9:59:59.000,9:59:59.000 This is the tale of two ancient cities and[br]the trees that determined their destinies. 9:59:59.000,9:59:59.000 In 3,000 BC Uruk was more densely [br]populated than modern day New York City. 9:59:59.000,9:59:59.000 This crowded capital had to continually[br]expand their irrigation system 9:59:59.000,9:59:59.000 to feed its growing population. 9:59:59.000,9:59:59.000 2,500 years later in Sri Lanka, the city [br]of Anuradhapura had a similar problem. 9:59:59.000,9:59:59.000 They were also growing constantly, 9:59:59.000,9:59:59.000 and like Uruk, their city relied heavily [br]on an elaborate irrigation system. 9:59:59.000,9:59:59.000 As Uruk grew, its farmers began chopping [br]down trees to make space for more crops. 9:59:59.000,9:59:59.000 In Anuradhapura, however, [br]trees were sacred. 9:59:59.000,9:59:59.000 Their city housed an offshoot of the Bodhi[br]tree 9:59:59.000,9:59:59.000 under which Buddha himself was said[br]to have attained enlightenment. 9:59:59.000,9:59:59.000 Religious reverence slowed farmer’s [br]axes and even led the city 9:59:59.000,9:59:59.000 to plant additional trees in urban parks. 9:59:59.000,9:59:59.000 Initially, Uruk’s expansion worked well. 9:59:59.000,9:59:59.000 But without trees to filter their water [br]supply, 9:59:59.000,9:59:59.000 Uruk’s irrigation system [br]became contaminated. 9:59:59.000,9:59:59.000 Evaporating water left mineral deposits, 9:59:59.000,9:59:59.000 which rendered the soil [br]too salty for agriculture. 9:59:59.000,9:59:59.000 Conversely, Anuradhapura’s irrigation [br]system was designed to work 9:59:59.000,9:59:59.000 in concert with the surrounding forest. 9:59:59.000,9:59:59.000 Their city eventually grew to more than [br]twice Uruk’s population, 9:59:59.000,9:59:59.000 and today, Anuradhapura still cares for [br]a tree planted over 2,000 years ago. 9:59:59.000,9:59:59.000 We may think of nature as being [br]unconnected to our urban spaces, 9:59:59.000,9:59:59.000 but trees have always been an essential[br]part of successful cities. 9:59:59.000,9:59:59.000 Trees act like a natural sponge, absorbing[br]storm water runoff 9:59:59.000,9:59:59.000 before releasing it back into[br]the atmosphere. 9:59:59.000,9:59:59.000 The webs of their roots protect against [br]mudslides 9:59:59.000,9:59:59.000 while allowing soil to retain water and[br]filter out toxins. 9:59:59.000,9:59:59.000 Roots help prevent floods, 9:59:59.000,9:59:59.000 while reducing the need for storm [br]drains and water treatment plants. 9:59:59.000,9:59:59.000 Their porous leaves purify the air by [br]trapping carbon and other pollutants, 9:59:59.000,9:59:59.000 making them essential in the [br]fight against climate change. 9:59:59.000,9:59:59.000 Humanity has been uncovering these [br]arboreal benefits for centuries. 9:59:59.000,9:59:59.000 But trees aren’t just crucial to the [br]health of a city’s infrastructure; 9:59:59.000,9:59:59.000 they play a vital role in the health of [br]its citizens as well. 9:59:59.000,9:59:59.000 In the 1870’s, Manhattan had few trees [br]outside the island’s parks. 9:59:59.000,9:59:59.000 Without trees to provide shade, buildings[br]absorbed up to nine times more solar radiation 9:59:59.000,9:59:59.000 during deadly summer heat waves. 9:59:59.000,9:59:59.000 Combined with the period’s poor [br]sanitation standards, 9:59:59.000,9:59:59.000 the oppressive heat made the city a [br]breeding ground for bacteria like cholera. 9:59:59.000,9:59:59.000 In modern day Hong Kong, tall skyscrapers[br]and underground infrastructure 9:59:59.000,9:59:59.000 make it difficult for trees to grow. 9:59:59.000,9:59:59.000 This contributes to the city’s dangerously[br]poor air quality, 9:59:59.000,9:59:59.000 which can cause bronchitis and diminished[br]lung function. 9:59:59.000,9:59:59.000 Trees affect our mental health as well. 9:59:59.000,9:59:59.000 Research indicates that the presence [br]of green foliage increases attention spans 9:59:59.000,9:59:59.000 and decreases stress levels. 9:59:59.000,9:59:59.000 It’s even been shown that hospital [br]patients with views of brick walls 9:59:59.000,9:59:59.000 recover more slowly than [br]those with views of trees. 9:59:59.000,9:59:59.000 Fortunately, many cities [br]are full of views like this – 9:59:59.000,9:59:59.000 and that’s no accident. 9:59:59.000,9:59:59.000 As early as the 18th century, 9:59:59.000,9:59:59.000 city planners began to embrace the [br]importance of urban trees. 9:59:59.000,9:59:59.000 In 1733, Colonel James Oglethorpe [br]planned the city of Savannah, Georgia 9:59:59.000,9:59:59.000 to ensure that no neighborhood was [br]more than a 2-minute walk from a park. 9:59:59.000,9:59:59.000 After World War II, Copenhagen directed [br]all new development along five arteries – 9:59:59.000,9:59:59.000 each sandwiched between a park. 9:59:59.000,9:59:59.000 This layout increased the city’s [br]resilience 9:59:59.000,9:59:59.000 to pollution and natural disasters. 9:59:59.000,9:59:59.000 And urban trees don’t just benefit people. 9:59:59.000,9:59:59.000 Portland’s Forest Park preserves the [br]region’s natural biodiversity, 9:59:59.000,9:59:59.000 making the city home to various [br]local plants, 9:59:59.000,9:59:59.000 112 bird species, and 62 [br]species of mammals. 9:59:59.000,9:59:59.000 No city is more committed to trees [br]than Singapore. 9:59:59.000,9:59:59.000 Since 1967, Singapore’s government[br]has planted over 1.2 million trees, 9:59:59.000,9:59:59.000 including those within 50-meter tall [br]vertical gardens called supertrees. 9:59:59.000,9:59:59.000 These structures sustain themselves [br]and nearby conservatories 9:59:59.000,9:59:59.000 with solar energy and collected rainwater. 9:59:59.000,9:59:59.000 Trees and vegetation currently cover [br]over 50% of Singapore’s landmass, 9:59:59.000,9:59:59.000 reducing the need for air conditioning 9:59:59.000,9:59:59.000 and encouraging low-pollution [br]transportation. 9:59:59.000,9:59:59.000 By 2050, it’s estimated that over 65% of[br]the world will be living in cities. 9:59:59.000,9:59:59.000 City planners can lay an eco-friendly[br]foundation, 9:59:59.000,9:59:59.000 but it’s up to the people who live in [br]these urban forests 9:59:59.000,9:59:59.000 to make them homes for more than humans.