Mature trees clean air, lower stress, boost happiness, reduce flood risk and even save municipal money. So why are they cut down when cities develop and how should the UNs new urban agenda protect them?
The skyline along Manhattans Upper Fifth Avenue, where it flanks Central Park, is dominated by vast, verdant clouds of American elm trees. Their high-arched branches and luminous green canopies form as historian Jill Jones puts it a beautiful cathedral of shade. When she started researching her new book, Urban Forests, shed have struggled to identify the species but now, she says, when I see one, I say Oh my goodness, this is a rare survivor, and deeply appreciate the fact that its there.
The American elm was once Americas most beloved and abundant city tree. It liked urban soil, and its branches spread out a safe distance above traffic, to provide the dappled shade that cities depended on before air conditioning.
Now, however, most of the big, old elms have been wiped out by Dutch elm disease. Many of them were replaced by ash, which have in turn been killed by another imported pest: the emerald ash borer. By the 1970s, writes Jones, much of Americas urban tree cover had fallen victim to disease, development and shrinking municipal budgets.
Thousands of miles away, in Bangkok, the main threat is construction work. After a group of residents tried in vain to save several mature trees on their lane, which were felled to make way for a car park, they formed a tree advocacy group, the Big Trees Project.
Within weeks, membership swelled to 16,000. Forestry officer at the Food and Agriculture Organisation of the United Nations (FAO),Simone Borelli tells me of similar tree advocacy groups in Malaysia, India and Central African Republic, where the capital, Bangui, has grown out of the forest and is eating it up.
Read more: https://www.theguardian.com/cities/2016/oct/12/importance-urban-forests-money-grow-trees