Some evolutionary biologists spend a large part of their time conducting field research.
Take every opportunity to get hands-on experience doing fieldwork. Some programs may require an internship.
You will also need strong oral and written communication skills. You often need to write technical reports and give presentations on many positions. Take a course in public speaking, if available.
Because environmental challenges require working with people from disciplines beyond the natural sciences, it helps to take some courses in social sciences, economics, geography, and environmental law.