Colorado's famous aspens expected to decline due to climate change


Date:
September 16, 2020
Source:
North Carolina State University
Summary:
Using computer modeling, researchers simulated how the distribution
of quaking aspen, a native tree known for its brilliant yellow
and orange foliage in fall and the sound of its trembling leaves,
will change amid rising temperatures over the next 100 years.



FULL STORY ========================================================================== Along three scenic drives through Colorado's Rocky Mountains in fall,
tourists will see less of a brilliant golden tree in the next 100 years, researchers from North Carolina State University projected in a new study.


========================================================================== Using computer modeling, researchers simulated how the distribution
of quaking aspen, or Populus tremuloides, a native tree known for its
brilliant yellow and orange foliage in fall and the sound of its trembling leaves, will change amid rising temperatures over the next 100 years.

They predicted quaking aspens will decline in visibility in 2120 under
climate warming scenarios. Visibility will also decline along three
scenic national byways in the Colorado Rockies -- even if climate
conditions remain at historical levels. They saw the greatest declines
in the visible landscape areas.

"Aspen are sensitive to drought and warming temperatures, and empirically
we are already starting to see declines," said the study's senior author
Jelena Vukomanovic, assistant professor in the NC State Department
of Parks, Recreation and Tourism Management. "Even if we keep current conditions, we will see declines in aspen. But under worsening climate
change, the decline in aspen will be worse." In the study, researchers
modeled the distribution of quaking aspen trees visible under three
scenarios: If climate does not change from historical conditions observed
from 1980 to 2010; under a 4-degree temperature increase with 15 percent
less precipitation; and with a 4-degree decline and 15 percent more precipitation.

For each scenario, their simulation modeled whether aspens were visible
from 32,949 different vantage points along three scenic roadways in
Colorado: Cache la Poudre, Trail Ridge Road and Peak-to-Peak Highway. They
used a computer model of forest dynamics called the Landscape Disturbance
and Succession (LANDIS-II) model to forecast where aspen will grow and
used U.S. Geological Survey elevation data to model visibility along
scenic roads.



==========================================================================
In addition to factoring in changes in temperature and precipitation,
they also modeled how wildfires, insects and wind events would impact
aspen tree growth and distribution. These trees are intolerant of drought
and shade, researchers said, but they are often the first to colonize
a burned area.

Overall, they found that aspen are expected to decline in all three
climate scenarios. In the two warmer scenarios, the losses were more
than two times greater overall, and aspen loss was even greater in the
visible areas from the scenic byways.

"We can say with good confidence that these main arteries of movement
through the mountains will see a noticeable decline in visible aspen,
and the loss of visible aspen is greater than the overall loss," said Vukomanovic. "It's hard to predict what people will do -- build new roads,
new outlooks, or create new opportunities to view the remaining stands
-- but there could be a negative impact to some of the communities along
these routes that rely on tourism dollars from aspen viewing." They saw
that the changes in aspen varied depending on the elevation. Aspen at the lowest elevations, where they are the least abundant, saw increases under
all three scenarios, but the increases were smaller with climate change.

Researchers hypothesized that at these elevations, the model was capturing aspen regeneration after wildfire, but they regenerate to a lesser degree
under the more extreme climate change scenarios.

"We think they are increasing at lower elevations because they're
colonizing recently burned places," Vukomanovic said. "Because there's
been such active fire suppression at the lower elevations where people
live, when fire comes, it creates opportunities for the aspen to colonize
new places. But these gains are tiny compared to losses at higher
elevations." At the middle elevations of 2,000 to 3,000 meters, where
aspen are most abundant, they saw consistent decreases across all three scenarios. At the highest elevations above 3,000 meters, they saw lower declines under the climate warming scenarios. They believe this means
aspen distributions will shift to higher elevations as the climate warms.

"As drought and higher temperatures at lower elevations start to increase
the vulnerability of aspens to pathogens like bugs, fungi and bacteria,
their suitable climate will shift upwards," said Nikki C. Inglis, a
research assistant and graduate student in the Center for Geospatial
Analytics at NC State and first author of the study.

Researchers said their study is important because it is evidence for how climate change will be visible to people. In addition, the aspen trees
in particular are an important feature of the Colorado landscape.

"They are part of how people who live in Colorado identify themselves,
and what makes this a unique landscape," Inglis said. "They draw people
in from all over because the aspen trees create a sensory experience with
sound and sight. And of course the color change is absolutely striking -- there's nothing like it."

========================================================================== Story Source: Materials provided
by North_Carolina_State_University. Original written by Laura
Oleniacz. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nicole C. Inglis, Jelena Vukomanovic. Climate change
disproportionately
affects visual quality of cultural ecosystem services in
a mountain region. Ecosystem Services, 2020; 45: 101190 DOI:
10.1016/ j.ecoser.2020.101190 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200916130845.htm

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