Very sad news: Bob May passed away yesterday. He was 84.
“Who’s the greatest ecologist in history?” isn’t a question worth taking seriously, except as a conversation starter. But Bob May is among those who’d come up in any conversation started by that prompt. Put simply, Bob May invented large chunks of modern ecology–both the questions we ask, and the standard approaches we use to answer those questions and others. He was part of the generation of now-household names who turned ecology from a peripheral, backwater discipline to a core biological discipline.
Bob May was born in Australia. After spending over a decade as a physics prof at the University of Sydney, he moved to Princeton and switched to ecology in 1972. He immediately made a massive impact. He began working on the question of when a “complex” community–meaning a community comprised of many species, all interacting strongly with one another–will be stable. In the simplest baseline case, the shocking answer was, basically, “never”. That is, increasing complexity is actually destabilizing in the simplest baseline case. The answer was shocking because it was completely contrary to the strongly-held intuitions of ecologists at the time. The notion that diversity or “complexity” begets stability dates back at least to Charles Elton. But according to May, that notion is wrong (or at least, so vague it might as well be wrong). Far from promoting the “balance of Nature”, high species richness and strong interspecific interactions actually inhibit that balance. Bob May first published that insight in a 1972 Nature paper, and then fleshed it out with related results in a now-classic Princeton Monograph, Stability and Complexity in Model Ecosystems. As of this writing, Stability and Complexity in Model Ecosystems has been cited over 8700 times, according to Google Scholar. One could fairly describe much of the subsequent 40+ years of theoretical and empirical community ecology research as an attempt to find ways around May’s result. Either additional biological realism that would reverse or overcome the destabilizing effects of increasing complexity. Or else other ways of defining “complexity” and “stability“, for which Elton’s intuition still holds. That the attempt has had successes doesn’t diminish the importance of May’s original result in the slightest. We wouldn’t have even known that that 40+ year research program needed doing, if not for Bob May.
Leaving aside the specific results in Stability and Complexity in Model Ecosystems, the approach it took also was massively influential. Along with Robert MacArthur, Richard Levins, and a few others, Bob May helped make ecology safe for what he called “strategic” models. Simple mathematical models that deliberately strip ecology down to the bare essentials, in order to capture the essence of one key phenomenon. The empirical research inspired by strategic models has something of a mixed track record. The history of ecology is littered with weak tests of model’s like May’s stability-complexity model. (Including from me! I think Fox and McGrady-Steed 2002 JAE was a creative attempt to test May’s idea, but looking back even I don’t find it especially convincing.) But that probably just illustrates how original and inspirational May’s work was.
Now, here’s a thing: Stability and Complexity in Model Ecosystems is probably only Bob May’s third most important achievement.
Number two is probably chaos. Bob May wasn’t the first to discover chaos–roughly, deterministic dynamics that are extremely sensitive to initial conditions, and so are effectively unpredictable more than a short time into the future. But as far as I know, his was the first work on chaos to attract widespread attention in biology. In 1976, May shocked the world by showing that the discrete time logistic equation–the dead-simplest model of density dependent population growth–could exhibit chaotic population dynamics for some parameter values (basically, sufficiently high r). His Nature paper reporting this result, “Simple mathematical models with very complicated dynamics”, has been cited over 7500 times. That paper led to a massive explosion of interest in what came to be known as “chaos theory”, ably chronicled in James Gleick’s popular book Chaos. The search for chaotic population dynamics in ecology bore fruit in the lab; whether there are any examples in nature remains somewhat debatable. But again, that doesn’t take away from May’s work in the slightest. We wouldn’t have even known to look for chaotic dynamics if it hadn’t been for Bob May.
And number one is probably his pioneering work with Roy Anderson, modeling the dynamics of infectious diseases. The first part of Anderson & May’s two-part 1979 Nature paper, “The population biology of infectious diseases”, has been cited over 3200 times. It’s the foundation of essentially all subsequent disease ecology and epidemiological modeling. Their 1992 book, Infectious Diseases of Humans: Dynamics and Control is a standard reference and has been cited over 12,000 times. It’s one of the odd coincidences of history that Bob May passed away during a coronavirus pandemic that has highlighted once again the tremendous importance of infectious disease modeling.
May wrote many other papers and was involved in several other books. Many of which have themselves been cited thousands of times, and which would be crowning career achievements for most any ecologist. Here’s his Google Scholar page.
During his illustrious career, Bob May held faculty positions at several of the world’s most prestigious universities, and won more or less every honor available to an ecologist. His most notable honors include the ESA’s MacArthur Award, the 1996 Crafoord Prize (the closest thing ecology has to the Nobel Prize), and the 2007 Copley Medal from the Royal Society of London. He was a Fellow of the Royal Society of London (and later its President), and an honorary or foreign fellow of several other national scientific academies. In 2001 he was created a life peer (choosing the title Baron May of Oxford), one of the first 15 “people’s peers” to be elevated to the UK’s House of Lords in this manner. He also served as Chief Science Adviser to the UK government from 1995-2000.
It was shortly after his term as Chief Science Adviser ended that I met him for the first and only time. He spoke on UK government science policy at Silwood Park, where I was a postdoc. Afterwards, I asked him to sign my copy of Stability and Complexity in Model Ecosystems. I felt a bit embarrassed, but he was very kind and happy to sign. I got the feeling I was far from the first junior ecologist to ask him to do this.
I’m not the only Dynamic Ecologist influenced by Bob May. Here’s Meghan’s old post on how she finds herself rereading Anderson & May (1979) over and over again, discovering new insights every time.
Having only met Bob May once, I have no personal memories to share. He was widely admired and famously competitive (even at croquet). Perhaps those who knew him will share their memories in the comments.
I’ve written before about feeling like the generation of ecologists I “grew up” admiring in grad school is now passing away. With Bob May’s passing, I feel it even more keenly. I don’t have any special connection to him, I’m just one of many, many ecologists he influenced. Indeed, “influence” doesn’t really do it justice. Bob May’s influence on ecology is ongoing in the same way that the sea’s influence on fish is ongoing. Rest in peace, Bob. You will be greatly missed. But your legacy lives on.
I will add links to obituaries and remembrances of Bob May as I find them; please share them in the comments.
The Life Scientific (2012 BBC radio interview)