If i were you, I'd go through past papers and scoring trends in both subjects to begin with. Also seek guidance from qualifiers/CSPs. Gender Studies in last couple of years have seen low scoring trends but people have passed it in flying colours too. Since you have opted out for Geography, a very high scoring and informative subjects that also compliments other compulsory subjects, Environmental Sciences shouldn't be a problem which is spread over common topics such as Climate Change & Global initiatives, Environmental Pollution, Sustainable Development Issues, etc. Furthermore, Environmental Sciences has a share in EDS & General Ability. I've had tremendous experience with Geography in both CSS and PMS scoring 70+ every time. Geography is a confidence booster, i must say. Your remaining optional combinations comprised of International Relations, Criminology, and History of USA is great. In a nut shell, what really matters is how you attempt it. Choosing optional subjects is very important for your score in these subjects, more or less, determines your final merit. One bad call can lead you to disaster. Research before you give it a shot. Once you have chose a combination, leave no stone unturned in preparing yourself the best for the D-day.

__________________
“What we need in this country today is more courage and more belief in the things that we have.”- Thomas J. Watson