Climate change: and trees blooming earlier

Despite the last surge of winter, spring is actually happening earlier;
Futures Forum: Climate change >>> Shifting Spring @ Costing the Earth on Radio 4

And this is happening across the northern hemisphere: 

Climate change causing trees to bloom weeks earlier, researchers say

James M. O'Neill, Staff Writer, @JamesMONeill

Published 6:47 a.m. ET April 13, 2018

Researchers are growing more interested — and concerned — about the role climate change and warming temperatures could have on blooming trees. Through the USA National Phenology Network, researchers over the past decade have been gathering annual data on the bloom times of various species across the country, and comparing them to more regional records that date back many decades.

Some of those old regional records show that tree bloom times are two to three weeks earlier today than in the past, said Jake Weltzin, an ecologist with the United States Geological Survey and director of the network. For instance, when he lived in his tiny cabin at Walden Pond in Massachusetts, the author Henry David Thoreau kept detailed records of plant species — some of which no longer thrive in that part of the state.

Boston University biology professor Richard Primack has studied Thoreau’s notes to determine that some tree species around Walden Pond now bloom two to three weeks earlier than they did when Thoreau lived at the pond in the mid-1840s.

Researchers have used notes compiled in the 1840s by Henry David Thoreau while living in a cabin at Walden Pond in Massachusetts to discover that trees are blooming on average two weeks earlier today. (Photo: Elise Amendola/Associated Press)

Some of the oldest data on bloom times come from notes kept by the explorers Lewis and Clark during their exploration in the first decade of the 1800s, Weltzin said.

Observations collected by the network so far this year showed that early season yardstick species such as lilac were starting to bloom 12 days earlier than the 30-year average in South Jersey, Weltzin said. But then the cold weather returned to New Jersey in late March, and the progressing “green wave” stopped around Route 195. Here in North Jersey, we’re just now starting to see some early species bloom, such as red maple.

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Some tree species are specialists — they rely on particular insect species to spread their pollen. If the trees bloom early in reaction to earlier warmth, before the insects have shown up, the trees’ seeds might not get fertilized. Conversely, if the insects that rely on the tree flowers for food show up too late and the flowers have already died off, they are without a food source.

“If the insect patterns are not in sync with the new flowering times of trees, that could be an issue,” said Nina Bassuk, a professor at Cornell University’s Urban Horticulture Institute. “It has not been proven to be a problem yet, but it is a concern.”

In addition, non-native species seem to adapt more quickly to warming climate, which gives them an advantage over native species, putting the natives at risk going forward, said Lena Struwe, director of the Chrysler Herbarium at Rutgers.

Lena Struwe, director of the Chrysler Herbarium at Rutgers (Photo: Rutgers University)

Climate change in the Northeast doesn’t create conditions favorable to tree species that don’t like change, said Richard Harper, an extension assistant professor at the University of Massachusetts Amherst. For instance, hemlocks can grow for 800 to 1,000 years, so as climate change occurs, during their lifetime they will lose the conditions favorable to them. Hemlocks and sugar maples don’t do well under extreme heat and drought conditions, and will contract their range, moving farther north, he said.

At the same time, some southern tree species, such as willows and turkey oaks, are expected to handle the change better, taking advantage of longer growing seasons and expanding their range deeper into the mid-Atlantic.

Climate change has also caused our winters to grow shorter, and our springs to be more variable.

“You get cold and warm and cold again and that can be damaging to trees,” said Bassuk. Several years ago, a few weeks of warmer weather in February caused many apple trees in upstate New York to bloom, but the buds were killed when cold weather returned. “Some farmers lost their entire apple crop,” Bassuk said.

Trees are finally waking up and will soon be using a wide array of wildly weird evolved attributes to help them engage in reproduction. Check a backyard near you. Wochit

So what of a particular bush or tree that consistently blooms ahead of others from the same species? That could be related to the microclimate where the tree is located. A tree planted against a south-facing wall of a house will enjoy more reflected light and warmth than one planted in a shaded part of the backyard, and will therefore start to bloom earlier, Harper said.

Bassuk said some southern magnolia trees have managed to thrive in chilly downtown Ithaca, N.Y. because they can take advantage of the “urban heat island” of the city landscape.

Climate change causing trees to bloom earlier, researchers say
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