Plant Communities

 

Mediterranean Ecosystem at Cabrillo National Monument

The Mediterranean ecosystem at Cabrillo National Monument is dominated by coastal sage scrub plants, which have adapted to warm, dry summers and cool winters with occasional storms. To survive the dry season, these plants have developed various adaptations:

• Water Storage: Some plants have large roots or bodies that store water for use during dry periods.
• Leaf Adaptations: These include leaves that:
  • Fall off during dry seasons to reduce water loss.
  • Curl up to create a small moisture chamber.
  • Have a waxy coating to protect against evaporation.
  • Have hairs that reflect light and reduce heat penetration.
  • Are small in size, minimizing the surface area for evaporation.

Pollination and Seed Dispersal

In the coastal sage scrub habitat, strong winds are rare, so plants rely on animals for pollination and seed dispersal:

• Pollination: The plants are highly aromatic, attracting pollinators like moths in the dark of night through their sense of smell rather than vision.
• Seed Dispersal: Some plant seeds easily stick to animals' fur, allowing foxes, coyotes, rabbits, or mice to carry them to new locations for germination.

Defense Mechanisms

These plants have evolved several defenses to deter foragers:

• Aromatic Leaves: The strong odors of the plants not only attract pollinators but also repel animals that might otherwise eat them.
• Tough Leaves and Branches: Some plants have tough leaves and branches, making them difficult to eat.
• Spines: Other plants have spines to further discourage herbivores.

The coastal sage scrub habitat at Cabrillo National Monument is a remarkable example of plant adaptation and resilience, showcasing the intricate balance of the Mediterranean ecosystem.

 

Coastal Sage Scrub and Southern Maritime Chaparral Communities

Cabrillo National Monument is located on a peninsula that features a rich diversity of natural habitats encompassing both terrestrial and marine ecosystems. From the 422-foot ridge of the peninsula down to the San Diego Bay on the east and the Pacific Ocean on the west, visitors can observe the unique scrubland habitat. The scrubland on Point Loma includes four distinct community types: southern coastal bluff scrub, maritime succulent scrub, Diegan coastal sage scrub, and southern maritime chaparral. These communities are home to a variety of plant species such as snake cholla, prickly pear cactus, Mojave yucca, Shaw’s agave, California coast poppy, Indian paintbrush, California buckwheat, California sagebrush, and lemonadeberry. Together, these plant communities make up the coastal Mediterranean ecosystem, supporting a variety of southern California animal species such as velvet ants, scorpions, shrews, mice, lizards, snakes, red-tailed hawks, foxes, and coyotes.

A Summary of Coastal Sage Scrub Habitat

For millennia, 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 occasionally experiences temperatures over 90 degrees F during the dry California summer.

Southern California's coastline, once covered by coastal sage scrub, is now largely developed. Only scattered pockets of this endangered habitat remain. One such pocket is the Point Loma Ecological Conservation Area, an area of 840 acres protected under the joint management of the U.S. Navy, Cabrillo National Monument, U.S. Coast Guard, Department of Veterans Affairs, and City of San Diego Wastewater Treatment Plant.

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. Park Rangers and Volunteers occasionally give coastal sage scrub walks. Please check at the visitor center or call [phone], extension 0, prior to your visit.

The Ecosystem During Cabrillo's Visit

Native plants found in the park today are part of the coastal sage scrub 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 response 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 through 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 and development 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). As a result of this highly fragmented habitat in urban San Diego County, it is not uncommon to find coyotes wandering residential streets, or raccoons foraging through neighborhoods.

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 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.