Galapagos of North America, uncontrollable fires, and shark teeth as big as a hand
I. Map boundaries: 30 to 40 degrees North; 110 to 120 degrees West
II. Country (State): Mexico (Baja California), United States (California). Note: This post focuses on Mediterranean ecosystems within the map boundaries. Other desert and montane ecosystems within these map boundaries will be described in future posts.
III. Overview
The Sierra Juarez and San Pedro Martir montane forests (NA526), Sierra Nevada (NA527, to be described in a future post), Central Valley (NA801), California coastal sage scrub and chaparral (NA1201), California interior chaparral and woodlands (NA1201), and California montane chaparral and woodlands (NA1203) are all in a region of dry summers and winter rain and snow. This climate leads to distinct ecosystems adapted to summer drought. The map area (30 to 40 degrees north and 110 to 120 degrees longitude west) intersects Mediterranean ecosystems in Baja California and California. There are three distinct mountain ranges. The Sierra Nevada and its southern extension, the Tehachapi Mountains, area a north-south range. The Transverse Ranges (Santa Monica, San Gabriel, and San Bernardino Mountains) extend east-west at about 34.5 degrees north. The Peninsular Ranges trend northwest-southeast and include the Santa Ana, San Jacinto, Palomar, Laguna, Sierra Juarez, and Sierra San Pedro Martir ranges on the map area. Coastal sage scrub is at the lower elevations and is typical of NA1201. Shrubs in the genera Artemisia, Salvia, and Encelia are common, along with woody deciduous shrubs such as Fraxinus, Aesculus and Rosa and succulents such as Agave, Echinocereus, and Opuntia. Chaparral genera are Adenostoma, Ceanothus, Arctostaphylos, Quercus, and Rhamnus.
Winter rains encourage carpets of grasses and shrubs to grow, then the vegetation dries out and dead litter accumulates. Inevitably, large, hot fires occur and burn the plants and everything else to the ground. Following a burn, there is typically rapid recovery of the coastal sage scrub and chaparral. In the urban-wildland interface, there is a dispute over whether efforts to control fires may actually make it worse. Minnich (1983) argues that fires in chaparral increase in size, spread rate, and intensity as initially successful suppression efforts create so much fuel that fires become uncontrollable. According to this view, creation of a mosaic of different ages in chaparral is desirable to limit fires (Minnich 1983). Keeley, Fotheringham, and Morais (1999), in contrast, argue that fire frequency, areas burned, and fire size have not increased due to fire suppression. This is in part because uncontrollable fires are driven by autumn foehn winds that blow at speeds exceeding 100 km/hour. Under these windy conditions, fires will burn through all age classes of fuels, and rotational burning programs in chaparral are unlikely to be effective in stopping these fires. At the southern tip of the Mediterranean ecosystems in Baja California lie the San Pedro Martir Mountains. Here, fewer efforts have been made for fire suppression, and frequent fires have kept the Jeffrey pine-dominated forests resistant to insects and disease (Shouse 2003).
Known as the “Galapagos of North America,” the Channel Islands harbor 145 endemic or unique species. One of the few remaining natural coastal ecosystems, the Channel Islands have coastal sage scrub and pristine marine tide pools. Ocean currents upwell at the islands, providing nutrients for remarkable marine productivity. Extensive kelp forests support marine life. The largest island, Santa Cruz, has been the site of an extensive ecological restoration effort to remove sheep and pigs. In addition, a protected species, the Golden Eagle, had moved into the islands to prey on the pigs and had the unintended consequence of further stressing the island fox, to the point of eliminating entire subspecies on several islands. Golden eagles were also removed from Santa Cruz. The removal of these exotic animals has allowed native vegetation, including oaks, and native animals, including the Santa Cruz Island fox and bald eagle, to make a comeback. On Anacapa Island, the removal of the black rat has allowed seabirds, lizards, and salamanders to make a comeback. Santa Catalina Island has also been the subject of eradication efforts, especially of herbivores, and the original vegetation is returning. This includes oak woodland, chaparral, and coastal scrub (Mohlenbrock 2001).
The San Andreas fault extends from the San Francisco area southeastward into the map area. At the Carrizo Plain National Monument, a unit of the National Landscape Conservation System, a record of earthquakes along the fault is provided in offset stream channels. This area of the fault last ruptured in 1857, and the slip was 5.3 m. This slip and stream offset occurred during a cluster of earthquakes that centered around the big event. The historic interval for large-earthquake recurrence is estimated at 140 years (Zielke et al. 2010). Since the 1857 earthquake, more than five meters of strain has accumulated (Ludwig et al. 2010).
The east-west Transverse Ranges that overlook the Los Angeles basin reach up to 11,000 feet in elevation. Although the mountains are mostly granite and quartzite rock, outcrops of limestone are found on the northern slopes and rare plant communities are in the San Bernardino National Forest, growing in the understory beneath pinyon pine and juniper. The plants are Parish’s daisy, Cushenbury buckwheat, Cushenbury milk vetch, San Bernardino Mountains bladderpod,a nd Cushenbury oxytheca (Mohlenbrock 1993a). Another unusual habitat in the San Bernardino National Forest is pebble plains. These are deep carpets of quartzite rocks. This inhibits forest vegetation, and 45 types of rare plants grow here, many of which have developed gray, hairy leaves to reduce aridity, or are succulent. Examples are the Baldwin Lake linanthus, and Munz’s hedgehog cactus (Mohlenbrock 1993b).
The mountains of southern California provide at least two major fossil sites from the age of mammals. One is Sharktooth Hill, a National Natural Landmark (NNL) northeast of Bakersfield, which is considered the best fossil marine site in the world, The Ernst Quarries at Sharktooth Hill are a Miocene-age deposit containing the bones of Pacific Ocean animals of 141 species, including sharks, sea lions, turtles, and whales. The area was first examined by Louis Agassiz in 1856 and is still being researched today. Sharkteeth as big as a hand have been unearthed. Rancho La Brea, in downtown Los Angeles, contains the largest and most diverse assemblage of terrestrial Ice Age mammals and plants. Mammals began to get stuck in the asphalt and sand site at least 36,000 years ago. Perhaps the most famous of the mammals at La Brea are the sabertoothed cats. Many other carnivores also were trapped in the tar pits, including dire wolves, spotted hyena, coyotes, three types of bears, wolves, pumas, and lions. The teeth of the carnivores have been studied, and many are broken at the tar pits, suggesting competition for food was intense (Van Valkenburgh 1994). The long dagger-like canines called sabertooths have evolved several different times during the Age of Mammals, including in Australia and South America. It is believed that the teeth were useful in slicing open the bellies of victims (Janis 1994).
IV. Terrestrial Ecoregions
Ecoregions of the Neararctic Biome
Temperate Coniferous Forests
NA526, Sierra Juarez and San Pedro Martir pine-oak forests. Two mountain ranges support pine and fir forests in a Mediterranean climate regime of winter rains. There are ten species of pine. Found in Baja California.
Temperate Grasslands, Savannas and Shrublands
NA801, California Central Valley grasslands. Perennial bunchgrass ecosystem and oak-grass savanna grade into desert grasslands in the south. Extensive mass flowerings of California poppy and other wildflowers are characteristic. Vernal pools are found in flooded depressions. Found in California.
Mediterranean Forests, Woodland, and Scrub
NA 1201, California coastal sage and chaparral. The fire-adapted coastal sage and chaparral plants are interspersed with oak woodlands. Higher elevations support pine forests. Found in Baja California and California.
NA 1202, California interior chaparral and woodlands. A zone of oak woodland and chaparral rings the Central Valley grasslands. Found in California.
NA1203, California montane chaparral and woodlands. The southern extension of the Sierra Nevada and the mountains surrounding the Los Angeles basin have plant communities consisting of chaparral, pinyon-juniper, oak woodlands, and pine forests. Found in California.
V. Freshwater Ecoregions
Temperate Coastal Rivers
125. Sacramento-San Joaquin. One of the richest ecoregions west of the Rockies for fish, with 40 natives. It has five endemic fish genera and a near-endemic salamander, Hydromantes. Rivers from terrestrial ecoregions 801, 1202, and 1203 are in this freshwater ecoregion.
Xeric Freshwaters and Endorheic (closed) Basins
128. Death Valley. Includes the eastern clopes of the Sierra Nevada and the northern slopes of the Transverse Range, with rivers such as the Mojave River. There are five endemic fish and 20 endemic mollusks.
159. Southern California Coastal-Baja California. The fish fauna is marine derived, with anadromous steelhead and Pacific lamprey. There are four endemic fish in the Los Angeles Basin.
VI. Marine Ecoregions
Temperate Northern Pacific Realm, Cold Temperate Northeast Pacific Province
58. Northern California. Found west of San Nicholas and north of Santa Rosa, Santa Cruz, and Anacapa in the map area.
Temperate Northern Pacific Realm, Warm Temperate Northeast Pacific Province
59. Southern California Bight. Found south of the Channel Islands along the coast of terrestrial ecoregion NA1201.
VII. Man and the Biosphere Reserves
Channel Islands, California (site 1). Known as the “Galapagos of North America,” the biosphere reserve preserves 145 endemic or unique species and includes Channel Islands National Park and Channel Islands National Marine Sanctuary. One of the few remaining natural coastal ecosystems, the Channel Islands have sage scrub and pristine marine tidepools. Ocean currents provide upwelling waters, providing nutrients for remarkable marine productivity. Extensive kelp forests support marine life. There are 11 marine reserves established by the state of California and NOAA where all fishing is prohibited. The western three-fourths of Santa Cruz Island is a privately owned Nature Conservancy preserve; access is available by permit. Hiking trail systems are found on Santa Rosa, Santa Cruz, Anacapa, and Santa Barbara. Mainland visitor centers are at Ventura and Santa Barbara. Anacapa is three islets that are joined at low tide. It is known for Arch Rock and wildflowers. Santa Rosa has a northern escarpment that drops off steeply into the ocean. Santa Cruz has sea caves and a diversity of terrestrial habitats. Santa Barbara Island is a nesting area for Xantus’s murrelets. The islands are part of the Northern Channel Islands IBA, the most important seabird nesting area in California. Endemics include Catalina California quail, Island loggerhead shrike, Catalina Hutton’s vireo, San Clemente spotted towhee, Santa Cruz Island rufous-crowned sparrow, Channel Islands song sparrow, and island scrub jay. Ecoregion NA1201.
San Dimas Experimental Range, Angeles National Forest, California (site 2). The watersheds of Little Dalton, Big Dalton, and San Dimas Canyons just to the north of the cities of Claremont, Glendora, and San Dimas in the Los Angeles metropolitan area. A chaparral research site with emphasis on fire ecology, water yield, and air pollution effects on vegetation. Included is the Fern Canyon Research Natural Area. Ecoregion NA1203.
San Joaquin Experimental Range and Research Natural Area, California (site 3). Located in O’Neals, California, this is an area of open oak woodland and chaparral, used for research and education on fire ecology, bird population dynamics, and livestock grazing impacts. Ecoregion NA1202.
VIII. Ramsar Sites
Punta Banda Estuary, Baja California (site 4). Tidal marshes, mud flats, and seagrass beds support dolphins, gray whale, seal, sea lions and breeding areas for 150 species of fish. Ecoregion NA1201.
Tijuana River National Estuarine Research Reserve, California (site 5). The finest saltwater marsh on the California coast contains coastal wetlands, sand dunes, and sage scrub and is home for eight endangered or threatened birds, invertebrates, and plants. A NNL and an IBA for light-footed clapper rail, northern harrier, California least tern, and California gnatcatcher; the NERR includes Tijuana Slough NWR, Border Field State Park, US Navy, and San Diego city and county property. Ecoregion NA1201.
IX. Western Hemisphere Shorebird Reserve Network
South San Diego Bay, California. Part of the San Diego Bay NWR, the site contains mud flats, eel grass beds, and salt marshes that support more than 20,000 shorebirds. It is also an IBA for breeding terns. Ecoregion NA1201.
X. National Estuarine Research Reserves
Tijuana River, California. See description under Ramsar sites.
To be continued with National Forests, National Landscape Conservation System, National Marine Sanctuaries, National Natural Landmarks, National Park System, Federal Recreation Lakes, National Scenic Trails, National Wild and Scenic River System, Wilderness Areas, and state and local sites.
XI. Further Reading
Courchamp, Franck, Rosie Woodroffe and Gary Roemer. 2003. Removing Protected Populations to Save Endangered Species. Science 302:1532.
Janis, Christine. 1994. The Sabertooth’s Repeat Performances. Natural History, April 1994, pp. 78-83.
Keeley, Jon E., C.J. Fotheringham, and Marco Morais. 1999. Reexamining Fire Suppression Impacts on Brushland Fire Regimes. Science 284:1829-1832.
Ludwig, Lisa Grant, et al. 2010. Climate-Modulated Channel Incision and Rupture History of the San Andreas Fault in the Carrizo Plain. Science 327:1117-1119.
Mohlenbrock, Robert H. 2001. Channeling in California. Natural History, September 2001, pp. 22-24.
Mohlenbrock, Robert H. 1993a. Cushenbury Canyon, California. Natural History, February 1993, pp. 58-60.
Mohlenbrock, Robert H. 1993b. Pebble Plains, California. Natural History, August 1993, pp. 14-17.
Mohlenbrock, Robert H. 1984. The Field Guide to U.S. National Forests. Congdon and Weed, Inc.
Noble, John et al. 2010. Mexico. Lonely Planet Publications.
Shouse, Ben. 2003. Old-Growth Forest Spared for Now. Science 299:802.
UNESCO-Man and the Biosphere Reserves Directory. http://www.unesco.org/mabdb/br/brdir/directory/database.asp (accessed 5/30/11).
Van Valkenburgh, Blaire. 1994. Tough Times in the Tar Pits. Natural History, April 1994, pp. 84-85.
Vidal, R.M., H. Berlangia, and M. de Coro Arimendi. 2009. Mexico In C. Devenish, D.F. Diaz Fernandez, R.P. Clay, I. Davidson, and I. Yepez Zabala, eds. Important Bird Areas Americas—Priority Sites for Biodiversity Conservation. Quito, Ecuador. BirdLife International. BirdLife Conservation Series No. 16.
World Heritage List. http://whc.unesco.org/en/list (accessed 5/22/11).
Zielke, Olaf, et al. 2010. Slip in the 1857 and Earlier Large Earthquakes Along the Carrizo Plain, San Andreas Fault. Science 327:1119-1122.
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