Thank you both very much for your answers. I don't mind a disturbing but true answer -- thank you Etownenviro!
Marsmat - both Duke and Yale provided extensive scholarship and fellowship links, but to offers which have been closed since January. I have been hustling, but haven't found anything that's open to apply to. There's loads that are open in August for next year, but nothing for 2014-2015 year. Any ideas?
Etownenviro: That's http://studentaid.ed.gov/repay-loans/understand/plans/income-based, right? That seems like the best option. (Quick sum up for people reading over: your loan is forgiven after 25 years of payments, or 10 years of public employment and 120 payments -- and your payments are based on your income, not your debt or a repayment term. Very good deal. It also extends retroactively to loans from Oct 2007.)
I do want to get into the USFS, EPA, or another public goods research organization. However, all the people I work with got their PhDs at a public university using an assistantship that got their tuition waived. They walked away with zero or minimal debt. Tempting!! I'm considering deferring (which Yale doesn't allow, so I guess I'd just reapply), and next year be more on top of scholarships - and apply to more public university programs. I hate the idea of missing a year, but I feel like there must be a better option than "Be in debt till you're over fifty."