multi-species modeling background selection approaches

[amandajoan]

Hello all, 

I have an undergraduate student who is doing some maxent modeling for 40 different species. We have talked about the importance of selecting a background that is suitable for each species, either through restricting the geographic area of the study or by using a bias file approach. I was wondering if there were any methods or tools for automating this process when each species has a radically different distribution? We have been clipping the environmental layers to an appropriate spatial scale on a species by species basis, but I wasn't sure if there was a better approach. 

Thanks!

Amanda

[Francisco Rodriguez Sanchez]

Hi Amanda,

If you use R you can easily clip the environmental layers automatically for every species, following this pseudocode:

library(raster)

library(dismo)

buffer <- 1   # e.g. 1 degree of buffer area beyond species coordinates

for (i in 1:length(species)){

    backgr.area[i] <- c(min.long[i] - buffer, max.long[i] + buffer, min.lat[y] - buffer, max.lat[y] + buffer)

    envir.spp <- crop(envir.global, backgr.area[i])

    models[[i]] <- maxent(envir.spp, occurrences[i])

}

Hope this helps,

Paco

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Dr Francisco Rodriguez-Sanchez
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[Милош Поповић]

I was using similar method in R to restrict background points to a bufer of eg. 50 km around occurence points. However I am not sure if there is any suggestion about the size of this buffer zone? Any suggestion about this? I guess it has to be species specific (i.e. species migration potential) and to differ according to a layer resolution.

Kind regards,

Miloš