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The growth of the city favors animals that are more likely to be carriers of disease



Rat in a pipe, London

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Rats are among the winners of our transformation of nature

Turning wild spaces into farmland and cities has created more opportunities for animal diseases to traverse humans, scientists have warned.

Our transformation of the natural landscape drives out many wild animals, but favors the species that are most likely to be disease carriers, a study suggests.

The work adds to the growing evidence that the exploitation of nature fuels pandemics.

Scientists estimate that three out of four newly emerging infectious diseases come from animals.

The study shows that, around the world, we have shaped the landscape in a way that has favored the species that are most likely to be carriers of infectious diseases.

And when we convert natural habitats into farms, pastures and urban spaces, we inadvertently increase the likelihood of pathogens passing from animals to humans.

“Our results show that animals that remain in more human-dominated environments are the ones most likely to carry infectious diseases that can make people sick,”

; said Rory Gibb of University College London (UCL).

How can changing the landscape cause disease?

The transformation of forests, grasslands and deserts into cities, suburbs and farmland has pushed many wild animals to extinction.

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More than half of the world’s habitable earth has been modified by humans

Short-lived animals that can survive in most environments, such as rats and pigeons, have thrived at the expense of long-lived animals such as rhinos, which have specialized habitat requirements.

Some rodents, for example, which carry a variety of viruses, thrive in urban spaces, where other species have been lost.

The new evidence comes from analyzing a dataset of 184 studies incorporating nearly 7,000 animal species, 376 of which are known to carry pathogens shared with humans.

What can we do to stop spillover events?

There are many factors involved in what scientists call spillover: when a pathogen passes from an animal to a human, causing disease outbreaks, which can become pandemics.

We know, for example, that close contact with wildlife through hunting, trading or habitat loss exposes the world to a greater risk of new disease outbreaks.

The coronavirus is thought to have originated in bats, along with other wildlife, which played a role in transmission to humans. There are strong indications of a wildlife source and a link to trade.

Wild animals at risk of extinction due to human exploitation have been found to carry twice as many viruses that can cause human disease than the threatened species listed for other reasons. The same is true for endangered species at risk due to habitat loss.

  • Exploiting nature “leads to the emergence of new diseases”

The new study, published in the journal Nature, shows that animals living in human-shaped environments carry more pathogens than those in pristine habitats.

And it highlights a widespread public misperception that wilderness, such as wild jungles, is the main source of disease crossover.

Indeed, the greatest threats appear to arise where natural areas have been converted into farmland, pastures, cities and suburbs.

UCL Professor Kate Jones said the findings indicate strategies that could help mitigate the risk of future public health threats.

“As agricultural and urban land is expected to continue expanding over the next few decades, we should strengthen disease surveillance and health care provision in those areas that are experiencing a lot of soil disturbances, as they are increasingly likely to have animals that could harbor harmful pathogens, “he said.

Why are species like rats on the rise?

The study builds on previous research showing how land modification to farm and build cities is favoring the same species everywhere.

Animals like rats and pigeons are taking the place of less common ones, which can only survive in certain habitats.

As humans change habitats, more unique species are constantly lost and replaced by species found everywhere, such as pigeons in cities and rats on farmland.

These survivors appear to be the ones harboring the largest number of diseases. They include some rodents, bats and birds.

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