Carbon By Numbers

Humans are disrupting a small part of the carbon cycle

Delores Broten

Rainforest, Roberto Marchegiani (CC BY-NC-ND 2.0), cropped from original

Carbon is the fourth most abundant element in the universe, after hydrogen, helium, and oxygen. Because of its structure, with easily available bonds, it is an essential building block for natural and for industrial processes, from growing trees to chemical engineering. Eighteen per cent of your body by weight is carbon.

Not surprisingly, this means the amount of carbon in Earth’s systems is, well, ginormous. Most of Earth’s carbon – about 65,500 billion metric tons – is stored in rocks. The rest is in the ocean, atmosphere, plants, soil, and fossil fuels. It cycles through the earth’s atmosphere, oceans, soil, rocks and vegetation in both slow (the weathering of rocks) and fast (vegetation) cycles, some of which are still being deciphered.

The planet’s carbon cycle has stayed in a pretty good balance – carbon moving into the earth and out to the atmosphere – for hundreds of thousands of years. That is, until humans started burning fossil fuels much faster than fossil fuels are created (by the decomposition of plants and animals under geologic pressure). Humans also started deforesting, draining bogs, and plowing the deep prairie soils.

About half of the relatively tiny bit of extra carbon we release with these activities is reabsorbed by planetary processes in the forests, plants, and oceans. The world’s vegetation, from Amazonian rainforests to Eurasian grasslands, may hold about 450 billion tonnes of carbon today, about as much as 50 years of human emissions. Researchers estimate that the planet’s vegetation could store double that amount, if there was no human disturbance.

According to almost all of the world’s scientists, the problem is in that tiny amount of extra carbon we are emitting to the atmosphere, creating the disturbance we call climate change.

The task now is to stop exceeding the natural cycle, and reabsorb the excesses now circulating in the atmosphere. It is not impossible but will indeed take every tool in nature’s toolbox.

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