Trees, the main allies to face the phenomenon of urban heat islands

03/11/2020

The "urban heat islands" are the result of the large extensions of asphalt that cover the metropolis and that, due to their low reflectivity and almost no capacity to capture water, result in microclimates that reach temperatures of more than 40 degrees Celsius (104 F).

In view of this, nature itself continues to have one of its greatest allies, the trees, whose shade becomes a refreshing oasis in which the ambient temperature is reduced by 8 to 10ºC (46 to 50 F). Hence the importance of the different programs that the Mexican Government is carrying out together with local authorities to recover green areas where asphalt and concrete predominate.

In the case of Mexico City, the phenomenon of "urban heat islands" has had a particular increase during the last 50 years, after the growth of the urban stain has been exponential since the 1970s.

This is without counting the previous work that previous administrations have carried out to dry out the lacustrine nature of this capital and that has brought as a consequence the disappearance of important bodies of water such as the channels of La Viga, Chalco, and the rivers of La Piedad and Churubusco, among many others that today are tubed.

That is why the current federal and local administration have focused their efforts on the recovery of green spaces, through various actions such as those outlined in the Environmental and Climate Change Program of Mexico City 2019-2024 and have promoted campaigns such as the so-called Green Challenge, whose first stage was expected to plant more than 10 million trees from June 2019 to November 2020.

These actions are more than urgent today, also due to the increase in the temperature recorded in recent years that has broken historical records. The participation of Mexico City's own inhabitants is also indispensable. With simple actions, they can help the recovery of the green areas required by this capital.

As observed by researchers at UNAM, simple actions such as placing plant pots on balconies and rooftops, as well as caring for and planting trees on ridges and sidewalks where conditions allow, can become small contributions that will mean a big change in reversing these "urban heat islands".

Of course, actions of this nature must be accompanied by adequate advice and care to not violate urban regulations, since it is not a question of planting any plant on balconies or patios, much less opening a hole in a sidewalk or planting any species of tree, since it is a federal area one must proceed as prescribed by law.

To do this, you should consult the current regulations on green areas and even take advantage of many of the programs that have been launched such as Reto Verde, in Mexico City, which have developed manuals to green urban and conservation areas and which recommend 47 species of trees, 21 types of shrubs, six of groundcovers, 12 herbaceous, in the case of urbanized areas.

To give us an idea of the impact that a tree can generate, Rob McDonald himself, a researcher at The Nature Conservancy, has revealed in several of his articles the cooling power of trees, which can help cool the environment in two ways: through the shade they provide to the pavement, thus preventing it from being heated by the sun, and through evapotranspiration, helping to maintain a cool microclimate thanks to the moisture emanating from their leaves.

Other benefits include psychological, since "taking a regular walk in nature can help reduce stress and blood pressure and can help counteract depression," as revealed by McDonald in a publication of The Nation's Health.

Therefore, the situation of staying at home, as we are now due to the health emergency caused by the coronavirus COVID-19, becomes again an opportunity to engage in actions that, besides generating personal satisfaction, can bring environmental benefits, by rescuing green spaces, whether it is a garden, a patio or even a balcony where green plants and shrubs can be placed.

In the end, this opportunity could help the environment with simple actions such as adopting or planting a tree, as long as care is taken and the characteristics of the trees to be planted are considered: such as whether it is a tree or a bush, whether it is a shade or an ornamental tree, whether it grows fast or slow, whether it is native or exotic, whether it grows fast or slow, and even how much its crown grows or how much it spreads its roots, because care must be taken not to damage sidewalks, ducts or pipes, as well as electrical wiring and even buildings.

In this way, one would also be attending to one of the recommendations of the World Health Organization, which states that for each inhabitant a minimum of 16 square meters of the green area should be guaranteed to ensure their well-being.