Nationalgeographic, By: Jane J. Lee, 04/23/2013

With an estimated seven billion people and counting, the world's population will only get hungrier. The advent of fertilizers and high-yield crops have helped growers keep pace with the demand for food.

But there's an unintended crop flourishing around the world that is not always so beneficial. Microscopic, plantlike organisms called algae thrive on the excess nutrients—like nitrogen and phosphorus—found in fertilizers that make their way from backyards and fields, producing blooms that can sometimes be seen from space.

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