Stress
You seek to solve problems that are more or less un-solvable. All you can usually do is "the best you can." Every now and then you'll manage to find or do something great, but most of the time, you'll be schlepping through what seems like an endless bog of problems.
You're something of a "nature detective." A "Recycle Green Poirot," if you will. (You probably won't.) While this makes your job interesting, it can also make it quite stressful if you're not solving your mysteries.