Most people think that most of our oxygen comes from trees. But with two-thirds of the Earth's surface covered with water, it actually comes from oceans full of plant plankton, who dutifully convert CO₂ to oxygen through photosynthesis. The biggest harm to plant plankton is not global warming, since a spike in CO₂ would just mean that plant life thrives. Instead, plant plankton's biggest predator is whales. Whales scoop up plankton by the truckload. It would seem obvious then, that the solution is to protect plant plankton by slaughtering whales. With an absence of predators, plant plankton will overpopulate and drastically cut CO₂ levels.