Carbon is the chemical element at the root of life on earth. Indeed, all living things are essentially made of the stuff.
Humans and animals eat carbon-based foods and exhale some of the carbon they contain as CO2, a gaseous mix of carbon and oxygen.
Trees and plants breathe in the CO2 and use energy from the sun to separate the carbon from the oxygen.
The carbon is used to build their trunks, stalks and foliage, and the oxygen is released to be breathed in by humans and animals. And so on...
When a tree or plant eventually dies, it will rot or be burned or eaten, and most of its stored carbon is returned to the atmosphere as CO2.
The rest decomposes into the ground to become part of the soil.
This neat solar-powered process is known as the carbon cycle. It's a cycle that makes life possible and also affects the temperature of the planet, because the more CO2 there is in the air, the more of the sun's energy gets trapped in the atmosphere.
Humans are disrupting this cycle in two ways. First, we're burning oil, coal and gas, which are made of carbon soaked up by plants from previous eras.
Second, we're destroying forests to clear farmland or collect firewood and timber. When we do this, much of the carbon stored in the trees and soils over the centuries is released back into the atmosphere. In addition, the forest stops absorbing CO2 from the air. (If the cleared land is used to ranch cattle, there will be a further impact, as cows belch up large volumes of globe-warming methane.)
Deforestation is sometimes ignored in the global warming debate but it accounts for almost a fifth of the human impact on the climate. That's more than all the world's cars and planes, more than the entire USA, or the whole of China.
Tropical deforestation - the destruction of rainforests - accounts for the majority of these emissions. That's partly because regions like Europe cleared many of their forests centuries ago. But it's also because the sun-soaked forests of the tropics are more effective carbon stores than those in temperate areas.
For rainforest nations such as Brazil and Indonesia, carbon emissions from deforestation can outstrip those from fossil fuels. And that's not to mention the massive impact on biodiversity - the rainforests are home to more than half the world's species, from irradescent butterflies to awe-inspiring beasts such as gorillas and jaguars.
The challenge is finding a way to stop this destruction. If we don't, then the world might not be able to avoid runaway global warming - even if we succeed in slashing our fossil fuel use.
Ironically, one of the 'feedback loops' that scientists fear could cause such runaway warming is the potential collapse of rainforest ecosystems. The concern is that, as the planet warms, precipitation patterns could change, taking the rain out of the rainforests. If this happened for long enough, the forest could die off - killing countless species and releasing even larger volumes of CO2 into the atmosphere.
The solution to deforestation will probably be based on western nations paying tropical countries to protect their forests - a rent for their 'carbon services', as it were, and an alternative to income from logging and farming. There are many details to work out but hopefully new and exciting projects in Peru will help the world to see that it can be done.
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