“Extinction is the rule. Survival is the exception.” — Carl Sagan

By DR. CAMERON BARROWS

Looking back across the multitude of species of plants and animals that have existed on Earth, far more have gone extinct than exist today. Major extinction events opened the evolutionary door for the existence of new species. If there had not been an asteroid impacting the Earth some 65-66 million years ago, we would most likely not be here to ponder the wonders of nature. After living on Earth for around 165 million years, most dinosaurs, along with most of the life on our planet went extinct in a geologic instant. The few dinosaurs that survived evolved into the birds we know today. The few mammals that survived the asteroid impact, probably fossorial scavengers, gave rise to the age of mammals, including us. The asteroid impact created a clean slate of open, available niches. The survivors found ways to fill those niches, to rebuild food webs, rebuild complex communities of interacting, interdependent plants and animals. The global extinction event 65-66 million years ago was the fifth such event to impact life on our planet since the first primitive organisms on Earth evolved. Each cause was different, but in every case life in new forms prevailed, although each time the process of rebuilding those complex communities of interacting, interdependent plants and animals took millions of years.

Despite the repeated patterns of extinction that have dominated the Earth’s history, we view extinction as an event to avoid. Laws have been enacted in almost every country worldwide aimed at trying to prevent the extinction of any species, plant or animal, fish, fowl, insect or slug. Perhaps it is because at some deep level extinctions remind us that our own existence is fragile. Or perhaps it is because, again at some deep level, we know that our existence is tied to a healthy, diverse biosphere (the sum of life on our planet). If species are allowed to go extinct, at some point the falling dominos will hit us. Or perhaps it is because when we experience wild, untamed nature, those dark moods associated with the frustration of dealing with the society we created disappear and our spirits are lifted. Here in the U.S. the federal Endangered Species Act, often coupled with individual State Endangered Species Acts, is among the strongest and most far-reaching anti-extinction legislation to be enacted world-wide. Nevertheless, we still have much to learn when it comes to balancing human economic development with protecting species from going extinct.

It seems straightforward that to prevent a species’ extinction, its home (its habitat) needs to be protected. This approach has been somewhat derisively termed “silo conservation,” protecting a species’ habitat as if it was an isolated site, and then allowing economic development to occur up to its boundary. It ignores the interconnectedness of habitats and the importance of that interconnectedness to the health of those habitats. That may work for some species and some habitats, but not for many.

An example is the Spotted Owl, a species protected and listed as threatened under the U.S. Endangered Species Act (ESA). Research I conducted (with my wife Katie) during the 1970s and 1980s showed that these owls need old-growth conifer forests because these majestic forests are where their preferred food (woodrats and flying squirrels) and nest sites (old snags, or in some cases abandoned goshawk nests) occur in the greatest abundance. Perhaps most importantly these deeply shaded forests provide a cool microclimate (Spotted Owls cannot tolerate high temperatures). To protect this threatened owl species, federal land management agencies identified the few remaining old growth forest stands and set them aside (as “conservation silos”) for the owls. All other lands were then managed for timber production. The problem is that these managed forests are not independent from the habitats around them. What has happened is that a related owl, the barred owl which is native to the eastern U.S. expanded its range to the west, moving across previously unforested grasslands using parklands associated with numerous cities. Barred owls are more aggressive and more adaptable to managed forest conditions, and quickly occupied managed western forests. Except they haven’t stopped there. They now are moving into the old growth forest “silos” and are pushing out the spotted owls. The spotted owls have nowhere to go. The proposed solution is to try to control the barred owl numbers, shooting thousands of them every year, probably forever. Even with such an extremely distasteful solution, there is no guarantee of success.

In 1980 the Coachella Valley fringe-toed lizard was listed as threatened under the ESA. The challenge was then how to protect a species whose habitat (wind-blown sand fields) was in near constant motion. Through floods delivering the sand, to the wind blowing the sand their habitat is very dynamic. Early on it was clear that a strictly ‘conservation silo” approach would not work; it would be like trying to protect a river by building dams and creating isolated lakes. Still, much of the habitat fragmentation that catalyzed the threatened species designation was irreversible. The Interstate10 freeway plus numerous roads and existing homes and golf courses already blocked sand movement. The conservation solution was the best of what was available. Almost 45 years after being listed as threatened under the ESA, the larger protected areas with the most intact sand ecosystems still have healthy fringe-toed lizard populations. Fringe-toed lizards on the smaller sites with blocked sand flows are declining, and some are locally extinct.

Even on sites where the fringe-toed lizards are doing well, another lizard species is not. The flat-tailed horned lizard has been proposed for protection under the ESA many times. It has the smallest distribution of any of the 16 known species of horned lizards, and most of that historical range has been usurped for agriculture and golf courses. Much of the rest is open to off road vehicle activity. Still, federal agencies have balked at extending more protection to this species, saying they can do what is necessary without an ESA designation. In 1980 within the Coachella Valley these lizards could be found from Indian Avenue in the west to the Dos Palmas Preserve in the southeast. Unlike the fringe-toed lizard that requires loose aeolian sand, flat-tails like more stabilized fine-grained sand and silt. That should be easier to protect, but the problem isn’t the habitat, it’s the impact of predators. In a pre-modern development landscape, the sand dunes and stabilized sand flats had just a few lizard predators: sidewinders, coachwhips, coyotes and, surprisingly, round-tailed ground squirrels (squirrels are very fond of animal protein). There were no nesting trees for ravens, roadrunners, kestrels, or loggerhead shrikes, so they were rare or absent. With planted palm trees on sprawling golf resorts, and tamarisk trees bordering railways and roads, nesting sites are no longer a limitation. Fences and especially power lines that border the habitats provide perches for these avian lizard predators. Flat-tails have not been seen in the western Coachella Valley since the late 1990s. Nor have they been seen in the Dos Palmas area since about 2015 (possibly due to climate warming). Their last stronghold in the Coachella Valley has been the Coachella Valley National Wildlife Refuge south of Thousand Palms Canyon. Surveys in the spring of 2024 found a few likely flat-tail tracks but for the first time since surveys were initiated in the 1990s, no lizards were sighted. Their habitat was covered in raven tracks, the birds clearly looking for prey.

These examples from the forests of Northern California to the deserts of Southern California illustrate that treating conservation lands as isolated “silos” is not enough. Conservation objectives need to be integrated across landscapes to expect long-term successes. Otherwise, extinction is the likely outcome.

Nullius in verba – Go outside, tip your hat to a chuckwalla (and a cactus), and think like a mountain