Surrendering Forests

tree david johnsonDavid Johnson (1827 – 1908)


by Jeff Tietz
Rolling Stone

From a tree’s perspective, excessive heat may be as deadly as lack of water.
To photosynthesize, a tree opens pores in its leaves called stomata and inhales CO2. Solar-charged chemical reactions then transform the CO2 into carbohydrates — the raw stuff of leaves and wood. During this process, a fraction of the tree’s internal water supply evaporates through its stomata, creating the negative pressure that pulls water from the soil into the tree’s roots, through its trunk and up to its canopy. But heat juices the rate at which trees lose moisture, and that rate escalates exponentially with temperature — so small temperature increases can cause a photosynthesizing tree to lose dangerous amounts of water.
“Forests notice even a one-degree increase in temperature,” says Park Williams at Los Alamos National Laboratory.

In the death scenario, the sky sucks water from the leaves faster than it can be replaced by water in the soil, and the resulting partial vacuum fatally fractures the tree’s water column. If a tree closes its stomata to avoid this, shutting down photosynthesis, it risks starvation.
Ultimately, the tree’s cellular chemistry will fail, but it will often die before that, as its defenses fall; the complexly toxic sap that repels predatory insects dries up.
Many insects can detect diminished sap levels within tree bark by scent — they smell drought stress and pheromonally broadcast news of deteriorating tree health. Other defenses – against microbes, for example — may also be compromised.
A hotter climate generally means more insects.
It also means more, and more intense, wildfires.

For decades, all over the planet, heat-aggravated drought has been killing trees: mountain acacia in Zimbabwe, Mediterranean pine in Greece, Atlas cedar in Morocco, eucalyptus and corymbia in Australia, fir in Turkey and South Korea.
In 2010 a group of ecologists published the first global overview of forest health. They described droughts whose severity was unequaled in the “last few centuries” and documented “climate-driven episodes of regional-scale forest die-off.”

Because global warming outpaces evolutionary adaptation, the question is: Can trees survive as they are?
The conifer forests of the Southwest United States, if climate projections are even minimally accurate, cannot, but what about the rest of the world’s forests?
That’s a critical question, because forests cover more than a quarter of the planet’s land, and they help stabilize the climate by pulling immense quantities of CO2 out of the air.
In August 2011, a team of scientists led by Dr. Yude Pan, a U.S. Forest Service researcher, reported that between 1990 and 2007, forests sequestered about 25 percent of all greenhouse-gas emissions — everything not in the air or seas.

Climatologists worry that if forests across the planet deteriorate, they could, on balance, begin releasing as much carbon as they absorb.
One of Pan’s collaborators, Dr. Richard Birdsey: “If the carbon sink in forests fails, a simple speculation is that global temperatures would increase proportionally to the increase of CO2 concentration, so about 25 percent above current climate projections.”
“The more forests die, the less carbon they take out of the air, the warmer it gets, the more forests die,”
says Dr. Nate McDowell at Los Alamos. “It’s a thermostat gone bad.”

The better we understand climate change, the more we seem to find that warming begets warming in unexpected and self-amplifying ways: Implacable heat engines materialize and run independently of all human effort.

There are an estimated 1 trillion metric tons of frozen carbon in the soils of the Arctic region — a century’s worth of global emissions, twice the amount stored in the global forest, another few Industrial Revolutions.
As the planet warms, permafrost thaws and decomposes, sending carbon into the air and further warming the planet. Higher temperatures also kindle increasingly intense and frequent wildfires in high-latitude forests, to quadruple effect.
And fire releases carbon directly; it burns off the insulating upper layer of vegetation, exposing more permafrost to warm air; it blackens the trees and land, which consequently absorb more solar radiation; and its soot can settle on and darken snow and ice sheets to the north, which then also absorb more solar radiation.

By the end of the century, the woodlands of the Southwest will likely be reduced to weeds and shrubs. And scientists worry that the rest of the planet may see similar effects.

 

http://www.rollingstone.com/politics/news/the-fate-of-trees-how-climate-change-may-alter-forests-worldwide-20150312?page=3

 

Trees Cry Out
https://secretgardening.wordpress.com/2013/05/27/trees-cry-out/

The Longevity of Trees

https://secretgardening.wordpress.com/2013/06/14/popular-science-monthlyjuly-1873the-longevity-of-trees/
A Living Miracle
https://secretgardening.wordpress.com/2010/05/25/%E2%80%9Ctrees-are-a-living-miracle-leaves-can-take-in-carbon-dioxide-and-create-oxygen-and-all-creatures-must-have-oxygen-%E2%80%9D/
Du Bon Usage des Arbres
https://secretgardening.wordpress.com/2012/01/08/a-plea-to-the-attention/

Trees Cry Out

Carl Blechen (July 29, 1798 – July 23, 1840), Young Oak
Carl Eduard Ferdinand Blechen (1798 – 1840)


By

When drought hits, trees suffer—a process that makes sounds.
Scientists have known for decades that microphones can pick up the sounds that trees make.
Now, scientists may have found the key to understanding these particular cries for help.
In the lab, a team of French scientists has captured the ultrasonic noise made by bubbles forming inside water-stressed trees.
Because trees also make noises that aren’t related to drought impacts, scientists hadn’t before been able to discern which sounds were most worrisome.

The findings could lead to the design of a handheld device that allows people to diagnose stressed trees using only microphones.
Such a device may be particularly important as droughts become more common and more severe.

Across western North America, from Mexico to Alaska, forest die-off is occurring on an extraordinary scale, unprecedented in at least the last century-and-a-half — and perhaps much longer. All told, the Rocky Mountains in Canada and the United States have seen nearly 70,000 square miles of forest — an area the size of Washington state — die since 2000.

In 2005 Colorado researchers noticed that aspens were suddenly dying in large numbers. The die-off is called Sudden Aspen Death, or SAD.
It’s growing at an exponential rate – and killing not only mature trees, but the root mass as well.
An aspen grove is the offspring of a large single underground clonal mass, which sends up shoots.  “The whole organism is disappearing and it has profound implications,” said Wayne Shepperd, of the Forest Service. “When the roots die, groves that are hundreds or thousands of years old aren’t going to be there anymore.”

A study published in Nature last fall suggested that trees in many places—from tropical rain forests in South America to arid woodlands in the U.S. West—already “live on the edge,” meaning their cavitation rate is almost as high as they can sustain.
Sizeable areas of forest in Australia, Russia, France, and other countries have experienced die-offs, most of which appears to have been caused by drought, high temperatures, or both.

Shifts in rainfall patterns and increasing temperatures associated with climate change are likely to cause widespread forest decline in regions where droughts are predicted to increase in duration and severity
.

http://bajandreamer.wordpress.com/2013/06/21/rains-no-cure/

http://www.nature.com/nature/journal/v491/n7426/full/nature11688.html

http://e360.yale.edu/feature/whats_killing_the_great_forests_of_the_american_west/2252/

http://news.nationalgeographic.com/news/2013/04/130415-trees-drought-water-science-global-warming-sounds/

Study Of A Flying Sparrow

Giovanni Nanni, also Giovanni de' Ricamatori, better known as Giovanni da Udine (1487–1564)

Giovanni Nanni, also Giovanni de’ Ricamatori, better known as Giovanni da Udine (1487–1564)

Carl Sagan, upon contemplating the rarity of life in the known universe said,

“The earth is a meadow in the sky . . .”
“If we ruin the earth, there is no place else to go”   ―