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Rainforests and Global Warming

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Published: 15Dec2008
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Introduction

This article is the first in a series of articles which will take the reader on an alphabetic journey on global warming, commencing with A for Amazon Rainforest

The phrase global warming is a term that has been in common usage for some time and usually refers to the warming of Earth's atmosphere, and which also implies a man-made or human influence.

Earth's atmosphere is comprised of many gases, oxygen, nitrogen, carbon dioxide and water vapour to name a few. These gases are collectively called greenhouse gases and they keep the Earth's temperature at a comfortable 15 degrees Celsius, without them Earth would be a chilly - 18 degrees Celsius. Since pre-industrial times, usually taken to be around 1750 we know from ice core records that Carbon Dioxide (CO2) levels were around 280 ppm, that's 280 parts of CO2 per million parts of air. As industrialisation got under way mankind started to farm the land more intensely than ever before, deforest for agriculture and settlements, and later since around 1850 or so, burn fossil fuels for energy and transport which have added considerably to greenhouse gas levels, particularly Co2.

This has resulted in CO2 levels increasing to around 385 ppm, an increase of around 37% from pre-industrial levels mainly as a result of burning fossil fuels.

How do we know this? Well, data from ice core records that go back at least 650,000 years now show us that CO2 levels have fluctuated naturally during this time between 280 and 300 ppm. CO2 levels have also been measured accurately from the top of Mauna Loa Volcano in Hawaii since 1958, and results show an increase in CO2 levels from 315 ppm to 385 ppm since that time. Therefore CO2 is now at 85 ppm more than it has been for at least 650,000 years of Earth's history. It is a known scientific fact that higher levels of greenhouse gases will lead to higher temperatures, which appears to be happening now. The world has warmed by an average of 0.74 degrees during the last 100 years or so.

As a result of this warming, polar ice has started to decrease and melt, and so are Earth's land based glaciers. This in turn is causing sea levels to rise which is putting low lying islands at risk of flooding or total submersion, and will eventually threaten more and more of the worlds coastal cities and regions.

As Earth's atmosphere starts to warm, the warming itself may cause further positive feedback mechanisms to kick in. A warmer atmosphere holds more water vapour, which is itself a powerful greenhouse gas. This will in turn cause further warming, and so on.

Melting ice means that more sunlight is absorbed by the surrounding "darker" water and land, meaning further warming, and more melting ice. Methane deposits currently held in a frozen but stable state under the sea and under the permafrost maybe released as the oceans warm and permafrost melts, which will cause further warming as methane is a potent greenhouse gas etc etc.

Where better place to start this A-Z journey on global warming than with The Amazon Rainforest, which has an incredibly important role to play in maintaining a balance in the Earth's climate. The Amazon as well as other rainforests are inextricably linked to the issue of global warming and have a considerable influence on Earth's climate.

Amazon Rainforest Facts

The Amazon river basin contains the largest rainforest on Earth and covers approximately 40% of the South American continent. The Amazon Rainforest is located within eight countries, Brazil contains 60% of the forest, with Colombia, Peru, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guyana containing the rest.

The Amazon forest is a natural reservoir of genetic diversity, containing the largest and most species rich tract of tropical rainforest that exists. The Amazon contains an amazing thirty-percent of Earth's species. One square kilometre of Amazon can contain about 90,000 tons of living plants! It's also amazing to consider that one in five of all the birds in the world make the rainforest their home.

The Amazon basin is drained by the Amazon river, the worlds second longest after the Nile and the river is essentially the lifeline of the forest. The river is the most voluminous on Earth.

A few hundred years ago tropical rainforests covered as much as 12% of the Earth's land surface, but today the figure is less than 5%. The largest stretch of rainforest can be found in the Amazon river basin, over half of which lies in Brazil.

Why is the Amazon Rainforest so important in the context of global warming?

The rainforest acts as a major store of carbon and produces enormous amounts of oxygen. The Amazon has been referred to as "The lungs of the Earth" because of its affect on the climate. The way this is achieved is of course through photosynthesis, the process by which green plants/trees use the energy from sunlight to produce food by taking CO2 from the air and water and converting them to carbon. The by-product of this is oxygen.

The Amazon therefore helps recycle CO2 by turning it into oxygen, and its estimated that the Amazon produces about 20% of this essential gas for Earth's atmosphere.

Trees, plants and CO2

Levels of CO2 in the atmosphere have been measured since 1958 from a monitoring station located on Mauna Loa volcano in Hawaii and they show sharp annual increases and decreases in CO2 levels, similar to the tooth on a saw. The readings almost mimic a breath of air being taken in and out; it's almost as if the Earth is breathing. The readings correspond to the amount of vegetation on the planet (most of which is contained in the Northern Hemisphere, as the landmass there is greater), taking in CO2, and giving out oxygen. During the Northern Hemisphere summer, when the Earth is tilted toward the sun, the Earth's vegetation is able to photosynthesise resulting in an uptake of CO2, causing worldwide CO2 levels to drop. During winter, when the Earth's axis is tilted away from the sun, the opposite happens causing CO2 levels to rise again.

When one becomes aware of the correlation between the Earth's vegetation and CO2 levels, it is easy to understand why the Amazon, and rainforests in general are such an important part of Earth's ecosystem. If global warming is to be tackled, the Amazon, and other rainforests must be saved.

This article is taken from a book entitled The A-Z of Global Warming which was published by Schmall World Publishing on 25th September 2008. Further information can be obtained from the following website- http://www.a-zofglobalwarming.com

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