Paul R. Ehrlich (Philadelphia, United States; 1932) completed a bachelor’s degree in zoology at the University of Pennsylvania then went on to earn a PhD in 1957 from the University of Kansas. Two years later, he joined the faculty at Stanford University, where he would spend the rest of his professional career. In 1966, he was appointed as Professor of Biological Sciences at Stanford and in 1977, as Professor of Population Studies.
President of Stanford’s Center for Conservation Biology since 1984, he has over 1,000 publications to his name, including fifty books. Among the awards earned for his professional achievements, he holds the Blue Planet Award, the Distinguished Scientist Award of the America Institute of Biological Sciences, and the Eminent Ecologist Award of the Ecological Society of America. He is furthermore a Fellow of the American Association for the Advancement of Science and of the UK’s Royal Society and a member of the U.S. National Academy of Sciences.
Speech
Ecology and Conservation Biology 6th edition
In his lengthy career, entomologist, ecologist and conservation biologist Paul Ehrlich has captured hundreds and thousands of butterflies of the sub-species ‘Euphydryas editha bayensis’. He observes them, marks their wing surface — to give each one a different identifying number — and lets them go. And it is precisely in tracking the life course of these butterflies over the past fifty years that Ehrlich has made discoveries now seen as key to the understanding of biodiversity: especially the nature of coevolutionary processes and of metapopulations. Ironically, these black, orange and white-winged butterflies endemic to the San Francisco Bay area are now under threat of extinction.
It was these contributions that earned Paul R. Ehrlich, Professor of Biological Sciences at Stanford University (United States), the BBVA Foundation Frontiers of Knowledge Award in Ecology and Conservation Biology. Ehrlich, in the words of the jury, “has contributed key conceptual advances in the science of ecology and conservation biology, with a long-standing influence in other academic disciplines.”
Ehrlich developed a passion for butterflies at the age of ten, when attending summer camp. After studying zoology at the University of Pennsylvania and completing a PhD at the University of Kansas with renowned entomologist Charles Duncan Michener, he joined the faculty at Stanford University in 1959. A short time later, he set up a study on Euphydryas edithain at the Jasper Ridge biological preserve — Stanford’s experimental station — which continues to churn out data to this day, making it one of the world’s longest-running fieldwork projects.
The initial goal of his research in this period was to determine the factors dictating the size of butterfly populations. But one of his first results came from an entirely tangential observation: Ehrlich realized that some of his butterflies ate plants of the Plantaginaceae family, while others went for a different family, Scrophulariaceae. This set him wondering. One day, returning from a field trip, he mentioned the fact to a colleague, botanist Peter Raven, among the laureates in the 2007 BBVA Foundation Awards for Biodiversity Conservation. “From that point on, it was a matter of brainstorming between two evolutionists, one with much experience with butterflies and the other with plants,” Ehrlich relates. Day by day, in successive coffee-table conversations, supplemented by detailed trawling through the literature, the two researchers gathered data on the dietary preferences of some 6,000 butterfly species, and concluded that they were linked to the kind of toxins the plants generated in order to ward off herbivores.
They had done the first comprehensive study of a phenomenon they named coevolution: selective pressure from butterflies favors plants that are capable of generating chemical defenses, which, in turn, confers an advantage on any butterflies that can deal with such toxins. The arms race between plant and butterfly unfolds in an endless cycle — theoretically at least — with the species coupled together in what some have called an evolutionary tango. The explanatory paper, “Butterflies and Plants: A Study in Coevolution,” published in Evolution in 1964, was a first step toward understanding “the huge importance of plant-herbivore interactions in the generation of terrestrial diversity.” Long considered one of the most influential texts in evolutionary ecology, it has spawned dozens of books and thousands of papers over the intervening decades.
Looking back, Ehrlich is still amazed that they could complete the study with “no additional experimental data whatsoever,” making do with the vast amount of dietary information supplied by butterfly collectors. “It was a fortunate case of two scientists who had an idea, gathered more information and then published a paper that changed a whole area of evolutionary biology.” He remembers that they worked on “with a rising sense of excitement, as we suspected that coevolution was generally an underrated process.”
Although the concept was already there in Darwin’s writings, “the critical thing in science is not just to have the idea, but to produce a lot of data to support it. And we had a huge quantity of data.” Ehrlich and Raven’s work revealed the importance of coevolution as an engine for generating biodiversity, and has gone some way to solving one of the big questions in science: why does our planet harbor so many different species?
Another discovery inspired by the butterflies of Jasper Ridge concerned the dynamics of what we call metapopulations, where Ehrlich’s insights again brought about a change of paradigm. For while the focus during the 1960s was on species and large populations, his work elucidated the vital role of small populations in preserving ecosystem health.
The catalyst yet again was his observation of an unexpected fact: that what had been thought to be a single population of E. editha on Jasper Ridge was actually three. In the mid-1960s, he and his group had been witness to the relatively fast extinction of one of the three butterfly populations. A few years later, they were even more surprised to see that this first population’s habitat had been colonized by members of the other two. We now know, thanks to this finding, that a population formed by distinct yet genetically interacting groups gains in resistance, providing us with a line of action to mitigate the impact of habitat fragmentation and climate change.
For Ehrlich, there is another crucial reason to analyze biodiversity at the level of local populations and not just species, “because it is populations that deliver ecosystem services.” A population of pollinating insects serves the region where it is located, and its extinction there is still a problem even if the species survives elsewhere.
This emphasis on ecosystem services is another of Ehrlich’s contributions, and reminds us that protecting biodiversity is a matter of survival as well as values. Society’s progress relies on natural processes like crop pollination, protection against erosion, the production of food, etc., and this, he points out, has important implications for the design of conservation strategies.
Ehrlich has also been a pioneer in quantifying the impact on nature of human activity, and refining the concept of ecological sustainability. One of his most cited papers, published in BioScience in 1986, reveals that human beings consume a large portion — almost 40 percent — of the biomass generated by photosynthesizing organisms. A statistic that not only reflects the sheer scale of humanity’s footprint in the biosphere, but suggests that the disappearance of the Jasper Ridge butterflies is, above all, a sign of the times.
