Is Los Angeles Truly A Hotspot for Biodiversity?

Published as part of an environmental storytelling partnership with the Laboratory for Environmental Narrative Strategies (LENS) at UCLA, with extensive contributions from faculty and MFA students in UCLA’s documentary film program in the School of Theater, Film and Television. The second storyline considers how Los Angeles has inadvertently become a sanctuary city for non-native animal species that are sometimes endangered in their native habitats. Find more Urban Ark stories here.


As an environmentally involved Angelena, I often hear people say that Los Angeles is a “biodiversity hotspot.” Looking out the window of my Koreatown home, that diversity is not immediately obvious. Sure, my neighbors have many different species of plants from all over the world, but how does this biodiversity compare with places that are more typically associated with the word “biodiversity,” like the jungles of Costa Rica?

It turns out, the answer to this question is only partly a scientific one.

Learn more about biodiversity in urban habitats in "Urban Ark Los Angeles."

The Natural History Museum of Los Angeles County tells people that we live in a “biodiversity hotspot” to get them excited about nature in the city. It is true that Los Angeles has rich biological diversity, but what exactly that means depends on whom you ask.

Photograph taken by the author near her home in Koreatown, Los Angeles, 2018. | Jenny Alemán-Zometa

Photograph taken by the author near her home in Koreatown, Los Angeles, 2018. | Jenny Alemán-Zometa

“It’s a win for more people to be aware that we are in this amazing biodiversity hotspot with all this unique and amazing nature around us,” said Lila Higgins, the museum’s Community Science Senior Manager, in an interview with the Los Angeles Times. “And we are getting people out there to look and hopefully begin and continue their relationship with nature.”

It is true that Los Angeles has rich biological diversity, but what exactly that means depends on whom you ask.

The term “biodiversity,” or biological diversity, itself is a hotly debated concept in ecology. And scientists use a variety of concepts to measure biodiversity. In practice, the definition of biodiversity is a litmus test for what people value about nature. Should every species be treated equally? Do nonnative species count or just natives? Or are some species more valuable because they serve as “keystone species”? Or should we be counting “functional groups” of species instead as a better way of measuring diversity? Even the basic unit of a “species,” it turns out, is not an objective feature of the biological world, but rather a convenient way of organizing it for human understanding. And different people, as one might expect, value different things.

So, “biodiversity” can be a fuzzy concept. What about “hotspot”?

The term “biodiversity hotspot” has a very specific meaning and, it turns out, a very specific role to play not just in science but also in advocacy for conservation. In 1988, British scientist and environmentalist Norman Myers coined the term “biodiversity hotspot” as part of his efforts to preserve Earth’s biodiversity. Myers argued that when it comes to conservation, not all places are created equal. In the global struggle for conservation, conservationists should focus their efforts where they can be most impactful. Myers is not a botanist, but he understood that the best data sets available were for plants, not animals. With this in mind, he decided that a hotspot must have at least 1,500 species of vascular plants that are identified as "endemic," meaning these plants are only found in one particular area of the world. Vascular plants make up the majority of plant species and are known as “higher plants,” primarily because they evolved later than other plants such as moss: Think giant sequoias and coastal redwoods.

But hotspots are not just about species; they're also about the presence of threat. In order to be considered a hotspot, habitat in the area in question must have decreased by at least 70 percent.

Los Angeles is a small part of the California Floristic Province. | Map created in QGIS from data in "Hotspots Revisited 2011," Conservation International 2012.

Los Angeles is a small part of the California Floristic Province. | Map created in QGIS from data in "Hotspots Revisited."


The California Floristic Province is one of 36 “biodiversity hotspots” worldwide as defined by Myers and the global advocacy group Conservation International. Los Angeles is just a small part of this “hotspot,” which stretches from Oregon to Baja California, and includes the entire California coast and most of the state’s interior. A key reason why this region is considered a biodiversity hotspot is because of the abundance of rare plant species here, over 2,000 different ones, according to the book “Hotspots Revisited.”

The California Floristic Province itself is another scientific and value-laden concept, with a rich history dating back to 1957. Botanists originally developed this concept because it helped explain California’s unique flora. In 1978, G. Ledyard Stebbins, a botanist and evolutionary biologist, argued that the region’s unique climate, topography, and soil enabled it to produce so many different plants, according to native plant journal Fremontia. California has a Mediterranean climate composed of “mild, wet winters and long, dry summers,” it has large differences in precipitation and available moisture throughout the state, as well as major differences in elevation. For all of these reasons, California is home to a wide variety of plant species that are found nowhere else in the world.

Learn more about how scientists are learning more about how species adapt in urban habitats in this segment of "Earth Focus."

But that, as we have seen, is not the only reason the California Floristic Province is considered a biodiversity hotspot. The definition requires threat, too. Myers confirmed this threat in the scientific journal Nature, saying California’s natural habitat for endemic vegetation is down to less than 25 percent of its original size.

Human activities and development put pressure on California’s unique ecosystems, such as coastal sage scrub and wetlands, but somewhat ironically, they are also responsible for increasing other types of biodiversity, especially in our big cities. “There’s often a misconception that Los Angeles is a concrete jungle, when in reality the city is home to one of the most diverse ecosystems in the world,” said Brian Brown, curator of entomology at the Natural History Museum of Los Angeles County (NHM) in an interview with The Guardian.

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However, if the Los Angeles’ biodiversity rivals that of places like Costa Rican cloud forests, it’s not in spite of the threat from people, but because of people. Mark Vellend explains in his contribution to the textbook “Effective Conservation Science: Data not Dogma,” that although global biodiversity has decreased thanks to human activities, in many cases local biodiversity has actually increased. Activities associated with urbanization activities, such as transportation of goods across seas, increase the number of nonnative species. Cities also create novel habitats that can contribute to the number of new species found, such as the borough-specific rat populations scientists have discovered in New York City’s subways or some of the more than 40 new species of flies museum researchers found in Los Angeles with the help of community scientists.

Jungles of Costa Rica. | Jenny Alemán-Zometa

Jungles of Costa Rica. | Jenny Alemán-Zometa

NHM’s Urban Nature Research Center celebrates this type of biodiversity through community science and other research projects that reveal the rich, often nonnative, ecology of urban Los Angeles. However, Myers and other proponents for the protection of biodiversity hotspots, such as the Critical Ecosystem Partnership Fund, do not include this type of biodiversity in their determination of hotspots worthy of conservation.

Unlike the theory of evolution or even the existence of climate change caused by human activities, biodiversity hotspots are not scientifically determined, but rather an idea developed for a conservation goal. Myers’ motivation came from trying to answer the question “How can we protect the most species per dollar invested?” His results serve a pragmatic end and were not an objective assessment of where the most “biodiversity,” already a fuzzy metric, is found. As a conceptual tool, the concept of the “biodiversity hotspot” has been wildly successful. Conservation International and partners have used it to raise $750 million dollars for conservation.

As a supporter of conservation, I have no problem with conservationists occasionally blurring the lines between science and activism if it helps to hold the line against destructive human impacts on the natural world. At the same time, I worry that our use of fuzzy ideas that sound scientific can backfire when intelligent critics and other astute observers see through the rhetoric.

Is Los Angeles a biodiversity hotspot? Well, it’s complicated. I don’t fault anyone for trying to get Angelenos interested in the amazing biological diversity that surrounds us, but personally, I think the real story is more interesting.

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