Humans have become more and more an urban species. Researchers have proven that cities with larger green spaces would make humans happier and vital to their well-being. For the first time in history, more than half of the earth’s population lives in cities. At the end of this century, researchers predict that the proportion could be as high as two-thirds of the planet.
Cities, “islands of heat”
Even without global warming, cities are heating up. This is due to the accumulation of carbon dioxide due to the burning of fossil fuels and the high absorption of heat by dark materials and hard surfaces of cities (tar, brick, cement, tiles, slates, Gutters, railways, motorways, etc.) which evaporate the rainwater and thus prevent damping the heat to a lower level.
This is why cities become “hot islands” that are warmer than the surrounding countryside. For example, according to a report in Nature, the average annual temperature in Los Angeles has increased by more than 2°C since 1878 and the megalopolis faces 22 days of extreme heat per year with temperatures above 35°C.
The project of a green city
Today, British and American scientists are trying to work together on a new form of the ideal city. The British argue that city dwellers must live together around green spaces and Americans that people must resist the heat by staying cool with trees, parks and rooftop gardens.
Dense peoples with large natural parks offer the greatest sense of well-being and the healthiest of urban ecosystems.
“As the population continues to grow, it is vital that we develop our cities and build more sustainably to promote ecosystems and bring the greatest benefits to city dwellers. “Said lead author Lain Stott of the University of Exeter of the Institute of Environment and Sustainable Development.
“Our research shows that dense developments that include large open spaces are essential for the delivery of ecosystem services. However, for humans to get the most benefits, the best method is to combine this approach with green constructions using trees in the streets and some small parks and gardens. ”
A team led by NASA scientists published in the “Environmental Research Letters” report that instead of focusing on the selected cities, it was necessary to focus on the problems caused by asphalt and Concrete. Indeed, satellite data confirm that in America, roads, sidewalks, roofs and parking lots were warmer in summer by 1.9°C than in rural areas and in winter by 1.5°C.
The idea is to use evapotranspiration thanks to the freshness of the greenery. Leafy trees with large leaves can cool cities better than pine forests with fine needles. The important message to remember is that green is great for cities and cities are good for the environment.
Limitation of water resources
Paradoxically, cities in arid environments, like Phoenix in Arizona, may be colder than the surrounding desert. The inhabitants have many lawns that must be watered and many trees that bring shade. This creates another problem, water is a scarce resource and rising urban temperatures could make water even rarer. Researchers from the University of Florida published in their report of the Journal of Technology and Innovation a survey of owners in Orange County, Florida. This report found that 64% of drinking water is used to irrigate lawns. In summer, this proportion would increase to 88%.
Whatever the urban problems, global warming and climate change will aggravate them. However, cities are proposing ways to reduce energy consumption, resources and carbon dioxide emissions.
Source: Eco Business