Monday, March 8, 2010
Think Week: Day 2
Ok, time for an update on think week - this'll help make me draw my thoughts together. Just got back from a lovely sunny walk to a park down the street... it was nice enough that I wore my spring jacket and sat on a bench in the sun writing for a while! Spring here we come!
At this point I've polished off pretty much all of the articles on the reading list I put up yesterday. Some I read with greater attention than others; several of them are reviews of books that I'm going to get out of the library when it's open again. Together though, they cover about 2 decades of an on-going discussion about whether or not general ecological laws can exist, and if they can what are they, do they matter, and have we found them yet? Lots of comparisons an analogies are made to physics and other disciplines (these are part of the 'physics envy' debate). I think collectively, too, they're part of a (relatively) young field attempting to define and justify itself, something that at least traditional physics has moved beyond long since. Some of these papers were suggested to me during a discussion I had with an empiricist about what theoretical ecology is as a field/discipline (a definition I'm still turning over in my head).
In an attempt to summarize:
Ecology is a complex field. Complexity varies with scale relative to the observer, and just how complex something is relative to our attempts to predict it depends on the number of interacting entities involved, the nonlinearity of their interactions, and the degree of precision desired in predictions relative to the scale of the interacting entities. By way of analogy to physics (as is so often done) - when we deal with systems of many interacting particles, like gases, we can predict their macroscopic properties really well, drawing statistical conclusions and looking at average behaviors. But any physicist would be pretty unhappy about having to predict the exact trajectory of an individual gas molecule, or even a collection of them.
In the same way, as Lawton and others point out, within ecosystems the number of interactions that occur between different species and their environments is large. Broad scale patterns as explained by a growing number of macroecological ideas are somewhat easy to capture, arising out of statistical relationships and generalizations (ie, we can predict general relationships between species abundances and distributions, body size and geographic range, etc). On the other hand, he points out that we're also increasingly good at working with population level dynamics, and developing general principles governing them, like physicists can predict the interactions of a few particles. But we get stuck at the intermediate scale of communities, which are a whole bunch of species interacting locally. A lot of this makes sense and rings true, although I think the outlook for community ecology is a little brighter than he made it seem; we are tracking down relevant mechanisms, and weaving them together and understanding more all the time.
The crux of the matter though, is that making good predictions at the community level is really important, because in many cases, that's where a lot of our visible ecological/environmental problems are taking place. That's the scale that managers work at, and the level at which endangered species are handled often. So some of the greatest need for strong predictions arise at scales that may be fundamentally the hardest to understand and generate predictions for, without the time and resources to do a lot of comprehensive and often case specific studies. Also, a lot of what we find most compelling about ecology are all of the fascinating stories of unbelievable species interactions, incredible organisms and wacky environments. Good thing I like a challenge.
Seems like there's a tricky balance between 1) throwing up your hands despairingly and saying we can never know anything general about communities and will have to studying all of them individually, and 2) looking too hard for a holy grail of generality that may not be feasible. You don't want to get so focused on a particular species or system that you lose all perspective. And at the same time, the only way we're going to get anywhere is by looking at a bunch of deep case studies of communities in particular systems and searching for patterns and interacting mechanisms. How does all of this fit in with the scope and time scale of a PhD thesis? Holy grails take too long and are risky, and organismal myopia is bad for job prospects down the road... I need to figure out how to trace a middle road.
Topical list for tomorrow (Time to start getting more concrete):
- whole lake manipulates by Steve Carpenter et al.
- check out papers, yet to be selected, on microcommunities in pitcher plants and bromeliads
- finish a great conceptual paper on spatial coexistence, drawing together a body of theory (Amarasekare. Competitive coexistence in spatially structured environments: a synthesis. Ecol Letters (2003) vol. 6 (12) pp. 1109-1122 doi: 10.1046/j.1461-0248.2003.00530.x)
- check out this crazy topic I stumbled on earlier, "Hierarchy theory"
- a few papers from the voluminous works of Bob Holt
- having finished off the ~17 papers in my big ideas folder, it's time to take a whack at the 52 in the regular to-read pile.
Stay tuned for more!
Two of the more formative papers from today's reading:
Lawton. Are there general laws in ecology?. Oikos (1999) pp. 177-192
Simberloff. Community ecology: is it time to move on?. Am Nat (2004) vol. 163 (6) pp. 787-799