If you're shortsighted, you do something without considering the long-term effects of your actions. It's shortsighted to eat a massive snack at 5:30 when you promised your grandmother you'd come for dinner at 6.
A city council might make the shortsighted decision to save money this year by drastically cutting the school budget. They're so focused on right now that they neglect to think about the negative consequences for students. Such a shortsighted action might even hurt the city itself in the future, when people move away in search of better-funded schools. In the UK, shortsighted also means "nearsighted," but in North America the more figurative meaning is most common.