The mesa contains four “arroyo” streambeds, one drainage area, a vernal pool complex, and multiple seasonal wetlands, all of which together control the flow of water across the site. The mesa ranges in elevation from 10-105 ft above mean sea level and includes coastal bluffs and canyons and riparian areas. The site does receive runoff from areas North and East of the mesa, and the arroyos on the mesa direct the water down to the lowlands and into the Slough. The water helps sustain the wetlands in the lowlands. Tidal influence from the ocean entering the Slough can also reach the wetlands in the lowlands.
The mesa of Newport Banning Ranch therefore must also be viewed in the larger context of its role in the integrated upland and wetland ecosystem. Similar to the Bolsa Chica wetlands and mesa near Huntington Beach, the mesas and the lowland wetlands are biologically interdependent according to both the California Department of Fish and Wildlife and the U.S. Fish and Wildlife Service. Together, the wetlands in the lowlands and the mesa with the riparian arroyos and vernal pool complexes, combine to make this area an important upland-wetland ecosystem. These biological interdependencies are vital to maintaining biological productivity and diversity.
Rare Plant Communities of the Mesa
Coastal sage scrub in southern California provides habitat for about 100 rare species, many of which are also endemic to limited geographic regions. Southern Coastal Bluff Scrub and Maritime Succulent Scrub are coastal scrub communities found on the bluffs and canyons of the site and are considered “very threatened.” Patches of purple needlegrass grassland were present in many areas in 2012, but because of the continuing severe drought, these native grasslands have been reduced to three areas on the southern mesa. Native grasslands are one the most endangered habitats in California. Both the native and non-native grasslands on the site provide dwelling habitat for burrowing animals and significant foraging habitat for numerous species of mammals, birds, and reptiles. Burrowing owls, red-tailed hawks, Cooper’s hawks, American kestrels, and peregrine falcons have been observed perching and foraging at various locations within and in the vicinity of the purple needlegrass grassland across the entire site. The riparian habitat found adjacent to drainage areas and arroyos on the Banning Ranch site is greatly reduced in extent from its historical distribution and it supports rare and endangered species such as the least Bell’s vireo, particularly in the lowlands.
Vernal Pools and Wetlands
A number of plant and animal species are endemic to (found only in) vernal pools. Wetlands that provide habitat for plants and wildlife only found in vernal pools may rise to the level of ESHA. Vernal pools typically occur on coastal terraces in southern California and historic aerial photographs suggest that they were probably common on Banning Ranch before the site was altered by agriculture and oil field development. There are 10 pools on the site, 8 of which support the endangered San Diego fairy shrimp, a diagnostic vernal pool species.
The mesa habitats are identified in these Coastal Commission maps: http://documents.coastal.ca.gov/reports/2016/9/w14d-9-2016-a2.pdf
Read the updated CCC biologist report from August 25th: http://documents.coastal.ca.gov/reports/2016/9/w14d-9-2016-a3.pdf