A lot of climate discussion revolves around time. Lines rise across charts predicting the next century. Scientists set deadlines for the coming decades. Each month seems to bring news of a new heat record. The sense that time is running out can be heady.

As the Earth warms, natural wonders — coral reefs, glaciers, archipelagos — are at risk of damage and disappearance. This has motivated some travelers to engage in “last-chance tourism,” visiting places threatened by climate change before it’s too late.

“For thousands of years, humans have raced to be the first to scale a peak, cross a frontier, or document a new species or landscape,” Paige McClanahan writes in a piece for The Times. “Now, in some cases, we’re racing to be the last.”

A vanishing glacier

One such destination is the Mer de Glace, the largest glacier in the French Alps, where thousands of people go each year to ski. (Early tourists included Mary Shelley and Mark Twain.)

The glacier, like many others, is melting rapidly. A new, higher lift opened recently to stay closer to the retreating ice. And a study published in the journal Science last year found that around half of the world’s glaciers will have melted by the end of this century, even if nations stick to the goals of the Paris climate agreement.

“For someone who doesn’t know how it used to be, it’s a beautiful scene,” a visitor to the glacier told Paige. “But when you know the difference, it really is sad.”