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16 | April 19, 2018 | Malibu surfside news News
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Scientists eye ideal
wildlife crossing locales
Submitted by the National
Park Service
A new report offers recommendations
on the location
and type of wildlife
crossing structures proposed
for two of the busiest
freeways in the world.
Interstate 15 in western
Riverside County and U.S.
101 in Los Angeles and
Ventura Counties bisect
large areas of natural habitat
and serve as major barriers
to wildlife movement
and gene flow, especially
for mountain lions.
The report summarizes
the input from some of the
world’s foremost experts on
wildlife connectivity and
crossing structures and combines
it with landscape characteristics
and wildlife data
to prioritize locations for
wildlife crossings. The experts
evaluated locations that
would improve connectivity
for all kinds of wildlife,
including for the imperiled
mountain lion populations
in the Santa Ana and Santa
Monica Mountains.
“The loss of mountain lions
in this area could have
potentially harmful impacts
on this ecosystem,” said
Seth Riley, report co-author
and wildlife ecologist at
Santa Monica Mountains
National Recreation Area.
“Wildlife in the Santa Monica
Mountains is essentially
trapped on an island of habitat,
and a crossing structure
would allow two-way
migration to increase gene
flow generally, and specifically
increase genetic diversity
for mountain lions.”
Genetic diversity levels
for mountain lions in the
Santa Ana and Santa Monica
mountains are lower
than have been measured
anywhere else in the west.
Only the endangered Florida
panthers, which suffered
from severe genetic defects
before the introduction of
females from Texas, have
been found to have lower
genetic diversity.
Wildlife crossing structures
would allow juvenile
mountain lions, among
other wildlife, to move
out of larger populations
from east of the Santa Ana
Mountains and north of the
Santa Monica Mountains
into the isolated coastal
mountain ranges.
The report evaluated 11
potential locations in the
Santa Ana Mountains and
seven in the Santa Monica
Mountains. Each site was
rated for evidence of wildlife
use, including mountain
lions, landscape connectivity,
and the extent to
which land was protected
or at risk of development.
Specific recommendations
include:
• Construction of a new
wildlife overpass over I-15
south of Temecula Creek
Bridge, as well as enhancements
to the area underneath
the existing bridge.
• Construction of a new
wildlife overpass over the
101 Freeway at the West
Liberty Canyon site. A tunnel
option was deemed inferior
because constructing
a tunnel large enough to
serve a broad range of species
would be prohibitively
expensive and complicated
from an engineering perspective.
• Accompanying measures
such as effective
wildlife fencing to funnel
animals to crossing points
and appropriate vegetative
cover on or near structures
are critically important.
• In both mountain ranges,
additional locations offer
the potential for new
construction or enhancements
that could provide
secondary crossing sites.
Caltrans, along with numerous
other partners, is
currently working on a plan
to build a wildlife crossing
over the 101 Freeway in the
Liberty Canyon area and
last fall released the draft
initial study and environmental
assessment for the
project.
Informed by this study,
last week The Nature
Conservancy acquired approximately
73 acres in
the Rainbow Canyon area
along I-15 near Temecula,
a critical property needed
for the placement of one of
the highest priority wildlife
crossings identified in the
report.
UC Davis researchers
are teaming with civil engineering
faculty and students
at Cal Poly Pomona
and Caltrans, with the support
of the NCCP Local Assistance
Grant program and
the San Diego Association
of Governments, to better
define the most feasible locations
and types of crossing
structure modifications
that could improve the ability
of mountain lions and
other wildlife to cross I-15
in the future, including a
future Rainbow Canyon
crossing in the area where
The Conservancy purchased
land.