The widespread lockdowns triggered by the COVID-19 pandemic in 2020 caused a number of unexpected effects on birdsong, air pollution and even seismic noise on planet Earth. Many Tweeted #EarthIsHealing to shine a light on the returning of wildlife to once anthropogenically noisy areas (though not all of these turned out to be true).

While the benefits for nature weren’t always as extensive as they were made out to be, it was perhaps unexpected that some wild animals might actually fare less well without a gaggle of tourists peering at their homes. New research published in the journal Biological Conservation has found that this was indeed the case for a colony of seabirds on the Swedish island of Stora Karlsö in the Baltic Sea. Without the hustle and bustle of tourists flocking to see the spectacle of so many cliff-nesting birds, the white-tailed eagle (Haliaeetus albicilla) saw a sevenfold increase in the area – much to the dismay of the common murre, Uria aalge.

While the eagles don’t directly predate on murres, which exist in the area in their thousands, data from long-term seabird monitoring revealed they had a significant impact on the reproductive success of these birds. By frequently hassling them and causing disturbances, the researchers found the eagles were indirectly delaying egg laying and actually made it easier for herring gulls (Larus argentatus) and hooded crows (Corvus cornix) to swipe the eggs.

The lockdown offered a rare opportunity for researchers to gain a better understanding of the influence of humans on the functioning of an ecosystem. Interestingly, their findings revealed tourists in this part of the world had a "guardian" effect on the seabird colony. When they were gone, the increased presence of white-tailed eagles – which are usually deterred by humans – caused a 26 percent decline in murre productivity compared to the long-term average.

“An emerging lesson from over a hundred years of biodiversity conservation is that humans are intrinsic parts of most ecosystems,” wrote the study authors. “Based on our findings, we suggest that human presence could be used as a strategic measure in guarding seabird colonies, and that a social-ecological systems perspective is vital for long-term success in protected area management."

It's not always in conservation that human interference is considered a good thing, but the researchers think this study could prove an interesting consideration for other areas.

"Future field studies will reveal whether the return of tourists to the island post-COVID-19 lockdown will reverse the state of the murre colony to 'normal', or if the anthropause has permanently shifted the behavior of eagles into a long-term threat to the breeding seabirds," they concluded. "If the return of tourists improves the conditions for seabirds, we suggest that human presence can be applied also in other areas to mediate eagle disturbances."