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Forests The Big Story

About a quarter of the country’s 200 million people now live in areas where rainfall is below historic averages.3

But it’s not just the coast that’s drying up; it’s the Amazon itself. The region has had three severe droughts over the past decade. All signs point to climate change as the culprit. Forecasters say the area affected by severe drought may triple by the end of the century. In addition, unpredictable feedback loops could accelerate the cycle. Carbon dioxide (CO2) released from a dead and dying forest will further disrupt rainfall patterns and increase drought – which kills more trees, releasing more carbon in an endless cycle.

It turns out that drought in the Amazon and drought in São Paulo is not just coincidence. Researchers have found a direct link between deforestation in the country’s heartland and water shortages in the densely populated southeast.

Scientists use the term ‘aerial’ or ‘flying rivers’ to describe the forest’s role in continental rainfall patterns.

Here’s how it works. As humid air rises from the Amazon, water vapour condenses, lowering the air pressure. Since air moves from high to low pressure, humid air from the Atlantic is continually sucked into the centre of the continent. Researchers call this phenomenon the ‘biotic pump’. When the moisture-rich air mass moves west, it eventually slams into the Andean Cordillera, then arcs south and eventually east, bringing rain to southeast Brazil and northern Argentina. If the biotic pump is turned off, or loses its energy, that spells trouble. And that’s essentially what’s happening as the rainforest disappears.

As Alexandre Uezu, an ecologist with São Paulo’s Ecological Research Institute, explains: ‘Were it not for the flying rivers the whole area would be desert.’4

Although the pace of deforestation has slowed recently, the country is still losing more than 500,000 hectares of jungle every year.

Many Brazilians accept this as the price of prosperity. They wonder why they shouldn’t be free to exploit their resources just as North Americans and Europeans did centuries ago. Biodiversity Since the dawn of the colonial era, our exploitation of the natural world has led to the obliteration of forests on a massive scale. The consequences have been dire – for plants and animals, and for communities that depend on forests for their livelihoods. In the broadest sense, forests are key to maintaining comfortable living conditions on Earth by providing what economists call ‘environmental services’ – storing carbon, filtering air and water, preventing floods and helping to regulate climate. Woodlands are home to 80 per cent of the world’s terrestrial biodiversity. Trees also provide food and shelter as well as healing medicines. It is estimated that a quarter of modern medicines originate from forest plants.

As the human population grew, so did our economic activity. Initially, most of the loss was in temperate regions where agriculture first developed. Later, industrialization, with its ceaseless craving for energy and raw materials, added to the pressure.

At the time of the Roman Empire, dense forests covered 80 per cent of Europe. By the medieval era that figure had dropped to 40 per cent. And in some places it began much earlier. Half of England had been cleared of forest by 500 BCE. Today, ancient forests in Europe have all but vanished. In Ireland, for example, native woodlands make up just one per cent of the land area.

A similar pattern emerged in North America as settlers pushed west, razing forests rapidly during

New I nter nat io nalist ● April 2016 ● 13

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