From Temecula, to Aguanga, Warner Springs, Julian, Lake Cuyamaca, and Descanso, Highway 79 winds, climbs, and wiggles 82 miles through deserts, mountains, foothills, valleys, and oases. Two botanists are showing me the entirety of Highway 79, because it passes through some of the most biologically diverse areas in San Diego County, a county that is, they say, arguably the most biologically diverse in the United States.
Tom Chester, Nancy Accola, and I are ready for the day — hiking gear, water, food, and plenty of extra dark chocolate.
We begin in Temecula around 10 am. Chester is driving, Accola’s positioned in the backseat. She will spot the plants and Chester will find the nearest shoulder on which to pull over when she shouts out a species. We head south toward Pine Valley, and in about ten minutes, we’re out of the city and driving towards Aguanga.
Palomar Mountain is ahead of us and and to the right. It’s carpeted by chaparral. The area near us by the highway looks like a field of dust, sometimes disturbed by shrubs such as buckwheat. Just south and east of Temecula, the area is low, flat, and in the rain shadow of the mountain. This is why it is so hot and dry here.
The mountain range is covered with chaparral because the north-facing slope shades it from evaporation, Chester says. “The rain shadow only comes in a couple miles away. When the rain clouds form [they] bring the water out of the atmosphere when storms are coming through. As it’s coming up the south slope, it’s still raining as they’re going a little to the north, and then the rain is all rained out. By the time it gets here, there’s not much left.”
On the south side of Palomar Mountain, where the area is not affected by the rain shadow, riparian woodlands cover much of the face of the mountain. That is closer to highway 76. But by the 79, the area gets only 12-14 inches of rain. Just a couple inches lower, and it would technically be a desert. “In our areas in California, you need to have 26 inches of rain to support trees... that’s why pine forests are at only higher elevations where there’s more rain and less evaporation,” Chester says.
Water is fate for microclimates, and it can be fate for some highways. Like many older roads, Highway 79 follows the drainages and water courses of San Diego County’s backcountry. Newer roads are straighter and modify the natural features of the environment to get people to their destination faster. Highway 79, adheres to the land’s natural countours. Driving it feels like a ride on a rollercoaster. It goes around and atop geographical features.
“It follows the Temecula River to Sunshine Summit, and then follows tributaries of the San Luis Rey River to, through, and beyond the Lake Henshaw area. It then follows the drainage to the Santa Ysabel Valley, and then Coleman Creek to Inspiration Point just beyond Julian. It quickly enters the Cuyamaca Lake drainages, and then follows the Green, Sweetwater, and Descanso Rivers,” Chester said in an email.
Our first stop is at the Dripping Springs Campground. Here, we’re by the Temecula River drainage and at an elevation of 1148 feet. Elderberry and Coast Live Oak trees provide us some shade as we step out of the car and go inspect a few patches of periwinkle flowers called the southern mountain woolly star.
Dripping Springs serves as a good example of riparian vegetation, Chester says. Even though this place doesn’t receive much rainfall, the trees are happy and the flowers are blooming. They are able to survive in such a dry climate with the help of year-round moisture from the Temecula River.
Another survivor of the dry climate, though endangered, is the Arroyo Toad. This warty and stocky toad hops quickly to feed on ants and hibernates when it needs to avoid dehydration. A native amphibian, zoologists say it has only 3000 of its total breeding population left in this area.
The feeling of being in a desert returns as we continue along the highway and arrive in Aguanga. At 1955 feet, Aguanga sits at a slightly higher elevation than Dripping Springs. We are now directly behind Palomar Mountain, and fully in its shadow. It feels as if we are in a mini Anza-Borrego desert. We drive past a life-size metal horse statue created by the Ricardo Breceda gallery. The horse provokes a prolonged stare, because it looks as if it’s about to gallop across the road in front of us.
We pull over across from Aguanga General Store and step into a scene out of a cowboy movie. A bush of Russian thistle, or tumbleweed, rolls by as we take our first few steps. Aguanga is a good example of a melting pot between the two Californias: the cowboy and the surfer. Here, desert plants coexist with coastal plants.
“Aguanga area, which shares a number of species with coastal southwest San Diego County, has a similar low rainfall. At Aguanga, the low rainfall is due to the rain shadow of Palomar Mountain. In coastal San Diego County, the low rainfall is due to the low elevations and its southern position, farther from the winter rain systems,” Chester says. “Both areas have coastal sage scrub vegetation, and both areas have a number of desert plants, such as yucca schidigera.”
The ground here, though it doesn’t look it, is half water, and the existing plants are able to pull out this moisture to live. Chester and Accola point out a large bush of sticky-leafed mule fat, a fourwing saltbush whose foliage has a tangy salty taste, and a sagging desert willow with trumpet-like flowers growing right next to a coastal fremont cottonwood supporting its spade-shaped and jagged leaves.
Coast live oak, a California tree that seems to line the whole of Highway 79, grows at Aguanga. Unlike the sycamores and cottonwoods in Dripping Springs, coast live oak is tough and doesn’t need to have its roots in Temecula River water. “[Coast Live Oak] has a much harder leaf so it doesn’t lose as much to evaporation. Whereas the other trees just shoot the water out, 30 gallons a day,” Chester says. Today is near the beginning of Aguanga’s hot season, so we leave before the temperature climbs into the 90s.