A Summary of Coastal Sage Scrub Habitat
For millenia, the southern California coast, foothills and western
slopes have been home to scrub and chaparral. Unlike plant and
animal relatives found in the mountains and deserts, coastal sage
scrub species have adapted to an ecosystem that rarely freezes in
the winter and only occasionly experience temperatures over
90-degress F during the dry California summer.
Southern California's coastline, once covered by coastal sage
scrub, is now largely developed. Only scattered pockets remain. One
such pocket is the Point Loma Ecological Reserve, an area of 840
acres protected under the joint management of the U.S. Navy,
Cabrillo National Monument, and other Federal agencies
The Bayside Trail, a 2½-mile self-guided round trip, is
located in Cabrillo National Monument. This trail offers a good way
to enjoy this special habitat. A variety of plants, small reptiles
and mammals as well as a number of indigenous and migrating birds
reside here. During the dry summer, many of the plants may appear to
be dead but they are actually dormant and will become green and
vibrant again with the winter rains. Spring wildflowers are a
special treat from February until May. Rangers and volunteers
occasionally give coastal sage scrub and bird walks. Please check at
the visitor center or call (619) 557-5450 prior to your visit.
The Ecosystem During Cabrillo's Visit
Native plants found in the park today are part of the coastal sage
scub community that Cabrillo encountered when he landed here in
1542. Then, as now, the community was comprised of an association of
woody shrubs ranging in height from one to ten feet. It was typified
by California sagebrush, white and black sage, California buckwheat,
toyon, and lemonadeberry. Plants as well as animals have adapted to
arid coastal climates.
Among the animals, Cabrillo and his crew may have seen during his
visit are mammals such as rabbits, squirrels, foxes and coyotes, a
variety of lizards and snakes, and birds such as the scrub jay,
red-tailed hawks, quail, and others.
The Evolution of Coastal Sage Scrub Ecosystem
This sage scrub environment evolved within the Mediterranean
climate. This term refers to climate belts found in both the
northern and southern hemispheres on the western coastline of
continents, approximately between 30 and 40 degrees latitude.
Mediterranean climate belts receive an average of 10 to 20 inches of
rainfall a year and experience only occasional frosts. These areas
typically have winter rains and dry warm summers with a fairly
constant temperature.
The coastal sage scrub and chaparral associated with Mediterranean
climates evolved in reponse to climatic changes beginning about 14
million years ago. In these latitudes, average rainfall decreased
from about 80 inches or more per year in the Eocene Epoch to only
about 12 inches by the middle of the Miocene Epoch.
Plant Adaptations
Coastal sage scrub plants can store moisture and reduce moisture
loss during the prolonged hot, dry months between April and October.
The plants either conserve water by specialized leaf structures or
dormancy. Tough leathery, wax-covered leaves, like those of the
lemonadeberry shrub, prevent water from escaping through leaf pores.
Minute white hairs keep leaf temperatures down by reflecting
sunlight. They also reduce moisture loss by slowing dry winds. Some
leaves are so reduced in size that they appear as spines, as on
cacti. Other plants simply drop their leaves during summer months.
Other species, especially the flowering ones, will dry up and go
dormant by middle summer. Although they appear to be inactive
during this time, growth is still occurring. Root systems can be
extensive, sometimes exceeding 30 feet. The roots anchor the plants,
hold soil in place and reduce runoff during winter and spring rains.
The community is both drought and fire-adapted. Fire is a
healthy and necessary component of their life cycle. Shrubs respond
to recurrent fires in several ways. They resprout from both crown
and roots, and, often at an early age, produce seeds that are both
fire resistant and dependent for germination (growth). Fire creates
a healthy plant mosaic of different ages and species. As a result,
fire increases the diversity of habitats.
While in the park, look for changes in the species which dominate
different sections of the trailside. Even within a small area,
subtle differences, such as exposure to light and moisture caused by
elevations and slope changes, will favor some plants at the expense
of others.
The Cycle of Life
Among the plants live a variety of animal species, some rare.
Within the ecosystem, there are levels of animal and plant life. The
bottom level includes decomposers such as fungi, bacteria and worms.
They live off decaying material and waste and return organic
compounds to the soil--providing nutrients for plants. Herbivores,
such as rabbits and squirrels, live off the plants. They, in turn,
are eaten by carnivores (meat eaters), such as foxes, hawks, and
owls. When these plants and animals die, the decomposers start the
cycle again.
Invasion and Preservation
Originally the dominant ecosystem, the coastal sage scrub
community now only exists in remnant San Diego County habitats, due
to heavy growth in the region. The small
native plant communities that do remain in canyons and other sites, like
Point Loma, are fragmented and invaded by exotics (non-native
vegetation and animals).
The National Park Service is committed to preserving and
protecting native communities wherever they occur within National Park
System boundaries. Fortunately, Cabrillo National Monument retains
its native community. Using National Park Service guidelines, we are
gradually removing exotics and are reintroducing native plants. We
also perform scientific studies to learn more about this unique and
shrinking ecosystem.
We ask you to help preserve this precious community by not picking,
removing, or otherwise disturbing any plant or animal life in the
Monument.
Want to Learn More? -- References.
Websites:
On our server:
On other servers:
- Fire
Characteristics of Plants and Animals. This site, developed
by the USDA Forest Service Intermountain Research Station,
provides up-to-date information on fire effects on plants and
animals. An excellent research tool for biology students and land
managers.
Other National Park Service Sites with Coastal Sage Scrub
Habitat:
Books and Publications:
- "Southern Coastal Scrub", an article by Harold A.
Mooney in: "Terrestrial Vegitation of California",
edited by Michael G. Barbour and Jack Major -- California Native
Plant Society, 1990. This paper is a must for serious biology
students studying the botany of the Coastal Sage Scrub community.
