Comment 1: MIMES/EPA Meeting - large scale implementation?
November 7th, 2007From Daniel J. McGarvey, Ph.D.
U.S. Environmental Protection Agency
Ecosystems Research Division
It seems to me that one potential hurdle to a large-scale implementation of MIMES could be its spatially-explicit structure. As I understand it (and please clarify if I am wrong), MIMES is designed to calculate any number of endpoints for each cell within a gridded landscape (much like its ‘precursor’, the Spatial Modeling Environment (SME) of the Landscape Modeling Framework (LMF)). Since we’re looking to be able to make predictions at the national scale, we’ll obviously need to be able to adjust model parameters (e.g. species lists) within distinct cells, depending upon the locations of those cells. This is certainly do-able (though it will likely be a huge time investment).
I’m wondering if a more systemic problem might be the use of
fundamentally different models within cells. Imagine, for example, that fish assemblage structure in one region (i.e. cluster of cells) is
mediated by deterministic (or quasi-deterministic) mechanisms, such as critical habitat availability; BASS might be a good way to model and ultimately predict the structure and productivity of such assemblages.
Now, imagine that fish assemblage structure in another region has more to do with stochastic immigration-extinction dyamics (re-colonization following flood events, for example); in this case, we might want to implement a literal Island Biogeography model. Given the radically different structures of these two (hypothetical) models, I’m skeptical that we could get away with simply adjusting model parameters; I think we’d need a routine that is capable of calling independent sub-procedures/models on demand (regardless of whether the call is automated or manual). This might be a trival issue to the high-powered comp. sci. folks, but it seems like a potentially signficant challenge to a lowly ecologist, such as myself. . .
Also, I’m wondering if MIMES can synchronously run model procedures at two different scales? That is, can we use model endpoints calculated for one size of grid cell to feed or parameterize model procedures within smaller, nested cells? Here’s an example of what I mean: there’s a lot of good evidence to suggest that species-area relationships (or species-discharge relationships in aquatic systems), though entirely correlative and empirical, are a robust means of predicting total community-level richness. Noting this, I can imagine using a species-area relationship to predict total species richness on a per-basin or per-region basis, then using a process model (again, I use BASS as an example) to predict particular species occurances and densities within each of the region’s cells. This “top-down THEN bottom-up” approach might provide robust predictions - I’m just not sure how easy it would be to automate.
Hopefully, the GUND meeting will provide answers. . .