We’re all familiar with migration: wildebeests dash across Africa, monarch butterflies fly across the Americas... but did you know that forests migrate, too?

In his new book The Journeys of Trees, science writer Zach St. George explores an extremely slow migration, as forests move bit by bit to more pleasant places.

“The migration of a forest is just many trees sprouting (发芽) in the same direction,” St. George writes. “Through the fossils (化石) that ancient forests left behind, scientists can track their movement over thousands of years. They move back and forth across continents, sometimes following the same route more than once, like migrating birds or whales.” This has happened over thousands of years, and climate change tends to be the driving force.

Of course, today, climate change is speeding up, and trees can’t keep pace. Take California: it’s getting hotter and dryer and scientists estimate that before too long, Sequoia National Park may not be able to keep giant sequoias (巨杉).

“The scientists there had never seen anything like it,” St. George says. “They are worried, and I think at some point we will lose these ancient trees and we will have to think about what we do with the places, and do we plant new trees where they are easy to grow?”

This is known as “assisted migration”— humans planting trees in other places where they’re more likely to grow. But this process carries risks — people can accidentally introduce insects and diseases to new places, where they may wipe out entire native populations. So, St. George writes, there’s a heated debate today: Should humans help the trees escape?

“There may be cases where people are probably going to step in and help species move to places where they’ll be more suitable in the future,” St. George says. “So far, there are no huge movements of citizen groups moving trees north. But that is kind of one vision of the future that the people I interview hope to see.”

Super typhoon Rammasun swept over Hainan, China, destroying at least 23,000 houses and causing 2 billion dollars in damage. It was not just people who experienced the impact, though. In Hainan Bawangling National Nature Reserve, home to the world’s 30 remaining Hainan gibbons(长臂猿), landslides tore through sections of the forest. The gibbons, a species living in trees, were forced to jump across a distance of up to 50 feet to get from one area to another.     

The gibbons sometimes would break their fall only by managing to catch hold of the tip of a particular palm leaf. As months passed, Bosco Chan at the Kadoorie Farm and Botanic Garden in Hong Kong noticed that constant use caused the leaf to wear and bend downward, threatening to lead to the gibbons crashing down and breaking the extremely rare species’ habitat into different islands. “It’s really a matter of concern. Moreover, I didn’t know how long the leaf would be able to hold the gibbons,” he said. “I thought it was time for us to build something.”

As recently described in Scientific Reports, Bosco Chan and his colleagues turned to aerial(空中的) bridges. They hired professional tree climbers to confront and get over the steep landform to fix a simple bridge, consisting of two parallel mountaineering-grade ropes. It took the gibbons over five months to catch on, but once they learned to use the ropes, they started regularly using them to make safe, quick crossings.

Till now, aerial bridges have been used in other countries to help a diversity of animals ranging from squirrels to capuchin monkeys. But many are small, one-off projects carried out by local organizations or even individuals; with little or no scientific study of what does or does not work. In addition, a solution for one species or habitat may not be applicable to another.

In a world on fire and underwater, scientists have announced some good news: Several important tuna(金枪鱼)species have stepped back from the edge of extinction.

Two bluefin tuna species, a yellowfin, and an albacore are no longer seriously endangered or have moved off the leading international list of endangered species entirely.

The unexpectedly fast recovery speaks to the success of efforts over the past decade to end overfishing. But tuna are not the only species scientists are thinking carefully at the 2021 World Conservation Congress in Marseille, France, which is organized by the International Union for Conservation of Nature (IUCN). Researchers warn that many other sea species continued to be imperiled. For example, more than a third of the world's sharks are still threatened with extinction due to overfishing, habitat loss, and climate change.

“I think the good news is that sustainable (可持续的) fishing industry are possible,” says Beth Polidoro, a biologist at Arizona State University. “We can eat fish without reducing the population to the point where it is on the road to dying out or extinction." At the same time, she warns that the recovery should not encourage us to catch as many fish as we want. “We need to keep doing what's working." Polidoro adds.

The IUCN, which determines the world's most endangered species on its Red List of Threatened Species, also announced at the meeting that some animals are moving in the other direction, onto the Red List. Like the Komodo dragon, an lizard (蜥蜴), it is at particular risk from climate change.

Of course, the work of protection is never over, and it will require close and continuous attention to make sure neither tuna nor Komodo dragons return to the edge of dying out. But for now, people can celebrate a few wins for the animal world.