Conservationists tend to be an educated bunch. While having a bachelor of science degree can get you an entry-level job, chances are that if you plan on working for the private industry or even the government, you'll be required to have a master's degree. As well, most environmental scientists who work in a university setting have Ph.Ds.
Getting a broad education in several areas of the physical sciences—biology, chemistry, zoology, geography, and physics to name a few—will prepare you to go on and pursue your focus of choice, such as pollution, the ecosystem, hydrology, etc.
Consider this: Getting an undergraduate degree in business administration or finance and a minor in a physical science, and then going on to get a higher degree in a very specific area such as environmental legislation or even environmental law will make you eminently hirable.