The Thermodynamic Theory of Ecology
Last edited Thu Sep 18, 2014, 09:50 PM - Edit history (1)
The Thermodynamic Theory of Ecology
John Harte, a professor of ecology at the University of California, Berkeley, has a wry, wizened face and green eyes that light up when he describes his latest work. He has developed what he calls the maximum entropy (MaxEnt) theory of ecology, which may offer a solution to a long-standing problem in ecology: how to calculate the total number of species in an ecosystem, as well as other important numbers, based on extremely limited information — which is all that ecologists, no matter how many years they spend in the field, ever have. Five years ago, the Ghats convinced him that what he thought was possible from back-of-the-envelope calculations could work in the real world. He and his colleagues will soon publish the results of a study that estimates the number of insect and tree species living in a tropical forest in Panama. The paper will also suggest how MaxEnt could give species estimates in the Amazon, a swath of more than 2 million square miles of land that is notoriously difficult to survey.
If the MaxEnt theory of ecology can give good estimates in a wide variety of scenarios, it could help answer the many questions that revolve around how species are spread across the landscape, such as how many would be lost if a forest were cleared, how to design wildlife preserves that keep species intact, or how many rarely seen species might be hiding in a given area. Perhaps more importantly, the theory hints at a unified way of thinking about ecology — as a system that can be described with just a few variables, with all the complexity of life built on top.
Harte has an impressive track record as an ecologist. But before he entered the field, he was trained as a theoretical physicist. In his first faculty job 46 years ago, he taught thermodynamics at Yale University. “That’s when I first really became enamored of the foundations of thermodynamics and statistical physics, when I realized the power of the ideas that those theories are based on,” he said. In particular, he was fascinated by the idea that you could look at, say, a container of hydrogen and infer micro values, like the velocities of the molecules, from macro values like temperature and volume.
The simplification of a complex ecosystem into just a handful of variables has fueled criticisms of MaxEnt, because it assumes that those numbers and whatever processes generate them are the only things shaping the environment. In essence, it generates predictions of biodiversity without taking into account how that diversity arises. It implies that the details many ecologists focus on might not matter if you want to understand the larger patterns of an ecosystem. Harte said he usually gets two responses: “You’ve opened up a whole new theory, and you’re an idiot, because we all know that mechanism matters in ecology.”
Well would you look at that!
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