Invasive Anole Evolution

One of the major challenges of studying evolution is that animals tend to evolve over time periods that extend far beyond the lifetimes of the scientists who study them. Evolutionary biologists generally make do with reconstructing evolutionary histories via clues left over in the present, and with decades of technological innovation and creative science, this approach has led to a robust patchwork of theory. That said, it is always nice when a capable scientist is blessed with a rare opportunity to study evolution in nature in real time. One of the most memorable papers I've come across in recent years happens to be written about exactly this kind of blessing. Stroud et al.'s "Observing character displacement from process to pattern in a novel vertebrate community," from November 2024, is the fascinating result of the kind of crafty and opportunistic science that I find exhilarating. 

The paper rests on a significant body of theoretical work on adaptive radiation, which is a subject that is a little broad to be covered thoroughly in a casual blogpost (and probably beyond my capability in any format). For those unfamiliar with the concept and looking for some resources to check out, I recommend starting with the work of Dolph Schluter, i.e. the adaptive radiation GOAT, and/or Peter and Rosemary Grant's prolific research on the Darwin's finch study system. Darwin's finches are the textbook example of an adaptive radiation, but other famous examples exist, for instance the cichlids of the central African crater lakes, the silverswords of Hawaii, and--most relevant to today's paper--the Anolis lizards of the Caribbean.

Stroud et al.'s 2024 paper builds upon theoretical work done particularly by Jonathan B Losos on the Anolis lizard system, and I would therefore be remiss if I didn't at least mention Losos' classic 1998 paper "Contingency and Determinism in Replicated Adaptive Radiations of Island Lizards." In this paper Losos shows that on each major Caribbean island, several species of anoles exist and fall into consistent "ecomorphs," or categories of behavior, habitat use, and corresponding morphological characteristics. On each island, anoles consistently occupy six distinct microhabitats that Losos defined as "crown-giant, grass-bush, trunk, trunk-ground, and twig," based on which parts of trees these arboreal lizards primarily spend their time. Observing a system with such remarkably consistent ecomorphs across multiple islands and dozens of species, Losos judged only two explanations to be feasible: either anoles evolved once into these distinct niches and then spread from island to island (which would be the parsimonious option), or anoles colonizing each island were repeatedly and separately driven into the same ecomorph categories. If the former hypothesis were true, anoles in each ecomorph would be more related to anoles in the same ecomorph class across islands, whereas if the latter hypothesis were true, this pattern would not be detected. After some genetic tests, Losos showed that anole relatedness was no stronger among ecomorph classes across islands than across species within islands, and the likelihood of these patterns being driven by repeated and regular adaptive radiation skyrocketed. 

Using genetics and carefully collected behavioral and morphological data, Losos provided strong evidence of some degree of determinism in evolution, as well as the power of adaptive radiations in generating diverse natural forms. While a massive contribution to science, Losos' conclusions still relied on a theoretical reconstruction of past events, leaving adaptive radiation-heads such as myself yearning for real-time, observational confirmation. This is where Stroud et al. 2024 (finally) comes into the picture. Stroud and his collaborators were busy studying invasive anoles in South Florida when one of his study sites that initially only had brown anoles (Anolis sagrei) was invaded and eventually dominated by crested anoles (Anolis cristatellus). Stroud jumped on the opportunity to observe the early phases of these novel competitive interactions, as these two species don't overlap in their native ranges. He and his collaborators observed that while in allopatry, both crested and brown anoles were happy to spend their time occupying similar regions of the lower sections of tree trunks, only spending 2% of their time on the ground. In Lososian terms, both species instantiated the same ecomorph class. In sympatry however, Stroud et al. were able to show that cristatellus individuals moved further up the trunk and sagrei further down, to the point where sagrei individuals were observed spending an average of 33% of their time on the ground. Novel competition had driven these anoles into separate ecomorphs! Aside from these behavioral observations, Stroud et al. showed that the newly ground-dwelling sagrei had developed significantly longer fore and hindlimbs, a result that conforms perfectly to the morphological characterizations made by Losos of Caribbean ground-dwelling ecomorphs. 

Fully-fledged adaptive radiations such as those found among anoles in the Caribbean may take thousands of years to develop, and what Stroud and his collaborators observed was character displacement, which is only a first step towards radiation. However, it is a crucial step, and one that is rarely observed so clearly in nature. The way that the results conform so exactly to the theoretical work laid out by Losos and others is also a lovely vindication of theory. Aside from these great qualities, as a biologist currently working in Florida, I also particularly love this paper because it draws a beautiful result from the invasive disaster zone that is South Florida and interrupts the steady stream of doomsday-level invasive news coming from that region with a terrifically exciting bit of science. 

Works Cited:

Stroud, J.T., et al. Observing character displacement from process to pattern in a novel vertebrate community. Nat Commun 15, 9862 (2024). https://doi.org/10.1038/s41467-024-54302-1
   
Losos, J. B., et al. Contingency and determinism in replicated adaptive radiations of Island Lizards. Science, vol. 279, no. 5359 (1998). https://doi.org/10.1126/science.279.5359.2115.

Snail Kites Prefer Escargot?

Two weeks ago I observed something quite unusual during a Snail Kite survey. I was tasked with meeting the project's Kissimmee area crew to survey a section of the Kissimmee river with them. As field lead of the state wide Snail Kite monitoring crew, I'm used to making some long drives to get to our daily surveys, but this site was only fifteen minutes from our field house. Basking in the luxury of a short drive, I rolled out of bed at the civilized hour of seven a.m., and met the crew for what I expected would be a short and kite-less survey. Kissimmee River can be an incredible spot to see kites when the river floods and creates a healthy floodplain. A rushing river is not much use to a Snail Kite, but when the grassy plains surrounding a river channel flood, shallow, vegetation-rich conditions can arise and provide perfect foraging habitat. A good rule of thumb for kite activity is too little water=no snails, while too much water=too deep for kites to successfully hunt snails. Anyway, in the fall the river floods, and in October we counted nearly 150 kites in one survey, which was among the highest counts we achieved in the state all month. Over the rest of the year however, water levels tend to drop, and our monthly surveys reflect the degraded conditions. Over winter, with water levels clearly already dwindling, we could muster a fifty kite survey, but across our last three spring and summer surveys, the river banks looked bone dry and we counted one measly, probably confused and disoriented kite. I had no reason to expect my most recent survey to be any different. 

As we launched our boat I planned to be on the water for no more than three hours, but rounding a bend in the river six miles in, I was rudely shocked. We came upon a section of the river where land managers had clearly done a prescribed burn recently, and my colleague Melisa pointed to a kite perched on some vegetation. "Oh nice," I thought, "at least we'll have one kite this survey." Shutting the boat off and pulling up to a steep river bank to inspect the bird more closely, I called out to Sandy, who on this day was recording data for us, and I asked her to note one un-banded male kite on the datasheet. Melisa quickly and politely contradicted me by pointing out that the bird was actually a banded female kite. Slightly embarrassed, I double check, and am filled with righteous indignation when I realize I had not made any mistake! My kite had orange legs unmarked by the color bands we apply, a fully blue head, striking red eyes, a bright orange cere, and could not have been anything but adult male. Before I had a chance to argue, it became clear that we were simply looking at different birds. After a cursory scan of the burnt area of the river bank, the three of us realized there were not one, not two, but dozens of kites present. 

What the hell was going on? Prescribed burns provide a whole bunch of ecological benefits, but I had never heard of them helping Snail Kites. Everything I knew about the species told me they need nice, shallow, freshwater wetlands where they can hunt live snails, but here I was watching them in a half mile section of bone dry, scorched, floodplain, scavenging dead apple snails. Melisa and I disembarked on the river bank while Sandy was left with the unenviable task of hanging back to make sure our airboat didn't float away down the river. Sensing I was witnessing an unusual ecological event, I took pictures of the chalky, scorched snail shells and their boiled meat, along with the coal-black mud and stripped bases of plant stems that the dead snails were resting on top of, and then I got to work counting kites. When so many kites are swirling around, actively hunting (or scavenging in this case), and territorially chasing each other, my job becomes quite tricky. In moments like these it's crucial to have a cool, calm, and collected voice assisting you, and luckily, as I was stressing myself out trying to keep track of which kites I had counted and which I hadn't got to yet, Melisa was my guiding light. With her help, after about an hour and a half, we were pretty confident in our count of fifty three total birds. 

After finally getting an accurate count, we continued with the remaining thirty miles of our survey track down the river channel, which turned out about as I expected it to that morning. The unburned river banks were lush and thick, and while beautiful to look at, would have completely concealed the scant puddles of water where apple snails may or may not have been eking out an existence, preventing kite foraging. We saw only two other kites for the rest of our survey. On my drive home that afternoon, I texted my boss to see if she had ever heard of kites scavenging dead snails on this scale, and she hadn't. Performing a cursory literature search online, I did not find any published accounts of such behavior either. 

Hopefully we'll be able to publish some account of this experience in a scientific journal, and maybe more experienced scientists than I can shed some light on this. For what it's worth, with my two years of involvement in this project, my best guess would be that the terrible drought plaguing the state is probably the root cause of this novel foraging strategy. Already, over the last few months, we have been making note of increased instances of unusual foraging. While apple snails make up ~99% of Snail Kite's typical diet, lately, we've observed unusually high instances of them deviating and eating musk turtles, dead fish, a few dead birds, some kind of large crab (pictured below), and now this scorched snail feeding frenzy. We have also observed some fierce intraspecific fighting, which I'm told is also generally uncommon for these kites, and may be another sign of resource scarcity and increased competition. Concealed within the excitement of observing a new and unexpected behavior, it's hard to avoid feeling that the root cause is related to degrading kite conditions throughout the state. 

Curious Side Effects of Invasive Species

I am currently working as the field crew lead of the University of Florida’s Snail Kite monitoring project, which comes with several perks. The most obvious is that I have the daily privilege of getting to zip around on airboats through beautiful, remote, wetland habitat across the southern half of Florida. I spend hours a day observing and occasionally handling and banding Snail Kites, which are unique and beautiful birds that I can’t imagine ever tiring of watching. On our crew we sometimes joke about how they lack the intimidating presence of a typical bird of prey; they’re simply too goofy. While they spend their days deftly plucking apple snails from fresh water marshes, unthreatening to anything other than their mollusk victims (outside of the rare times they find an unlucky musk turtle to gruesomely excavate and consume), in this cruel and unforgiving world of ours they still get relentlessly mobbed by grackles and red-winged blackbirds, as if they were any other egg-stealing, fledgling-hunting, run-of-the-mill bird of prey. Their strained, nasal, almost mechanical calls are another incongruity separating them from their raptor relatives, but as with their other quirks, they are simply delightful. It’s definitely worth a Google if you’ve never heard the various calls they make, by the way.    

Young male Snail Kite with a musk turtle. ~99% of their diet is made up of apple snails but they will rarely catch other prey.

Getting back to the point, one of the other major benefits of my job is that I get to be part of one of the longest running wildlife monitoring projects in the country, and I can claim some association with the incredible wealth of research that biologists in the lab have been putting out about Snail Kites for decades. A few years ago, the UF Snail Kite lab published a paper that was exciting enough to generate a certain amount of mainstream attention. Cattau et al.’s 2018 paper, “Rapid morphological change of a top predator with the invasion of novel prey,” has been covered by all sorts of outlets including the New York Times. The paper is an elegant and reassuring example of what the daily toil of my field crew and the many field crews before us can contribute to. Cattau et al. analyzed the previous 11 years of meticulously collected nestling morphological data and coupled it with quantitative genetic analyses to show conclusively that since the invasion of the larger Chinese apple snail species into Florida in the late 2000s, Snail Kites had grown significantly larger beaks, talons, and tarsi. A fascinating result, especially given that in 2007, just 11 years before Cattau et al.’s paper, Snail Kite researchers Darby et al. published “Food-handling Difficulties for Snail Kites Capturing Non-native Snails,” in which they recount numerous observations of kites dropping the significantly larger Asian snails and otherwise failing to extract their meat. In a matter of a mere 11 years, researchers went from worrying about invasive snails acting as ecological traps that could hurt the kite population, to showing clearly that kites have adapted in a very short time span and are now actually benefiting from their new invasive prey.

A crucial and underrepresented detail I want to highlight from the paper is that the researchers make it very clear that these morphological changes come not quite from strict evolution but from phenotypic plasticity. The quantitative genetic analyses they used show that the genetic components of these traits did not significantly change over their study period. This suggests that “cryptic genetic variation,” e.g. preexisting variation in the population that is only made visible phenotypically by some novel environmental condition, is primarily behind the rapid shift. Researchers point to the increased overall growth rate in kite nestlings in areas with higher invasive snail availability as an indication that this richer food source may be triggering a shift to longer beaks and talons somewhat incidentally. They also highlight that these traits show a high degree of “additive genetic variance,” which is the genetic heritability component that is uncluttered by epistatic and dominance effects and otherwise known as “narrow-sense heritability.” This is good news for the kites since it means that real evolution in the form of genetic change may be easier/faster to generate in these traits, compared to a situation where more complicated dominance and epistatic hierarchies among alleles were involved and slowing down the adaptive process.  

Even though phenotypic plasticity is not technically evolution, this rapid morphological change is an incredible example of how the complex web of interactions between genes, phenotypes, and the environment is always changing and bringing about unique forms of life. Human beings are challenging wildlife in ways that go beyond habitat degradation and destruction and include the reshuffling of wildlife interactions via the promulgation of invasive species, and native wildlife must be resilient. In many cases these changes only bring devastation, but it is nice from time to time to read about a positive case, especially when it involves a species as unique and wonderful as the Snail Kite.

Citations:

Cattau, C.E., Fletcher Jr, R.J., Kimball, R.T. et al. Rapid morphological change of a top predator with the invasion of a novel prey. Nat Ecol Evol 2, 108–115 (2018).

Darby, Philip C., David J. Mellow, and Miranda L. Watford. Food-handling difficulties for Snail Kites capturing non-native apple snails. Florida Field Naturalist 35.3 (2007): 2.

 

 

The Limits of Delimitation

Those of us who aren’t so well-versed in speciation research--or perhaps even biologists from a few decades ago who were in their day but are just now waking up from some kind of cryogenic chamber--may be puzzled by the question of why relatively easy access to full genome data has not cleanly solved the problem of how to define species. We live in a modern world where genomes of numerous species have been fully mapped out, but determining what constitutes enough genomic divergence to define a species unit remains a surprisingly nuanced issue. Even a complete understanding of a species’ genome may not always be a skeleton’s key. A recent review article by Singhal et al., titled “A Genomic Perspective on Species Delimitation,” provides a succinct summary of many of those lingering difficulties.

I remember a few years ago being amused by a (now paywalled) episode of the Big Biology podcast with entomologist Michael Sharkey, about a paper he produced that used genetic barcoding techniques to identify over 400 new species of South American wasps in one fell swoop. Despite the waves of backlash he received from concerned taxonomists claiming a simple “cut and paste” barcoding method provided nowhere near enough information to accurately identify “real” species, Sharkey maintained in a fairly convincing way that in the face of our ever-growing ecological crisis where so many unidentified species are in danger of extinction, his methodology is the only feasible way to immortalize a good share before it’s too late. Hymenoptera, the most diverse order on earth, contains over 150,000 identified species, with an estimated 1 million more remaining unidentified. Sharkey argued that without high-volume identification methods, an inestimable number of these species will go extinct before being recognized by science. He goes on to mention that his article contained supplementary material pointing to the museum specimens he collected, as well as detailed methodology that anyone can follow to develop his work. It is an interesting philosophy that highlights the diverse assortment of practical challenges biologists face these days, but it clashes somewhat with the gist of this review article.

Singhal et al. begin with a nice summary of genomic delimitation techniques, followed by several brief case studies, one of which focused on redpolls. They highlight research that led to the collapse of three existing redpoll species into one (and ruthlessly took a hard-earned Hoary Redpoll from my life list, damn them!). In this case, RADseq and Multispecies Coalescent data revealed no significant difference between the three putative species, yet populations showed clear differentiation in certain genomic regions that were associated with the subtle morphological differences that previously formed the basis of their species status. “Whole-genome resequencing data” revealed the culprit: a large inversion in an area of the genome coding for plumage and beak morphology. Inversions tend to be relatively immune to recombination, so it’s natural that even in a freely breeding population, an inverted chunk of genes could persist as a separately diverging region. Without a careful understanding of these and related structural factors, such divergence can be interpreted as meeting an arbitrary threshold of difference that could justify species demarcation, but with no effect on reproductive isolation, this would be a mistake.

I took this picture of one of the hundreds of Common Redpolls that were eating seeds in this winter field in Vermont a few years ago. Birders had reported one or two Hoary Redpolls in this large flock, so I spent a few hours sifting through trying to convince myself that one was paler with a smaller bill. I finally did and even though my lifer was ripped away from me a few months later when the species were lumped, it was not a bad way to spend a morning! 

Genomic data is significantly more accurate than single-locus barcoding techniques, and even more accurate than purely morphological approaches. It is becoming cheaper and more effective to use, but that doesn’t mean it offers a perfect solution. As the redpoll example illustrates, and as Singhal et al. go on to hammer home, it is still only a proxy for understanding what is really happening at the ecological level. The researchers recommend thinking of genomic data not as a neutral and objective sequence of nucleotides, but as one (albeit important) factor in a broader context of ecological and phenotypic relationships. Sequence divergence is not always enough to characterize real world reproductive barriers. As a quick aside, they also briefly highlight the utility of relating bacterial symbiont divergence to host species divergence, a fascinating topic which reminded me of this very cool paper from Marcella Baiz et al. on wood warblers (Baiz 2022).

Looking back at De Quieroz’s seminal 2007 “Species Concepts and Species Delimitation” paper, it bears asking, how much progress have we made on this front? At the time, De Quieroz tried to reassure us that a lot of the acrimony in the field stemmed from confusing “species delimitation” with “species conceptualization.” Maybe it’s wise to leave these controversial questions to more experienced researchers than myself, but perhaps we can agree that by defining species simply as a “separately evolving metapopulation lineage,” De Quieroz mostly solved the species conceptualization side of the problem (or at least neatly cleaned it up), giving us the freedom to toil entirely over the delimitation side. As genomic techniques have exponentially developed since 2007, I think it’s fair to say researchers have made huge leaps on this more technical rather than philosophical side, though as Singhal et al. illuminates, there are still many subtleties and pitfalls to watch out for.

 

Works Cited:

Singhal, Sonal, et al. “A Genomic Perspective on Species Delimitation.” Annual Review of Ecology Evolution and Systematics, 3 Sept. 2025, https://doi.org/10.1146/annurev-ecolsys-102723-055311.

“Hymenoptera - an Overview | ScienceDirect Topics.” Www.sciencedirect.com, www.sciencedirect.com/topics/agricultural-and-biological-sciences/hymenoptera.

Baiz, Marcella D, et al. “Gut Microbiome Composition Better Reflects Host Phylogeny than Diet Diversity in Breeding Wood‐Warblers.” Molecular Ecology, vol. 32, no. 2, 20 Nov. 2022, pp. 518–536, https://doi.org/10.1111/mec.16762.

De Queiroz, Kevin. “Species Concepts and Species Delimitation.” Systematic Biology, vol. 56, no. 6, 1 Dec. 2007, pp. 879–886, https://doi.org/10.1080/10635150701701083. Accessed 13 Oct. 2019.

  

Birding Needs Gatekeeping

Every once in a while a phenomenon in birding transcends its niche and achieves its highest possible level of notoriety: your non-birder relatives start texting you about it. The most recent topic to reach this status is the Reiser brother’s big year documentary Listers: A Glimpse into Extreme Birdwatching. It’s a well-made, creatively-edited, and largely well-researched documentary, and as of writing this it sits at nearly two million views on youtube. The film’s reception has been overwhelmingly positive from birders and nonbirders alike, but it makes some serious mistakes that threaten the integrity of birding culture. 

Even before he speaks, Quinten Reiser’s first appearance in the film tells us this is NOT your grandma’s birding documentary. To remain committed to the mullet and mustache look in 2025 is in a way more impressive than to have jumped ship a few years ago when the zeitgeist began to sour on it. Rocking the style these days announces, “I know I look like a TikTok caricature but I don’t care,” which is significantly braver than moving on to the more up-to-date matcha and tote bag look, and almost as brave as ignoring such trends in the first place. Add to Quinten’s picture a timbre and cadence of speech that is so laidback it borders on vocal fry, and what we end up with is unequivocal: birding is finally getting the trendy, gen-z, ironically-detached treatment it’s been waiting for. Our little hobby will be pried from the cold dead grip it’s been languishing in and launched headlong into youthful freedom. But is that really such a good thing? 

The cracks begin to show early in the film when they introduce Ebird, a popular website for reporting and viewing bird sightings from around the world. Their first experience with an Ebird reviewer, a volunteer who monitors the Ebird database for mistakes, comes after they misreport a Red-shouldered Hawk as a Golden Eagle. The reviewer who politely corrects them is referred to dismissively as an “Ebird cop.” Later on when their erroneous Gray Flycatcher sighting is corrected by a different reviewer, Quinten announces sarcastically, “thank you guys for being so on our fucking dick about bird ID’s, I super appreciate it,” as if it’s such a pain to be held to even the most basic standard of accuracy. At another point, he refers to the well-established convention of including as much detail in the reporting of rare bird sightings as possible with smug disbelief: “You’ll see people describing a bird with sometimes full paragraphs, they describe it like it’s a huge scientific finding.” 

Their biggest sin comes around the 35 minute mark, when they introduce “swallow-gate,” North American birding’s most infamous cheating scandal. For the uninitiated, the story centers on a talented young birder from North Carolina who started reporting dubious sightings, many of which went uncorroborated. After reporting a state first Violet-Green Swallow and attaching a picture as proof, other birders became suspicious, checked the photo’s metadata, and realized it had been taken months earlier in the west coast, where the bird is common. Just about as cut and dry as it gets when it comes to cheating. It’s a story that has been told to death, but the Reiser brother’s novelty was that they managed to interview the perpetrator. They introduce him anonymously and boldly with the claim, “he’s actually kind of the man, and I’m convinced he really saw the bird.” Incredible investigative journalism is on display as the cheater proceeds to trot out some utter nonsense in defense of his behavior without any pushback from Owen. He laments that the high-pressure world of birding was too much for him, and he was at once so excited about finding this massive rarity and anxiety-ridden about having to prove it that he caved to the pressure and used a picture of a different bird. On its face an unlikely story, besides the obvious point that it’s still unethical, but apparently it was enough to convince the Reiser’s (Woodward and Bernstein, I like to call them). To add insult to injury, in an interview in the following scene, Owen has the nerve to ask a record committee member who presided over the ordeal, “is it a funny story to you yet? It’s all kind of ridiculous, right?” To which the committee member, with much more composure than I would’ve mustered in his place, gives a measured and obvious response about how without the honor system, the whole hobby falls apart. 

The flippancy that defines their approach to these issues is based on a naive and superficial “us-vs-them” mentality. It’s clear the Reiser’s haven’t given it much thought, but the position they’ve landed on is that they are young and hip and know that birding is nothing more than a bit of a joke. In their minds, they are righteously taking on birding’s overly serious gatekeepers. I wouldn’t be shocked if they were so quick to lump the swallow-gate cheater into their in-group simply because he is also young and tuned into their Zoom interview with a “badass” profile picture holding a big venomous snake. The record committee member on the other hand, with his gray hair, glasses, and monotone voice, interviewed with a professorial backdrop of a bookshelf-lined study, and didn’t stand a chance. This is the fundamental and shallow dichotomy that makes Listers so frustrating to watch. 

Of course there are many aspects of birding that are pretty silly, and there is nothing inherently wrong with making fun of them. The problem is aside from the elements of silliness, birding is also fundamentally a giant citizen science project, deserving of all the rigors and guardrails that come naturally to the rest of science. Ebird is not, as the film is so eager to make it out to be, just a place for neurotic, hyper-obsessed listers to fan their egos, it is also a massively valuable resource fueling research on bird movements, population trends, and conservation. The many reviewers and record committee members who volunteer tirelessly all over the world to maintain the integrity of this resource do so not out of some self-satisfying impulse to nag, but in order to uphold scientific values. To treat their hard work with such adolescent disdain is not only quite rude, it also risks tainting the whole enterprise. 

Besides these concrete issues, a subtler one remains. Birding has always been a rare bastion of sincerity in this increasingly detached world. There is very little clout to chase in birding, since most of the time, no one really cares what we’re up to. The only reason to get involved is to pursue a real connection with nature. The Reiser’s stale, ironic approach in this film may have attracted a lot of trendy interest, but in my view it is antithetical to the heart and soul of the hobby. Birding has always been about the “doing” rather than the “being seen,” and Listers is an attempt to invert that and drag our hobby into the vacuum of middle-of-the-road, easily-accessible mediocrity that so much of modern culture has already succumbed to. “Gatekeeping” is almost always interpreted negatively, but birding absolutely needs *some* gatekeeping. At the very least we need the kind that will maintain birding’s scientific integrity, and is it really too much, on top of that, to expect that to call oneself a “birder,” one should at least be curious about the difference between a Golden Eagle and a Red-shouldered Hawk? Birding is for everyone, and focusing on welcoming as many people as possible into the fold is admirable, but not if it undermines the integrity and sincerity that make the hobby so special.   

 

Bulldozing Desert for Solar Power

 *Disclaimer* I wrote this a little over a year ago before Trump won the election. There's a good argument to be made that in light of that this is not the most pressing environmental issue to be discussing, but especially with the AI data centers etc that are increasing the strain on wildlands, particularly desert land, the point remains relevant. 

The solar energy boom is well on its way. A recent article in The Economist claims “installed solar capacity doubles roughly every three years,” and solar will likely be “the biggest source of electrical power on the planet by the mid 2030s” (The Economist, 2024). In most ways, this is great news: we are in a global energy crisis, fossil fuels are destroying our planet, and over its full life cycle, solar power emits a tiny fraction of greenhouse gas relative to fossil fuels (Mehedi et al., 2022). Under these circumstances, many feel that we ought to be pushing solar as far and as fast as possible. I for one am not so sure.

As a wildlife biologist and life-long nature-lover, I approach this topic with a particular bias. This past winter, when the Bureau of Land Management announced their ambitious “Western Solar Plan” to convert roughly 700,000 acres of public land across the west for solar development, while earmarking 22 million more acres for potential leasing (Streater, 2024), I was trepidatious. A few months later as the project developed and my social media was flooded with footage of trucks packed with bulldozed Joshua trees, I was angry. Taking a step back, I wondered if I had any right to feel this way. We all know there is no perfect, easy solution to the climate crisis, and that trade-offs are inevitable. The question is are these particular trade-offs justifiable?

Firstly, if you think deserts are inhospitable wastelands that might as well be cleared for any purpose, let alone one as urgent as renewable energy development, let me disabuse you of that notion. The Mojave Desert, for instance, supports a complex ecosystem made in part by over 3300 plant species, roughly 700 of which are found nowhere else on earth (Dunlap et al., 2024). To the untrained eye, the generally small shrubs, cactuses, and yuccas that populate these arid landscapes may seem insignificant, but many live for hundreds of years and support a wide array of unique animals. Bulldozing such ancient and special land is the aesthetic equivalent of burning down the Metropolitan Museum of Art, along with its similarly aged artifacts. These are ecosystems that, once destroyed, won’t return to any kind of fully-fledged state for thousands of years, in the unlikely event they return at all.

Beyond the visceral tragedy of such loss, deserts also turn out to be crucial carbon sinks. Desert carbon sequestration has often been overlooked, as these ecosystems lack the well-characterized organic carbon-storing mechanisms that are prevalent in forests and wetlands. Ignoring arid lands in this way is a mistake, as new research has shown that calcites, a byproduct of the respiratory processes of desert plant root-systems, are an effective form of carbon storage. One report estimates California’s deserts alone can sequester roughly 262 million tons of carbon (Allen et al., 2024). Bulldozing old-growth desert will not only destroy the potential for future sequestration but also release stored carbon into the atmosphere as soils are disturbed and calcites dissolve upon exposure to air.  

If it turns out the BLM’s western development plan is the best or only way to transition to a renewable energy grid, these and the myriad other good reasons for preserving desert may be insufficient. In the face of challenges as daunting as global climate change, we must occasionally make hard choices after all. Luckily for the desert, there are many better ways to make this transition. If you spend any time online following critics of the BLM’s plan, you are sure to encounter the repetition of a simple idea: until every parking lot and rooftop in American is topped with solar canopies, we shouldn’t be converting public lands. At first glance, this seems like a no-brainer solution, and that’s how it mostly turns out to be. Parking lots tend to be in urban centers, and therefore closer to energy-consumers than remote desert plots, foregoing the need for costly and destructive transportation methods such as underground cable networks. Solar canopies create shade for parking lot customers, cutting down on heat island effects and attracting people trying to beat the heat (Ralston, 2023). Parking lots are also extremely low value for wildlife use (Davis et al., 2010).

So why isn’t every parking lot in America converting and storing energy from the sun? As is the case with many unactualized but frustratingly obvious solutions, the stumbling block boils down to cost incentives. It turns out that developing and managing many small-scale solar farms versus one massive remote plot is logistically and financially challenging. Building solar panels on already developed land requires building structures to support them, which can amount to 40% higher upfront costs than ground-mounted solar (Blok, 2023). Despite these challenges there are options that make such investment more enticing: government incentives such as the EPA’s Green House Gas Reduction Fund can significantly cut down on building costs. Solar canopies can also be profitable long-term by providing EV charging ports and high-value shaded parking. In 2020, Evansville Regional Airport in Indiana spent $6.5 million to build a solar canopy that covered 368 parking spots, which in one year brought in $310,000 in parking fees (Fella, 2020). 20 years to make up those upfront costs may seem daunting, but economists will tell you that investing in long-term projects generating 4-5% returns can be more than worthwhile (Conniff, 2021). 

It is true there are serious hurdles in the way of developing wildlife friendly solar farms. The last few decades of renewable energy development have felt as if pressure has been building against a dam of high prices, and recently as cost incentives have started making sense, cracks in that dam have allowed solar to flood down lines of least resistance. After all the work in technological development and government policy to bring us to this point, the idea of redirecting that stream towards temporarily costlier alternatives can understandably be unappealing. Overcoming these challenges comes down to our values. As urban sprawl chips away at our dwindling wild lands, does it make sense to mow-down up to 22 million more acres of biodiverse desert when other good options exist? Ask anyone who has watched sage-grouse lekking in Nevada’s Ruby Valley, or camped under the stars in Utah’s Canyon Country, or felt the shade of a thirty-foot tall, two-hundred-year-old saguaro cactus, and I am confident they will tell you this land is absolutely worth preserving.  

 

Citations:

Allen, M., Barrows, C., Barrows, C., Boyd, S., Flanagan, P., Kobaly, R., McCulloch, A., & Taylor, J. (2024). The California Desert’s Role in 30X30: Carbon Sequestration and Biodiversity. In Desert Report. https://assets.nationbuilder.com/mbca/pages/3434/attachments/original/1707332189/C_Sequestration_Desert_Sector_Report_Revised_2.7.24.pdf?1707332189

Blok, A. (2023). Solar parking lots are a Win-Win energy idea. why aren’t they the norm? CNET. https://www.cnet.com/home/energy-and-utilities/solar-parking-lots-are-a-win-win-energy-idea-why-arent-they-the-norm/

Conniff, R. (2021). Why putting solar canopies on parking lots is a smart green move. Yale E360. https://e360.yale.edu/features/putting-solar-panels-atop-parking-lots-a-green-energy-solution

Davis, A. Y., Pijanowski, B. C., Robinson, K., & Engel, B. (2010). The environmental and economic costs of sprawling parking lots in the United States. Land Use Policy, 27(2), 255–261. https://doi.org/10.1016/j.landusepol.2009.03.002

Deshmukh, S. S., & Pearce, J. M. (2021). Electric vehicle charging potential from retail parking lot solar photovoltaic awnings. Renewable Energy, 169, 608–617. https://doi.org/10.1016/j.renene.2021.01.068

Dunlap, A. A., Sovacool, B. K., & Novaković, B. (2024). ‘A Dead Sea of Solar Panels:’ solar enclosure, extractivism and the progressive degradation of the California desert. The Journal of Peasant Studies, 1–35. https://doi.org/10.1080/03066150.2024.2388051

Evans, S. (2017). Solar, wind and nuclear have ‘amazingly low’ carbon footprints, study finds. Carbon Brief. https://www.carbonbrief.org/solar-wind-nuclear-amazingly-low-carbon-footprints/

Fella, L. (2020). EVV Completes Construction on Largest Solar Covered Airport Parking Canopy in the Midwest. Evansville Regional Airport. https://flyevv.com/index.php/about-evansville-regional-airport/news/evv-completes-construction-on-largest-solar-covered-airport-parking-canopy-in-the-midwest

Greenhouse Gas Reduction Fund | US EPA. (2024). US EPA. https://www.epa.gov/greenhouse-gas-reduction-fund

Mehedi, T. H., Gemechu, E., & Kumar, A. (2022). Life cycle greenhouse gas emissions and energy footprints of utility-scale solar energy systems. Applied Energy, 314, 118918. https://doi.org/10.1016/j.apenergy.2022.118918

Ralston, W. (2023). Why not cover ugly parking lots with solar panels? WIRED. https://www.wired.com/story/france-solar-panels-parking-lots/

Segini, N. (2024). The government has a new solar energy plan. What’s in it?. The Wilderness Society. https://www.wilderness.org/articles/blog/government-has-new-solar-energy-plan-whats-it

2023/2024 Solar Programmatic EIS Information Center. (n.d.). Bureau of Land Management. https://blmsolar.anl.gov/solar-peis-2023/

Streater, S. (2024). BLM plan aims to dramatically expand Western solar. E&E News by POLITICO. https://www.eenews.net/articles/blm-plan-aims-to-dramatically-expand-western-solar/

The Economist. (2024). The exponential growth of solar power will change the world. The Economist. https://www.economist.com/leaders/2024/06/20/the-exponential-growth-of-solar-power-will-change-the-world