They grow faster and absorb more CO2. The trees of the world's most famous park hide an incredible secret: a group of researchers has discovered it in New York.
Not only is it the green lung of Manhattan, but it is a symbol known throughout the world, the backdrop of countless films and one of the unmissable stops on any trip to New York. With its magnificent autumn colours, the frozen lake that fills with skaters in winter and the explosion of greenery that makes its way between the skyscrapers in the warmer months, Central Park is shrouded in an aura of magic. And now researchers are proving it too: this park truly has something magical about it.
"In the green heart of Manhattan, man-planted trees would grow as much as eight times faster than their closest relatives planted in the surrounding countryside," reports the meteorology website 3Bmeteo.com. The discovery was made by the research team led by Columbia University in New York, which in the spring of 2007 and that of 2008 planted red oak seedlings in four different locations: in Central Park, in two woodland areas in the Hudson Valley, and in the Catskill Mountains about 160 kilometres north of Manhattan. By the end of summer, the trees planted in the city had already developed a biomass eight times greater than the others, owing mainly to the extraordinary growth of their foliage, which resulted in a photosynthetic area ten times larger.
In part, this is due to the amount of nitrogen in the air, which acts as a fertiliser: in cities it is higher because of pollution. However, as Carlo Migliore of 3Bmeteo.com explains, the main reason for the plants' growth would be the "urban heat generated in city environments which, compared to uninhabited areas, produce a greater amount of heat by trapping the sun's rays in concrete and road surfaces." In Manhattan, night-time temperatures are up to 8 degrees higher than in the surrounding rural areas.
What the researchers discovered is useful for understanding how organisms adapt to warmer temperatures, and therefore to global warming as well. The forests of the New York area are already evolving, with northern species making way for southern ones. There is something positive: having more leaves, city trees are able to absorb more carbon dioxide. New York has high levels of pollution, but 5.2 million trees working tirelessly to return oxygen to the city.