With their help, plants in the Devonian period were able to mine minerals like calcium and silica. Once unlocked, these minerals react with carbon dioxide, pulling it out of the atmosphere. The resulting compounds – carbonates and silicates – find their way into the oceans where they are used by marine organisms to make their shells. When the organisms die, the shells sink and pile up hundreds of metres thick on the ocean floor, which becomes an enormous burial ground for carbon. Add all of this up and climates start to change.
