40k???? well hang up conservation officer, get your Phd and get into wildlife biology
I have one of those - mine is in wildlife toxicology. Getting a PhD in science is not a good route to get a head on the financials. I was 29 years old before finishing 2 graduate degrees, a post-doc and then landed a professor's job. I'm considered lucky because I only spent 1.5 years in post-doc, which is sort of like the equivalent of the academic farm team. In the end spending 12 years of university education at near poverty living doesn't really get you up to speed with people who start a regular job earlier in life. Even though you make more in the end - little things like visiting the dentist after 5 or 6 years of not visiting one, buy a car and first house set you back considerably.
That said, as a prof. I have quite a bit of freedom - well total freedom - in how I spend my research time (estimated as 40% of total work time). I fund myself by submitting research proposals to various funding agencies to support research projects and graduate student salaries and to keep the publications flowing which for us is the measure of our productivity. In many respects, being a prof is like running a buisness - marketing your research, hiring graduate students keeping your lab stocked ect. I spend a lot of time on field boats performing research on the Great Lakes, working on a number of inland lakes as well as some marine work. For the most part, my graduate students end up doing a lot of the leg work but I try to keep my fingers in most aspects of my projects including the forays into the wilds. Actually when I think of it, the graduate students really have the best life because their focus is fully on doing their science and making their respective projects work aside from courses. Unfortunately they have to do this making 17,000/year and paying 5000 in tuition.
Sometimes a PhD can be pretty limiting in terms of getting a job because you become pretty specialized and your education makes your paygrade a bit too high for certain types of employment. Today, a masters degree in science is considered about the most marketable in terms of salary and variety of positions available. Many folks I talk to in government look at hiring people with MSc's even when requirements state the position to be BSc-level. The reason for this is that people with an MSc are seen as candidates who can be promoted to management levels a later time points. This doesn't seem to be the case in engineering where bachelor's degree and P-eng status are the mainstay in the workforce. That said there are many career opportunities with a bachelor's degree in sciences, but you tend to get more professional autonomy with more advanced degrees. The geologists I work with tend to get a lot of field time in forests as do a number of field ecologists. At the level of a research scientist it really depends on how you shape your skill sets and market your research interests.
Getting good jobs with the government usually requires some type of networking. Many universities offer co-op programs that can help get you in the door. Also a lot of hiring in government agencies occurs with known, semi-internal candidates. Often times people will work short and long term contracts (6 mo or 1 year renewable) and when a job is posted it has been tailored with someone in mind. Of course this is always denied, but I've seen it often enough to know it is normal procedure. The trick is getting yourself one of those contracts and making the right connections and impressions while you are there.
Good luck with your decision!
. I have several other offers I am considering at the moment so it is all good. I have a B.Sc. in geology, and about to finish a M.Sc. in geology. I am looking for full time salary work, but contract work is really common as well. I spent several working, mapping mostly for the governenmt and a small mining exploration company. Smaller companies like to take on contractors. Now I am looking for work with either a consulting firm or major compmany. More long term/stable work with full benefits. 
