Is Los Angeles A Desert?

A couple of weeks ago, I wrote an article in which I — perhaps cavalierly — described Los Angeles as a desert.

In the interest of transparency, it was a sentence I tossed off without really thinking. I've heard L.A. described as a desert many times in my 18 years of living here, and it just flowed through my fingers as I typed, much as one might describe water as wet without necessarily reaching out to several geologists to confirm the matter.

There was a small part of me that raised a red flag as I pounded the words into my keyboard. Is L.A. a desert, though? I thought. Haven't I also heard that it isn't? My editor reviewed the story and made no note about the desert comment either, so fatefully — tragically — I ignored the thought and hit publish.

No sooner did the piece go live than LAist began receiving emails and messages. One reader told us that, "By characterizing Los Angeles as a desert, it perpetuates the myth that Los Angeles is unable to grow trees, and therefore is unable to address climate change with a simple solution like planting trees."

Another wrote, "In a recent article... the authors unfortunately stated that 'Los Angeles is located in a desert.' This a common misconception. Our region is actually best described as having a Mediterranean climate or more specific to our local sense of place and history a Coastal Sage and Chaparral environment."

Several readers (as well as some people here in our own newsroom) sent us a link to a story published by KCET, quite unreservedly titled, "Los Angeles Is Not A Desert. Stop Calling It One."

LOS ANGELES, DESERT OR NAH?

My mistake seemed relatively clear-cut, and it looked very much as if I would need to publish an update or issue a correction. But I am stubborn, and did not want to issue a correction without confirming that I indeed needed to be corrected. So, I reached out to a professor of earth sciences at the University of Southern California, expecting a scientific slap on the wrist and to be sent back to my computer to publicly admit my wrongdoing.

But that is not what happened.

Lowell Stott wrote me back. "The answer to your question is best answered by calling upon a simple quantitative measure, the difference between annual precipitation and evaporation," he said in an email. "In Los Angeles, the difference between these two variables is effectively zero... This measure is a clear depiction that Los Angeles, and much of Southern California, is a 'Desert' environment."

I reread his email. "Los Angeles... is a 'Desert' environment."

I picked up the phone and called him.

"Using a very straightforward, quantitative measure," he said, "I don't think that there is a hydrologist or a climate scientist that would argue that [L.A.] isn't a desert."

Altogether by accident, I was suddenly embroiled in a climatological scandale. What if the city's big geological secret is that L.A. actually is a desert after all? The KCET article was published in 2012. For all I know, things have changed. I mean, the glaciers are melting. Maybe L.A. became a desert in the past nine years. I'm not a doctor.

What I did know for sure after receiving Stott's reply was that I had a duty to the readers, to the community, to the entire city to see this through.

My next step was to get a second (or, really, third) opinion. I reached out to experts at the University of California, Irvine; the California Institute of Technology; the Association of Environmental and Engineering Geologists' Southern California chapter; and the California Department of Conservation. Several ignored my request, and several politely declined, saying that climate classification in Southern California is not their area of expertise.

Eventually, I was connected with Jon Keeley, a research scientist at the U.S. Geological Survey. Stationed at Sequoia National Park, Keeley spent 20 years teaching at Occidental College. If anyone could clear this up, I hoped it would be him.

"I don't know any geologist who would call [L.A.] a desert," said Keeley. "There is a technical definition of a desert — that it is a biome where precipitation is generally less than 10 inches a year, and most importantly, the annual evaporation exceeds the annual precipitation. Neither of those apply to Los Angeles. The city of Los Angeles gets 15 inches of rain a year and generally, evaporation doesn't exceed precipitation."

Aha, I thought. Here it is. One more question, and I'd be able to get my correction of shame over with.

"Aha," I said. "What is the amount of evaporation in L.A., then?"

"I don't have numbers on that," Keeley said. "I don't know that anybody does."

The wind went swiftly and abruptly out of my sails. I could take Keeley's word for it, but if I couldn't confidently cite both precipitation and evaporation figures, how could I be sure? Citing those very same figures, Stott argued that L.A. is a desert. Keeley, using the same measurements, said it is not.

Keeley added that there are other important factors to consider in determining an area's desert-or-nah status. L.A. is widely agreed upon to be a Mediterranean climate, he said, a delineation provided by the Köppen-Geiger Climate Classification System. It's the same measurement on which Clarke relied in his KCET treatise. Mediterranean climates have rainy winters, hot and dry summers, denser vegetation and are very fire prone, Keeley said.

He also noted that in the grand scheme of things, it doesn't really matter whether L.A. is a desert or not.

"Why is the classification important, for both professionals and laypeople?" I asked.

"I don't know that it is wildly important, really," said Keeley. "It's one way of defining the world."

THE DEBATE RAGES ON

Despite Keeley's lukewarm feelings about how important this actually was, I pressed on. Via email, I reached out to almost a dozen more scientists specializing in earth sciences, and as they responded, a pattern began to emerge. There were those who hewed strictly to the Köppen-Geiger classification, and those who did not.

Among those who did, all sat firmly in Camp Los Angeles Is Not A Desert.

• "Technically, the climate of Los Angeles is Mediterranean, characterized by warm, dry summers and wet, cooler winters." — Sarah Aarons, a geochemist and assistant professor at the University of California, San Diego's Scripps Institution of Oceanography.
• "No L.A. is not considered a desert... it [is] a semi arid Mediterranean climate." — Jennifer Cotton, an assistant professor in the department of geological sciences at California State University, Northridge.
• "Los Angeles is not a desert. Its climate is not classified as arid. It is a warm temperate climate with a warm and dry summer," — Dennis L. Hartmann, an atmospheric scientist at the University of Washington who penned a textbook called Global Physical Climatology.
• "I wouldn't consider L.A. to be a desert... technically, it's referred to as a Mediterranean climate, with hot dry summers and a mild winter, when it does rain." — Robert Allen, an associate professor of earth sciences at the University of California, Riverside.

Matthew Kirby, professor of paleoclimatology at California State University, Fullerton, agreed that L.A. is not a desert, but offered one reason to consider using the term anyway.

"I would not say by any means that we are a true desert climate," he said. But, "I tell my students, when you think about water conservation, it doesn't hurt to think about SoCal as a desert [because] water is a precious resource, and one that, in particular in California, we must be aware of at all times and conserve as best we can."

Keeley also conceded that there may be some gray area.

"'Desert' is just a term people used to indicate low productivity," he said. "I can see that the average person might see L.A. as a desert. I would not be upset if someone called the L.A. basin a desert."

Still, two others hypothesized that L.A. is a desert, although both noted that this is not their area of specialization and suggested that I clarify the question with their colleagues.

• "Well, I am not an expert on this (in terms of rainfall amounts, other definitions). But I grew up in the LA Basin. Yes, it is most definitely a desert, IMO!" — Kristie Boering, a professor of earth and planetary science and a professor of chemistry at the University of California, Berkeley.
• "Although I believe the answer is 'yes', it's not really my area of specialization and might be missing a subtlety there." — Morgan Raven, an assistant professor in the earth sciences department at the University of California, Santa Barbara.

Finally, on Boering's suggestion, I reached out to Inez Fung, a professor of atmospheric science at UC Berkeley. Fung served as the 2009-2010 Edward P. Bass Distinguished Visiting Environmental Scholar at Yale University, was a contributor to the 2007 Nobel Peace Prize awarded to the United Nations Environmental Programme Intergovernmental Panel for Climate Change and was the 2002 Henry W. Kendall Memorial Lecturer in Global Change Science at the Massachusetts Institute of Technology. She was also named one of Scientific American's 2005 Scientific American 50, which honors visionaries from the worlds of research, industry and politics.

Fung wrote a one-sentence reply to my query: "I suggest that you consult the chapter about L.A. in John McPhee's book, Control of Nature,'" she said, and then, quoting the chapter: "'Moisture evaporates off your eyeballs so fast that you have to keep blinking.'"

I do not know whether that is a yes or a no with regards to L.A. being a desert, but I appreciate the poetry inherent in leaving it unexplained.

THE BOTTOM LINE

So, at the end of the day, is Los Angeles a desert? Here's what we know.

Going by the widely used Köppen-Geiger Climate Classification System, Los Angeles is not a desert. It is located in a warm temperate climate, or a Csb, which is the sub-designation to which people are referring when they call it a Mediterranean climate, according to Hartmann.

However, there are other ways of thinking about the climate and the world, and those may allow for the possibility of using the word "desert" with respect to the L.A. area.

All that being said, I acknowledge that I knew none of this when I initially wrote that Los Angeles is a desert, so it's not like I can claim that I had any of it in mind at the time.

Instead, I will supply Keeley's totally unprovoked take.

"Anything can be debated, depending on what your focus is," he said. "In other words, you're vindicated."

For everyone who made it to the end of this journey with me, we have officially issued a clarification on the original story. For everyone who wrote in, thank you. We appreciate you reading, your diligence and your time.

Fin.

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