The Dark Warning of an Early Spring

The woods are waking up. The stolid hardwood trees are still mostly bare, but the forest understory is already greening and greening and greening. Dormant ground cover is greening up through moldering leaf litter, and tiny green shoots are opening at the tips of saplings and woody shrubs.

On Presidents’ Day, the high in Nashville was 76 degrees; the next day it hit 80. This, we all assured one another, was nothing more than our annual false spring, an idyll of sunny skies and temperate breezes that briefly gives us all heart before winter crashes back and turns the saucer magnolia’s pink blossoms into a brown smudge against the cold blue sky.

I woke up early that February day because a cardinal was singing “Birdy-birdy-birdy-birdy” so loudly there was no sleeping in, even on a national holiday. Birds rarely sing in winter. Partly that’s because they don’t need to — they sing primarily to find a mate and defend nesting territory — and partly it’s because singing burns precious calories. In winter, food is hard to come by just when it takes enormous energy to keep warm.

But our resident cardinal didn’t know it was only Feb. 19. He sat outside our bedroom window at dawn, singing his heart out. “Birdy-birdy-birdy-birdy! Birdy-birdy-birdy-birdy!” Thanks to his exuberance, I was up early enough to find a parking place at the edge of a little lake I like to walk around — a little lake the rest of Nashville likes to walk around in fine weather, too — and that’s how I noticed the woods were already waking up.

Winter was brutal this year, highs in the teens day after day after day, torrential rains whenever the mercury rose into a more normal range for Middle Tennessee. A polar vortex prompted the president of the United States, who apparently does not know the difference between climate and weather, to tweet, “Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!”

In this context, even a person who knows the difference between climate and weather might be forgiven for welcoming a warm day in February — a gorgeous day when birds are singing and little creatures are stirring in the brush, and all the sleeping turtles have crawled out of the deep mud at the bottom of the lake and lumbered onto the slick trunks of fallen trees. I paused to study them sunning themselves, all lined up in a row like prehistoric rosary beads.

“When spring came, even the false spring, there were no problems except where to be happiest,” Hemingway famously wrote in “A Moveable Feast.”

But this, it turns out, was not a false spring. This was actual spring arriving very early.

The symptoms of climate change are well known, and its risks to some of our favorite creatures — tigers, sea turtles, elephants, giant pandas, mountain gorillas, monarch butterflies — are equally clear, though it’s easy to forget that in the comings and goings of our own daily lives. In December a National Geographic video of a starving polar bear went viral as people faced at a gut level the undeniable consequences of a phenomenon that can sometimes seem mainly theoretical.

A storm system that moved through the country last week temporarily brought colder temperatures to Nashville and a blizzard across the Northeast, but that won’t change anything. There will be consequences to this absurdly early spring.

We tend to assume that the cardinal in my yard is typical of the way nature works. If spring comes early, the birds will sing their lusty songs into the trees and the turtles will awake from their watery winter sleep, and small rodents will emerge from their burrows and blink in the sunshine. And that is the way it works for many species. But not all of them.

Last year a study published in Nature found that climate change significantly disrupts the migratory patterns of nine familiar songbirds. Birds that spend winter in South America depend on light, rather than temperature, to tell them when to head north — as the days grow longer, they know it’s time to fly. The amount of light on any given day isn’t affected by climate change, so the birds keep to ancient patterns. They have no way of knowing that spring is now arriving earlier than normal. Or what used to be normal.

And if spring arrives earlier than expected in the Northern Hemisphere, migrating birds will show up, right on schedule, to find their typical food sources vanished, with terrible implications for the survival of their young.

The study in Nature spanned 12 years. Even within that relatively short window and following a relatively small number of species, scientists were able to track a growing disparity between the migration schedule and the onset of spring. “This mismatch is increasing for a large number of migratory bird species,” the study notes.

That study ended in 2012. The three hottest years on record, according to the National Oceanic and Atmospheric Administration, were 2015, 2016 and 2017.

The Article First Appeared In New York Times

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