How One City Is Using Plant Walls To Curb Rising Temperatures

Spain's capital city of Madrid is known for offering historic buildings, impressive museums, and exquisite regional cuisine. But, due to a combination of geography and a phenomenon known as "heat island effect," Madrid is also one of the hottest, driest cities in the world. As global temperatures continue to rise, officials in Madrid have become increasingly concerned. As Juan Azcarate, a Madrid official in charge of efforts to fight climate change, told NPR, "We are a city where the main risks [of climate change] will be related to heat and the scarcity of water resources."  

According to the Environmental Protection Agency (EPA), heat island effect occurs when heat-absorbent materials like asphalt and concrete--commonly found in urban areas--trap heat within the city. This can cause cities like Madrid to be several degrees hotter than surrounding, non-urban areas. This is especially troubling considering that, according to NPR, scientists predict that by 2050, Madrid will have 20 percent less rainfall and 20 percent more unusually hot days.

But Madrid is busy creating solutions to their temperature problem. And almost all of those solutions have one ingredient in common: plants. From city-wide tree plantings to rooftop gardens, Madrid is literally going green in order to stay cool. 

It's a sensible approach to take. Due to a recent recession, Madrid doesn't have a lot of money to invest in high-tech heat solutions. Plants are a relatively inexpensive, provably effective way to reduce the impact of heat island effect. According to the EPA, rooftop gardens serve to insulate the roofs below them, thus preventing buildings from absorbing too much heat. As an added bonus, this can also save on energy costs. Trees and vegetation planted throughout a city can cool the air via the natural process of  evapotranspiration and by providing shade. Such plants also clean particulates from the air, helping to curb air pollution; a common problem in almost every large city. 

While it may be incidental, plants also come with another benefit: beauty. At the famous CaixaForum arts foundation building, located amongst other famous art museums on the stretch of Paseo del Prado thoroughfare known as "museum mile," a vertical wall of over 300 native plant species stands near the main building's entrance. Since the vertical garden's installation in 2008, it has become a tourist attraction largely because of its striking appearance. 

The CaixaForum's Director, Isabel Fuentes, told NPR that the wall's many benefits, including its beauty, make it an asset to Madrid. "You can see it changing — in summer, it's an incredible panel of colors. It helps to avoid noise, and it also helps to fight contamination because 460 [square] meters of plants give a considerable amount of oxygen to the air."

In 2003, when an intrusive and neglected highway was rerouted to underground tunnels and trees were planted above, the resulting park, called Madrid Río, became one of the most popular destinations in the city. With the success of the CaixaForum's vertical garden and the Madrid Rio, it isn't hard to imagine that tourism in Madrid could see an upswing, should the city decide to create similar installations in the coming years. With luck, Madrid may be able to cool itself, reduce pollution, and attract more people to the city simply by utilizing the natural power and beauty of plants.