Section 3 Conservation of Vegetation and Ecological Communities
Total Page:16
File Type:pdf, Size:1020Kb
Section 3 Conservation of Vegetation and Ecological Communities 3.0 CONSERVATION OF VEGETATION AND ECOLOGICAL COMMUNITIES This section summarizes expected conservation of biological resources by the MHCP. It first summarizes conservation levels for the major vegetation community types and the overall preserve configuration. Next, we summarize conservation of ecological communities, or groups of species that tend to co-occur in similar habitat types. These analyses are presented primarily in support for the final section, which analyzes each of the 77 MHCP species independently. The species evaluations also provide the species-specific permit conditions, including management and monitoring conditions, that must be met for the MHCP to ensure species persistence and qualify for take authorizations. 3.1 CONSERVATION OF VEGETATION COMMUNITIES This section briefly summarizes the level of conservation for each vegetation community in the MHCP study area, along with the landscape configuration that would result at ultimate “build out” of the preserve. This information serves as a foundation for the species-specific analyses that form the bulk of this document. 3.1.1 Conservation Levels Table 3-1 summarizes the level of conservation estimated using the May 1999 FPA. It summarizes total acreages and percentages (relative to total acreage in the study area) by each vegetation community type within the FPA. It also summarizes the acreages and proportion of the BCLA that would be conserved for each vegetation community. The BCLA conservation figures represent conservation of the biologically most valuable lands. Existing Vegetation—The study area (111,865 acres) currently supports approximately 29,895 acres of natural vegetation (or about 27% of the area) as depicted in Figure 2-2. The distribution of the natural vegetation communities is described in the MHCP Biological Goals, Standards, and Guidelines document (Ogden 1998), which also provides conservation goals and management guidelines for each vegetation community. The largest blocks of natural vegetation (greater than 1,000 contiguous acres each) occur in north Escondido (Daley Ranch) and in the hilly areas of southeast Carlsbad and southwest San Marcos. Other relatively large blocks of habitat (at least several hundred contiguous acres each) occur along the northern boundary of Oceanside (adjacent to Camp Pendleton), and in scattered areas in east and central Carlsbad, north San Marcos, and south Escondido. Otherwise, natural habitats in the MHCP area are already highly fragmented and occur primarily in small (less than 200-acre), scattered patches surrounded by development or agriculture. The remnant natural vegetation occurs disproportionately on developmentally constrained lands, such as steep slopes and canyons, and lands at the periphery of incorporated cities. Approximately 8,570 acres (8% of study area) of Diegan coastal sage scrub remain in the study area. The largest blocks are in southeast Carlsbad (La Costa area), central Carlsbad (Macario Canyon/Agua Hedionda area), and northeast Carlsbad (Calavera/Carlsbad Highlands area). Smaller remnants of coastal sage scrub are scattered across Oceanside to Camp Pendleton, and on steeper slopes and canyons scattered throughout the coastal cities. Other significant stands of coastal sage scrub in the study area are found in north Oceanside (near the mouth of the San Luis Rey River and adjacent to Camp Pendleton), north San Marcos, and scattered areas around the outskirts of Escondido. 314552000 3-1 PUBLIC REVIEW DRAFT MHCP VOL. II Section 3 Conservation of Vegetation and Ecological Communities Table 3-1 CONSERVATION ACREAGES OF NATURAL VEGETATION COMMUNITIES IN THE MHCP STUDY AREA FOCUSED PLANNING AREA (FPA) Total Net Total Conservation Total Existing Conservation Conserved in inside the Vegetation Community in Study Area inside FPA Study Area BCLA1 Southern coastal bluff scrub 2 0 0 (0%) 0 (0%) Maritime succulent scrub 32 30 30 (91%) 29 (93%) Coastal sage scrub 8,569 5,171 5,171 (60%) 4,845 (68%) Chaparral 8,313 5,488 5,488 (66%) 5,335 (69%) Southern maritime chaparral 968 770 770 (80%) 737 (82%) Coastal sage/chaparral mix 462 233 233 (50%) 225 (51%) Grasslands 5,209 1,597 1,597 (31%) 1,491 (45%) Southern coastal salt marsh 272 251 272 (100%) 270 (100%) Alkali marsh 165 163 165 (100%) 165 (100%) Freshwater marsh 533 434 533 (100%) 457 (100%) Riparian forest 676 526 676 (100%) 404 (100%) Riparian woodland 250 191 250 (100%) 133 (100%) Riparian scrub 1,514 1,055 1,514 (100%) 969 (100%) Engelmann oak woodland 230 170 170 (74%) 167 (81%) Coast live oak woodland 650 492 492 (76%) 464 (80%) Other oak woodlands 1 1 1 (100%) 1 (100%) Freshwater 444 396 444 (100%) 396 (100%) Estuarine 955 944 955 (100%) 954 (100%) Disturbed wetland 202 117 202 (100%) 87 (100%) Natural floodchannel/streambed 396 395 396 (100%) 381 (100%) Beach 48 9 9 (18%) 9 (37%) Saltpan/mudflats 3 3 3 (100%) 3 (100%) Total 29,895 18,435 19,371 17,523 (65%) (71%) Note: Numbers may not sum to total as shown, due to rounding. Vernal pools were mapped as an overlay and thus their acreage is included in this total. Source: Vegetation acreage calculations from May 1999 SANDAG GIS calculations. 1 Acreage and percentage of each vegetation community inside the biological core and linkage area that will be conserved. PUBLIC REVIEW DRAFT MHCP VOL. II 3-2 314552000 Section 3 Conservation of Vegetation and Ecological Communities Several sizable patches of coastal sage scrub in the study area are dominated by black sage (Salvia mellifera), a shrub also often associated with chaparral vegetation. Black sage-dominated coastal sage scrub is thought to be of lesser habitat value to the California gnatcatcher (Polioptila californica) than other subassociations of coastal sage scrub, such as Artemisia-dominated or Eriogonum-dominated coastal sage scrub. Significant areas of known black sage-dominated coastal sage scrub occur in northeast Carlsbad, in southwest and north San Marcos, and west Escondido. Only about 32 acres of maritime succulent scrub remain in the study area, on steep, south-facing slopes near lagoons in Carlsbad. Only about 2 acres of coastal bluff scrub are mapped in the City of Solana Beach. Chaparral communities, particularly southern mixed chaparral and chamise chaparral, dominate on higher and steeper slopes in south San Marcos, northeast Carlsbad, and north Escondido. In addition, 968 acres of a rare chaparral assemblage–southern maritime chaparral–occur on slopes and terraces in the coastal cities of Encinitas and Carlsbad. Grassland habitats are scattered throughout the study area (5,209 acres), with the largest stands in north Oceanside (along the boundary with Camp Pendleton) and in central Carlsbad. Significant grassland areas are also found in the valleys of Daley Ranch in north Escondido. See Appendix F for how the MHCP defines annual grassland vegetation. There are about 5,410 acres of wetland vegetation communities in the MHCP study area, including a variety of riparian, marsh, and other wetland communities. The four coastal lagoons support a mixture of salt marsh and freshwater marsh habitats, along with open water. Riparian forests, woodlands, and scrub communities are found along many of the drainages in the study area, with the most significant stands found associated with Pilgrim Creek, the San Luis Rey River, Guajome Lake, and Loma Alta Creek in Oceanside; Buena Vista Creek upstream from Buena Vista Lagoon along the Oceanside/Carlsbad border; Agua Hedionda Creek and Macario Canyon, upstream from Agua Hedionda Lagoon in Carlsbad; Encinitas Creek near the Carlsbad/Encinitas border; San Marcos Creek and Twin Oaks Valley in San Marcos; Kit Carson Park in Escondido; and Escondido Creek in south Encinitas. In the MHCP study area, vernal pools are highly restricted in distribution, with concentrations in two critical locations and a few scattered pools outside these areas. A narrow, linear configuration of pools exists along a railroad right-of-way in west Carlsbad (the Poinsettia Lane pools), which is a critical location for several narrow endemic species. The second critical location includes a large number of scattered pools and pool complexes in central, urbanized San Marcos. This location, which also supports critical populations of several narrow endemic species, is not included in the current MHCP plan or San Marcos Subarea Plan, but is a Major Amendment Area on which conservation planning will be done later. Outside of these two locations, scattered vernal pools, with lesser concentrations of MHCP species, are located in central Carlsbad and possibly in other cities. The majority of oak woodlands in the study area are Engelmann oak woodlands (230acres) and coast live oak woodlands (650 acres). Most of the extensive oak woodland habitat occurs in the northern portions of Escondido, although there are a number of small patches in several other MHCP cities. Sizable agricultural areas remain in northeast Oceanside, central and east Carlsbad, central Encinitas (Ecke Ranch), and around the margins of Escondido. In some places, these fields function as foraging habitat or habitat linkages for a variety of MHCP species. They also help buffer native 314552000 3-3 PUBLIC REVIEW DRAFT MHCP VOL. II Section 3 Conservation of Vegetation and Ecological Communities habitats and species against adverse effects from other land uses, such as edge effects from residential development. Future Vegetation—Table 3-1 summarizes the acreages of vegetation expected to remain at ultimate build-out of the study area under the assumptions outlined above. Development is expected to remove up to about 10,524 acres (35%) of the natural vegetation communities, with about 19,371 acres (65%) of natural habitats conserved. The conserved acres include about 18,435 acres within the FPA plus about 936 acres of wetland vegetation communities outside the FPA. The level of conservation varies greatly among the various natural vegetation types. Overall conservation of upland vegetation communities varies from a low of 18% for beach to a high of 91% for maritime succulent scrub.