As the World Warms, Researchers Warn That Many Ecosystems Are Nearing a Point of No Return

Growing up in southeast Alaska, Jeremy Aantiyéili Timothy says his summers were defined by the Mendenhall Glacier, or Áakʼw Tʼáak Sítʼ. He’d sprint up the ­moraines—steep hills of silt and debris deposited by the glacier—­getting in shape for the winter ski runs ahead.

Now 48, he has witnessed the landscape transform since his youth. “Seeing how much the glacier has receded in that timeframe is heartbreaking,” says Timothy, a cultural ambassador program manager for the Central Council of Tlingit and Haida Indian Tribes of Alaska. “You feel like this glacier is a part of you.”

Here, the climate crisis isn’t a theory; it’s a visible, rapidly unfolding reality of thawing and thinning ice, unstable moraines, and shifting habitats. “Outburst” floods, which occur when glacial lakes suddenly breach the ice dam containing them, now regularly send dangerous torrents into the Mendenhall River and through Juneau, costing the city tens of millions in damages. Locals and tourists can no longer easily walk up to the glacier or its ice caves. “We can still see it, but we can’t reach it,” says Gwen Baluss, conservation chair for the Juneau Audubon Society.

As the planet barrels toward 1.5 degrees Celsius of warming, scientists warn that climate change may push Áakʼw Tʼáak Sítʼ, along with other mountain glaciers, over a “tipping point.” If temperatures rise enough, the glacier could break into segments, setting off a cycle of ever faster ice loss. Passing these points would be like falling off a cliff instead of sliding down a predictable slope.

A report published in October by 160 scientists found that many Earth systems are similarly in danger of crossing irreversible thresholds, triggering feedback loops that can lead to total ecosystem collapse—and facilitate even more warming. “The biggest picture is that we’re sadly already starting to cross climate tipping points, and the risk of crossing others increases with every fraction of a degree of global warming,” says Tim Lenton, University of Exeter climate scientist and lead author of the Global Tipping Points Report.

Already, researchers say Earth has reached its first major tipping point: the widespread dieback of warm­-water coral reefs, which are unable to regenerate as the ocean grows hotter and more acidic. Many other essential systems are also at risk. Drought and deforestation threaten to turn the Amazon rainforest—the lungs of the planet—into a dry savanna. Melting sea ice is shifting the Arctic from a white, sunlight-reflective sheet to a dark, heat-absorbing ocean that can, in turn, melt more ice. If thawing permafrost releases trapped greenhouse gases or if warming water causes ocean currents to collapse, the ripple effects could destabilize global weather patterns and food webs.

The future doesn’t have to be so grim, however. While scientists have worried about these dire thresholds for years, the new report also identifies “positive tipping points” that can correct the course. These social, economic, and technological drivers set off chain reactions, too—flipping failing systems toward stability and locking in progress for the planet.

Lenton says there is evidence that movement toward positive tipping points is accelerating globally, from the rising use of solar energy—the fastest-growing source of electricity in history—to the growing adoption of electric vehicles. As these technologies spread, they become cheaper and more attractive compared to fossil-fuel-based alternatives, further speeding up decarbonization. Restoration and conservation efforts can also tip degraded systems back to health, the report says, buying struggling habitats time to survive. 

In Juneau, Indigenous groups are playing a central role in adapting to the new normal. Last year, the Mendenhall River hit a record-high water level that could have decimated the city if not for recently installed flood barriers. Sabrina Grubitz, the Tlingit and Haida public safety manager, says tribal leaders are working proactively with state and federal partners to protect the community from these increasing risks. The tribal government is also partnering on co-stewardship of the glacier and the surrounding land with the U.S. Forest Service. This effort includes hiring cultural ambassadors to educate visitors and shedding colonial labels in favor of ancestral ones, such as calling the glacier by its native name.

Such on-the-ground collaboration, especially with Indigenous communities, is essential to staving off ecosystem collapse, Lenton says. When local projects succeed, they create a blueprint. Replicating them at scale—and combining them with policies that incentivize clean energy—builds momentum toward a safer and healthier planet. That’s a tipping point, too. “It very much involves people and communities and bottom-up action deciding to make the change,” Lenton says. “That change becomes infectious.”

This story originally ran in the Spring 2026 issue as “Balancing Act.” To receive our print magazine, become a member by making a donation today.