Plants suck 123 billion tonnes of CO2 a year

Measurements were taken from 253 flux towers around the world, including this one high above the tropical forest in Ghana.

Trees, shrubs and grasses around the world take in 123 billion tonnes of carbon dioxide a year through photosynthesis, an international research team has calculated.

Altaf Arain, an associate professor of geography and earth sciences at McMaster University in Hamilton, said:

• The results published online in Science Xpress on Monday mark the first time researchers have based such a calculation on such a large number of actual measurements instead of mainly computer modelling.
• During photosynthesis, plants take in carbon dioxide, storing it as energy in the form of sugars. However, they also release large amounts of carbon dioxide while consuming the sugars as energy for growth and sustaining themselves or when they die and decompose — a process known as respiration.
• Plant photosynthesis and respiration together control a large part of the carbon exchanged between the land and air. That may partly offset some of the carbon released through the burning of fossil fuels, estimated to be around seven billion tonnes a year. However, plants ultimately give off nearly as much carbon dioxide as they consume.
• Rainfall important – the combined data from around the world showed that availability of water, including rainfall, plays a large role in the amount of photosynthesis that plants undergo.
• Respiration response to the temperature was the same in various regions across the world, including tropics and the temperate forests.

Source: Plants suck 123 billion tonnes of CO2 a year – cbc.ca

Date: 06 July 2010