Has nature healed itself during the anthropopause imposed by the pandemic?

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In a typical spring, breeding seabirds — and humans watching them — migrate to Stora Karlsö, an island off Sweden.

But in 2020 the Covid-19 pandemic canceled the tourist season, reducing the human presence on the island by more than 90%. In the absence of humans, bald eagles have taken up more space, becoming much more abundant than usual, scientists have found.

It might seem like a pretty parable about how nature recovers when people disappear from the landscape — if it weren’t for the fact that ecosystems are complex. The now numerous eagles flew again and again along the side of the cliffs where a sheltered population of common auras, or auks, laid their eggs, scaring the smaller birds away from the ledges they occupied.

In the midst of the confusion, some eggs fell from the cliffs; others were stolen by predators while the airas were away. The reproductive performance of snooks dropped by 26%, as marine ecologist Jonas Hentati-Sundberg of the Swedish University of Agricultural Sciences found. “They flew away in panic and lost their eggs,” he explained.

The pandemic was and still is a worldwide human tragedy. For ecologists, however, it has also been a unique opportunity to find out more about how humans affect the natural world. To that end, they documented what happened when we suddenly moved away from this natural world.

A growing body of studies paints a complex picture of the slowdown in human activity, which has become known as the “anthropopause”. It was clear that some species benefited from our absence, which is consistent with early media narratives that without people roaming around, nature would finally be recovering. But other species struggled when deprived of protection and human resources.

“Humans play a dual role,” said Amanda Bates, an ocean conservationist at the University of Victoria in Canada. According to her, humans act “as threats to wildlife, but also as guardians of our environment.”

Scientists say the research has useful lessons for conservationists, suggesting that even modest changes in human behavior can have big benefits for other species. It is especially important to analyze these changes at a time when human life enthusiastically resumes its normal rhythm and tourism grows in the summer, potentially generating an “anthropopulsion” of intense activity.

“A lot of people are going to want to make up for lost time in terms of vacation travel, business travel — they’re going to want to make up for what they’ve missed in life,” said behavioral ecologist Christian Rutz of the University of Saint Andrews, who introduced the concept of “anthropopulsion” in a recent scientific article. (He and Amanda Bates were also on the team that coined the term “anthropopause”).

“Humans go and should travel and enjoy nature,” he added. “But I think we can make very subtle changes to the way we do things, and they can have a tremendous impact.”

the positive

When the pandemic arrived, many human routines were suddenly suspended. On April 5, 2020 – the peak of lockdowns due to the pandemic – 4.4 billion people, or 57% of the planet, were subject to some kind of restriction on their movements, scientists estimated. Car travel has decreased by more than 40%, and air traffic has dropped by 75%.

These sudden changes allowed researchers to differentiate the effects of human displacement from the many other ways in which we affect the lives of other species.

“We know that humans impact ecosystems by changing the climate. We know that humans have dramatic impacts by modifying land use, such as destroying animal habitats to build shopping malls,” said Christopher Wilmers, a wildlife ecologist at the University of California in Santa Cruz. “But this study addresses the question ‘what are the impacts of human mobility itself?’.”

Scientists have discovered that with humans locked up in their homes — with their cars locked in garages, planes in hangars, ships parked in ports — air and water quality has improved in some places. Noise pollution has decreased on land and below the sea surface. Habitats cluttered by humans began to recover.

Hanauma Bay Nature Preserve in Hawaii, a popular destination for snorkelers, closed in March 2020 and remained closed for nearly nine months. “The pandemic has reset visitor impacts to almost zero,” said Ku’ulei Rodgers, an ecologist at the Hawai’i Institute of Marine Biology who specializes in coral reefs.

With no swimmers stirring up sediment, water clarity improved by 56%, Rodgers and her colleagues found. Fish density, biomass and diversity have increased in waters that were once full of divers.

Indeed, scientists have found that many species have moved into new habitats as pandemic lockdowns have transformed the “landscape of fear,” as it is sometimes described by ecologists.

“All animals spend their lives trying not to die,” explained ecologist Kaitlyn Gaynor of the University of British Columbia. This survival drive drives them to keep their distance from potential predators, including humans. “We are loud, unknown and we resemble their predators – and in many cases we are their predators,” Gaynor said.

For example, pumas that live in California’s Santa Cruz Mountains typically keep their distance from cities. But in 2020, after quarantine orders took effect, the animals more frequently selected habitats near the urban periphery, Wilmers and his colleagues found.

Wilmers speculated that the pumas were reacting to changes in the urban soundscape, which would normally be filled with the sounds of human speech and passing cars. “But once those auditory stimuli were gone, the animals had a ‘let’s go check if there’s anything to eat’ reaction,” he said.

the negative

But the effects of human absence were nuanced, varying according to species, place and time.

Several studies have concluded that when vehicular traffic slowed in the spring of 2020, the number of wild animals run over and killed by cars dropped. But the number of collisions between wild animals and vehicles has risen again, although vehicle traffic has remained below normal levels, according to a team of researchers.

“During the pandemic, there were more accidents per mile traveled,” said Joel Abraham, an ecology graduate student at Princeton University and one of the study’s authors. “We interpret this as changes in the animals’ use of space. Animals started using roads. And it was difficult to get them to stop, even when traffic started to return to normal levels.”

The lockdowns appear to have encouraged some invasive species, increasing the daytime activity of Florida rabbits in Italy, where their rapid expansion could threaten native hares, while hampering efforts to control others. For example, the pandemic postponed a long-planned project to shoot down giant predatory mice on Gonçalo Álvares Island (or Gough) in the South Atlantic Ocean, a critical habitat for endangered seabirds.

The mice, which likely arrived with sailors in the 19th century, prey on the live pups and eat them, often leaving large open wounds. “I dubbed them ‘vampire mice,'” said Stephanie Martin, environmental and conservation policy director for Tristan da Cunha, the archipelago of which the island of Gonçalo Álvares is a part. Many of the puppies do not survive the injuries.

Scientists were about to launch a massive mouse eradication effort when the pandemic began, delaying the project for a year. In the following breeding season, with the giant mice still running free, not a single offspring of MacGillivray’s prion survived, an endangered bird that breeds almost exclusively on the island of Gonçalo Álvares. “We lost an entire breeding season,” Martin said. “It’s been another year without puppies.”

The lessons to be learned

As people resume their normal lives, researchers will continue to monitor wildlife and ecosystems. If an ecosystem that seemed to benefit from the absence of people suffers when people come back in weight, that will bring stronger evidence of the impact we have had.

“This reversal of experimental or semi-experimental intervention scientifically allows us to have really strong insights into the workings of environmental processes,” Rutz said.

Understanding these mechanisms can help experts design programs and public policies that channel human influence more carefully.

“If we strengthen our role as guardians and continue to control pressures, we can really make the role of humans in the environment more positive,” said Carlos Duarte, a marine ecologist at King Abdullah University of Science and Technology in Saudi Arabia.

When Hanauma Bay Nature Preserve reopened in December 2020, it instituted a new cap on the number of visitors it accepts daily. Today it is closed two days a week, whereas before the pandemic it was just one day, Rodgers said.

Other modifications could also have benefits, experts said. Building wildlife walkways over highways can prevent some animals from being run over. Requiring car engines and boat propellers to be less noisy can reduce noise pollution on land and at sea.

“No one else can say that we can’t transform the whole world in one year, because we can,” said Bates. “We’ve already done that.”

Translation by Clara Allain

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