Destroying Habitats Creates the Perfect Conditions for Coronavirus to Emerge

(The following account is based on an article on www.ensia.com. Ensia is a solutions-focused nonprofit media outlet reporting on our changing planet.)

As habitat and biodiversity loss increase globally, the novel coronavirus outbreak may be just the beginning of mass pandemics. Only a decade or two ago it was widely thought that tropical forests and intact natural environments teeming with exotic wildlife threatened humans by harboring the viruses and pathogens that lead to new diseases in humans like Ebola, HIV and dengue. But a number of researchers today think that it is actually humanity’s destruction of biodiversity that creates the conditions for new viruses and diseases like COVID-19, the viral disease that emerged in China in December 2019, to arise — with profound health and economic impacts in rich and poor countries alike. In fact, a new discipline, planetary health, is emerging that focuses on the increasingly visible connections among the well-being of humans, other living things and entire ecosystems.

Is it possible, then, that it was human activity, such as road building, mining, hunting and logging, that triggered the virus epidemics of the 1990s and that is unleashing new terrors today? We invade tropical forests and other wild landscapes, which harbor so many species of animals and plants — and within those creatures, so many unknown viruses. We cut the trees; we kill the animals or cage them and send them to markets. We disrupt ecosystems, and we shake viruses loose from their natural hosts. When that happens, they need a new host. Often, we are it.

Increasing Threat

Outbreaks of animal-borne and other infectious diseases like Ebola, SARS, bird flu and now COVID-19, caused by a novel coronavirus, are on the rise. Pathogens are crossing from animals to humans, and many are now able to spread quickly to new places. Some diseases, like rabies and plague, crossed from animals centuries ago. A few, like COVID-19, which emerged last year in Wuhan, China, and MERS, which is linked to camels in the Middle East, are new to humans and spreading globally.

Other diseases that have crossed into humans include Lassa fever, which was first identified in 1969 in Nigeria; Nipah from Malaysia; and SARS from China, which killed more than 700 people and traveled to 30 countries in 2002–03. Some, like Zika and West Nile virus, which emerged in Africa, have mutated and become established on other continents.

Increasingly, these zoonotic diseases are linked to environmental change and human behaviour. The disruption of pristine forests driven by logging, mining, road building through remote places, rapid urbanization and population growth is bringing people into closer contact with animal species they may never have been near before.

The resulting transmission of disease from wildlife to humans is now a hidden cost of human economic development. There are just so many more of us, in every environment. We are going into largely undisturbed places and being exposed more and more. We are creating habitats where viruses are transmitted more easily, and then we are surprised that we have new ones.

There are countless pathogens out there continuing to evolve which at some point could pose a threat to humans. The risk of pathogens jumping from animals to humans has always been there. The difference between now and a few decades ago is that diseases are likely to spring up in both urban and natural environments. We have created densely packed populations where alongside us are bats and rodents and birds, pets and other living things. That creates intense interaction and opportunities for things to move from species to species.

Tip of the Iceberg

Pathogens do not respect species boundaries. Shrinking natural habitats and changing behavior add to the risks of diseases spilling over from animals to humans. The majority of pathogens are still to be discovered. We are at the very tip of the iceberg.

Humans are creating the conditions for the spread of diseases by reducing the natural barriers between virus host animals — in which the virus is naturally circulating — and themselves. Wildlife everywhere is being put under more stress. Major landscape changes are causing animals to lose habitats, which means species become crowded together and also come into greater contact with humans. Species that survive change are now moving and mixing with different animals and with humans.

There’s misapprehension among scientists and the public that natural ecosystems are the source of threats to ourselves. It’s a mistake. Nature poses threats, it is true, but it’s human activities that do the real damage. The health risks in a natural environment can be made much worse when we interfere with it. When we erode biodiversity, we see a proliferation of the species most likely to transmit new diseases to us, but there’s also good evidence that those same species are the best hosts for existing diseases.

The Market Connection

Viruses and other pathogens are also likely to move from animals to humans in the many informal markets that have sprung up to provide fresh meat to fast-growing urban populations around the world. Here animals are slaughtered, cut up and sold on the spot. The “wet market” (one that sells fresh produce and meat) in Wuhan, thought by the Chinese government to be the starting point of the current COVID-19 pandemic, was known to sell numerous wild animals, including live wolf pups, salamanders, crocodiles, scorpions, rats, squirrels, foxes, civets and turtles.

Equally, urban markets in west and central Africa see monkeys, bats, rats and dozens of species of bird, mammal, insect and rodent slaughtered and sold close to open refuse dumps and with no drainage. Wet markets make a perfect storm for cross-species transmission of pathogens. Whenever you have novel interactions with a range of species in one place, whether that is in a natural environment like a forest or a wet market, you can have a spillover event.