What are your interests?
That should drive your diretion of study. Most all reas will require math, either through calculus (modelling is a big area of our sciences. Many models are fairly crappy in that theyve been written for computer jocks rather than the scientists who use em. So they are clunky and develop answers to sub-obvious stuff.
Statistics is another area where "patterns" are sought and analyses of features that can be analyzed via surface stats and specific expansions (like for field geophysics-we do a lot of kriging ,"Spectral analyses " and Fourier transforms)
Dont lock yourself into a program at the undergrad level (I assume thats where you are). Try to get a wide view of the science and see what interests you. Be careful of "hot" areas ,as they, will, cool down very quickly after we determine how to commoditize these skills or the market goes away (sorta like the shale gas industry is experiencing now)..
GEt lots of field training and experience , if you just hang around the lab and work on data sheets, youll miss out on what the science is about.