By Alex Fernández Muerza
Trees, like other plants, use photosynthesis to transform energy from sunlight, water and carbon dioxide - one of the main greenhouse gases involved in climate change - into sugars and starches for use as food. Chlorophyll, for its part, a green pigment present in the leaves, is responsible for absorbing light.
While this process takes place, the trees release oxygen, although not all specimens emit the same amount of this gas. This depends on several factors, such as the species to which they belong, their age, where they are found or how high they grow. But to get an idea, we can take the sycamore as a reference - its scientific name isFicus sycomorus-, a moracea about twelve meters high that produces around 100 kilos of oxygen per year. In that time, a human being breathes approximately 9.5 tons of air. Of course, oxygen only represents about 23% and, in addition, only a little more than a third of it can be extracted from each breath. This equates to about 730 kilos of oxygen per year. Therefore, it would take seven or eight trees, at least in the case of sycamores, to satisfy our ration of vital gas.
In 2015, a team of researchers from different institutions coordinated by Thomas Crowther, an expert in forestry and environmental studies at Yale University, published a study inNature where they claimed that the planet is home to three billion trees, more than 400 per person. In it they warned that 43% are in tropical areas and that about 15,000 million of them are lost each year.