Chapter 7 – Areas of High Ecological Significance
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Chapter 7 Chapter 7 – Areas of High Ecological Significance The problem, then, is how to bring about a striving for harmony with land among a people many of whom have forgotten that there is any such thing as land, among whom education and culture have become almost synonymous with landlessness. — Aldo Leopold, 1949 Key Questions public lands and declining in the southern part of the assessment area (fig. 7.1). • Which areas have particularly high Public lands and habitat reserves are patch- ecological significance and what ily distributed in the San Diego ranges. As makes them significant? development intensifies in the foothills, far- • What factors threaten the ecological sighted planning is needed to ensure that integrity of these areas? habitat connectivity is maintained between the mountains and the remaining natural areas in This final chapter identifies areas of par- the coastal and inland valleys. ticularly high ecological significance in each of the assessment area’s nine mountain re- gions. These “key places” include critical Upper San Luis Rey River habitats for rare and vulnerable species, areas and the Warner Basin of high ecological integrity, and locations with An approximately 4-mile stretch of ripar- unique ecological associations. Primarily they ian habitat along the San Luis Rey River below are places where a number of ecologically sig- Lake Henshaw supports the largest southwest- nificant features overlap. Thus, the need for ern willow flycatcher population in southern effective stewardship of these areas is particu- California. Above the lake, there are signifi- larly important. cant populations of arroyo toad and arroyo The areas identified in this chapter clearly chub in the West Fork, North Fork, and Agua do not represent all areas of ecological im- Caliente Creek. Extensive grasslands in the portance and should not be interpreted as Warner Basin are occupied by Stephens kan- such. The purpose of highlighting these places garoo rat. The basin is also one of the few areas is to increase public and agency awareness of in southern California where the red-sided their regional significance. They are key parts garter snake has recently been observed. Lake of the ecological heritage of southern Cali- Henshaw supports a wintering population of fornia and should be recognized as such. approximately four to ten bald eagles. Gray vireos occur in redshank chaparral habitats on San Diego Ranges the north end of the basin. The mountains and foothills of San Di- Factors affecting the ecological integrity ego County contain a large number of rare of this area include surface and groundwater species and habitats. The list of key ecologi- extraction on private lands above Lake cal areas for this region is dominated by some Henshaw. The San Luis Rey River below the of the best remaining occurrences of low-el- lake is regulated by water releases from the evation ecosystems (e.g., riparian woodland, dam. Much of the Warner Basin is intensively coastal sage scrub, grassland, and Engelmann grazed by cattle. Brown-headed cowbirds are oak woodland) that are poorly represented on common in the area. Several roads and developed 335 Figure 7.1. Areas of high ecological significance in the San Diego ranges. Chapter 7 recreation sites are located in riparian habitats Factors affecting ecological integrity in the occupied by willow flycatchers and arroyo toads. upper San Diego River include housing devel- opments along the canyon’s rim, increased fire Pine Valley and Cottonwood Creeks starts, and non-native species. The area has burned Pine Valley and Cottonwood creeks are several times in the last eight years, resulting in adjacent drainages that come together at degradation of coastal sage scrub habitat. Barrett Lake. Both have high-quality riparian habitat and significant populations of arroyo Pamo Valley toads, least Bell’s vireos, and pond turtles. The Pamo Valley is a broad foothill valley that pond turtle population on Pine Valley Creek surrounds the confluence of Temescal and is one of the largest remaining in southern Santa Ysabel creeks. The area supports a large California (D. Holland, pers. comm.). The arroyo toad population and also contains high- arroyo toad population on upper Pine Valley quality riparian woodland, Engelmann oak Creek is probably the largest aggregation of woodland, and some coastal sage scrub. Least this species on the Cleveland National Forest. Bell’s vireos, California gnatcatchers, and The population of least Bell’s vireos on Cot- golden eagles occur in this valley. Red-legged tonwood Creek is the largest on the Cleveland frogs historically occurred in this area. National Forest. Pine Valley Creek is Most of Pamo Valley is owned by the City undammed and one of the longest free-flow- of San Diego, although the surrounding hills ing, low-elevation streams in the assessment are part of the Cleveland National Forest. Fac- area. The lower portion of the creek is in a tors affecting the ecological integrity of this designated wilderness area. area include year-round cattle grazing, unau- Factors affecting ecological integrity in- thorized and unmanaged recreation use, illegal clude high recreation use, livestock grazing, dumping of trash, and high numbers of inva- and non-native species. The upper portions sive, non-native species. Aquatic habitats along of Pine Valley and Cottonwood creeks are Santa Ysabel Creek are highly impacted by popular recreation areas. A recreation residence bullfrogs, sunfish, bass, and crayfish. tract occurs along Pine Valley Creek as do sev- eral popular trails and trailhead facilities. These Guejito Valley are popular areas for mountain bike and horse- Guejito Valley lies just to the west of Pamo back riding. Several cattle grazing allotments Valley and is another broad foothill valley that exist in the area. Stream flows on Cottonwood contains extensive Engelmann oak savanna, Creek are regulated by dams at Morena and grassland, and low-elevation riparian habitat. Barrett lakes. Invasive non-native species such Arroyo toads, Stephen’s kangaroo rats, and as tamarisk, bullfrogs, sunfish, and cowbirds golden eagles occur here. The valley is privately are a problem in some areas. owned and is heavily grazed by cattle. Upper San Diego River Mesa Grande-Santa Ysabel Valley- Pine Hills Oak Woodlands The San Diego River canyon above El Capitan Lake contains extensive stands of This area supports the largest remaining coastal sage scrub vegetation that support a expanse of Engelmann oak woodland habitat population (twenty to thirty pairs) of Califor- in southern California. Most of this area is nia gnatcatchers. Along the river are several private or Indian land and the primary factor stretches of high-quality riparian woodland affecting its ecological integrity is the likeli- and populations of arroyo toad and southwest- hood of increased subdivision and ern pond turtle. Coastal rosy boas, horned development of those lands. Cattle ranching lizards, orange-throated whiptails, and two- is a common use of land in this area. Non- striped garter snakes also occur in this area. native annuals are the dominant grasses in the oak savannas and grasslands. 337 Mendenhall Valley Santa Ana Mountains In this valley near the top of Palomar The Santa Ana Mountains region is an is- Mountain there is a large montane meadow land of wildland habitat that is nearly that supports the largest known population surrounded by urban development. It contains of the Laguna Mountain skipper butterfly. a number of important ecological areas. From Populations of Parish’s meadowfoam and San an ecosystem conservation standpoint, the Bernardino bluegrass also occur here. This most significant areas are probably along the valley is the headwaters for the West Fork of base of the mountains where imperiled low- the San Luis Rey River. Downstream resources elevation habitats extend up into the foothills. include arroyo toads, arroyo chub, and a self- These habitats include Engelmann oak-grass- sustaining wild trout fishery. land savanna, low-elevation riparian, and The primary land uses in Mendenhall coastal sage scrub (fig. 7.2). Valley are cattle grazing and several private residences (over half of the valley is in private San Mateo Creek ownership). Altered fire regimes and non- and Surrounding Uplands native grasses and forbs may be affecting plant San Mateo Creek is probably the most species composition in the meadow. Bullfrogs pristine coastal stream south of the Santa occur in several ponds within the valley and un- Monica Mountains. It flows unimpeded into doubtedly affect native amphibian populations. the ocean. The upper watershed is mostly unroaded and primarily within the San Mateo Laguna Meadow Canyon Wilderness Area. Its lower reaches run On top of Laguna Mountain is an exten- through Camp Pendleton Marine Corps Base sive montane meadow that supports a number and San Onofre State Beach. The creek and of rare plant species and the Laguna Moun- its principal tributaries contain significant tain skipper butterfly. It is one of the few large populations of arroyo toads, pond turtles, and montane meadows in the mountains of San California newts. In 1999, juvenile southern Diego County that is predominately on pub- steelhead were documented in San Mateo lic lands. Pine-oak forests surrounding the Creek (A. Vejar, CDFG, pers. comm.). meadow contain spotted owls. Ecological in- Factors affecting ecological integrity in- tegrity on Laguna Mountain is affected clude recreation use, military activities, and primarily by high levels of recreation use and exotic species. However, this may be one of cattle grazing. the few streams where conditions are condu- cive for extirpating aquatic exotic species. Viejas, Poser, and Guatay Mountains and King Creek Santa Rosa Plateau These areas have gabbro soils that support The Santa Rosa Plateau contains a large several unique, endemic plants. The largest expanse of undeveloped, Engelmann oak sa- population of San Diego thorn-mint vanna that is well managed and in good (Acanthomintha ilicifolia) occurs on Viejas condition.