Forests are vital. Its plants and fruits feed extensive ecosystems, subsequently sustaining global biodiversity. They produce the oxygen that fills our lungs. They are even good for our mental well-being.
In recent years, we have also become very aware of the role that forests play in regulating animal diseases that can spread to humans. The Covid-19 pandemic highlighted this point and led scientists to redouble efforts to understand how pandemics can be linked to deforestation. The research suggests that zoonotic diseases, health and forests exist in a feedback loop with dire consequences.
A study published Wednesday in the journal Frontiers in veterinary science extends this understanding to deforestation related to agricultural production of goods, such as palm oil.
Palm oil is found in about 50% of packaged household products, from peanut butter to lipstick. Researchers now associate their harvest with disease outbreaks that can spread to humans. This is the first study to examine the cause and effect relationship between changes in forest cover and subsequent disease outbreaks on a global scale.
What’s new – Perhaps against intuition, the study also suggests that reforestation – or an increase in forest cover – may Furthermore accelerate disease outbreaks.
Lead author Serge Morand, research director at the Center National de la Recherche Scientifique (CNRS) in France, explained this scratching phenomenon in a press release.
“We still don’t know the precise ecological mechanisms at stake, but we hypothesized that plantations, such as oil palm, develop at the expense of areas of natural forest, and reforestation is done mainly from monospecific forests made at the expense of pastures,” said Morand.
In the case of this study, “forest” does not refer to the idyllic, century-old forest that normally comes to mind. Instead, “forest” follows a more specific definition: “land that measures over 0.5 hectares with trees.”
Planting an acre of monoculture – like an orchard of fruit trees – is technically considered forest growth, although monocultures are unsustainable and ultimately reduce biodiversity. This new study shows how this type of commercialized “reforestation” contributes to disease outbreaks as well as deforestation.
“Both changes in land use are characterized by loss of biodiversity and these simplified habitats favor animal reservoirs and disease vectors,” said Morand.
Necessary background – According to the United States Food and Agriculture Organization (FAO), primary forests have shrunk in size by 80 million hectares since the 1990s. A single hectare is about 2.5 times the size of a football field standard, which measures about an acre.
The study found that a quarter of the global forest loss occurred due to increased demand for food products like beef and palm oil, which requires cutting down forests to build plantations or raise livestock.
The cultivation of palm oil on plantations has been especially destructive to Indonesia’s forests, which are also home to a large number of diverse animals.
Cutting a hectare of forest for palm oil also contributes 174 tonnes of carbon dioxide, equivalent to the carbon production of an airplane, the study suggests.
The authors link rapid deforestation and the associated increase in palm oil plantations between 1990 and 2016 with the spread of vector-borne diseases – diseases like dengue that are transmitted by insect bites like mosquitoes – and zoonotic diseases that jump from animals to humans .
How did they do that – Scientists collected country-by-country data on World Bank deforestation, FAO palm oil and infectious human disease rates from GIDEON, an online computer network.
Then they generated two statistical models to examine the relationship between forest cover and outbreaks of diseases and palm oil plantations and infectious diseases between 1990 and 2016.
These models demonstrate a clear increase in disease outbreaks linked to deforestation and the construction of palm oil plantations, with the most severe increases in disease outbreaks occurring in the few years prior to 2016.
Ultimately, data collected from 47 countries suggests a connection between loss of forest cover and an increase in zoonotic diseases. Meanwhile, reforestation practices may have been responsible for the loss of animal biodiversity and the increase in outbreaks of zoonotic diseases in 27 countries.
“Reforestation can increase the loss of biodiversity when the expansion of the forest is done at the expense of pastures, savannas and open canopy forests”, writes the study team.
Surprisingly, reforestation correlated more strongly with disease outbreaks in areas with more grassland and less tropical climates, including the United States and Europe.
Why does it matter – Deforestation due to palm oil plantations – and certain types of agricultural “reforestation” – makes the transmission of zoonotic diseases more likely because it removes the animals’ natural habitats, including bats that carry new diseases.
“Our result shows that oil palm plantations can also pose a threat to global health by favoring zoonotic and vector-borne diseases,” write the researchers.
These animals then get closer to humans, increasing the possibility of disease transmission.
What is the next – Now that there is more data supporting the link between deforestation and disease outbreaks, the study team argues that we must act quickly to reduce the chance of future pandemics.
They also say it is necessary to ensure that future reforestation efforts – even well-intentioned ones – do not end up creating outbreaks of unintended diseases and loss of biodiversity by planting too much of a tree and creating a monoculture.
With these concerns in mind, the researchers propose three key recommendations for policymakers.
- Stopping deforestation through international treaties that govern forest management
- Developing additional research on how forests and other ecosystems regulate disease
- Hold responsible predatory corporations that profit from deforestation
“We hope that these results will help policy makers to recognize that forests contribute to a healthy planet and people and that government agencies need to prevent forestry and agricultural conversion of pastures,” said Morand.
Summary: Deforestation is a major cause of biodiversity loss with a negative impact on human health. This study explores on a global scale whether the loss and gain of forest cover and the increase in oil palm plantations can promote outbreaks of zoonotic and vector-borne diseases. Taking into account the growth of the human population, we found that the increases in outbreaks of zoonotic and vector-borne diseases from 1990 to 2016 are related to deforestation, mainly in tropical countries, and to reforestation, mainly in temperate countries. We also found that outbreaks of vector-borne diseases are associated with an increase in areas of palm oil plantations. Our study offers new support for a link between global deforestation and outbreaks of zoonotic and vector-borne diseases, as well as evidence that reforestation and plantations can also contribute to infectious disease epidemics. The results are discussed in the light of the importance of forests for biodiversity, livelihoods and human health and the need to urgently build an international governance structure to ensure the preservation of forests and the ecosystem services they provide, including disease regulation. . We develop recommendations for scientists, public health agents and policy makers who must reconcile the need to preserve biodiversity, taking into account the health risks posed by the lack or poor management of forests.