Pictured above is a California Scrub Oak (Quercus berberidifolia). It’s endemic to the coastal chaparral biome that spreads from the coat to the foothills and mountains east and north of San Diego. It’s not an impressive oak tree; it usually tops out at 12 to 15 feet tall, and has multiple trunks and twisted branches. It is not a picturesque species.
But it is hardy. In a biome that typically receives 10-15 inches of rain per year, it is highly adapted to utilize and retain water efficiently. We have a Mediterranean climate here, meaning the winters are typically wet, and the spring, summer and fall are dry. It is not uncommon for our area to go without rainfall for months at a time, even as long as 8-9 months. Everything that grows natively out here, then, has to be dry-adapted. It has to be able to survive under conditions where rain is scarce. Grasses grow at the end of winter when it’s wettest, turning the hills around our place a verdant green. They then produce seeds, and die. As spring progresses, those grassy hills turn the golden brown so commonplace in the California foothills. Trees need a different strategy, however.
Scrub oaks are a good example of a tree species that has developed dry-condition strategies to help it survive. Principle among these is the development of a root ball — a sizable chunk of wood (sometimes as large as a mid-size car tire) from which trunks and roots alike sprout and are nourished. It is a source of carbohydrates and water for the scrub oak. (The root ball also helps the scrub oak survive wild fire. I have seen ground completely burned out by the 2003 Cedar Fire, a moonscape of ash and blackened ground from which it would seem nothing would ever grow again. And yet the scrub oaks resurfaced and thrived the following year.)
So it has been distressing to me to hike trails close by, and wander the fire road on the back of our house lot, and see the scrub oaks start to die.
It’s not just the scrub oaks, of course; we’ve been steadily losing California Live Oaks at our local trail over the last few years, too. Typically they look fine, then in the course of a summer, wither and die from a combination of water stress and bark beetle predation.
I know it’s been dry. We have a water retention dam build during a wetter winter several years ago; it’s purpose was to prevent soil erosion. It’s about 3 feet deep at its deepest, and that winter one series of rains overtopped it. Last winter we had so little rain no water collected behind the dam at all. Southern California undergoes well-known cycles of wet and dry winters, of course, driven by El Nino and La Nina conditions, respectively. Southern California is currently in its third year of La Nina conditions. Southern California is caught in a 22-year-long megadrought, the most extreme in 1,200 years, is linked to climate change according to climate scientists. But this year feels different because the scrub oaks are dying. They’ve never looked this way before in my experience.
It’s not just the dry winters, either. We used to see summer monsoons in late July through the middle of August — the development of thunderstorms, sometimes heavy, over the mountains east of us — that would dump inches of much-needed rain onto the forests there, and into riparian water systems down hill of them. Over the last five years, I’ve seen fewer and fewer monsoon thunderstorms; none over some of those summers.
It’s one thing to read about climate change and understand the threat and contemplate the political dynamics. It’s quite another to experience the absence of things previously commonplace, and to see even the hardiest of near-desert trees starting to die off in front of you. It really feels like things are slipping away from us — the tragedy of absence.