One billion hectares of forest against global warming

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Global temperatures may increase of 1.5°C by 2030 – as compared to pre-industrial levels – if current tendencies keep maintaining the same direction. However, trees can help containing this climatic crisis. A new research shows that the addition of circa one billion hectares of forest may remove 205 gigatonnes of the approximate 300 gigatonnes of carbon that have been released into the atmosphere since the 1800s.

Biologist Thomas Crowther of ETH University in Zurich has published a research on Science in 2019, in which he explains how many trees should be planted in order to help regulate the climate, considering that on the earth there should be enough space for such an intervention. In 2015 the scientist had been able to count for the first time the number of trees on the planet, and he had reached a staggering figure of 3.000 billion, which is over seven times more than a previous estimate made by NASA. In order to collect the data he combined both field research and satellite images. 

The study evaluates the fact that on the earth there is space enough to grow further 900 million hectares of trees (which is roughly the size of the USA), to be added to the current 2.8 billion hectares. In order to reach this figure, researchers have analysed forests, the soil and the climate and in order to consider how trees could grow, excluding cities and lands inhabited by humans.

According to researchers, the level of forestation is feasible if these results could influence political strategies, because the re-establishment of the right ecosystem could be the best solution available to contrast climate change.

Other researchers think that this method is too simplistic and imperfect, because new forests can indeed help absorbing excess carbon emissions, but the only way to stabilise the climate is to reduce to zero the emissions of greenhouse gases. As a matter of fact, each forest absorbs CO2 with its own typical efficacy. For example, the capacity of trees to reduce CO2 depends on climatic conditions: when a persistent drought occurs, a forest’s ability to absorb carbon is critically interrupted. 

The point is that during a prolonged drought some forests – especially those located in northern Europe and around the tropics – can temporarily emit CO2. Moreover, when a forest reaches its maturity after a century of life and as a consequence trees both grow and die, the woodland emits approximately the same amount of CO2 as that which it absorbs. That is to say, it is hard to estimate how much carbon these new forests could actually absorb. Not to mention that the forestation of all identified locations is unrealistic. 

Nowadays the activity of planting trees is recognised as a fundamental action to preserve life on earth, because forests are beneficial vehicles for the absorption of carbon dioxide, they help creating a better biodiversity and quality of life.

Photo: ETH Zurigo / Crowther Lab
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Umberto Andolfato is the headmaster of ITT CAT Carlo Brazzi in Milan and Vice President of AIAPP Lombardy. He is also a freelance worker who has developed significant experience on landscape both on a private and public level, in Italy and abroad. He has started getting involved in landscape studies in 1994, from 2010 to 2016 he has been professor of Landscape Architecture at Politecnico di Milano, where he has developed research and projects on Landscape and smart land. He is also professor of Garden design at the Scuola Arte e Messaggio. Since 2015 he is consultant for Myplant & Garden and responsible of Myplantech.