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<div><font face="Geneva">PNAS Early Edition published ahead of print
October 11, 2016, doi:10.1073/pnas.1604974113</font><font
face="Arial"><br>
</font><font face="Geneva"><br>
Sackler Colloquium on Coupled Human and Environmental Systems -
Biological Sciences - Sustainability Science:</font></div>
<div><font face="Arial"><br>
</font><font face="Geneva"><b>Timescales and the management of
ecological systems</b><br>
Alan Hastings</font><br>
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<div><font face="Geneva">Abstract<b> [bold added]</b></font><font
face="Arial"><br>
</font><font
face="Geneva"><u
>http://www.pnas.org/content/early/2016/10/10/1604974113.abstract</u></font
><br>
<font face="Arial"></font></div>
<div><font face="Geneva"><b>Human management of ecological systems,
including issues like fisheries, invasive species, and restoration, as
well as others, often must be undertaken with limited information.</b>
This means that developing general principles and heuristic approaches
is important. Here, I focus on one aspect, the importance of an
explicit consideration of time, which arises because of the inherent
limitations in the response of ecological systems.<b> I focus mainly
on simple systems and models,</b> beginning with systems without
density dependence, which are therefore linear.<b> Even for these
systems,</b> it is important to recognize the necessary delays in the
response of the ecological system to management. Here, I also provide
details for optimization that show how general results emerge and
emphasize how delays due to demography and life histories can change
the optimal management approach. A brief discussion of systems with
density dependence and tipping points shows that<b> the same themes
emerge</b>,<b> namely, that</b> when considering issues of restoration
or management to change the state of an ecological system, that<b>
timescales need explicit consideration</b> and may change the optimal
approach in important ways.</font></div>
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<div><font face="Verdana" size="-1" color="#000000">"These large
recharge events are vital in replenishing and maintaining groundwater
storage, especially after multiple years of below average
precipitation across the region," said Melissa Masbruch, a
hydrologist at the U.S. Geological Survey in Salt Lake City and lead
author of the study. "Without them, groundwater resources become
depleted."</font></div>
<div><font face="Verdana" size="-1" color="#000000"><br></font></div>
<div><font face="Verdana" size="-1" color="#000000"><b>Large
groundwater recharge events are characterized by</b> above-average
annual precipitation and<b> below-average</b> seasonal<b>
temperatures, especially during the spring</b> (April through
June).</font></div>
<div><font face="Verdana" color="#000000"><b><br></b></font></div>
<div><font face="Verdana" size="-2"
color="#000000"
><<http://blogs.agu.org/geospace/2016/10/11/large-precipitation<span
></span>-events-critical-replenishing-groundwater-resources/>></font
></div>
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color="#000000"><b>========================================</b></font></div
>
<div><font face="Verdana" size="-1" color="#000000"><b>Alaska is
getting warmer earlier in the year</b>...Over the past 60 years, the
average annual temperature in Alaska has increased by over 3 degrees
Fahrenheit, with most of the change happening in winter<b> and
spring</b>.</font></div>
<div><font face="Verdana" size="-1" color="#000000"><br></font></div>
<div><font face="Verdana" size="-2"
color="#000000"><u
>https://nccwsc.usgs.gov/content/ecological-drought-alaska</u></font><br
>
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