly pathogenic avian influenzas – bird flus – emerge repeatedly due to contact between domesticated poultry and wild waterfowl, which “maintain a large, genetically diverse pool of influenza A viruses”. A pandemic of highly contagious bird flu is probably the biggest looming threat to humanity. A study in China found that protecting lakes and wetlands significantly reduce the probability of avian flu spillover.

PNAS: Amazon deforestation drives malaria transmission, and malaria burden reduces forest clearing

National Geographic: Deforestation is leading to more infectious diseases in humans

Nature Communications:Combined impacts of deforestation and wildlife trade on tropical biodiversity are severely underestimated

The Guardian: Monkeypox isn’t the disease we should be worried about

National Library of Medicine: Protection of wetlands as a strategy for reducing the spread of avian influenza from migratory waterfowl

4.) What can we do to reduce the impact of deforestation on public health?

”Unfortunately, current discussions about how to prevent future pandemics almost entirely exclude environmental “root causes”. This despite a 2020 analysis published in Science that addressing spillover in emergence hotspots through ecosystem conservation and One Health approaches would cost US$ 22-31 billion yearly – minuscule compared to the costs of COVID-19 to the global economy. So the number one thing we can do is pull down our siloes, get informed and help to shift this discussion in key public health funding and policy spaces.

One important voice to follow and amplify is the Preventing Pandemics at the Source Coalition, made up of research, conservation, advocacy, One Health and even pandemic survivor organizations like Marked by COVID And for folks who want to delve deeper, the Ecosystem Health Alliance produces peer-reviewed studies and tools like Spillover, a platform that assesses and ranks zoonotic viruses to inform public health research and interventions.

Preventing Pandemics at the Source Coalition: WE CAN PREVENT THE NEXT COVID-19

Marked by COVID

EcoHealth Alliance

Spillover Viral Risk Ranking

For more information about where Andrea works, click here.

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