“Monarchs are an organism where the city actually can matter,” Doug Stotz, a conservation ecologist at the Field Museum, attested. “We can make a huge difference by getting milkweeds and native flowering plants into city gardens, city parks, vacant lots, all sorts of places where we can grow habitat.” If you’ve got a porch or a fire escape, you could plant milkweed in a window box or a pot. (Just try to avoid tropical milkweed, a nonnative variety). A bonus: You get to watch contented caterpillars munching and growing.