Science Sunday: San Juan Glaciers, Marijuana Psychos, Wolves

Going, Going, Gone Glacier

Colorado scientists weren’t pulling their weight this week. We could only find one paper from local researchers. Fortunately it’s an interesting piece of work from Zackry Guido, Dylan Ward and Robert Anderson of CU-Boulder’s Department of Geology and Institute of Arctic and Alpine Research

Published in the journal Geology, the researchers track the disappearance of a 5,000 square kilometer ice cap that covered the San Juan Mountains until about 20,000 years ago. The glacier began to melt about 19,400 years ago, and was completely gone by 12,300 years before the present.

“The sensitivity of alpine glaciers to precipitation and temperature makes the lengths of glaciers valuable climate proxies,” the authors say.

The only other study of how fast a glacier retreats was of the Fremont glacier in Wyoming’s Wind River Mountains. Researchers there found that the glacier retreated 29 kilometers in the 4,000 years between 17,100 years ago and 13,100 years ago, a rate of retreat of about seven meters a year.

The San Juan glacier retreated twice as fast, the authors say, at a rate of about 15 meters a year.

Killer Weed

As if we didn’t already have enough psychos in Denver, this week’s issue of the British medical journal The Lancet says that:

“There is now enough evidence to warn young people that using cannabis could increase their risk of developing a psychotic illness later in life by more than 40 percent.”

The Denver City Council is currently considering an initiative, according to Safer Choice, that:

“Would create a city ordinance designating private adult marijuana possession Denver’s lowest law enforcement priority … on July 24th the measure was transmitted to the Denver City Council for its consideration. It will now be assigned to a committee, and then it will be presented to the entire council, at which time it will either be enacted or referred to the November ballot.”

The British research was a “meta-analysis” of 35 studies done prior to 2006 to determine whether cannabis sue led to psychotic or mental health disorders.

They found that individuals had used cannabis ever were 41% more likely than those who had never used the drug to have any psychosis. The risk increased relative to dose, with the most frequent cannabis users more than twice as likely to have a psychotic outcome.

Nonetheless, psychosis is fairly rare with or without marijuana. The results indicate only about 800 additional psychosis cases in all of Great Britain.

The study was also coy about other psychological effects. “Depression, suicidal thoughts, and anxiety outcomes were examined separately, and findings for these outcomes were less consistent,” the authors said.

Ecology of Fear

It sounds like a public relations disaster, but the “ecology of fear” is restoring aspen ecology in Yellowstone National Park, according to Oregon State University researchers.

Prior to the reintroduction of wolves in the Yellowstone ecosystem, elk herds flourished, eating up the tender new aspen shoots, which elk apparently love. I found them hard on the stomach myself, but to each species its own.

Anyway, wolves are now chivvying the elk around the park — elk numbers have declined by about half, not all of that the result of wolf reintroduction — so that they don’t munch up all new aspen. For the first time in 50 years, young aspen trees are growing on YNP’s northern range.

In some areas of the West, 90 percent of the aspen have disappeared. This wolf-to-elk-to-aspen interaction is known as a “trophic cascade.”

“When I first looked at these degraded ecosystems in the mid-1990s in Yellowstone, I had doubts we would ever be able to bring the aspen back,” said Robert Beschta, a professor emeritus of forestry at OSU and co-author on the study. “There were so many elk, and the stream ecosystems were in such poor shape. The level of recovery we’re seeing is very encouraging.

There has been some muttering about reintroducing in Rocky Mountain National Park, which also has lots of elk. The aspen there, however, are not in the same dismal shape that Yellowstone were, apparently. A 2006 paper by Colorado State University scientists found that in RMNP:

“Evidence of elk browsing is widespread but evidence of aspen decline is not.”

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