- Author: Greg Ira
- Author: Cameron Barrows
A "Natural History Note" From UC California Naturalist's lead scientist, Dr. Cameron Barrows.
In nature, species are constantly “striving” to be “better” species. To be clear, this is not a conscious effort, rather that improvement can occur through reproduction, there are new combinations of genes being created with every generation, both through mutations and through the mixing of genes through sexual reproduction. For asexual species, gene mutations are the avenue for change; for species capable of sexual reproduction, there is both mutation and the unique gene combinations of the two parents. Change (evolution) for asexual species is slow. Change for sexual species is much faster. The arbiter of whether a mutation and/or a unique gene combination is “better”, more successful at surviving and ultimately reproducing themselves, is the environment, and the environment is always changing. Slowly or quickly, change is happening. Now, through climate change and the introduction of invasive species, we are often the catalysts of change. Before we arrived on the scene climates still changed (but more slowly), and new species did show up and disrupt the status quo, and once in a great while an asteroid slammed into the earth. Change has always been a feature of nature, and the species that make up the nature we all love are there because they were “better” than their predecessors at surviving and reproducing in today's environment. Tomorrow's environments will be different.
Creosote bush is successful by any measure. They have become one of, if not the, most numerous species in each of the Chihuahua, Sonora, and Mojave Deserts. I can think of a handful of plant species that straddle two of those deserts, but only Creosote bushes thrive in all three. Over the eons they have evolved, via mutation and unique gene combination, a cocktail of chemicals in their tissues that repel over-browsing by rabbits and pronghorn antelope and tortoises and desert iguanas and chuckwallas. That same cocktail appears to repel damaging bacteria and possibly viruses, and so has the potential to benefit human health as our disease vectors develop immunities to the antibiotics we use today. But you might object, what about the 60 or so insects that are specifically associated with creosote bushes, what about the 14 species of creosote gall midges that lay their eggs in the plant's tissue to create abnormal growths for their larvae to eat and be protected from parasites? The answer is that none of those pesky bugs kills or reduces the reproductive potential of their creosote bush hosts. That which does not kill them makes them stronger.
The creosote bush's strategy is longevity. They can live for hundreds and in some cases thousands of years, in part because nothing eats them (enough) to kill them. During their long lives there will be many droughts and many wetter periods. Only occasionally will the conditions be right for long enough to allow for successful reproduction. “Young” creosote bushes are rare compared to the densities of their parents. If you live for centuries you do not have to be successful at reproduction very often, and the cost of producing flowers, fruits, and seeds almost every year is not enough to subtract from their longevity. So far, in our analyses of how species are responding to the levels of climate change we are currently experiencing, creosote bushes seem to be shrugging their leafy shoulders.
If longevity is good, then perhaps desert tortoises are also adapted to surviving climate change. Desert tortoises do not live centuries, but they might live as long as we humans do, which is much longer than most wildlife species. Through their lives they too will experience droughts and wetter periods. Like creosote bushes, there are increasingly rare combinations of wet years that foster survivorship in the vulnerable hatchling tortoises. Not being able to predict the future any better than we can, except for in the driest years, female tortoises will lay a clutch of eggs in most years, hedging their bets that the eggs will hatch into a wet weather cycle. If it is a wet spring with lots of food, the females may lay larger clutches and sometimes multiple clutches, all depending on the health and condition of the females. Unlike creosote bushes, there is a considerable cost to the female tortoises for each clutch they lay. If conditions are dry and there is little or nothing for the tortoises to eat for multiple years, there can be a terrible cost in terms of the females' body condition, health, and survivorship. Dr. Jefferey Lovich has been studying desert tortoises for decades. In recent years he has found high tortoise mortality in some populations, and when examining the dead tortoise shells, he has found that the vast majority of dead tortoises were females. Those areas with high female mortality have been hit particularly hard by increasing aridity born by modern climate change.
At the opposite end of the longevity spectrum are side-blotched lizards, which typically live for one, or more rarely two years, especially in our hot deserts. Dry year or wet, they need to breed and produce viable young within a year, or at most two years, or their population is kaput. What we are finding is that this lizard's preferred habitat, as evidenced by where we find them at the highest densities, is shifting to higher elevations. There are still some at lower elevations, but those are usually in or near desert washes where rainwater can be concentrated, and so conditions are not quite as arid as those in the open desert. Or they occur in appropriately landscaped suburban yards where conditions are also less arid (if cats or the high concentration of roadrunners do not eat them). Otherwise, side-blotched lizard populations are moving up in elevation. Those living at higher elevations reproduce better than those at the lower elevations, so that upper elevation edge is expanding while the lowest elevation edge is incrementally contracting. In dry years that shift is clear; in wetter years there is a bit of a reprieve and the lower edge lizards do ok. Every year is different, but the overall trend is pushing these lizards, along with other species, up in elevation.
Long-term observations are essential to discover these patterns. A community of naturalists that help collect these data at multiple locations across gradients of aridity, are equally essential.
Nullius in verba
Go outside, tip your hat to a chuckwalla (and a cactus), and be safe.
- Author: Eliot Freutel
Southern California Mountains Foundation Urban Conservation Corps receive the Corps Network's Project of the Year Award.
Our California Naturalist partners at Southern California Mountains Foundation Urban Conservation Corps were recently honored for their work making the national parks and public lands of the Inland Empire more accessible to the communities that frequent these areas. In 2018, UCC members surveyed Spanish-speaking community members and the results showed that these community members were left out of learning and recreation opportunities due to a lack of representation and a lack of language support. With funding from the National Forest Foundation and support from bilingual instructor Claudia P. Diaz Carrasco (UC ANR Cooperative Extension Riverside Co.) and the UCC's own Gaby Nunez, the first bi-lingual California Naturalist program, Los Naturalistas, was born.
Meeting every Saturday for 4 months, the original cohort of 12 corps-members learned to interpret their parks and open spaces: Translated materials, various teaching methods, a diverse and multi-lingual expert speaker pool, and culturally relevant content were all deployed to ensure that the cohort was ready to address their audience. All 12 emerged as Los Naturalistas with their California Naturalist certifications, ready to make positive changes in environmental justice and access to public spaces for their community through nature and language interpretation.
The Corps-Network's 2020 Project of the Year award highlights Corps-member's work across the nation. This year, Los Naturalistas share the honor with one program that focuses on pollinators and 2 others working to break down barriers for differently abled & LGBTQ+ Corps-members. The takeaway is that empowering young people to represent and advocate for their communities yields incredible and innovative results. As more and more CalNat courses look towards bilingual delivery, we envision a network that represents the true demographic make-up of our diverse state.
In December, amidst the holiday Zoom parties and anticipation of the end of a rough year, we said "Happy Retirement" to one of the California Naturalist Program's favorite colleagues, environmental educators and mentors, Sandy Derby. To mark this milestone, the CalNat team held a small but meaningful surprise Zoom celebration, attended by some of Sandy's colleagues spanning decades. A quiet, "very 2020" way to celebrate a kind and generous person with a wide-reaching, impactful career.
Sandy came to UC ANR in 2013 as an academic coordinator within the Youth, Families, and Communities Initiative to lead California Project Learning Tree (PLT). PLT is a long-running international environmental education program that provides professional development and curriculum to formal and informal environmental educators alike. PLT uses trees and forests as windows on the world to increase students' understanding of the environment and actions they can take to conserve it. PLT in California consists of a network of educators, scientists, forestry professionals, naturalist, and community stewards that work together to educate and take action to build a strong and sustainable California future.
Happy retirement to our friend Sandy. We miss you already and we wish you endless days of relaxation and fun adventures. You can retire from your day job, but you can't retire from being amazing!
PS: Don't worry, California PLT is now in the capable hands of Cynthia (Cyndi) Chavez, California PLT State Coordinator, based in Los Angeles. You can find her contact info here.
- Author: Cameron Barrows
A "Natural History Note" From UC California Naturalist's new lead scientist, Dr. Cameron Barrows.
When scientists underestimate complexity, they fall prey to the perils of unintended consequences. Siddhartha Mukherjee
About five million years ago the uplifting Colorado Plateau changed regional drainage patterns and in doing so created the Colorado River. The Colorado River extends into western and southern Colorado where, depending on the year, the annual snowpack can yield very different flows down the river. Some years, by summer the river would run dry. Other years massive floods scoured through the Plateau's layers of sandstone (creating the Grand Canyon) and would sometimes shift the course of the river into the Salton Trough forming an immense lake (christened by geologists as “Lake Cahuilla”). Water flows toward the lowest point on a landscape, and at 277 ft (84.3 m) below sea level, the tough is one of the 10 lowest terrestrial elevations on earth. The lake's historical shoreline can be easily seen on the hillsides along the eastern edges of the Santa Rosa Mountains. Once the lake filled to an elevation equivalent to sea level, the river would return to its bed and empty into the ocean where it formed one of the largest estuaries and riparian forests in North America. After decades of summer heat the lake would incrementally evaporate and then finally disappear leaving a salt pan coating the lowest regions of the basin. Eventually the river would flood again, resurrecting Lake Cahuilla and repeating this cycle again and again…. a pattern of establishment, decline (drying), and then renewal (re-filling to its former self), again and again. An extensive sand dune system formed at the southeast edge of Lake Cahuilla, formed from sands carried by the flooding Colorado River, sand that eroded out of the sandstone that once filled the space that is now the Grand Canyon. When the basin was dry, northwest winds would blow those lake bottom sediments into sand dunes. We now call those dunes the Algodones, and where those dunes formed along the edges of the great estuary, they form what is the Gran Desierto in northwest Sonora, Mexico. Those sands, as well as other dune systems created by the flood cycles of the Colorado River, provided isolated dune fields where fringe-toed lizards thrived and eventually diverged into what today are six recognized species.
It would be hard to fully appreciate the biological richness created by Lake Cahuilla. The river would have delivered both water and fish to fill the lake. The fish then would form the base of a food web that would include millions of pelicans, cormorants, terns, grebes, and ducks, with storks, cranes, herons, rails, and egrets hunting along the shores. Some would have formed nesting colonies on the islands that would have been created by the lake. The filling of the lake would increase groundwater levels resulting in cottonwood, willow, desert fan palm, and mesquite forests becoming established along what are now ephemeral drainages. Those forests would have been populated by warblers, flycatchers, cuckoos and vireos. Some early visitors suggested jaguars may have hunted for deer and peccaries beneath the canopies of those forests. When the lake was dry, lush vegetation and aquatic species would then be concentrated at a few perennial springs and creeks. The millions of birds would have needed to shift elsewhere, to the Colorado River's estuary in the Gulf of California to the south and to lakes along the eastern base of the Sierra Nevada. Those isolated springs and creeks within the Salton Trough would sustain some species, albeit in low numbers, until the next filling of the lake. Sometimes that isolation, resulted in the evolution of new species. The Salton Sea Springsnail, Pyrgulopsis longinqua, is found only in the Salt Creek wetlands and nowhere else on earth.
The first humans to experience and document this ebb and flow and renewal of sand and water were the Cahuilla, as told through their oral traditions. For thousands of years, they enjoyed the cornucopia of resources when the lake was full, and their populations swelled. They caught fish and birds, enjoying the riches the lake provided, that were in contrast to the surrounding parched desert. When the lake was dry the Cahuilla moved into canyons where perennial water was still available and migrated seasonally up or down the mountain slopes to take advantage of agaves, pinyon seeds, acorns from oak trees, and junipers, along with deer and bighorn sheep. It was sometimes many decades and even centuries between floods sufficient in magnitude to jump the banks of the Colorado River, finding the low Salton Trough and filling the lake once again, so the Cahuilla needed versatility to survive. Prior to modern times, the last time Lake Cahuilla filled was in the 1400s, just before Christopher Columbus landed in the Caribbean Islands and set-in motion a migration from Europe to North America that would alter the lives of the first people of North America, and the natural diversity of this continent, forever.
In modern times the Colorado River may have flooded sufficiently to jump its banks for the final time in 1906. Engineers were creating a canal system to deliver water to meet the needs of a shift in land use to agricultural expansion in both Imperial and southeastern Riverside Counties when floodwaters broke through their canal and filled Lake Cahuilla once again. Multiple dams subsequently built on the Colorado river to siphon away water to quench the thirst southwestern cities will eternally regulate flows down the river, preventing any future flooding, preventing any future inputs of relatively fresh water to the Salton Trough. The building of dams on the Colorado River has forever changed the ebb and flow, flooding, drying and renewal cycle of what was once Lake Cahuilla, changing its character and changing its name to the Salton Sea. Entrepreneurs once thought that the Salton Sea would become a sportsman's mecca, providing fishing, boating, and waterskiing experiences like no other. There were a few decades where that dream seemed to be true. Then it wasn't.
Rather than drying up as it had so many times before, water running through the canals, through agricultural fields to hydrate crops and to dilute salts accumulating in the soils, drains into the Salton Sea and has, until recently, kept the lake from drying. That agricultural wastewater – “drool” – adds four million tons of salt into the Salton Sea annually. The Salton Sea currently has a salt concentration of 44 g/L, or about 25% saltier than the ocean. Some of that water once dedicated to solely to agriculture is now being sent to fill the faucets of a rapidly growing population in San Diego, so less drool for the Salton Sea, and it is now shrinking fast.
The flood and drying cycle that created the ephemeral Lake Cahuilla is what is called an ecosystem process – energy and resource inputs that create ecosystems that are the foundations for biodiversity. Alter an ecosystem process and there will be consequences to biodiversity. Fish can no longer live in the Salton Sea – it is too salty. The food web has been severed for fish-eating birds. There is little doubt that the Salton Sea will continue to shrink and continue to get saltier. There are of examples of what the Salton Sea's future could be. Those lakes that occurred along the eastern base of the Sierra Nevada have been similarly altered by water diversions to fuel Los Angeles' growth. One, Owens Lake, is now dry and toxic alkali dust blows off its dry bed. Another, Mono Lake, was headed in that same direction. A friend and mentor, David Gaines, spearheaded a battle to redirect a couple Sierra creeks back to their natural flow to stabilize Mono Lake. In a true David and Goliath fight, David won. Mono Lake has a salinity of 79.8 g/L, far saltier than the Salton Sea, but there is life there. There are of course no fish, but a food web does exist with algae, brine shrimp, and brine flies at its base. California gulls nest there and thrive, and eared grebes and Wilson's phalaropes use it as a critical refueling stop on their annual migrations, all gorging themselves on shrimp and flies. Back at the Salton Sea, the food web is already in transition from fish to invertebrates. No longer kept in check by hungry fish, the population of an insect called a water boatman (Corixa punctada) has exploded. The boatmen populations are so large that they are expanding beyond the confines of the Salton Sea, sometimes landing in backyard swimming pools throughout the Coachella Valley. Birds that are not fish-eating specialists can and do make a meal of the boatmen, and over time brine shrimp populations may become established when the waters become too saline for the boatmen. Nevertheless, pelicans, cormorants, terns, and other fish-eating specialists are among the first losers in this ecosystem transition.
Unlike before water diversions, there are no remaining lakes on the eastern side of the Sierra Nevada that can replace what was Lake Cahuilla, and due to the water diversions from the Colorado River that take nearly every drop before it reaches the Gulf of California, the estuary the estuary at the once great river's mouth no longer supports the biodiversity it once did. The Salton Sea was a last refugium, until it wasn't. Other losers are the people who live anywhere near the Salton Sea. As the Sea shrinks, exposing an ever-widening shoreline, winds blow alkali dust into communities of the folks, many of whom work the agricultural fields that put food on our tables. Respiratory diseases are already showing up. The cascade of impacts stemming from altering this ecosystem continues.
There are places that, at a much smaller scale, provide some resemblance of what Lake Cahuilla once was. One is the Dos Palmas Preserve, but that will be another story.
Go outside, tip your hat to a lizard (and a cactus), and be safe.