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On this week's effervescent Independent comics page: Red Meat doesn't much care for negativity; Jen Sorenson examines the phenomenon of "trigger trash"; The K Chronicles discusses what it's really like to be in prison; and This Modern World looks at objections to The Proven Thing.

Published in Comics

Aspen trees are the rock stars of the tree world. They have a bold fashion sense, gilding the mountains in gold each fall. And they engage in risky behavior: In the competitive world of plant biology, their strategy is to grow fast and die young. Juniper trees, which grow slowly, invest much of their carbon in building strong vascular tissue; aspen trees instead put carbon toward growing tall quickly.

Yet the two trees adopt the same strategy when drought hits: Unlike pines, they leave their stomata open. Those tiny pores on their leaves allow the trees to take up carbon dioxide from the atmosphere and photosynthesize. But the atmosphere demands water in return, which escapes through the tree's stomata. During drought, the process creates extra tension in the plant's tissue, since the trees have less water to give, and the parched atmosphere is especially thirsty.

This is when the juniper's investments in building tough tissue pays off: The tubes that transport water through the tree can withstand an increase in tension. The Aspen tree, on the other hand, becomes vulnerable. Their tubes are more likely to collapse, which can eventually lead to the tree's death.

A few years ago, Bill Anderegg, a forest who is now an assistant professor at the University of Utah, figured out that this was what was killing aspen trees in his native Colorado. (Around 2004, aspen trees throughout the Rocky Mountains began mysteriously dying in droves, a phenomenon that was dubbed "sudden aspen decline.") But he noticed something else curious about their pattern of death: There seemed to be a lag between the drought and its consequences. Tree growth would slow for a few years, but they often wouldn't start to die until three to eight years after the drought.

"There was an interesting paradox of trees being stressed and dying from drought in completely wet soils," Anderegg says. "Which prompted me to ask the question: How widespread are these legacy effects?"

It turned out they were quite widespread, according to the results of a study Anderegg recently authored in the journal Science. Using data from a global tree ring archive, Anderegg measured tree growth following severe drought at 1,338 sites, primarily in the Northern Hemisphere and outside the tropics. Growth is a good proxy for forest health, Anderegg explains, and it's also the primary way trees store carbon. That's important, because globally, forests take up about a quarter of anthropogenic carbon emissions. Their continued ability to sequester carbon at that level is critical to blunting the most severe effects of climate change.

With a few exceptions, tree growth slowed for two to four years after severe drought, with the most enduring effects appearing in arid environments—another indication of the troubles Southwestern forests are likely to face as the climate warms.

"It does seem like species that took more risks during drought seemed to recover more slowly," he says, like aspen, which don't close their stomata and conserve water. "Which does indicate that there's some role of this damage to their hydraulic systems that could slow their growth in subsequent years."

Scientific models of the global carbon cycle—which are important for projecting climate change—don't account for this slow-down in growth. "The models assume there is no lag, so as soon as climate is better, so is growth," says Nate McDowell, who researches the physiology of tree death at Los Alamos National Lab in New Mexico. That means that models may overestimate the ability of ecosystems to store carbon—and underestimate the severity of future climate change.

If droughts do become more frequent and severe, Anderegg says, as climate models predict, "this suggests that more forests are going to spend more and more of their time recovering, and become less good at taking up carbon." Anderegg estimates that in Southwestern forests, the lag could amount to a 3 percent reduction in their carbon storage over a century. That may not sound like much, but when it comes to squirreling away the emissions we stubbornly keep spewing, we need all the help we can get.

Plus, the meaningfulness of such numbers is a matter of scale, notes Adrian Das, a forest ecologist with the U.S. Geological Survey in the Southern Sierra Nevada. While we don't know what the precise effect of that reduced carbon storage might be, locally or globally, "these changes can translate into really large absolute numbers," he says. "Three percent is not very much if it’s five trees. It means something different if it’s thousands of trees."

Cally Carswell is a contributing editor to High Country News, where this story originally appeared.

Published in Environment

On this week's exciting Independent comics page: This Modern World deals with an alien invasion (but not very well); Jen Sorenson has a proposal for defenders of fracking; The K Chronicles packs up and moves cross-country; and Red Meat seeks some medicine, of sorts.

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On this week's humble and modest Independent comics page: The K Chronicles is finally somebody; This Modern World ponders the Trans-Pacific Partnership; Jen Sorenson sells some science; and Red Meat looks for some aluminum cans.

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On this week's sexy Independent comics page: This Modern World looks at Ted Cruz's path to the White House; Jen Sorenson says goodbye to South Florida; The K Chronicles struggles with liberal guilt; and Red Meat gets ready to go bowling.

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On this week's semi-treasonous Independent comics page: In the wake of the letter to Iran from congressional Republicans, The K Chronicles wonders what else Republicans have been doing to mess with the White House; This Modern World similarly wonders what other "cheeky" acts the GOP has been up to; Jen Sorenson looks at advances in Internet trolling; and Red Meat cancels a trip to the beach.

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On this week's spirited Independent comics page: This Modern World looks back at the hottest year on record with some GOP help; Jen Sorenson examines "webcam abortion"; The K Chronicles has a drink with the father-in-law; and Red Meat makes a wish.

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On this week's revealing Independent comics page: Jen Sorenson borrows some useful tips from Sen. Joni Ernst; The K Chronicles looks at the rights of a police officer who shoots a black man; This Modern World checks in with the Right Wing Science Dude; and Red Meat has a chat with God.

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On this week's delicious Independent comics page: Red Meat enjoys some food at camp; Jen Sorenson suggests changing the phrase "climate change" to "globola"; The K Chronicles joins a white riot; and This Modern World enters the Right-Wing House of Fear.

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Last spring, Joshua trees put on a magnificent show in the Mojave Desert: Nearly all at once, nearly all of them bloomed, sprouting dense bouquets of waxy, creamy-green flowers from their Seussian tufts of spiky leaves.

The bloom was so sweeping and abundant—and such a contrast to the typical pattern, where only a small number of trees bloom in any given year—that it was called “a once-in-a-lifetime phenomenon.”

This spring, the bloom was far less flowery, and yet standing among the giant yuccas in late March, in the Tikaboo Valley north of Las Vegas, U.S. Geological Survey ecologist Todd Esque still had the sense he was witnessing something historic.

This, he suspects, is the leading edge of the entire species—“leading,” because the trees appear to be marching in the same direction in which the climate that suits them is marching, with an old, established population of Joshua trees flinging out new recruits in a distinctly northern pattern.

That’s exactly what scientists believe the shaggy beasts need to do—quickly—to survive in a warming world.

The pattern is obvious to the naked eye here, because it’s occurring where the Mojave Desert gives way to the Great Basin, where stands of Joshua trees fade to sagebrush. ”I get chills when I look at that population,” says Esque. ”We know from the paleo record that plants and animals have moved north and south by hundreds of miles—if not more—in response to climate change. To see it in our lifetime, at a time when it really matters if they can move or not, it’s neat.”

The news about Joshua trees of late has mostly been gloomy, so much so that some people have begun to imagine a future in which Joshua Tree National Park is without Joshua trees. Fires carried by non-native grasses have been picking off the plants. There is evidence that in the hottest, driest spots it occupies, the trees are already plodding down the road to extinction by failing to reproduce. One study projected that 90 percent of their current habitat could be inhospitable by century’s end.

And so Joshua trees face the modern mandate familiar to so many species: move or die. The same study projecting a 90 percent reduction in habitat also cast doubt on Joshua trees’ ability to migrate far enough quickly enough to keep them on the map in significant numbers. It found evidence that the Shasta ground sloth was once one of the plant’s major seed-dispersers. The sloth, of course, is extinct, and the trees now mostly depend on smaller creatures—squirrels and kangaroo rats—to spread their seed. The sloths, large mammals that they were, are assumed to have dispersed the seeds over greater distances than the rodents now do, meaning Joshua trees might be able to make small steps to new territory, but not the great leaps that may be necessary.

But really, says Esque, we don’t know how quickly Joshua trees are capable of moving, or even if they can move at all. It’s possible the new trees in the Tikaboo Valley represent a “static front,” he explains, “where they keep casting out young trees, but every 30 years, there’s a drought that might kill them, so the population can never really move.”

Nor do we know for certain that sloths dispersed seed across great distances, because we don’t know how widely the animals actually ranged. “There are a lot of questions, probably way more than answers,” he says. Which is why it’s so exciting that he and his colleague Chris Smith, an evolutionary biologist, may have discovered the trees’ forward march. If they can confirm that it is the species’ leading edge, they can begin to gain greater insight into its potential mobility, and with that its prospects for the future.

In March, Esque, Smith and a group of citizen scientists spent four days collecting data to do just that, by mapping the distribution of old and young Joshua trees in the Tikaboo Valley. As it happens, the Tikaboo is the only place scientists know of where the distinct eastern and western populations of Joshua trees meet and mingle. So they took tissue samples from the burgeoning population, too, in hopes of identifying whether either the eastern or western trees, or their hybrids, were winning the “race north.”

“As you move northward (in the Tikaboo), the big Joshua trees thin out, they get shorter and shorter, younger and younger, then you get to a point where there aren’t any anymore,” Esque explains. The youngest, he believes, are less than a decade old. “That’s the edge of Joshua trees as we know them. The potential is right there for the species’ migration.”

Cally Carswell is a contributing editor of High Country News, where this article was initially published. The author is solely responsible for the content.

Published in Environment

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