Earth Notes
12:06 pm
Thu November 21, 2013

Earth Notes: Tracking Climate Change In Northern Arizona

In late September, the Intergovernmental Panel on Climate Change released its Summary for Policymakers for part-one of its  massive Fifth Assessment Report. Its message? Earth's climate is warming, and human influence on that warming is clear.

Grand Canyon
Credit Northern Arizona University

Northern Arizona University research scientist Ken Cole and his colleagues are charting the impacts of this warming trend on the Colorado Plateau.

Temperature records for northern Arizona have been reliably recorded since 1924. They show that temperatures were fairly consistent for a half century after that. But, mean temperatures since 1972 rose nearly half a degree per decade. This closely follows computer model predictions, suggesting that northern Arizona is on track for a 7.3 degree Fahrenheit temperature increase by the end of this century.

To understand the ecological effects of this change, Cole has tapped an unlikely treasure - pack-rat trash piles, or middens. As pack rats discard plant debris near their nests, they create a record of local vegetation. Pack rat urine turns the debris into a solid mass that can last tens of thousands of years.

Studying pack rat middens in Grand Canyon, Cole focused on plant residue from 11,700 years ago, a period of warming similar in rate and magnitude to current changes.

His findings suggest that, within this century, many native plant populations will plummet. Species will migrate to higher elevations, a process that will favor fast-spreading, weedy species. Fire will further alter species dominance.

Bottom line? Big changes for northern Arizona's plant communities and for the countless organisms - including people - that inhabit them.

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