Guest essay by Jim Steele, Director emeritus Sierra Nevada Field Campus, San Francisco State University.
What Good Conservation Science Reported
Good stewards of the environment are compelled to engage in good science. In 1980, butterfly experts in the United Kingdom predicted that both the Silver-spotted Skipper and the Large Blue butterfly were doomed to extinction. The widespread Silver-spotted Skipper was gradually restricted to just 46 locations. The more rare Large Blue had been declining from over 90 estimated colonies supporting tens of thousands in the 1800s to just two colonies and about 325 individuals by 1972. The question that had continuously eluded conservationists was why?
Disturbed by repeated failures to correctly identify the causes of the decline, Dr. Jeremy Thomas embarked upon extensive research that ultimately unraveled the mystery. It is a model of superb scientific research and demonstrates why good environmental stewards must employ carefully detailed studies. For those of you who enjoy bizarre nature stories, the life of the Large Blue is a fascinating tale of deception and betrayal in which plump, seemingly helpless caterpillars turn the tables on voracious ants. And oddly enough, despite global warming, the Large Blue went extinct in England because its microclimate had cooled.
In earlier attempts to stave off the Large Blue’s extirpation, UK conservationists had protected nine areas in order to minimize any human impact on the remaining populations. However this habitat protection uncharacteristically failed to slow the species’ decline, so conservationists inferred that the most likely culprits must be unscrupulous butterfly collectors who were trying to cash in on the value of its increasing rarity. So conservationists hurriedly erected protective fences, only to watch hopelessly as the last population continued to decline. Ironically, the fence itself, not greedy collectors, was the final nail in the Large Blue’s coffin.1
Europe’s Large Blue belongs to a group of butterflies whose survival has been eternally entwined with the fate of local ants. In a process that sounds lifted from a Disney or Pixar screenplay, Large Blue caterpillars summon ant bodyguards with special calls and scents. The discovery of talking caterpillars is a fascinating story in itself, but the story gets better. Upon arriving, the summoned ants are fed with a sugary reward oozed from special pores in the caterpillar’s bodies. The caterpillars also exude intoxicating chemicals that make their new ant bodyguards more aggressive against other less friendly ant species. (Search YouTube for “ant caterpillar mutualism” for a 2-minute real-life video)
One species of the Blues not only beckons the ants to come to its protection, but then seduces the ants to carry it into the ant colony. Once inside, the caterpillar then mimics the sounds of the queen ant, demanding to be fed in royal ant fashion. This is not quite the royal treatment imagined by humans: the caterpillar’s instinctual impersonation induces the worker ants to approach and regurgitate their stomach contents, upon which the caterpillar gratefully dines.
The Large Blue’s relationship with ants has an added twist more reminiscent of a grade B movie depicting the horrors of adopting a mysterious orphan. After hatching, Large Blue caterpillars feed on their host plant just as all other caterpillars do. And like other species of Blues, they soon drop to the ground to summon and then mesmerize a local ant species. Because the ants’ worm-like larvae resemble the size and shape of the early stage of these caterpillars, the intoxicating charade is sufficiently convincing, and the ants quickly carry the caterpillar into their nest.
Once the caterpillar is safely nestled into the ant’s nursery, the hideous betrayal commences. One by one the ungrateful adoptee devours the ant’s larvae. The Large Blue’s very existence has evolved to become completely dependent on eating “baby ants.” And only this one species of ant will do. Ironically, these butterflies often cause the extirpation of the adopting ant colony, which in turn limits the butterfly’s population.
Earlier conservation solutions had been simply based on the prevailing biases that failed to prevent extinction. Thomas lamented, “every hypothesis [collectors, insecticides, fragmentation, inbreeding, climate, pollution] on which the conservation measures of the previous 50 years had been based was untenable.”
To be kind to those earlier researchers, the critical changes in the Large Blue’s protected habitat were barely perceptible. These changes created a baffling illusion that something was oozing across the boundaries of their protected conservation areas and decimating the species. So blaming collectors, pollution, climate change, or disease made sense simply because those phenomena readily cross artificial boundaries. But further observations never supported these suspicions. To unravel the Large Blue’s extinction mystery, Jeremy Thomas painstakingly identified and measured every possible confounding factor that might affect not only the butterfly directly, but also its host plants and the host ants. In addition to general weather variables, he tallied the various local ant species, measured temperatures above and below ground, differences in turf height, plant species composition, and the amounts of bare ground available.
It was laborious and detailed work, but exactly what good science dictates. Why the real agent of extinction had gone unnoticed finally became clear. Thomas discovered that just a few millimeters of change in the height of the grass, during the spring and autumn, could lead to the butterflies’ local extinction. The species of ants that the Large Blue plundered requires a very short grass habitat, which allowed the sun to warm the soil and their underground colony. When the grass grew from 1 to 2 centimeters, the temperatures just below the surface in the ants’ brood chamber dropped by 3–5°F. When the turf exceeded 3 cm, the microclimate below the grass cooled enough that competing ant species overran the Large Blue’s host ants. Three centimeters is less than your little finger, so such a small change in the height of the grass had been understandably overlooked.
Over the years, as more efficient animal husbandry reduced sheep and cattle grazing, pastures were increasingly abandoned. Biologists assumed that as more pastures returned to their natural state, wildlife biodiversity and abundance would also increase. That assumption is often true, but without human management, not only did the grass grow taller, but shady trees and shrubs soon invaded. The increasing shade was killing not only the Large Blue but was also endangering a diverse array of the United Kingdom’s other warmth-requiring butterflies like the Silver-spotted Skipper.
In addition to reduced grazing, earlier attempts to control UK rabbit populations added to the demise of these warmth-loving butterflies. Rabbits are not native to the British Isles, or to Australia, but had been introduced long ago as a source of meat. As growing populations of escaped rabbits competed for grasslands with the sheep and cattle (also nonnative), people attempted various forms of pest control. In Australia, humans erected the “great rabbit fence” to separate western and eastern Australia. Eventually, they turned to germ warfare, employing a newly discovered myxomatosis virus, which decimated the Australian rabbit population. In France a bacteriologist introduced the disease to rid his estate of rabbits. It then quickly spread, killing 90% of France’s native rabbit population. The virus then spread, either naturally or intentionally, into Great Britain. By the mid 1950s it had devastated the rabbit populations there. With fewer cattle, fewer sheep, and fewer rabbits grazing, the grasslands became increasingly overgrown, and warmth-loving butterflies became increasingly scarce. Not realizing the importance of grazers, the well-intentioned conservationists who had erected the protective fence unwittingly destroyed that which they sought to protect.
Once informed by the detailed work of Jeremy Thomas and his colleagues, by 1980 conservationists had begun efforts to successfully reintroduce the extinct Large Blue. Government subsidies and environmental schemes were enacted to encourage grazing, while conservationists mowed abandoned pastures to the optimum turf height. Individuals from Large Blue populations that still survived in Sweden were shuttled to England’s “terra nova” for a second chance. Under careful management, the reintroduced Large Blue is slowly rebounding.
But why should people need to intervene so directly and so intensively? Why couldn’t the Large Blue and other butterflies just exist “naturally”? Another ironic twist to this story is that humans actively created much of England’s grasslands, starting between four and six thousand years ago when new colonists introduced farming and grazing to England. To feed their sheep and cattle, early Britons increasingly cut down the natural forests that had once covered most of Great Britain. These human-generated grasslands were then maintained by grazing sheep and cattle that ate the sprouts of any trees that dared to recolonize. Similarly, the Victorians set fires to clear much of Scotland’s forest to encourage heather for grouse hunting. Much of Great Britain’s “natural” habitat is actually the product of millennia of human design. To maintain human-made biodiversity requires human stewardship.
Metamorphosing Conservation Success into Climate Alarm
“We search for a climate fingerprint in the overall patterns, rather than critiquing each study individually” 3
– Dr. Camille Parmesan, University of Texas
While serving on the Intergovernmental Panel on Climate Change (IPCC), Dr. Camille Parmesan (whose work was introduced here Fabricating Climate Doom – Part 1: Parmesan’s Butterfly Effect) issued the paper “A Globally Coherent Fingerprint of Climate Change Impacts Across Natural Systems.” In contrast to Jeremy Thomas’s detailed investigations, Parmesan again advocated that biologists should ignore local details. She wrote, “Here we present quantitative estimates of the global biological impacts of climate change. We search for a climate fingerprint in the overall patterns, rather than critiquing each study individually.” However, critiquing individual studies is always the essential first step. Otherwise the overall pattern will be distilled from faulty information. And in order to support her supposed pattern of global warming disruption, she again omitted crucial contradictory details.
Parmesan tactfully offered lip service to altered landscapes, but stated that her “probabilistic model” accurately separated the effects of land use from climate change. To demonstrate her model’s power, she wrote, “Consider the case of the silver-spotted skipper butterfly (Hesperia comma) that has expanded its distribution close to its northern boundary in England over the past 20 years. Possible ecological explanations for this expansion are regional warming and changes in land use. Comparing the magnitudes and directions of these two factors suggests that climate change is more likely than land-use change to be the cause of expansion.” That was a very odd claim.
This was the very same Silver-spotted Skipper that Jeremy Thomas’ detailed studies and subsequent conservation prescriptions had saved from extinction along with the Large Blue. Parmesan was hijacking a conservation success story to spin a tale of climate disruption. Her “proof” that climate change was driving the Silver-spotted Skipper northward came from the work of her old friend C.D. Thomas, known for predicting that rising CO2 levels had committed 60% of the world’s species to extinction.5 Using a mesmerizing statistical model, C.D. Thomas argued that because the Silver-spotted Skipper “needs warmth,” only global warming could account for its recent colonization of a few cooler north-facing slopes of England’s southern hills.
The Skipper is indeed fond of hotter south-facing slopes. However, the butterfly had historically inhabited cooler northern slopes if those slopes had been grazed. Like the Large Blue, the Skipper had disappeared from both cool north-facing slopes and warm south-facing slopes whenever the turf grew too high.6,7 C.D. Thomas’ model was statistically significant only if he ignored recent conservation efforts to promote warmer, short-turf habitat. At the end of his paper, relegated to his methods sections, he quietly stated, “we assumed that grazing patterns were the same in 1982 as in 2000.”4 Parmesan and C.D. were guilty of grave sins of omission.
I emailed Dr. Jeremy Thomas regarding the study by C.D. Thomas and asked, “I assume due to earlier collaboration, you are aware of the habitat his study referenced? If so, is his implied assumption of no changes to turf height valid?” He replied, “No, it’s not valid. There was a massive change in turf height and vegetation structure …between 1980 and the 1990s onwards for 2 reasons. (emphasis added)” First, since the 1986 paper, several of the key surviving sites were grazed more appropriately by conservationists and most of them, and many neighbors, are today in “agri-environmental schemes” to maintain optimum grass heights. Second, from 1990 onwards the rabbits had gradually returned and did the same job on several abandoned former sites.
Although he did not have local climate data for the Silver-spotted Skipper’s recovery, Jeremy Thomas suggested that at least two thirds of the Skippers’ recovery and their subsequent recolonization had resulted from both the increased grazing and the rabbits’ recovery. He was willing to attribute as much as a third of the butterflies’ recovery to climate warming between the 1970s and the present.
If, for argument’s sake, we accept that one-third of the recovery was due solely to CO2 warming and ignore published arguments that the warming in England have been caused by the warm mode of the North Atlantic Oscillation9 (and recent cooling by the cool mode), habitat improvements still account for at least two-thirds of the skippers’ expansion. Furthermore, the Silver-spotted Skipper had yet to expand further northward than its previous 1920s boundary. Yet that was Parmesan’s best example of a “coherent fingerprint of global warming” disruption! It was bad science, but the consensus flocked to it in agreement.
To date more than 3500 papers have referenced her interpretation as evidence of climate disruption. It is a consensus built on misleading results that hijacked legitimate conservation science. In contrast, Jeremy Thomas’ successful preservation of two species on the brink of regional extinction had unequivocally demonstrated that the long-term changes were due to the quality of the caterpillar’s habitat. Although weather change causes short-term fluctuations in butterfly populations, a change in habitat quality affects populations 100 times more powerfully than weather.8 But such successful conservation efforts do not get funded in the same way as global warming horror stories do, and Jeremy Thomas’ “Evidence Based Conservation of Butterflies” has been cited by just 17 papers. Such a gross imbalance is a sad testimony to how the politics of climate change has corrupted the environmental sciences. I fear it is a hijacking that will only breed distrust for our legitimate green concerns in the future.The misguided obsession with CO2 and Parmesan’s faulty probabilistic model has supported equally bad analyses regards the fate of polar bears, penguins, frogs, pika and marine ecosystems, but that takes a whole book to document.
Why have so few scientists celebrated the good science like Jeremy Thomas’ when it empowers us with the critical understanding that allows us to locally build a more resilient environment? Why instead have thousands of scientists uncritically pushed false scenarios of catastrophic climate change? Although some skeptics have suggested a nefarious scientific conspiracy, I believe it demonstrates the ease with which the human mind embraces illusions. Once those scientists accepted CO2 warming as a reasonable explanation for ecological disruptions, despite never thoroughly examining the issue, they embraced whatever supported their choice. Their intellectual identity became intimately entwined with any validation of their chosen hypothesis. Like an avid sports fan, they feel great when their team is “winning” and distraught when their team is “wrong”. They brand anyone who challenges their hypothesis as a denier, stupid, traitor or infidel, and do not hesitate to brutalize anyone on the wrong team.
Robert Bolton wrote, “A belief is not merely an idea the mind possesses; it is an idea that possesses the mind.” Once we make a choice, that choice possesses us. One of the more active areas of psychological research deals with “change blindness” and “choice blindness”. An international team from Harvard, the University of Tokyo, and Lund University in Sweden cleverly demonstrated how humans are hardwired to defend their choices despite contrary evidence. Test subjects were asked to choose who was the most attractive person in a set of two pictures displayed on the other side of the table. The researchers would then retrieve the pictures and ask the subjects to explain why they made their choice. However the lighting in the room was designed to allow the researchers to switch pictures and the test subjects were handed the picture they did not choose. Most subjects never noticed the switch, and believing it was their choice proceeded to explain in great detail how the picture they never chose was the most attractive.10 A National Geographic series called Brain Games modified that experiment on a recent segment called “You Decide” and I urge you to watch it. Once you believe CO2 is destroying the world, any “search for a climate fingerprint” will always be “found” even when it is not there. Whether you are a CO2 advocate or skeptic, we are all victims to “choice blindness.” More critical analyses and respectful debate are the only paths to follow if we are ever to free ourselves from the shackles of our own illusions.
Adapted from Deceptive Extremes in Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism
1. Thomas, J., et al., (2005) Successful Conservation of a Threatened Maculinea Butterfly. Science, vol. 325, p.80-83.
2. Thomas, J., et al. (1986) Ecology and Declining Status of the Silver‑spotted Skipper Butterfly (Hesperia Comma) in Britain. Journal o Applied Ecology. Vol. 23, p. 365-380.
3. Parmesan, C. and Yohe, G. (2003) A globally coherent fingerprint of climate change impacts across natural systems. Nature, vol. 142, p.37-42
4. Thomas, C.D, et al., (2000) Ecological and evolutionary processes at expanding range margins. Nature, vol. 411, p. 577‑581.
5. Thomas, C.D, et al., (2004) Extinction risk from climate change. Nature , vol. 427.
6. Thomas, C. D. and Jones, T. M., (1993) Partial recovery of a Skipper Butterfly (Hesperia comma) from Population Refuges: Lessons for Conservation in a Fragmented Landscape. Journal of Animal Ecology, vol. 62, p. 472-481.
7. Thomas, J., et al. (1986) Ecology and Declining Status of the Silver‑spotted Skipper Butterfly (Hesperia Comma) in Britain. Journal o Applied Ecology. Vol. 23, p. 365-380.
8. Thomas, J et al. (2011) evidence based Conservation of butterflies. J. Insect Cons., vol. 15, p. 241‑258.
9. Hurrell, J. and Deser, C. (2009) North Atlantic climate variability: The role of the North Atlantic Oscillation. Journal of Marine Systems, vo. 78, p. 28–41.
10. Johansson, P., et al. (2008) From Change Blindness to Choice Blindness. Psychologia, vol. 51, p. 142-155.