San Lucan xeric scrub

Category: Grassland, Tundra, and Human Biomes.

Geographic Location: Mexico.

Summary: This ecoregion retains much of its original flora and fauna because of geologic isolation. Notably, the area has been established as an Endemic Bird Area.

The San Lucan Xeric Scrub biome, sometimes referred to as the Cape Region, is located at the southern tip of the Baja California Peninsula of Mexico. It covers an area of approximately 1,500 square miles (3,900 square kilometers). This diverse landscape of granitic mountains, valleys, arroyos, and plateaus is covered with a variety of xeric (or low-moisture) vegetation, and is part of the greater ecoregion complex of the Sonoran-Baja Deserts. Plants and animals of this region evolved isolated from the greater landmass before joining the Baja Peninsula. In this sense, many species found here have evolved independently from others found in adjacent areas. Hence, the biome is sometimes referred to as an island of vegetation.

The average annual high temperature is 85 degrees F (30 degrees C); the average annual low is 64 degrees F (18 degrees C). Annual precipitation is about 16 inches (40 centimeters). This warm, arid climate supports a variety of wildlife, about 10 percent of which are endemic, or found nowhere else on Earth. The region supports a number of endemic birds, for example, and is listed as an Endemic Bird Area by BirdLife International.

The Cape Region contains the highest proportion of intact xeric scrub—315 endemic species—of any Mexican state, due primarily to its difficult topography. This ecoregion includes the plateaus between the coast and the lower limits of the dry forests that begin at around 800 feet (250 meters). There are two national parks here dedicated to protecting the xeric scrub and other flora and fauna: Bahía de Loret, with 798 square miles (2,070 square kilometers), established in 1996, and the much smaller Cabo Pulmo, with 27 square miles (70 square kilometers), established in 1995.

Flora and Fauna

The xeric plant communities that dominate the San Lucan ecoregion include: the cactus cholla, elephant tree (Bursera microphylla), Lysiloma divaricata, organ pipe cactus (Stenocereus thuberii), mala mujer (Cnidoscolus angustidens), Yucca spp., and barrel cactus (Ferocactus spp.). Other plants found here include the boojum tree (Fouquieria columnaris), date palm, giant coreopsis, ponderosa pine, the grass hairy grama (Bouteloua hirsuta), and spiderwort (Commelina coelestis).

An amazing variety of animal wildlife inhabits this hot, dry ecoregion. In total, 238 species have been identified here. Mammals include: Mexican long-nosed bat (Leptonycteris yerbabuenae), ring-tailed cat (Bassariscus astutus), black jackrabbit (Lepus insularis), desert kangaroo rat (Dipodomys deserti), mule deer (Odocoileus hemionus), coyote (Canis latrans), bobcat (Lynx rufus), cougar (Puma concolor), American badger (Taxidea taxus), gray fox (Urocyon cinereoargenteus), and kit fox (Vulpes macrotis).

Baja California has great biodiversity along its coasts, including populations of California sea lions and gray whales. The region has been called the World’s Aquarium by conservationists, as the Gulf of California, Sea of Cortez, and Baja California’s Pacific Ocean shores are home for up to one-third of Earth’s marine mammal species.

There are 199 species of birds identified in the San Lucan Xeric Scrub biome, with two of these endemic. Some avifauna found in this ecoregion include: Cooper’s hawk, sharp-shinned hawk, golden eagle, great blue heron, short-eared owl, burrowing owl, ring-necked duck, cedar waxwing, great horned owl, red-tailed hawk, California quail, Costa’s hummingbird, Xantus’s hummingbird, and Belding’s yellowthroat, a highly threatened species. There are 56 reptile and amphibian species in the San Lucan, including the rosy boa and San Lucan rock lizard, and a remarkable variety of spiders.

Human Impact

It is believed that people first settled on the Baja Peninsula over 11,000 years ago, and that the region was dominated by only a few Native American groups. Europeans did not reach the area until 1539. Population density is low; there are fewer than 700,000 inhabitants in the entire California Baja Sur, but impact to the land is still significant. Due to its unique nature, climate, and surrounding coastal areas, the San Lucan Xeric Scrub region has seen rapid growth in tourism. Adventure-tourism has affected desert and coastal sandridge ecosystems; off-road driving damages soils and vegetation that are not easily regenerated in this environment.

More immediate and broadly distributed threats include cattle ranching, fuelwood extraction, and exploitation of wildlife and plants by locals. The poverty and the dependency on natural resources for survival of local inhabitants poses another problem. Perhaps the largest concern for the region are the effects of climate change. A 2010 study—sponsored by the Autonomous University of Baja California Sur (UABCS) in conjunction with Mexico’s Northwest Center for Biological Research, the National Polytechnic Institute, and the Center for Scientific Research and Higher Education of Ensenada—lays out some of the possible consequences of global warming in the ecologically fragile Baja California Peninsula. These include more frequent and stronger hurricanes, loss of vegetation and soils, accelerated desertification, and negative impacts on fisheries and terrestrial biodiversity. However, a 2019 study by the Department of Biology at the University of Puerto Rico found that the San Lucan ecoregion was one of three in Mexico that did not lose a significant amount of vegetation cover.

Bibliography

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