TREES, VEGETATION AND ALGAE

Trees convert carbon in the form methane (CH4), carbon dioxide (CO2), carbon monoxide (CO) etc, from the atmosphere into cellulose and oxygen.  When trees die, some of the carbon is released back into the atmosphere due to rotting, but most of the carbon ultimately becomes buried in sedimentary basins, and converted to coal, oil or gas. see map of Austalia's coal reserves here .

Let’s say that the average life of a tree is 400 years (a high estimate) and it occupies an area of 10 m x 10 m (100 sqm).  Trees first appeared on the planet around 385-400 million years ago.  That means every 100 sqm of vegetated area on the planet, has sustained around one million (1,000,000) trees .  To put that in perspective, a suburban block of 800 sqm may have supported 8,000,000 trees over time.  Take some time to consider that, and the amount of carbon extracted from the atmosphere, now buried in the ground.

On top of that amount of buried carbon, also consider that in the preceding 230 million years, the planet was covered in algae – that is a lot of algae that lived and died and became coal, oil or gas.

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When considering the above example, note that deserts are relatively recent phenomena, varying in age up to 50 million years.  Also note that small plants grasses, shrubs etc (undergrowth of shorter lifespan), have not been included. 

Worldometer website provides some easy to understand data on world energy use and the remaining fossil fuels available.

Estimates of remaining fossil fuel reserves are;

Coal - 863 billion tonnes

Oil - 262 billion tonnes

Gas - 0.13 billion tonnes (that's a lot of gas)

This leads to the question of what the atmospheric mix will be if we continue to re-release carbon into the atmosphere.  Will Earth become as toxic as it was 400 million years ago before trees evolved and contributed to cooling the planet?