A cura di Billy Pilgrim
I danni prodotti dal riscaldamento globale sono noti e destano preoccupazione. Tuttavia, contrariamente all’opinione comune, il riscaldamento globale genera anche alcuni benefici. Ne parla Matt Ridley in un articolo su Human Progress, in cui evidenzia come i crescenti livelli di CO2 nell’atmosfera stiano causando un aumento della vegetazione sulla terra.
Amid all the talk of an imminent planetary catastrophe caused by emissions of carbon dioxide, another fact is often ignored: global greening is happening faster than climate change. The amount of vegetation growing on the earth has been increasing every year for at least 30 years. The evidence comes from the growth rate of plants and from satellite data.
In 2016 a paper was published by 32 authors from 24 institutions in eight countries that analysed satellite data and concluded that there had been a roughly 14% increase in green vegetation over 30 years. The study attributed 70% of this increase to the extra carbon dioxide in the atmosphere. The lead author on the study, Zaichun Zhu of Beijing University, says this is equivalent to adding a new continent of green vegetation twice the size of the mainland United States.
Global greening has affected all ecosystems – from arctic tundra to coral reefs to plankton to tropical rain forests – but shows up most strongly in arid places like the Sahel region of Africa, where desertification has largely now reversed. This is because plants lose less water in the process of absorbing carbon dioxide if the concentration of carbon dioxide is higher. Ecosystems and farms will be less water-stressed at the end of this century than they are today during periods of low rainfall.
There should have been no surprise about this news. Thousands of experiments have been conducted over many years in which levels of CO2 had been increased over crops or wild ecosystems and boosted their growth. The owners of commercial greenhouses usually pump CO2 into the air to speed up the growth of plants. CO2 is plant food.
This greening is good news. It means more food for insects and deer, for elephants and mice, for fish and whales. It means higher yields for farmers; indeed, the effect has probably added about $3 trillion to farm incomes over the last 30 years. So less land is needed to feed the human population and more can be spared for wildlife instead.
Immagine: Miroslav Horàk