Thursday, August 14, 2014

#ESA2014 - Day 3 bringing together theory and empiricism

I was tied up in a session all afternoon, so most of the interesting comments below are from Topher Weiss-Lehman, who caught what sounds like a pretty thought provoking session about theory and conservation biology, with thought provoking talks from Hugh Possingham and David Ackerly. This concept of bringing theory and empiricism together permeated through a number of talks, including the session I moderated on using microbes in theoretical ecology and applying theory to microbial ecology (although at the moment, the distance between those things still feels large).

The most thought-provoking talk I saw was Peter Chesson's, on "Diversity maintenance: new concepts and theory for communities as multiple-scale entities". Chesson discussed his discomfort with how his coexistence theory is sometimes applied (I suppose that is the definition of success, that you see your ideas misused). His concerns fall with those of many ecologists on the question of how to define and research an ecological community. Is the obsession with the looking at 'local' communities limiting and misguided, particularly when paired with the ridiculous assumption that such communities are closed systems? Much like Ricklef's well known paper on the defining a 'regional community', Chesson suggests we move to a multi-scale emphasis for community ecology.

Rather than calculating coexistence in a local community, Chesson argued that ecologists should be begin to think about how coexistence mechanisms varied in strength across multiple spatial scales. For example, is frequency dependence more importance at smaller or larger scales? He used a concept similar to the idea of Ricklef's regional community, in which a larger extent encompassed a number of increasingly smaller scale communities. The regional community likely includes environmental gradients, and species distributions that vary across them. Chesson presented some simulations based on a multi-scale model of species interactions to illustrate the potential of his multi-scale coexistence theory framework. The model appears to bring together Chesson's work on coexistence mechanisms-- including the importance of fitness differences (here with fitness calculated at each scale as the change in density over a time step) and stabilizing forces, and the invasion criteria (where coexistence has a signal of a positive growth rate from low density)--and his scale-transition theory work. This is a very obvious advance, and a sensible way of recognizing the scale-dependent nature of ecology in coexistence mechanisms. His approaches allows ecologists to drop their obsession with defining some spatial area as "the community" and a regional community decreases the importance of the closed system assumption. My one with is that there be some discussion of how this concept fits with existing ideas about scale and communities in ecology. For example, how compatible are existing larger scale approaches like macroecology/biogeography and other theoretical paradigms like metacommunity theory with this?  

#Notes from Topher Weiss-Lehman

Applied Theory I spent the morning of my third day at ESA in a symposium on Advancing Ecological Theory for Conservation Biology. Hugh Possingham started out with a call for more grand theories in a talk titled “Theory for conservation decisions: the death of bravery.” Possingham argued for the development of theory tailored to the needs of conservation managers, identifying the SLOSS debate as an example of the scientific community agonizing over the answer to a question no managers were asking. He described the type of theory he meant as simple and easily applicable rather than relying on intensive computer simulations that managers are unlikely to be able to use for their own systems. Possingham is right that conservation managers need theory to help guide them in decisions over where and what species to protect, however I can’t help but think about the scientific advances that arose specifically as a result of the SLOSS debate and computational models. The talk left me wondering if theoretical ecology, like other scientific fields, could be split into basic and applied theory.

The other talks in the session approached the topic of theory for conservation from a number of perspectives. Justin Kitzes discussed the ways in which macroecology can inform conservation concerns and Annette Ostling explored how niche and neutral community dynamics affect extinction debts. H. Resit Akakaya provided a wonderful example of the utility of computer simulations for conservation issues. He presented results predicting the extinction risk of species due to climate change via simulations based on niche modeling coupled with metapopulation dynamics. Jennifer Dunne then explored how the network structure of food webs changed as a result of human arrival and hunting in several systems. The session ended with a presentation by David Ackerly calling for a focus on disequilibrium dynamics in ecology. Ackerly made a compelling case for the importance of considering disequilibrium dynamics, particularly when making predictions of species reactions to climate change or habitat alteration. However the most memorable part of his talk for me was the last 5 minutes or so. He suggested that we reconsider what conservation success should mean. Since systems are changing and will continue to change, Ackerly argued that to set conservation goals based on keeping them the way they are is setting ourselves up for failure. Instead, we need to understand that systems are transitioning and that while we have a crucial role in deciding what they might transition into, we can’t and shouldn’t try to stop them from changing.

The talks today gave me lots of ideas and new papers to read, but they also left me pondering more questions on the philosophy of science (what we do, why we do it, and what our goals should be) than I expected.

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