More is different in ecology

Day three of the INTECOL / British Ecological Society meeting here in London. I was asked to give a talk on a paper that influenced my thinking as an ecologist. Biology was never what I expected to do – I started out in physics, then found that ecology was closer to my heart – more immediately relevant questions and more tangible scales. More beautiful and casual places to work, too – here I am with a Fuchsia flower in the Andes.

ben

The paper that immediately came to mind was “More is different”, by Philip Anderson. It was published in Science in the 1970s, and you can read a PDF here.

mid

Anderson writes about the danger of reductionism in science. Reductionism is the idea that a system can be better understood by breaking it into simpler pieces – for example, understanding chemistry by studying atoms, understanding atoms by studying particle physics, understanding particles by studying string theory, and so on. Coming from physics, I naturally thought that ecology could be studied the same way – take apart a very complex system, study its part, and then reconstruct the workings of the whole. But things are not always so simple. Anderson writes,

The main fallacy in this kind of thinking is that the reductionist hypothesis does not by any means imply a “constructionist” one: The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe. In fact, the more the elementary particle physicist tells us about the nature of fundamental laws, the less relevance they seem to have to the very real problems of the rest of science, much less to those of society …

But it’s not immediately obvious what approach should work best for ecology. The field has historically been dominated by two perspectives. One is a holistic viewpoint, emphasizing the overwhelming complexity of natural systems, Darwin’s ‘entangled bank’ of diversity. This approach is not useful for synthesis or prediction, since it explicitly denies such an approach can work. The other perspective is that same reductionism, a popular viewpoint in past decades that claimed that ecosystems could be controlled, managed, and subdued. As, for example, in this 1968 photograph by Robert Adams entitled Colorado Springs, Colorado:

colorado copy

But the approach that has brought us the moon landings and the sequencing of the human genome may not work so well for ecology – somewhere between holism and reductionism is the constructive science we need. On one hand, we have ideas like West, Brown, and Enquist’s metabolic scaling theory or Harte’s maximum entropy theory, which argue that simple mathematics and simple variables (like body mass, or total species richness) can explain a wide range of macroecological patterns like the energy usage of organisms and the rarity of individuals. We also have developments in population biology (for example, Tony Ives’ recent work on fluctuations in midge populations in lakes) that involve complex modeling and single scales of analysis, but that make very accurate predictions. But theory has its limitations – for example, dynamic global vegetation models, which make predictions about how carbon storage by forests will respond to climate change, require many scales of modeling to make any progress, yet still make predictions for the next century that range from an increase of five or six billion tonnes of carbon per year to a decrease of the same amount. So then, what is the right way forward?

I now think that bridging scales is critical in building a more predictive ecological science. To focus on one scale, to build reductionist models (think a simulation of every gene in an organism, or every tree in a forest) are probably not the right approach. We have to find different ways to construct our understandings. Anderson argues,

… we have yet to recover from [the arrogance] of some molecular biologists, who seem determined to try to reduce everything about the human organism to “only” chemistry … Surely there are more levels of organization between human ethology and DNA than there are between DNA and quantum electrodynamics, and each level can require a whole new conceptual structure.

peru copy

Anderson, perhaps unwittingly, is presenting a challenge to ecology. As scientists we are faced with the challenge of explaining and predicting change in very complex systems. ranging from natural ecosystems to completely artificial ecosystems of modern cities (such as Lima, seen below).

lima

This is a hard challenge. After two centuries’ of ecology, we are just beginning to fully delineate the processes that work at each scale – piecing it together into a more coherent whole is still a major challenge. We may not yet even know how much we need to know, but I find it a worthwhile call to action for us all in the coming decades.

Anderson ends his article with an apocryphal conversation between two writers, which perhaps best illustrates the point he (and now I) are trying to convey:

Fitzgerald: The rich are different from us.
Hemingway: Yes, they have more money.

One Comment Add yours

  1. Abel says:

    amazing!! read. Thanks so much for sharing Ben

Leave a Reply