One-Two Punch Does in Colorado Pines, Creates Further Disruption

Here is a story that seems to go out of its way to prove the necessity of scientific research at every level of our ecosystem and how close to breaking our world we can get if we are not careful; and even if we are. New research has found that the one-two-punch of drought and attack by the mountain pine beetle are the main cause for the destruction of more than 2.5 million acres of pinyon pine and juniper trees in the American Southwest over the past 15 years.

And this is more than likely only a precursor to greater ecological disruption in the years to come.

“Pinyon pine and juniper are naturally drought-resistant, so when these tree species die from lack of water, it means something pretty serious is happening,” said Wendy Peterman, an OSU doctoral student and soil scientist with the Conservation Biology Institute. “They are the last bastion, the last trees standing and in some cases the only thing still holding soils in place.”

Pinyon pine forests near Los Alamos, N.M., had already begun to turn brown from drought stress in the image at left, in 2002, and another photo taken in 2004 from the same vantage point, at right, show them largely grey and dead.

Pinyon pine and juniper are the dominant tree species across much of the Southwest of America. They have long been known to be capable of withstanding one or two years of drought and have grown in many mountain areas at moderate elevations. Common throughout Utah, Colorado, New Mexico, and Arizona, they are thought to have expanded their range over the what has been a wetter than normal century.

However, in some places, up to 90 percent of these trees have died out, many of them during the drought in 2003 and 2004. The research — published in the journal Ecohydrology by scientists from the College of Forestry at Oregon State University and the Conservation Biology Institute in Oregon — found that the majority of the mortality took place in shallow soils with less than four inches of available water in about the top five feet of the soil column.

Now while the loss of so many trees is in and of itself worrying, the implications that now arise only serve to enforce the seriousness of the situation.

The pinyon pine and juniper were not considered to be trees of any real value, only occasionally used for firewood. However, their role in the environment was much greater than that. They stabilised soil and prevented erosion, while providing a small measure of food for local animals as well as storing carbon in their biomass and in the soils beneath their canopies.

“These areas could ultimately turn from forests to grasslands, and in the meantime people are getting pretty desperate about these soil erosion issues,” she said. “And anything that further reduces flows in the Colorado River is also a significant concern.”

That last part relates directly back to the trees’ ability to prevent erosion. Soil erosion in the particular region where the pinyon pine and juniper were resident is caused by wind erosion. Dust that is blown from eroded hills will end up covering snowpacks, which cause them to absorb heat from the sun and melt quicker, further reducing the already critically-short water supplies in the Colorado River basin.

There is no real evidence to suggest that any of this is a result of global warming. Increased levels of drought were predicted in 2007 by the report of the Intergovernmental Panel on Climate Change, but there is obviously more at play. And this is exactly the sort of thing that has been predicted by climate scientists for decades now.

All of which leads back to what I said at the start: there is always need for more scientific enquiry and discussion.

Source: Oregon State University
Image Source: Craig Allen, U.S. Geological Survey

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