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--></style><title>US forests now more vulnerable to climate than to
logging</title></head><body>
<div><font face="Arial" size="-1" color="#1A1A1A">Forest Ecology and
Management<br>
Volume 360, 15 January 2016, Pages 242-252<br>
doi:10.1016/j.foreco.2015.10.042<br>
<br>
<b>Forest disturbance across the conterminous United States from
1985-2012: The emerging dominance of forest decline</b><br>
Warren B. Cohen et al<br>
<br>
Highlights<br>
*We characterized annual rates of forest disturbance between 1985 and
2012.<br>
*Landsat time series were visually interpreted, with support of
ancillary data.<br>
*A probability design was used to scale estimates and provide
uncertainties.<br>
*Harvest was the most important disturbance agent class prior to the
mid-90s.<br>
*Forest decline is now more important than harvest as the dominant
agent class.<br>
<br>
Abstract<br>
</font><font face="Arial" size="-1"
color="#0040C2"><u
>http://www.sciencedirect.com/science/article/pii/S037811271500599X</u
></font><font face="Arial" size="-1" color="#1A1A1A"><br>
<br>
Evidence of shifting dominance among major forest disturbance agent
classes regionally to globally has been emerging in the literature.
For example, climate-related stress and secondary stressors on forests
(e.g., insect and disease, fire) have dramatically increased since the
turn of the century globally, while harvest rates in the western US
and elsewhere have declined. For shifts to be quantified, accurate
historical forest disturbance estimates are required as a baseline for
examining current trends. We report annual disturbance rates (with
uncertainties) in the aggregate and by major change causal agent class
for the conterminous US and five geographic subregions between 1985
and 2012. Results are based on human interpretations of Landsat time
series from a probability sample of 7200 plots (30 m) distributed
throughout the study area. Forest disturbance information was recorded
with a Landsat time series visualization and data collection tool that
incorporates ancillary high-resolution data. National rates of
disturbance varied between 1.5% and 4.5% of forest area per year, with
trends being strongly affected by shifting dominance among specific
disturbance agent influences at the regional scale. Throughout the
time series, national harvest disturbance rates varied between one and
two percent, and were largely a function of harvest in the more
heavily forested regions of the US (Mountain West, Northeast, and
Southeast). During the first part of the time series, national
disturbance rates largely reflected trends in harvest disturbance.
Beginning in the mid-90s, forest decline-related disturbances
associated with diminishing forest health (e.g., physiological stress
leading to tree canopy cover loss, increases in tree mortality above
background levels), especially in the Mountain West and Lowland West
regions of the US, increased dramatically. Consequently, national
disturbance rates greatly increased by 2000, and remained high for
much of the decade. Decline-related disturbance rates reached as high
as 8% per year in the western regions during the early-2000s. Although
low compared to harvest and decline, fire disturbance rates also
increased in the early- to mid-2000s. We segmented annual
decline-related disturbance rates to distinguish between newly
impacted areas and areas undergoing gradual but consistent decline
over multiple years. We also translated Landsat reflectance change
into tree canopy cover change information for greater relevance to
ecosystem modelers and forest managers, who can derive better
understanding of forest-climate interactions and better adapt
management strategies to changing climate regimes. Similar studies
could be carried out for other countries where there are sufficient
Landsat data and historic temporal snapshots of high-resolution
imagery.<br>
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<div><font face="Bookman Old Style" size="-2"
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>========================================================<br>
</font><font face="Geneva" size="-1" color="#262626">Study co-author
Dr Amanda Bates, from Ocean and Earth Science at the University of
Southampton, said: "In 100 years from now, 100 per cent of
species in many communities will be lost and replaced by new species
able to tolerate warmer conditions, leading to a redistribution of
species across the globe."</font></div>
<div><font face="Geneva" size="-1" color="#262626"><br>
</font><font face="Bookman Old Style" size="-2"
color="#FFFF00"><u
>http://www.eurekalert.org/pub_releases/2015-11/uos-tso111015.php</u></font
><br>
<font face="Bookman Old Style" size="-2"
color="#FFFF00"><u></u></font></div>
<div><font face="Bookman Old Style" size="-2"
color="#000000">and/or:<br>
<br>
</font><font face="Cambria" size="-2"
color="#FFFF00"><u
>http://www.nature.com/nature/journal/vaop/ncurrent/full/nature16144.<span
></span>html<br>
<br>
</u></font><font face="Bookman Old Style"
color="#000000"></font></div>
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