[MCN] Streamflow after forest dieoff: Evidence against popular hypothesis

[Lance Olsen]

When trees die, water slows
UNIVERSITY OF UTAH
Public Release: 16-Dec-2015

Summary:
Mountain pine beetle populations have exploded 
over the past decade, and these insects have 
infected and killed thousands of acres of western 
pine forests. Researchers predicted that as trees 
died, streamflow would increase, but a new study 
disproved this hypothesis.

JOURNAL
Water Resources Research
MEETING
2015 AGU Fall Meeting

Excerpt:
A recent study by University of Utah geology and 
geophysics professor Paul Brooks and his 
colleagues in Arizona, Colorado and Idaho, found 
that if too many trees die, compensatory 
processes kick in and may actually reduce water 
availability. When large areas of trees die, the 
forest floor becomes sunnier, warmer and windier, 
which causes winter snow and summer rain to 
evaporate rather than slowly recharging 
groundwater.

Brooks presented this research at the American 
Geophysical Union's annual meeting this week in 
San Francisco. The AGU annual meeting is the 
largest Earth and space science meeting in the 
world.

###
Full press release here:
http://www.eurekalert.org/pub_releases/2015-12/uou-wtd121615.php

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"Irrigation begins to significantly reduce 
temperatures and temperature trends during boreal 
summer over the Northern Hemisphere mid-latitudes 
and tropics beginning around 1950; significant 
increases in precipitation occur in these same 
latitude bands. These trends reveal the varying 
importance of irrigation_climate interactions and 
suggest that future climate studies should 
account for irrigation, especially in regions 
with unsustainable irrigation resources."

Puma, M. J., and B. I. Cook (2010), Effects of 
irrigation on global climate during the 20th 
century, J. Geophys. Res., 115, D16120, 
doi:10.1029/2010JD014122.
============================================
"New assessments of decades' worth of snowpack 
measurements show that snowpack levels have 
dropped considerably throughout the American West 
in response to a 0.8°C warming since the 1950s."

"'Snow is our water storage in the West,' says 
Philip Mote, a climatologist at the University of 
Washington (UW), Seattle, who leads a team that 
has produced much of the new work. 'When you 
remove that much storage, there is simply no way 
to make up for it.'

"The impacts could be profound."

Robert F. Service. As the West Goes Dry.
Science  February 20, 2004
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