Our Projects.
Vernal Pools
Vernal pools are shallow depressions in the clay soils. They were once abundant on the mesas, and due to development, it is estimated that only 3% remain. In summer, they look like dry puddles, but in wet winters the rains fill the pools with water. Tiny cysts in the soil hatch into small transparent “fairy shrimp” when the pools fill, sometimes surviving decades of drought. Frogs breed and lay their eggs here, and snakes and birds visit the pools to catch and eat the fairy shrimp and tadpoles. Four rare and endangered plants occur in the vernal pools: Otay Mesa mint (Pogogyne nudiuscula) PONU, San Diego Mesa mint (Pogogyne abramsii), POAB, Spreading navarretia (Navarretia fossalis), NAFO, San Diego button-celery (Eryngium aristulatum var. parishii). The Friends lead a hike every year, weather conditions permitting, to visit local vernal pools, see here for the most current schedule.
The Friends currently sponsor a comprehensive vernal pool restoration project in Del Mar Mesa, in partnership with the Chaparral Lands Conservancy, which will begin breaking ground in 2024 https://www.chaparralconservancy.org/projects/del-mar-mesa/.
Oak trees & GSOB
Several hundred coast live oak trees in the Preserve and all over San Diego County are infested with Gold spotted oak borer (GSOB). The insect larvae feed under the bark and destroy the cells that transport water and nutrients inside the tree. As adults, they bore a small D-shaped exit hole in the bark to fly and lay eggs on the bark of other oak trees. The GSOB has spread on firewood, so infested wood must not be moved or used as firewood until a tree has been dead for two years. beginning in 2018 the Friends have conducted field surveys recording the location of infested trees in the Preserve, and currently sponsor management actions with the goal of slowing but not eliminating the infestations and the tree mortality. Read more about GSOB and our efforts here.
Weed removal
Many non-native plants now grow in the canyon, replacing native plants. Rye grass, oats and other grasses were first introduced in the 1800s to provide grazing for cattle. Others have grown from seeds in bird droppings, horse manure, and adjacent yards. They now also include artichoke, wild geranium, black mustard, horehound, curly dock, pineapple weed, and several filaree species. These plants crowd out the native plants, that provide important food and shelter for wildlife, and help with erosion control.
The Friends sponsor and carry out weed removal in the Preserve and Black Mountain Open Space. Volunteers also help remove these plants by weeding and planting native species.
New interventions finalized to the removal of invasive weeds in high -value areas are ongoing in Darkwood Canyon Trails and in Harrier Hill: both will be multi-year projects, co-financed by grants from Protect Our Preserves.
Surveys and Restoration
Most of the native habitats of chaparral, coastal sage scrub and grasslands have been destroyed by development. In some areas of the preserves, non-native grasses and weeds dominate.
The Friends have recently completed the restoration of two separate areas to suitable habitat for the endangered Cactus Wren. More promising locations have been identified and new restoration projects are ongoing.
The Friends conduct a yearly census of other endangered species that still survive in the Preserve, such as Willowy Monardella (Monardella viminea), San Diego thornmint (Acanthomintha ilicifolia), and Threadleaf Brodiaea (Brodiaea filifolia). Some of these populations have been continuously managed by us in the last 10 years and their numbers are increasing.
Volunteer Restoration Projects
Volunteers and plant restoration experts work together to remove invasive thistle plants and other weeds, plant native species, water the plants in dry months, and remove competing weeds.
Restoration events can be joined by volunteers and are posted on our calendar. They run all year long and include a large project underway in the Santa Luz area, with work parties on many Sunday afternoons.
Boy Scouts, Girl Scouts, and high school students have often volunteered for the work parties.
In addition, the San Diego Hang Gliding and Paragliding Association has done cleanups and restoration work in areas they launch and land.