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Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things

Wild Things

Insects may undermine trees’ ability to store carbon

forest tent caterpillar

Forest tent caterpillars, like this one resting on an aspen leaf, are found in U.S. hardwood forests. A new study finds that when carbon dioxide levels are higher, herbivorous insects eat more vegetation. 

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Trees are often promoted as an important tool for combating climate change. That’s because trees take in carbon dioxide from the air and lock it away in wood and soil for years. But trees may not be as great of carbon sinks as we thought, a new study finds. Why? Blame hungry insects.

This revelation comes from a tree-growing experiment in Wisconsin. In the mid-1990s, scientists planted groves of aspen and birch trees. They then set up 12 rings of PVC pipes that vented gases into those dozen groves. Some tree patches got extra carbon dioxide, reaching levels of about 560 parts per million — about what might be expected in 2050 or sooner. Others were exposed to ozone levels about 50 percent higher than normal.

Then from 2006 to 2008, once the trees had grown tall, researchers collected leaves, scraps and insect fecal droppings so that they could measure how tree biomass changed, where nutrients were going and how insects were affecting the system. John Couture of the University of Wisconsin-Madison and colleagues published their findings March 2 in Nature Plants.

On average, stands of trees grown with high carbon dioxide saw 88 percent more damage to the tree canopy from hungry insects than those grown without the extra CO2. As a result of the increase in insect feeding, trees in the higher-carbon forest stored about 70 grams less carbon per square meter than trees grown in open air, the team found.

“Insects have the potential to ‘level the playing field’ for forest stands under future atmospheric CO2 conditions, disproportionately limiting stands that would grow rapidly under high CO2 environments,” the researchers write.

The insects probably eat more because when grown under high CO2, trees produce less nutritious leaves. Insects would have to eat more leaves to compensate for the lower nutrition.

However, the ultimate ability of forests to store our extra carbon will depend on more factors than simply carbon dioxide levels and hungry insects. And those other factors may change the equation. In the forest experiment, for instance, increased ozone resulted in an average 16 percent decrease in damage. And insects — and their droppings — move nutrients around the food web, further complicating things.

Trees may still be the easiest way to tackle our carbon problem, but it remains unknown how much — or how little — help they’ll be able to provide. 


Delicate spider takes down tough prey by attacking weak spots

By Sarah Zielinski 3:05pm, February 27, 2015
The Loxosceles gaucho recluse spider can take down a heavily armored harvestman by attacking its weak spots, a new study reveals.

Where an ant goes when it's gotta go

By Sarah Zielinski 12:17pm, February 24, 2015
Scientists found black garden ants defecating in certain spots inside their nests. The researchers say these spots serve as ant toilets.

Five surprising animals that play

By Sarah Zielinski 2:33pm, February 20, 2015
No one is shocked to find playful behavior in a cat, dog or other mammal. But scientists have documented play in plenty of other species, including reptiles and insects.

Cliff swallow breeding thwarted by bird version of bedbugs

By Sarah Zielinski 12:15pm, February 18, 2015
A 30-year study of cliff swallows in Nebraska finds that the birds will abandon nests, rather than have a second brood, when their homes are infested with swallow bugs.

Fertile hermit crabs turn shy

By Sarah Zielinski 11:00am, February 13, 2015
Male hermit crabs that aren’t carrying much sperm are bolder than their more fertile brethren, a new study finds.
Animals,, Ecology,, Conservation

Cats and foxes are driving Australia’s mammals extinct

By Sarah Zielinski 11:56am, February 11, 2015
Since the arrival of Europeans in Australia, a startling number of mammal species have disappeared. A new study puts much of the blame on introduced cats and foxes.
Animals,, Biophysics,, Evolution

Toads prefer to bound, not hop

By Sarah Zielinski 2:30pm, February 6, 2015
The multiple hops made by toads are really a bounding motion similar to movements made by small mammals.

Huge, hollow baobab trees are actually multiple fused stems

By Sarah Zielinski 11:54am, February 4, 2015
The trunk of an African baobab tree can grow to be many meters in diameter but hollow inside. The shape, researchers say, occurs when several stems fuse together.
Climate,, Animals,, Oceans

Warming Arctic will let Atlantic and Pacific fish mix

By Sarah Zielinski 12:00pm, February 2, 2015
The ultra-cold, ice-covered Arctic Ocean has kept fish species from the Atlantic and Pacific separate for more than a million years — but global warming is changing that.

Ant-eating bears help plants

By Sarah Zielinski 5:44pm, January 27, 2015
A complex web of interactions gives a boost to rabbitbrush plants when black bears consume ants.
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