** REferences to update**
- part 5 - tipping points
"It’s very important to keep repeating these concerns [about the Amazon]. There are a number of tipping points, which are not far away. We can’t see exactly where they are, but we know they are very close. It means we have to do things right away. Unfortunately that is not what is happening. There are people denying we even have a problem."
Philip Fearnside, Professor at Brazil’s National Institute of Amazonian Research
Since the onset of agriculture about 12,000 years ago, the number of trees worldwide has dropped by 46% - that’s the loss of a staggering 3 trillion trees. Forest cover is now at only 68% of what it was in preindustrial times, and around 15 billion trees are now being cut down each year. In the temperate zone, we retain only 1-2% of the original forest cover. The majority of tropical deforestation is driven by our demand for just four commodities: beef, soy, palm oil, and wood products. Palm oil is found in a myriad of popular products such as soaps, shampoo, chocolate, bread and even crisps.
In the Amazon - home to one in ten known species - a lethal combination of human-caused burning and climate change have now resulted in the destruction of nearly one-fifth of the rainforest: 17% across the entire Amazon basin and approaching 20% in the Brazilian Amazon. Deforestation of the Brazilian Amazon is now occurring faster than three football fields a minute, pushing the world’s biggest rainforest closer to a dangerous tipping point beyond which it would not be able to recover. In July 2019 alone, Brazil lost an area of forest bigger than the size of Greater London.
Deforestation is not only severely compromising the Earth’s natural ability to protect us from the devastating impacts of climate change; it is actually making global heating worse. Natural processes such as tree growth remove about half of human carbon dioxide emissions from the atmosphere every year. In this way, trees act as what’s called a carbon ‘sink’. The fewer trees, the less carbon dioxide can be mopped up.
However, new research has found that due to higher temperatures, droughts and deforestation, trees in the tropics are now taking up a third less carbon than they did in the 1990s. Simon Lewis, Professor in the School of Geography at Leeds University, said: "We’ve found that one of the most worrying impacts of climate change has already begun. This is decades ahead of even the most pessimistic climate models. Humans have been lucky so far, as tropical forests are mopping up lots of our pollution, but they can’t keep doing that indefinitely. We need to curb fossil fuel emissions before the global carbon cycle starts working against us. The time for action is now."
To make matters worse, when cleared trees are burnt, enormous quantities of stored carbon are released back into the atmosphere. It has been calculated that clearing carbon-rich forests releases the same amount of carbon every year as driving 600 million cars. Indeed, global deforestation is responsible for nearly a fifth of all greenhouse gas emissions.
Worrying new research has revealed that up to one fifth (20%) of the Amazon rainforest is now emitting more carbon dioxide than it absorbs, suggesting that it could be "showing the beginnings of a major tipping point", past which the forest would lose its ability to renew itself. The authors had previously calculated that a tipping point could occur at around 20-25% deforestation (see section on tipping points). They warn that in the next 30 years, more than half of the Amazon could transform from rainforest to savanna. Indeed, another study has revealed that it is possible that the entire Amazon will rapidly decline and to go from a carbon ‘sink’ to a carbon ‘source’ within the next few decades.
If forests become sources of carbon rather than absorbers of it, their role would switch from one of slowing climate change, to one of amplifying it.
Forests and woodlands do more than capture carbon. They are also important across the globe in preventing floods, stopping soil erosion, cleaning air and water, providing habitats for wildlife and food and other resources for local people. Indeed, tropical rainforests are the most biodiverse areas on the planet. Losing these forests would greatly contribute to the loss of other species.