The Sky Islands of San Diego County
An ode to the Cuyamaca, Laguna and Palomar Mountains
FIRESTORM 2003
In late October of 2003 a hunter’s errant signal fire grew out of control and proceeded to be one of the largest and most destructive wildfires to then burn in California. Overnight, westerly dry Santa Ana winds amplified the fire’s spread causing it to burn around 3,000 acres per hour. As the westerly winds pushed the fire into San Diego County’s urban wildland interface, it consumed structures and rural communities at an alarming pace. Throughout the dark of night, the fire raced through the gorges and canyons that spread out from the foothills of the Cuyamaca Mountains, making it exceedingly impossible to provide advanced warning to any communities down wind. By mid-morning the next day, 12 people were killed and thousands of acres of property had burned. The fire jumped interstates and overran fire crews with ease. And that was only the beginning. For weeks on end, the land burned.
The Cedar Fire was not alone in the devastation it rained upon southern California. At the time of the Cedar Fire, a dozen or so fires burned throughout southern California. Other sizeable fires were burning in the mountains and foothills surrounding Los Angeles, Orange County, and other parts of San Diego County. In October of 2003, a firestorm had descended upon southern California. Years of drought and a subsequent summer of hot and dry conditions had desiccated the native vegetation. Santa Ana winds ripened the conditions and made containment virtually impossible.
The scars of those events still remain evident today. But what is equally evident is the process of renewal that followed. The ecology of southern California's chaparral and mixed evergreen habitats are no stranger to fire. Fire is a part of its ecology and thus, through eons of evolution, that ecology has adapted itself to periodic fires. And so, when the landscape burns like it has before and very likely will again, the seemingly destructive force of fire is followed by a beautiful process of renewal.
A WINDOW TO THE PAST
A TRANSECT: FROM COASTLINE TO SUMMIT TO DESERT FLOOR
Along the east facing exposures of the higher ridgelines, the conditions can be both cold and dry due to both the montane elevation and a slight rain shadowing effect. Ericameria species can be great at sustaining cold, dry environments, like that of the east facing Laguna Mountain escarpment.
Quite often the Peninsular Ranges rise in stark contrast to the semi-arid or arid landscape that surrounds the range. When that happens, an island effect takes place whereby the ecosystems throughout the upper elevations of the mountains are unique when compared to the surrounding terrain. This can result in isolated species, similar to those species growing on an island. The term 'sky island' is sometimes used to describe mountains that rise in contrast to a different lowland environment, much like the Peninsular Ranges do.
Species confined to such sky islands are limited in their ability to spread and disperse across the landscape due to a lack of suitable habitat and growing conditions throughout the lowland environment. As such, some of these isolated species undergo speciation events that effectively give birth to new species. And, as quite often happens, the isolated growing conditions results in a plant edging out an existence within a niche environment, which is a great recipe for producing rare plants.
The Laguna Mountains Goldenbush (Ericameria cuneata var. macrocephala) is a rare plant found only within the Laguna Mountains. However, the parent specie, Cliff Goldenbush (Ericameria cuneata), remains widespread throughout California. Presumably, the unique growing conditions and/or isolation of the Laguna Mountains has lead to the birth of a subspecie - the rare Laguna Mountains Goldenbush (Ericameria cuneata var. macrocephala).