Restricting where the Background Points are Taken

[Kristin]

Hi Everyone,

I am attempting to restrict the amount of area that my background points can be selected from (testing some things from Thuiller et al (2004) and VanDerWal (2009)). I'm using the GUI version of Maxent and not the R version (although I do know how to use R). As per instructions that I have found, I created a smaller extent in ArcMap and gave the rest of the area null values and included it in with my environmental layers. However, the result (as maybe I should have expected) was also masking out the area that I had declared as null. What I want is to give Maxent a smaller, more geographically restricted layer where it can take the background points from, but to predict habitat for the entirety of the environmental layers (something like having it take background points from the western half of the county but predict habitat for the whole county (the environmental layers are set to the extent of the whole county). I'm sure there's a way to do this and maybe I've just not found it in my searches. Any thoughts?

-Kristin

[Pablo Riul]

Dear Kristin,

I think you should use the swd background option to build your models (select the background.csv in environmental layers) and then project these on your whole study area (select your environmental vars in projection layers). The way you do this is described maxent tutorial.

Cheers,

P