Trees and climate change – it’s complicated

The scenario of planting trees to halt global warming is a popular one that some researchers warn is a little specious.

Put simply, global warming is due to the sun’s energy being trapped in our atmosphere by so-called greenhouse gasses such as carbon dioxide. Our petrol driven cars and aeroplanes and coal-fired power stations etc, are the prime cause of increased carbon dioxide in the atmosphere.

(Other greenhouse gasses include methane, nitrous oxide and even water vapour. Pound for pound, methane is the worst – best? - gas in the atmosphere for trapping the sun’s energy and warming the planet. Methane is produced in the production of natural gas, coal mining, decomposition of rubbish, even cows produce a measurable amount of atmospheric methane.)

Trees, (all vegetation in fact), absorb carbon dioxide from the air and store the carbon in their trunks, branches, leaves and roots and give off life-sustaining oxygen.

Part of a Greening Australia re-vegetation project in East Gippsland

So, it would seem that it is a ‘no brainer’ – plant more trees and save the planet.

However, when trees die, (all vegetation in fact), their stored carbon is returned to the atmosphere. Also. their carbon is released to the atmosphere when they burn.

When forests burn the carbon in the trees is returned to the atmosphere

The carbon in rotting vegetation returns to the environment.

Added to this, recent calculations estimate that if we continue to produce carbon dioxide at today’s rate, the number of trees needed to just barely hold steady the rise in global temperature would be many millions. These millions of trees would require billions of hectares of land and not all of the currently available land is suitable for growing trees. It is estimated that about 10% of the world’s most productive agricultural land would be required as well, reducing the calories available to the global food system by as much as 40% - not a good outcome for the nearly 8 billion humans on the planet!

Should arable agricultural land be sacrificed for planting trees?

China’s Green Great Wall is a tree planting project that has planted more trees than the rest of the world combined. It has been blamed for absorbing precious ground water reserves in arid regions and for creating worse smog conditions in Beijing!

Yefu Mountain National Forest Park in Lujiang county, Anhui province. (Photo – theasian.asia)

The unmistakable conclusion is that we cannot halt global warming without reducing emissions and we cannot plant our way out of climate change.

 

National Tree Day Sunday July 28th Come and meet the ‘friends’ at Clifford Dr, Drouin, 10 – 12noon All of Australia’s capital cities and many regional centres are conducting urban tree planting projects to provide a multitude of benefits to the environment, the economy and the community.