New research has found that megacities would be dramatically healthier for urban populations if they planted more trees in and around cities. Who’d have thought it?!

A megacity is generally defined as a city with a population greater than 10 million and they are home to nearly 10% of the global population. The vast majority of these cities can be found in Asia, with many in China and India, and the largest city in the world in Japan. Behind these, there are a number of global cities like London, New York, and Mexico City which have growing populations that will class them as megacities over the coming decades.

Shanghai has developed at a very rapid rate

A study on how green megacities are found that around 20% of these urban areas are in the form of urban forests. This new research has found that if megacities increase the percentage of urban forest, there can be huge benefits including air pollution reduction, carbon sequestration, and energy reduction. Urban forests can be defined as anything from a tree in a back garden to a forested area in the city. Trees along road and pathways that connect forested areas are also considered part of the urban forest. So what benefits would an increase in trees and greenery bring to the city?

A Natural Filter of Air Pollution

Looking at some of the biggest and the most-rapidly expanding cities in the world, air pollution is a common problem. As cities grow and become increasingly wealthy, so do its population and this often leads to increased car use. In the developing world, air pollution and smog from surrounding industrial areas can have disastrous impacts on the health of city populations. In the last few years, research has found that around 9,500 people living in London died due prematurely because of long-term exposure to air pollution In many countries with megacities, however, this number could be much higher.

An increase in urban forests could dramatically reduce air pollution in cities. Trees and plants act as a natural air filter and increase the amount of clean air in the city making it a lot healthier for the population.

Trees can reduce the air pollution around a city’s roads

Trees Can Be Cool

Increasing the number of trees in a city has a cooling effect that lowers air and ground temperatures, and in a warming world, it could be vital for some cities to remain habitable during the hottest months of the year. This natural cooling effect also means that there is less of a need for air conditioning during warm weather, thus reducing the cost of artificial air coolers and the amount of energy required in buildings.

Holding Back the River

If you look at many cities around the world, a vast majority of them are located close to rivers meaning that flooding can often be a problem. If you haven’t noticed, concrete doesn’t absorb water particularly well… Trees, on the other hand, can act as interceptors, reducing the amount of water that reaches the ground and naturally reducing the chances of a city to flood.

Cities are recognising the role that trees and green areas have in naturally regulating rainfall. In many American cities (in particular), decided it upon a more ‘man-made’ solution to flooding with the use of storm drains, but cities that have chosen to deal with heavy rain and flooding with a more natural approach are reaping the money more benefits that this offers.

Green areas in cities can dramatically reduce the risk of flooding

Food, Glorious Food

Away from ground level, buildings are embracing the need for cities to become greener. Rooftop gardens and ‘vertical gardens’ are becoming increasingly woven into building design and this provides huge opportunities for people to grow their own food and benefit from growing plants and trees in spaces that have previously not been considered somewhere that food can grow.

Return to Nature

As cities grow, natural habitats are reduced and nature must either move or adapt to its new, concrete surroundings. As highlighted in the BBC documentary ‘Planet Earth II’, there are a number of animals that are adapting and benefitting from the built environment, but adding greenery and much more natural habitats for many species that are affected by urban growth can only have positive effects on nature, which also benefits local people living in megacities that can get much closer to nature without having to travel miles outside the city.

Cherry Blossom in Tokyo

The combination of urban expansion, industrialisation, population growth, and a changing climate has had disastrous effects on the natural environment. Development has occurred at the expense of the environment and humans are beginning to pay for it. Bringing nature back to the city is vital if we are to become more sustainable in a changing climate, and the benefits of doing so are endless!


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