Investing in green spaces can help transform cities into more sustainable, resilient, healthy, equitable and pleasant places to live, the United Nation Food and Agriculture Organisation said ahead of the International Day of Forests on Wednesday.
"Well managed forests and trees in and around cities provide habitats, food and protection for many plants and animals, helping to maintain an increase biodiversity," said FAO director-general Jose Graziano da Silva in a video message to mark the day.
He stressed the need "to join forces to protect forests and trees to make urban environments more sustainable".
FAO will on Wednesday celebrate the International Day of Forests and this year's theme 'Forests and sustainable cities' at a webcast special ceremony at FAO headquarters in Rome attended by city administrators from Lima, Ljubljana, Philadelphia and Mantova.
More than half the world's population now lives in cities, and by 2050 almost 70 percent of the world will be urbanized. Although cities occupy only three percent of the Earth's surface, they consume 78 percent of energy and emit 60 percent of carbon dioxide, FAO said.
Woodlands, forests and trees in a city and on its fringes perform a wide range of vital functions - such as storing carbon, removing air pollutants, assisting in food, energy and water security, restoring degraded soils and preventing drought and floods. In a medium-size city, for instance, urban trees can reduce the loss of soil by around 10,000 tons per year.
By shading and cooling the air, forests and trees in urban areas can reduce extreme temperatures and mitigate the effects of climate change. In fact, trees properly placed around buildings can reduce air conditioning needs by 30 percent. In cold climates, by shielding homes from the wind, they can help save energy used for heating by 20-50 percent, according to FAO.
Urban and peri-urban forests can increase the resilience and quality of watersheds and water reservoirs by preventing erosion, limiting evapotranspiration and filtering pollutants. And planting fruit-bearing street trees can increase the availability of food within cities, the UN agency said.
Many cities are already demonstrating their commitments to a more sustainable future and there are many excellent examples of green urban development, according to a new FAO publication called "Forests and sustainable cities - Inspiring stories from around the world" which launched to mark the International Day of Forests.
The publication highlights different ways in which cities around the globe have used forests and trees to improve the living conditions of their citizens, which may serve as inspiration for others.
The Chinese capital Beijing is one of the world's most populated and polluted cities. Without large forests and other green areas the city risks becoming concrete jungle with increasingly serious effects on health and wellbeing of urban dwellers.
In 2012, Beijing initiated the largest afforestation programme in its history. In suburban and peri-urban areas, most lands were afforested after moving low-end industries. Forests, which cover now more than 25 percent of the city plain - an increase of 42 percent - provide neighbourhoods with more space for recreation.
Another success story is Kenya's capital, Nairobi. The Karura forest in the central north of Nairobi was once a crime-ridden area. The forest's proximity to the rapidly growing city led to plans to reduce the forest area to make way for property development. But when the local communities became involved in its management, its fortunes turned around.
Conservationists, led by environmental activist Wangari Maathai, launched a highly publicized campaign to save the forest. Collaboration with various stakeholders, including local authorities, private sector, community and resident associations, donors and non-governmental organisations, played a decisive role in improving management of the Karura forest.
Local people have benefited considerably from direct participation. The forest is no longer a place of danger for them but rather a source of opportunities. It employs 46 permanent workers, 36 of whom are from surrounding communities. It has also become a significant tourist attraction and now welcomes on average 16 000 visitors per month.
FAO's work supports the adoption of urban forest solutions for cities with guidelines as well as technical and communication tools, the agency said.
In Niger, for example, FAO said it helped the government develop a national policy for the management of green spaces in and around cities to protect the environment and mitigate the effects of climate change.
