From the lush Amazon rainforest to the frigid Arctic Ocean, the world’s landscapes — and all the wildlife they contain — are under threat, and the world needs to set aside a third of all land and sea territories to save them, UN experts say.

The call is central to the global agreement being hashed out this month at the UN biodiversity summit in Montreal. If approved at the end of the summit next week, governments would be agreeing to set aside 30% of their land and sea territories for conservation by 2030 – doubling the amount of land area and more than tripling the ocean territory currently under conservation.

More than 110 countries have come out in support of the 30-by-30 goal, including Canada, the United States and France.

Proponents argue that the goal is crucial to reversing the destruction of nature. Currently, more than 1 million species are at risk of extinction, while the global insect population declines at up to 2% every year and about 40% of the world’s remaining plant species are in trouble.

But as is often the case with science-based policy, the details matter to whether a 30% global conservation goal can truly save the world’s imperiled species and places.

“The danger, as with all these sorts of events populated by politicians, is they want a simple number,” said Stuart Pimm, a biologist at Duke University. “They would like to be able to leave Montreal and say we’re going to protect 30% of the planet. But that alone is not enough.”

This driving question ultimately comes down to quantity versus quality.

There is not a strong scientific argument behind 30% as the threshold for staving off species loss, experts said. In reality, it could take a much greater percentage of land or sea — or a lower percentage — depending which areas are selected.

“30% is neither necessary nor sufficient,” Pimm said. “If we do things the right way, we protect most biodiversity by being smart — by protecting the areas that matter.”

There is a temptation, he said, to conserve vast tracts of land that are already without many people, but also have relatively little biodiversity, such as the Arctic tundra or Saharan desert.

But it is important to protect areas with lots of different species, known as biodiversity hot spots, even if they are more challenging to conserve because people live there or there are extractive industries.

Protecting narrow slices of land and sea such as Australia’s Great Barrier Reef or the Andes mountains, can offer far more reward than protecting large swathes of prairie, for example.

“A numerical target isn’t going to work,” Pimm said. “If we were to just protect 50% of the planet, and we protect the least populated 50%, it will do very little for biodiversity.”

A June 2022 study in the journal Science found that at least 44% of global land area would be needed to protect areas with a high diversity of species, prevent the loss of intact ecosystems, and optimize the representation of different landscapes and species. But more than 1.8 billion people live in these areas.

However, co-author Hugh Possingham, a researcher at the University of Queensland, noted that “while there is nothing magical about 30% … targets help focus the attention of nations.”

“I see 30% as a goal that most countries can reasonably achieve by 2030,” he said, adding some countries, such as Bhutan, had already passed this goal.

One of the key tension points that has emerged in the 30-by-30 debate at COP15 is whether the target should be carried out globally or at a national level. —Reuters