Carbon is found in all living things –plants, animals, and humans- and nearly everywhere on the Earth. It is found in the atmosphere in the gas carbon dioxide, and dissolved in water in oceans and lakes. It is also found in soil, fossil fuels stored deep in ground, certain types of rocks, and in the shells of animals.
The carbon cycle is a complex cycle that circulates carbon between plants, animals and soils. The exchange of carbon between living and non-living things is very closely balanced. About 100 gigatonnes of carbon is captured by plants and oceans each year and about the same amount is released back into the environment. But this natural balance is disturbed by human activities such as burning fossil fuels and deforestation. Burning fossil fuels releases more carbon dioxide into the air. Deforestation or thin forest cover on the other hand, results in less carbon being removed from the atmosphere. It is clear from the pictures below where more carbon concentration (in Red colour) is seen in the atmosphere on the areas (Northern Hemisphere) where the forest cover is thin as compared to southern hemisphere where forest covers are sufficient. Green plants are known as carbon sinks. This means that they remove carbon from the atmosphere and store it.
source: NASA's Terra satellite.
Fig.2. [Red colour is the concentration of carbon dioxide. Concentration of CO2 is high where forest cover is thin.]
An international team of scientists, including researchers from CIFOR, have discovered that rainforest trees are getting bigger, storing more carbon from the atmosphere and slowing climate change.
According to the findings, tropical trees in undisturbed forests around the world are absorbing nearly a fifth of the carbon-dioxide (C02) released by burning fossil fuels. That is significantly more than the greenhouse gas emissions produced by the world’s transport sector.
The researchers estimate that remaining tropical forests remove a massive 4.8 billion tonnes of CO2 emissions from the atmosphere each year. This includes a previously unknown carbon sink in Africa, mopping up 1.2 billion tonnes of CO2 each year.
Published on February 19 in Nature, the 40-year study of African tropical forests, which account for one third of the world’s total tropical forest, shows that over decades each hectare of intact African forest has trapped an extra 0.6 tonnes of carbon per year.
Over the past 140 years, forest clearing and fossil-fuel burning have pushed up the atmosphere’s CO2 level by nearly 100 parts per million. The average surface temperature of the Northern Hemisphere has mirrored the rise in CO2. the 1990s was the warmest decade since the mid- 1800s, and 1998 the warmest year.
While all living plant matter absorbs CO2 as part of photosynthesis, trees process significantly more than smaller plants due to their large size and extensive root structures. In essence, trees, as kings of the plant world, have much more “woody biomass” to store CO2 than smaller plants, and as a result are considered nature’s most efficient “carbon sinks.”
According to the U.S. Department of Energy (DOE), tree species that grow quickly and live long are ideal carbon sinks.
Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area.
As the human population increases, forests are cleared for land and to provide firewood and timber to build houses. Today, almost all of the forests in Europe and North America have been cleared. The forests that remain are mostly in tropical areas like the Amazon region of Brazil and Southeast Asia.
The terrifying fact is that tropical forests are also being destroyed across the planet at accelerating rates. Current estimates indicate that as much as 17 million hectares of tropical forests are being destroyed each year, with up to six million hectares alone of that destruction taking place in the Brazilian Amazon. Saranda forest (one of the biggest forest area of Asia} of Jharkhand State of Eastern India is also being destroyed due illegal iron ore mining which is rampant in the area.
These forests are disappearing at an alarming rate. Data obtained from satellites show that the rate of destruction in these places has increased to between 64,000 square kilometres and 204,000 square kilometres. Scientists estimate that by 2030, 80 percent of the world’s forest will be lost forever. As wood decomposes or is burned for fuel, the carbon stored in trees goes back into the atmosphere as carbon dioxide. According to the scientists, deforestation accounts for about 20 per cent of the increase in the release of human related carbon dioxide since the beginning of the Industrial Revolution.
In the mid-1700s, people began to invent machines to help them do work. Like vehicles today, these machines burned fossil fuels for energy, which released green house gases into the atmosphere. More and more machines were built and used. In less than 200 years, the amount of carbon dioxide in the atmosphere increased from 280 parts per million to 360 parts per million. This means that if we divided a sample of air into a million parts, 360 of those parts would be carbon dioxide.
Forest scientists have come to a surprising conclusion regarding old growth forests and their majestic, mature trees: They’re not just relaxing in their arboreal old age, but are still actively taking in carbon dioxide from the atmosphere. The new study suggests that protecting old growth forests may be just as important as planting new trees in efforts to reduce carbon dioxide levels and fight global warming.
Previously, researchers believed that only young, fast-growing trees absorbed enough carbon dioxide to be considered significant “carbon sinks.” Old, crowded forests don’t allow for much new growth: The only new growth occurred in the small spaces that opened up when large old trees died and decomposed, releasing their accumulated carbon. The forests at large were therefore considered to be carbon neutral, and accounted as such in climate models [Nature News]. But the new study shows that the slow but continuous growth of old trees means that they continue to suck up more carbon than they release. These forests need to be protected not just because they help to absorb carbon dioxide, but also because destroying them could release huge stores of greenhouse gases.
Already we have pumped out enough greenhouse gases to warm the planet for many decades to come. We have created the environment in which our children and grandchildren are going to leave.
Bunyard, P.,1999. Eradicating the Amazon rainforests will wreak havoc on climate. The Ecologist. Volume.29, no.2.
National Geographic Magazine, September,2004.
Our Warming Planet, 2004. Times Editions, Singapore.