Planting 20% more trees in megacities would increase the benefits of urban forests, such as pollution reduction, energy reduction and carbon sequestration, according to a research in Ecological Modelling. The authors of the study, which was conducted at Parthenope University of Naples in Italy, say city planners, residents and other stakeholders must look within cities for natural resources and conserve the nature in the urban areas by planting additional trees. Their research has been chosen by an international scientific committee for the Atlas award.
Closely 10% of the world’s population resides in megacities – cities with no less than 10 million people. While those people habitually rely on nature outside of the city for their recreation and food, nature within the city in the form of urban forests can provide huge benefits. An urban forest contains the single tree in someone’s backyard, a wooded area in a public park or the row of trees along a street; joining these areas with more trees spreads the size of the urban forest.
Many well-known examples of urban forests in the megacities were analyzed, from Central Park in New York City to St. James’ Park in London and Bosque de Chapultepec in Mexico City. On average today, around 20% of the area of each of the world’s megacities is urban forest. But the recent study reveals that an additional 20% could be converted into forest – something that would transform residents’ lives for the better.
“By cultivating the trees within the city, residents and visitors get direct benefits,” explained Theodore Endreny, Ph.D., PH, PE, lead author of the paper and now professor of the Department of Environmental Resources Engineering at the State University of New York ESF campus. “They're getting an immediate cleansing of the air that's around them. They're getting that direct cooling from the tree, and even food and other products. There’s potential to increase the coverage of urban forests in our megacities, and that would make them more sustainable, better places to live.”
In the study, the team used a tool known as i-Tree Canopy to estimate the existing tree coverage in cities and the potential for additional urban forest cover. They listed out the benefits that would offer. They estimated the existing tree cover in ten megacities over five continents, looked at the benefits of urban forests – including eliminating pollution from the air, providing food and saving energy – and approximated the present-day value of those benefits at more than $500 million annually.
Developing a model for each megacity they estimated advantages such as reductions in air pollution, building energy, stormwater, and carbon emissions, and evaluated how those benefits altered as the tree cover was increased. The model took into consideration the local megacity tree cover, climate, human population, air pollution, energy use and purchasing power. The team was amazed to discover that each city has the potential to host an additional 20% coverage of forest canopy.
However, city planners and authorities will have to alter their perception of the natural resources available to cities before residents can relish the advantages of more trees: the less cities depend upon nature outside the metropolitan area and the more they emphasis falls on conserving nature within the cities, the healthier and more sustainable those cities will be.
Everyone can take action to increase the urban forest areas in our cities, not just city planners. You can visit the free resource itreetools.org to find out how much coverage there is in your city now, find out where you could plant more trees in your area and see how the benefits of the urban forest increase as more trees are planted.
Dr. Theodore Endreny, Lead Author