Humans: Reversing What Fungi Helped Plants to Do?

There is an intriguing hypothesis, mentioned in Merlin Sheldrake's book Entangled Life. Hypotheses can always be extrapolated. The Devonian was a geological period, some 300 to 400 million years ago. At that time, the Earth's atmosphere contained lots of carbon dioxide and very little oxygen. There would have been a strong 'greenhouse gas' effect. The Devonian period was also, when plants moved from the seas on to land. This plant invasion was aided and abetted by a close, mutually-beneficial association with mycorrhizal fungi in their 'roots'. These mycorrhizal fungi enabled the plants to access to essential chemicals, such as phosphates. The fungi could even 'find' these chemicals in rocks. Plant life flourished and became more complex, in a way that would have been impossible, without access to phosphorus etc. Photosynthesis (using sunlight, to power the production of organic chemicals from carbon dioxide and water) by the plants, resulted in a 'draw down' of atmospheric carbon. This markedly reduced carbon dioxide levels in the atmosphere, cooling the planet. The carbon was stored away in the bodies of plants and fungi as well as in their remains. The remains became coal, oil and gas. Oxygen is a waste product of photosynthesis and markedly increased in the atmosphere. Animal life, consequently flourished in these new conditions and also invaded land. The net conclusion of a cited author in the book is " that mycorrhizal relationships have played a role in the evolution of much of life on Earth". Rather obviously extrapolating, human activity, burning trees, coal, oil and gas, returns carbon to the Earth's atmosphere. That makes humans the dominant agent, perhaps returning the planet to a new Devonian period?