As large as it is, income from the endowment covers about a third of the total operating costs of the university. There are contractual limits on what different funds can be spent on, though you can bet that as we speak, accountants at Harvard are going through ledgers to see what funds can be shifted around. You can bet that calls and letters are going out to donors and alumni. In fact, this is incentive to make the endowment bigger, so that it can cover more.