Everything in nature—flowering, breeding, migration—lives and dies by a clock that is being recalibrated by climate change. We don’t yet know how severe the consequences may be.

Timing is everything in nature. From the opening notes of a songbird’s spring chorus to the seasonal percussion of snapping shrimp, every important ecological process lives and dies by a clock.

Flowering. Egg laying. Breeding. Migration. It’s as true on the Mongolian steppe as it is in the Arabian Sea or a Costa Rican rain-forest. Centuries of evolution honed these patterns. Now climate change is re-calibrating them.

And that is reshaping life for almost everything. In every ocean and across every continent, seasons are in flux. Earlier warmth, delayed cold, and shifts in the frequency and fierceness of precipitation are toying with established rhythms in both predictable and unexpected ways.

So researchers the world over are straining to document the timing of life cycle events, a scientific discipline known as phenology. That timing is being upended by our fossil fuel emissions.

Across much of the United States rising average temperatures are pushing spring to speed up its arrival. Plants and pollinators found at high elevations in the western U.S. are especially affected.

To better understand how species are interacting and responding to these changes, scientists are tracking the timing of biological events—a field known as phenology.

Changes are discovered almost everywhere scientists look. The timing of leaf appearance and leaf dropping has already shifted dramatically across more than half the planet.

Humpback whales in the Gulf of Maine are gathering 19 days later than they once did, while jack mackerel, hake, and rockfish are spawning earlier in the North Pacific.

In North Dakota’s Red River Valley, scientists found 65 of 83 bird species arriving earlier, some by as much as 31 days. South Carolina’s dwarf salamanders are arriving at breeding grounds 76 days later.

What’s harder to grasp is the severity of the consequences—for plants, animals, and us. If everything shifted in the same direction and by roughly the same amount, our new calendar might prove insignificant. As with daylight saving time, we’d muddle through together.

But that’s not how nature works. Species are not responding identically, said David Inouye, a University of Maryland professor emeritus and leading phenology researcher.

Too many patterns are shifting at the same time, each influenced by countless others, which are themselves also in motion. It’s everything, everywhere, all at once. Even beings that don’t appear to be changing are seeing their world change around them.

Snowshoe hares, Siberian hamsters, collared lemmings, and long-tailed weasels all turn white in winter as a form of protective camouflage in snow. Now they’re often out of sync with their surroundings.

Many are increasingly seen with halogen-bright white bodies crouched in green forests or brown brush or on yellow tundra. That’s because snow is arriving later and melting earlier, but their color transition is triggered by seasonal shifts in daylight, which, of course, isn’t changing at all.

So what happens then, when we revamp nature’s schedule in every wild system on Earth at once, altering timing for some things but not others?

Few understand the implications better than Inouye. Study any species in isolation, and you may know if they’re changing as we stood in a meadow in thin air near 10,000 feet. But to understand why that change is happening—and what it means—scientists must cast a wider net. No species lives in isolation.

As we strolled through cool green fields of wild parsnip and false skunk cabbage as we toured the nearly century-old Rocky Mountain Biological Laboratory, one of the most important phenology research sites in the world.

It’s no ordinary field station: Science labs and housing are tucked into aging buildings—all that remains of board-and-batten Gothic, an abandoned 19th-century mining town eight miles north of Crested Butte. Around us, hummingbirds wing-whistled among the lupines, aspen sunflowers, and dwarf larkspurs.

Nearby, graduate students counted bumblebees by netting and loading them into plastic vials. To avoid tallying any bee twice, they dotted each fuzzy thorax with a marker, then set the insect free.

Inouye has tracked biological cycles here for 50 years. He speaks in the tranquil, measured tones of someone who has spent a lifetime counting flowers.

Thin, tall, with a bearded angular face reminiscent of Abe Lincoln’s, Inouye, 73, can name on sight 150 or so of the valley’s wildflower species. He can identify which bird, wasp, bee, or fly spreads their nectar. He knows this place better than I know my living room.

Few can top their firsthand observations of the ways planet warming is contorting nature’s timing. In 2000, before anything like it had been done in North America, the group, which by then included his ecologist son, Brian, showed migrating American robins were arriving 14 days earlier.

In 2008, Inouye found that climate-driven changes to the growing season have paradoxically increased frost events, killing more sunflowers and lavender-hued daisies.

The discoveries in Colorado come amid budding global interest in timing as researchers start cataloging profound costs. From 2015 to 2016, up to a million common murres, large seabirds sometimes dubbed flying penguins, starved to death along the United States’ West Coast, their emaciated carcasses washing up on beaches.

A severe ocean heat wave made more likely by climate change had altered timing cycles for their food. Musk oxen in Alaska are increasingly born smaller as melting snow refreezes, coating in ice the vegetation pregnant cows need.

Previously, winters stayed so cold and dry they could paw through snow to eat greenery below it.) With sea ice melting earlier, polar bears spend more time on land.

Grizzly bears already are venturing farther north. The two species have occasionally mated in the past, but hybrid “pizzly” bears, while still rare, are now expected to become more common.

There are risks for us too. Globally, markets for insect-pollinated crops, such as cacao, watermelon, cumin, and coriander, are worth up to $577 billion annually.

Changes to nature’s clock also may influence agriculture in dozens of hidden ways, not all of which can be addressed by shifting planting or harvest seasons. Farms may be exposed to more frosts or previously unseen crop-killing pathogens.

A Colorado legend, barr (who does not capitalize his name) has been profiled on television, in newspapers, books, and films. He visited Gothic as a Rutgers University student and came back for good in 1973—and holed up in a mining shack without electricity or running water.

So barr measured things—temperature and snowfall and snow depth. He tracked moisture content and noted in spring when snow melted. (He used a yardstick and a scale.) He heard each year’s first birdsong and recorded his first marmot spotting. He jotted it all in notebooks.

Less modern-day Thoreau than restless data geek, barr enjoyed comparing year-to-year observations. And while barr and Inouye knew one another, it wasn’t until the late 1980’s that the two chatted in depth about barr’s records.

They could show, in detail, reductions in snow seasons. It was barr who first noticed robins arriving early, barr who provided data that helped others link marmot emergence with early spring.

As far back as 1991—just three years after NASA scientist James Hansen told Congress that greenhouse gases are warming the planet—Inouye and a colleague used barr’s notebooks to show how reduced snows could change flowering in the mountains, potentially harming bees and hummingbirds.

It’s a riotous, mixed-up world, with species colliding in new ways. Far more forces influence the timing of events than even Inouye had imagined. Too many factors are at play.

We’re all now part of a giant experiment, with everything that is familiar in motion. The potential for negative consequences is magnified. But the world may also surprise us.

As long as birds have insects and nectar to eat, maybe they won’t care if the smorgasbord changes. Some pollinators may simply switch to different plants, while others may not. Then again, insects too are in stark decline, even in Gothic.

And although marmots are mostly winning, staying fat with plenty of food during longer, warmer summers, ever lighter winter snows can diminish the cocoon effect that insulates their burrows. Some have actually frozen to death while hibernating.

How timing mismatches may reorganize systems remains unclear, even in Gothic, where scientists have now tracked nearly six million flowers. In most ecosystems on Earth, we’ve only just begun to look closely enough to notice.

We’ve forgotten what we used to do, which is watch—just observe things, Nora Underwood told me. I hear it at meetings: Everybody now wishes they started counting things 50 years ago.

National Geographic / Crickey Conservation Society 2023.