WEBVTT 00:00:07.484 --> 00:00:10.461 This is the tale of two ancient cities 00:00:10.461 --> 00:00:14.071 and the trees that determined their destinies. 00:00:14.071 --> 00:00:19.930 In 3,000 BC Uruk was more densely populated than modern day New York City. 00:00:19.930 --> 00:00:24.802 This crowded capital had to continually expand their irrigation system 00:00:24.802 --> 00:00:26.902 to feed its growing population. 00:00:26.902 --> 00:00:33.784 2,500 years later in Sri Lanka, the city of Anuradhapura had a similar problem. 00:00:33.784 --> 00:00:36.246 They were also growing constantly, 00:00:36.246 --> 00:00:42.019 and like Uruk, their city relied heavily on an elaborate irrigation system. NOTE Paragraph 00:00:42.019 --> 00:00:48.290 As Uruk grew, its farmers began chopping down trees to make space for more crops. 00:00:48.290 --> 00:00:51.543 In Anuradhapura, however, trees were sacred. 00:00:51.543 --> 00:00:54.843 Their city housed an offshoot of the Bodhi tree 00:00:54.843 --> 00:00:59.112 under which Buddha himself was said to have attained enlightenment. 00:00:59.112 --> 00:01:02.212 Religious reverence slowed farmer’s axes 00:01:02.212 --> 00:01:06.947 and even led the city to plant additional trees in urban parks. NOTE Paragraph 00:01:06.947 --> 00:01:10.146 Initially, Uruk’s expansion worked well. 00:01:10.146 --> 00:01:13.326 But without trees to filter their water supply, 00:01:13.326 --> 00:01:16.706 Uruk’s irrigation system became contaminated. 00:01:16.706 --> 00:01:19.556 Evaporating water left mineral deposits, 00:01:19.556 --> 00:01:23.080 which rendered the soil too salty for agriculture. 00:01:23.080 --> 00:01:27.390 Conversely, Anuradhapura’s irrigation system was designed to work 00:01:27.390 --> 00:01:29.890 in concert with the surrounding forest. 00:01:29.890 --> 00:01:34.120 Their city eventually grew to more than twice Uruk’s population, 00:01:34.120 --> 00:01:40.773 and today, Anuradhapura still cares for a tree planted over 2,000 years ago. NOTE Paragraph 00:01:40.773 --> 00:01:44.912 We may think of nature as being unconnected to our urban spaces, 00:01:44.912 --> 00:01:49.657 but trees have always been an essential part of successful cities. 00:01:49.657 --> 00:01:53.974 Trees act like a natural sponge, absorbing storm water runoff 00:01:53.974 --> 00:01:56.782 before releasing it back into the atmosphere. 00:01:56.782 --> 00:01:59.562 The webs of their roots protect against mudslides 00:01:59.562 --> 00:02:03.639 while allowing soil to retain water and filter out toxins. 00:02:03.639 --> 00:02:05.669 Roots help prevent floods, 00:02:05.669 --> 00:02:09.598 while reducing the need for storm drains and water treatment plants. 00:02:09.598 --> 00:02:14.761 Their porous leaves purify the air by trapping carbon and other pollutants, 00:02:14.761 --> 00:02:18.351 making them essential in the fight against climate change. NOTE Paragraph 00:02:18.351 --> 00:02:23.026 Humanity has been uncovering these arboreal benefits for centuries. 00:02:23.026 --> 00:02:27.132 But trees aren’t just crucial to the health of a city’s infrastructure; 00:02:27.132 --> 00:02:30.602 they play a vital role in the health of its citizens as well. 00:02:30.602 --> 00:02:36.225 In the 1870’s, Manhattan had few trees outside the island’s parks. 00:02:36.225 --> 00:02:38.215 Without trees to provide shade, 00:02:38.215 --> 00:02:42.311 buildings absorbed up to nine times more solar radiation 00:02:42.311 --> 00:02:44.630 during deadly summer heat waves. 00:02:44.630 --> 00:02:47.780 Combined with the period’s poor sanitation standards, 00:02:47.780 --> 00:02:53.229 the oppressive heat made the city a breeding ground for bacteria like cholera. 00:02:53.229 --> 00:02:57.943 In modern day Hong Kong, tall skyscrapers and underground infrastructure 00:02:57.943 --> 00:03:00.343 make it difficult for trees to grow. 00:03:00.343 --> 00:03:04.223 This contributes to the city’s dangerously poor air quality, 00:03:04.223 --> 00:03:07.903 which can cause bronchitis and diminished lung function. 00:03:07.903 --> 00:03:10.213 Trees affect our mental health as well. 00:03:10.213 --> 00:03:15.492 Research indicates that the presence of green foliage increases attention spans 00:03:15.492 --> 00:03:17.910 and decreases stress levels. 00:03:17.910 --> 00:03:22.056 It’s even been shown that hospital patients with views of brick walls 00:03:22.056 --> 00:03:26.056 recover more slowly than those with views of trees. NOTE Paragraph 00:03:26.056 --> 00:03:29.452 Fortunately, many cities are full of views like this— 00:03:29.452 --> 00:03:30.902 and that’s no accident. 00:03:30.902 --> 00:03:32.884 As early as the 18th century, 00:03:32.884 --> 00:03:37.619 city planners began to embrace the importance of urban trees. 00:03:37.619 --> 00:03:43.290 In 1733, Colonel James Oglethorpe planned the city of Savannah, Georgia 00:03:43.290 --> 00:03:48.241 to ensure that no neighborhood was more than a 2-minute walk from a park. 00:03:48.241 --> 00:03:53.879 After World War II, Copenhagen directed all new development along five arteries— 00:03:53.879 --> 00:03:56.509 each sandwiched between a park. 00:03:56.509 --> 00:03:58.849 This layout increased the city’s resilience 00:03:58.849 --> 00:04:01.272 to pollution and natural disasters. 00:04:01.272 --> 00:04:04.262 And urban trees don’t just benefit people. 00:04:04.262 --> 00:04:08.421 Portland’s Forest Park preserves the region’s natural biodiversity, 00:04:08.421 --> 00:04:11.271 making the city home to various local plants, 00:04:11.271 --> 00:04:16.237 112 bird species, and 62 species of mammals. NOTE Paragraph 00:04:16.237 --> 00:04:20.007 No city is more committed to trees than Singapore. 00:04:20.007 --> 00:04:26.353 Since 1967, Singapore’s government has planted over 1.2 million trees, 00:04:26.353 --> 00:04:32.070 including those within 50-meter tall vertical gardens called supertrees. 00:04:32.070 --> 00:04:36.070 These structures sustain themselves and nearby conservatories 00:04:36.070 --> 00:04:39.180 with solar energy and collected rainwater. 00:04:39.180 --> 00:04:44.129 Trees and vegetation currently cover over 50% of Singapore’s landmass, 00:04:44.129 --> 00:04:46.259 reducing the need for air conditioning 00:04:46.259 --> 00:04:49.409 and encouraging low-pollution transportation. NOTE Paragraph 00:04:49.409 --> 00:04:55.331 By 2050, it’s estimated that over 65% of the world will be living in cities. 00:04:55.331 --> 00:04:58.968 City planners can lay an eco-friendly foundation, 00:04:58.968 --> 00:05:02.068 but it’s up to the people who live in these urban forests 00:05:01.806 --> 00:05:04.940 to make them homes for more than humans.