How humans disrupted a cycle essential to all life

Carbon cycles through earth at a steady pace. Plants and microorganisms absorb carbon, which helps them grow. Animals and bacteria eat the plants, breathe out carbon into the atmosphere, and take some carbon underground when they die. And a similar process happens in the ocean. It's nearly a closed loop, although some plants and animals don't decay fast enough so they turn into fossil fuel, which traps the carbon underground. But one animal started to dig up that carbon — and burn it.