The slow collapse of the world’s forests

It is hoped that the upcoming COP21 climate talks in Paris will produce legally binding limits to emissions of carbon dioxide, country by country. The Earth is already an average of more than one degree warmer than in pre-industrial times. Areas of western North America are 1.5 degrees warmer. The result is widespread death of pines and spruce. Billions of dead trees are found from Alaska all the way down to Mexico. Reese Halter describes the slow collapse of world forests underway and evident now. This underlines the urgency for a strong outcome from the imminent Paris talks.

Listen to the audio on the ABC website


Robyn Williams: And so from London to California and a more flamboyant take on the predicament we face. Dr Reese Halter broadcasts in the USA and did his PhD in Melbourne, on trees.

Reese Halter: Planet Earth’s forests are breathtaking. Did you know that ancient trees are the greatest carbon warehouses to have ever evolved? For every metric tonne of ancient wood created, 1.5 metric tonnes of carbon dioxide was removed from the atmosphere, and one metric tonne of oxygen was released. Frighteningly, Earth’s forests are dying on every forested continent, from warming temperatures and associated insect infestations, prolonged heatwaves, intense wildfires, and vicious droughts.

It’s crucial to understand why we as a species want to stay away from crossing the two-degrees Celsius threshold because thereafter, according to a 2009 International Union of Forest Research Report, if Earth passes the 2.5-degrees Celsius temperature threshold above preindustrial times, forests globally could lose their entire carbon storage capacity. In other words, instead of removing and storing carbon, they would release all their stored carbon. The result of crossing that threshold would be an uninhabitable world for civilisation as we know it.

Already across parts of western North America that have heated up above 1.5 degrees Celsius, the ominous tell-tales vividly reveal the outcome; mass death of mountain forests. When nature’s cold blanket was removed, populations of indigenous bark beetles exploded into the trillions. There are at least 30 billion dead pines and spruce from Alaska and the Yukon extending thousands of kilometres into Mexico and west into California, and everywhere in between. Those forests were vital as living snow forests, slowly releasing water in the springtime via trillions of tree roots, sustaining 50 million people across western North America, including California and the eighth largest economy on the globe.

In Australia, ancient trees are dying too. In Western Australia the iconic tuart, wandoo, flooded gum, marri and WA peppermints have begun dying from extreme heat waves and prolonged droughts. Near Perth, over 16,000 hectares of jarrah forests have collapsed, 10 times greater than previously recorded death rates. The knock-on effect, in 2010 and 2011 the Carnaby black cockatoo population in the greater Perth area crashed by 34%. No big trees, no food equals death.

In Tasmania, extreme heat in the north in 2012 and 2013 resulted in white and blue gums cooking to death. My colleagues dubbed it the ginger syndrome from the blood-like discolouring of the oozing bark. The Cooma-Monaro region of New South Wales also shows the eerie death of an entire iconic landscape of eucalyptus, an area almost 2,000 square kilometres.

Rising greenhouse gases from burning climate altering fossil fuels have begun to destroy the Amazon rainforest with vengeance. In 2005, 1.9 million square kilometres experienced intense drought and winds that blew down half a billion mature trees. Later that year, a one-in-100-year drought event prevented trees from absorbing 1.5 billion metric tonnes of carbon dioxide. And, as the dead, blown-down trees decomposed, they released 5 billion metric tonnes of greenhouse gases.

In 2007, an extreme drought in southeast Amazonia created epic wildfires, 10 times more than the average, an area equivalent to burning 1 million World Cup Brazilian soccer fields. In 2010, a subcontinental drought enveloped 3.5 million square kilometres of the Amazon Basin, a gigantic swathe of mature forest died and released 8 billion metric tonnes of carbon dioxide, or what the United States spends in a year.

Not only has the Amazon lost billions of oxygen producing mature trees since 2005, but also their phenomenal ability to make daily rain clouds, regulating the water cycle, providing massive afternoon white cloud surfaces, reflecting incoming solar radiation, ameliorating Earth’s temperatures. Instead, solar radiation penetrates denuded forest floors all day long, heating them and in turn heating our atmosphere.

The climate delegates in Bonn Germany and later this month in Paris at the climate talks must understand that a global 25% greenhouse gas reduction by 2020, then a 40% reduction by 2030, followed by a complete phasing out of fossil fuels by 2050 won’t prevent more wild weather. But it might ensure that our civilisation, with 9 billion people, can survive to mid-century.

For The Science Show, I’m Dr Reese Halter in Los Angeles, California.

Robyn Williams: And I think he means it.

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