Trees and carbon storage

Since the industrial revolution, the amount of carbon dioxide (CO₂) in the atmosphere has been steadily increasing. This has mostly been due to the burning of fossil fuels, such as coal and oil, and land clearing, especially when it involves burning forest areas.

The problem with carbon dioxide is that it’s a greenhouse gas.

Greenhouse gases form a layer around the earth and trap the warmth from the sun’s radiation, just like a greenhouse with a glass roof.

Although the ‘greenhouse effect’ is necessary to keep the average surface temperature warm enough to sustain life on earth, a continual increase in atmospheric CO₂ has the effect of causing an ‘enhanced greenhouse effect’ where the temperature gradually increases year after year.

This is sometimes referred to as ‘global warming’, one of the main indicators that the planet has entered a period of climate change which is likely to have far-reaching consequences on the natural environment.

Trees, however, help to reduce the level of CO₂ in the air through the process of photosynthesis. They do this by breathing in CO₂ through their leaves, combining it with water from the ground and producing the food products needed for growth. A by-product of this process is oxygen, which is breathed out through the leaves.

Fast growing forests can remove an enormous amount of CO₂ from the air. For example, one hectare of pine forest takes an average of 7.5 tonnes of CO₂ out of the air each year. Other types of forests, such as plantation hardwoods and native forests, tend to remove less CO₂, since the net consumption depends on how fast the trees are growing and how much CO₂ is being released back into the air through decomposition.

Basically, about half the weight of dry wood in all timber species is made up of carbon. The carbon remains locked up in the cells until the wood either decomposes or is destroyed by fire.

Tim Flannery, environmentalist and former Australian of the Year, expressed this concept in a speech he gave in 2008 when he said: ‘A lot of people somehow imagine trees grow from the ground, they don’t, they grow from the air, they are congealed carbon dioxide and all of that carbon is stored in them, otherwise it would be out there in the atmosphere heating our planet.’