Forests can transform cities into more resilient, sustainable and healthy places. An editorial by Hiroto Mitsugi, Assistant Director-General of the Fao Forestry Department, on the occasion of the International Day of Forests.
Walking along a tree-lined avenue in a bustling city, we don't always stop to consider the benefits those trees bring, or what life in the city would be like without them. And yet the shelter that trees provide — whether elms, palms or mandarin trees — offers far more than welcome shade and a more pleasant urban landscape.
It has been shown that trees can actually improve our mental health, reducing the stress and anxiety of urban life. A study from Toronto argues that having just ten more trees on a city block improves the perception of health in ways comparable to a $10,000 increase in annual personal income, or to being seven years younger. More people than ever in history now live in cities, but rapid urbanisation need not necessarily mean uncontrolled urban sprawl.
On the busy streets of many cities, trees play an invaluable role in cooling the air, filtering pollutants and mitigating the effects of climate change. They serve as highly efficient air filters, absorbing the harmful carbon produced by vehicles and industry. A very large tree can absorb 150 kilograms of carbon dioxide per year and filter pollutants from the air. In London alone, trees remove 2.4 million tonnes of air pollution every year.
Consider how much noisier cities would be without trees to absorb noise pollution and shield our homes from surrounding roads and industrial areas. Acting as buffers, trees and shrubs can significantly reduce city noise levels — by as much as 50 per cent to the human ear.
It may come as a surprise, but by shielding homes from cold winds, trees have the ability to help reduce the energy needed for heating by around half. At the other extreme, trees act as natural air conditioners, lowering temperatures by as much as 8 degrees.
Beyond city boundaries, often hundreds of kilometres away, trees and forests in rural settings provide a range of services to cities, such as protecting watersheds, supplying energy, building materials and recreational opportunities for city dwellers.
All of this, in addition to improving the quality of life of the millions of people living in cities, also has an economic value. A study conducted by the New York Department of Parks and Recreation estimates that the benefits of trees in cities amount to $120 million a year. These include protecting the city's water reserves and flood prevention. Properly managed forests in cities and surrounding areas provide habitat, food and protection for plants and animals, helping to maintain and enhance biodiversity. In addition, in many urban and peri-urban areas, trees become a source of fuel, food and medicine. One example is the Jamun trees lining the streets of Delhi, India, which produce 500 tonnes of fruit a year for sale and consumption.
Often, however, in some contexts trees are felled to make way for new roads and buildings. Yet when space is limited, trees do not necessarily have to grow at ground level. As cities grow and expand, innovative ways of integrating trees into urban landscapes are also being developed, such as creating a vertical forest in Milan or planting trees on buildings, as in Singapore — although this should always be a last resort.
The theme of this year's International Day of Forests is Forests and sustainable cities, and it is our commitment, here at the FAO, to support member countries on issues relating to urban forests.
Read also: International Day of Forests, 21 March celebrates the lungs of the Earth
The good news is that several cities around the world are committing to planting urban forests, and not all of them are from the wealthy North. In China, 170 cities have signed up to a greening programme that has dramatically increased forest cover. In Manila, in the Philippines, mini parks are being created on abandoned spaces, at intersections and along railway lines. In Seoul, South Korea, urban planners removed an entire motorway from the city centre and replaced it with trees and plants.
The key to success is forward planning. The most successful urban landscapes are those that factor in trees from the earliest stages, rather than incorporating them later in the design phase. After all, a tree takes an average of ten to twenty years to develop and grow. Managing urban areas has become one of the most important development challenges of the twenty-first century, but trees and urban forests can make our cities greener, healthier and happier places to live. Let us make sure that trees are included first and foremost in urban design strategies.
