WillisF

Whether or not a master's degree is required in order to get into the PhD program at a school will depend on the individual school. For example, the program I will be attending (OSU) requires a master's degree in order to be considered for admission to the PhD program. On the other hand, another school I had applied to, Minnesota, has just recently changed their requirements, so you can apply directly to the PhD program with just a bachelor's degree.
Whether or not you should get a master's is more of a personal preference, combined with funding, academic, and coursework considerations. I chose to do a master's degree because my undergraduate GPA was not especially strong and I wanted to have a body of work to show PhD programs that I could handle the rigor of graduate study, and to show them that I had a focused research question (developed through my master's work). Of course, rising_star and geographeyyy have mentioned already that it is perfectly possible to get your M.A./M.S. funded at many schools, and not just the top ranked ones either---my undergrad alma mater has a small M.S. degree program that offers several assistantships, for example. 
As far as coursework, having a master's does make it possible for you to bypass some of the coursework at programs that incorporate "master's level" classes into their PhD coursework---Minnesota, in dropping the master's requirement for admission to their PhD program, also made it so that if you enter the PhD program with a master's degree, you will receive "advanced standing" and do not need to take several courses that you would otherwise need to take.

@WillisF, there are definitely many more options for a funded master's than what I listed. I just listed the first schools that I thought of but, there are others, including Alabama, Auburn, a couple of SUNY schools, Ohio University, Miami University of Ohio, University of Arkansas, University of Tennessee, UW-Madison, UW-Milwaukee, Indiana-Bloomington, Idaho, Montana State, Utah State, University of Nevada-Reno, UC-Boulder, Syracuse, UConn, Temple, Penn State, Virginia Tech, University of South Carolina, Georgia State, etc. Most of the state universities which have a master's program offer funding through teaching assistantships, which typically means either teaching a lab section (or two) or leading discussion sections.

I applied to three PhD programs this admissions season without a Master's, mainly because 1) I figured I'd want to get my PhD eventually and 2) of the funding reasons you mentioned. Is the PhD something you anticipate wanting to pursue? If yes, go for it! You'll catch up on the MA training anyway (the doctoral programs I got accepted to require Master's coursework and a Master's project on the way to my PhD). Another possible outcome that I hadn't expected: U of Oregon accepted me to the Master's program, even though I applied to the PhD, but offered me two years of funding to complete it. I don't know if that's because they know I'm planning on moving on to the PhD, but either way, it is still possible to get your MA funded!
If you decide to apply to the PhD, I think the most important thing you can do is reach out to the faculty you want to work with and to learn about/express interest in the available research opportunities. I feel like that strengthened my application considerably, and also helped me understand what I was getting into a little better (:
Best of luck!

Actually, a number of geography programs offered funded master's programs, @geographeyyy, so it's unlikely that you received funding simply because they expect you to move on to the PhD. For example, UNC, Florida State, UGA, Kentucky, Arizona, Rutgers, Ohio State, UIUC, Louisiana State, Kansas, and Kansas State all offer funding for master's students, regardless of whether or not you plan to subsequently pursue a PhD (and whether you plan to pursue the PhD there or elsewhere). Some of the programs I've just listed do require you to have a master's before you do the PhD, which you can either do on the way to the PhD or as a standalone degree. 
@WillisF, doing a master's first has a few potential advantages. 1) It gives you a chance to further refine your interests and show that you're capable of graduate work, which could help you get into better programs. 2) It often buys you an additional year of funding. At Kentucky, for example, MA students get two years of funding and PhD students 4 years of funding. If you do both the MA and PhD there, you get a total of 5 years of funding (see here, scroll to bottom of the page). By comparison, if you did your MA at, say, LSU and then your PhD at Kentucky, you'd get 2 years of funding at LSU and four at Kentucky, for a total of 6 years of funding. This isn't to say that you'll need or should take that long to finish but, it does potentially give you more options.
Also, FWIW, many programs do require that you meet the MA requirements before you can move on to the PhD. The UGA Geography PhD Student Handbook says this: "Acceptance to the Ph.D. program will normally presuppose that the student has met the minimum requirements of the departmental M.A./M.S. program, except for a thesis in the case of students with the M.A./M.S. from a school where no thesis is required. In all cases, at least three full years of study beyond the bachelor's degree are required for admission to candidacy." (from this PDF file).
If you do want to improve your application to compete against MA/MS students at a place like Clark where everyone does the PhD, you'll need to have clear research interests, relevant research experience, knowledge of any languages or techniques required for your intended project, and strong recommendation letters.