The Amazon is vital to the global ecosystem but it is nobody’s ‘lung’

The idea that 20% of atmospheric oxygen comes from the Amazon is widely stated – the region has been described as the ‘lungs of the world’. There are millions of websites making the claim, but it is fake news.

Trees pump out oxygen only during daylight. At night they respire by drawing in oxygen and releasing carbon dioxide. The oxygen we breathe came from ancient microbes producing rocks (like limestone) that locked away carbon dioxide. People have been buying oxygen cylinders to breathe when the air runs out, but if everything in the world were suddenly to combust, it would make no discernible difference to the levels of oxygen in the air.

The average tree locks away about a tonne of carbon, but trees die and, as they decompose, every atom of carbon trapped in the tree’s tissues is released as carbon dioxide. Between germination and the end of its existence, a tropical tree leaves no legacy of oxygen.

We each put about 6.5 tonnes of carbon into the atmosphere every year, a national total of over 400 million tonnes. You’d need half a billion trees to absorb this. Since forests contain about 2,000 trees per hectare, it would cover 900 square miles – larger than Leicestershire. You’d need to repeat that every year so, over the next 60 years, the whole of England would be covered by forest. To complete the cycle, you’d fell half a billion mature trees each year and store the seasoned timber for eternity.  

This provides a clue to something we could do: timber needs to be utilised so it doesn’t break down. Make houses, bus-shelters, public walkways, boats and buildings, with wood. The Treet building in Bergen was the first wooden skyscraper, standing 49 metres high, and there are plans in Japan for a largely wooden skyscraper to mark the 350th anniversary of the Sumitomo Forestry company. Appropriately, it will be 350 metres tall.

Does this mean the decimation of the Amazon doesn’t matter? Of course not – rainforests are a crucial component of the global ecosystem. They are rich in spectacular wildlife, jaguars and tapirs, sloths and macaws; and have given us valuable products from rubber and rattan to cocoa and kola nuts. Modern medicine derives about 25% of pharmaceuticals from rainforest plants, of which curare is the best known. One hectare of rainforest will typically contain over 2,000 different species of vascular plants, 750 of them trees, and 99% of these species have yet to be analysed for medicaments they may contain.

We once had bison and bear, wolves and wolverines, elk and auroch, but Bronze Age farmers destroyed about half our forests, so only 10% of England is left as woodland. The draining of the fens destroyed an ecosystem so that land could be profitably farmed; Brazil is only trying to catch us up. Don’t blame thoughtless developers, hungry for money, until you have paused to consider what we have done. People regard the Lake District as natural and unspoiled – but it began as rich forest, and today’s bare hillsides are the result of early industries, mining copper, zinc and lead, iron and arsenic. The original forests were wiped out, burned in the toxic furnaces of our forebears.

One of the worst polluters in the world is – Australia. For all its reputation as liberal and forward-thinking, Australia is the world’s second biggest exporter of coal and their government long promoted the view that anthropogenic global warming didn’t exist. China is building coal-fired power stations (many of them using Australian coal) at the rate of one per week for the next ten years. There was much excitement in March 2020 when the world’s first tanker carrying liquid hydrogen was launched. But where did it come from? The electricity to split the atoms of liquid water into hydrogen and oxygen was created by burning ignite (brown coal) in huge amounts at Latrobe Valley in Victoria, Australia. It’s the filthiest and most polluting fuel on earth, releasing five times as much CO₂ as natural gas, contaminating the environment with heavy metals. Those supposedly ‘clean’ vehicles in Japan which are burning this fuel are actually the most damaging to the environment anywhere in the world.  

The UK produces only 1% of the world’s CO₂ and most industrialised countries have a carbon footprint twice the size of ours (Australians produce almost three time as much as us).

Conserving all rain forests is a matter of high priority. But we cannot be self-righteous about it - and we need to understand the real reasons why.   

Pic: Diego Rezende

Professor Ford is an award-winning research biologist, lecturer and best-selling author. His latest book is Nonscience Returns.