Tuesday, February 22, 2005

How science works

Flowers in Arcata, CASean Carroll, at Preposterous Universe, has a neat graph showing how ideas migrate between fields, and how discoveries in one field cascade into others. Enough theorists read the phenomenological literature that results gradually seed the theory and push new questions to the front. As with cancer vaccines, there will be some who stick with the old research programs, keeping the hearth warm for the next great discovery. But as more is learned about the universe, theorists realize that they are trying to prove something different than they thought, and new research flourishes.
The other end of the spectrum has other useful qualities. Plant ecologists developed a set of tools to deal with competition and predicting when competition would lead one species to take over, and when the competitors could co-exist. Because plants are stationary and compete for carbon and nitrogen, it's easy to develop some straightforward models of competition.

Why carbon and nitrogen? Carbon is structural, and also energy. Cellulose, the building block of plants, is mostly carbon with oxygen and hydrogen thrown in, so taking up carbon allows height and width. Nitrogen is protein, chemical activity. Since there's rarely enough nitrogen, and carbon is available as carbon dioxide, it's easy to talk about a single limiting resource, and competitive strategies for extracting that resource. In certain environments, other resources are limiting, like water, iron, salts, or potassium. But every plant is looking for the same thing in the same places.

Animals move around. Some are big, and can move around a lot. Others are small, and can get into little nooks and crannies. The stuff they want is different. They still need carbon and nitrogen, but it has to be in a particular form, plant, other animal, fungus, etc. They need to sleep, to mate, to stay warm. They have to watch for predators and care for offspring. And they do all that in complicated spatial ways.

So animal ecologists developed different theories and approaches. The language of the communities shifted. The focus changed. Plant ecologists developed robust theories of resource competition. Animal ecologists developed more sophisticated models of the niche. Niches are ways of talking about resources, but plant ecologists don't talk in ways that animal ecologists do, and I think there's a lot of duplicated effort.

One question that constantly hovers in the back of my mind is: how to integrate these approaches? How do I take the sophisticated plant ecology and generalize it to motile species which compete for different resources at different times and by different means.

Maybe it's impossible. Maybe plants are special. But maybe plants are just as complicated as animals, and it's just a matter of seeing the simplicity in animal ecology, rather than imposing complexity on plants.

Ecologists all read papers from both sides. Why do these divisions persist, even though we recognize our common purpose and we use almost identical language? The interchange between disciplines is much freer among ecologists than between different branches of physics. The great theoretical ecologists don't care whether their theory is applied to plants or animals.

Does that mean that habits of thought are separating these groups, or that there are real and irreconcilable differences? I don't know which it is. So we just move ahead.

Move” by Miles Davis from the album Birth Of The Cool
(1949, 2:34).