The San Ysidro Mountains are a mountain range in southern

San Diego County, California San Diego County (), officially the County of San Diego, is a county (United States), county in the southwest corner of the U.S. state of California, north to its Mexico-United States border, border with Mexico. As of the 2020 United States Cen ...

, and Baja California, Mexico. The mountains are a rugged coastal foothill range of the

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Pacific Coast Range ...

system. Major peaks include the highest summit of the range, Otay Mountain, and the Cerro San Isidro which forms the southern extrusion of the range on the Mexican side of the border. The majority of the range is within the Otay Mountain Wilderness area, in the United States.

Geography

Lying only inland from the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, this mountain range rises out of the coastal plain of San Diego and Tijuana until it reaches a maximum height of on the summit of Otay Mountain. On the western side of the mountain lies Lower Otay Lake and Otay Mesa, with Richard J. Donovan Correctional Facility and other detention centers and law enforcement properties lying on the southwest slope of the mountain. On the eastern flank, Mine Canyon and Marron Valley separate the San Ysidro Mountains from Tecate Peak (Kuuchamaa).

Cerro San Isidro

The Cerro San Isidro, located in Tijuana, is separated from the rest of the range by the border fence and the Rio Alamar, and forms the southern portion of the mountains. The summit of the Cerro San Isidro reaches approximately , and supports many of the same endemic and rare plants found on Otay Mountain. A '' colonia'' of Tijuana, Valle Imperial, stretches across the western slope of the mountain. On December 31, 2014, a rare snowfall event blanketed the Cerro San Isidro after low temperatures of .

Ecology

The native vegetation of the San Ysidro Mountains represents the

coastal sage scrub Coastal sage scrub, also known as coastal scrub, CSS, or soft chaparral, is a low scrubland plant community of the California coastal sage and chaparral subecoregion, found in coastal California and northwestern coastal Baja California. It is ...

of the

California coastal sage and chaparral ecoregion The California coastal sage and chaparral () is a Mediterranean forests, woodlands, and scrub ecoregion, defined by the World Wildlife Fund, located in southwestern California (United States) and northwestern Baja California (Mexico). It is part o ...

(western faces); and plants of the California montane chaparral and woodlands ecoregion (inland). The San Ysidro Mountains are one of the few locations the rare Tecate Cypress (''Cupressus forbesii'') is found. This tree was once abundant in the higher elevations of the range as well as in its canyons. The San Ysidro Mountains were deforested of living foliage by

wildfire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

s in 2003 and 2007. ''Cupressus forbesii'' is a

fire ecology Fire ecology is a scientific discipline concerned with the effects of fire on natural ecosystems. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vit ...

dependent species, and there has been some evidence of regrowth starting.

References

{{- Peninsular Ranges Mountain ranges of San Diego County, California Mountain ranges of Baja California Mountain Empire (San Diego County) Mountain ranges of Southern California

Geography

Cerro San Isidro

Ecology

See also

References