Which, it turns out, is exactly what coffee trees evolved to provide.
The New York Times Science section today has a fascinating, if a little technical, story about the way caffeine offers advantages to coffee trees. To make a long story short, in large doses, as when the trees' leaves fall to the ground and degrade, the chemical hinders germination of other plants that might compete with coffee. Small amounts in nectar from the trees' flowers, however, give bees and pollinating insects a little buzz of energy that encourages them to come back.
Apparently coffee trees are not alone in this. The ability to make caffeine is not exclusive to them: among others, tea, yerba mate, and cacao plants also produce it, although in different ways. This "convergent evolution" suggests just how useful caffeine is the plant world, the story quotes scientists involved in a study just published in the journal Science.
"Every second, people around the world drink more than 26,000 cups of coffee. And while some of them may care only about the taste, most use it as a way to deliver caffeine into their bloodstream. Caffeine is the most widely consumed psychoactive substance in the world," the story says.
Okay, my coffee's finished. Time to get to work before the buzz wears off...