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This is the tale of two ancient cities and
the trees that determined their destinies.

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In 3,000 BC Uruk was more densely 
populated than modern day New York City.

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This crowded capital had to continually
expand their irrigation system

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to feed its growing population.

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2,500 years later in Sri Lanka, the city 
of Anuradhapura had a similar problem.

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They were also growing constantly,

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and like Uruk, their city relied heavily 
on an elaborate irrigation system.

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As Uruk grew, its farmers began chopping 
down trees to make space for more crops.

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In Anuradhapura, however, 
trees were sacred.

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Their city housed an offshoot of the Bodhi
tree

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under which Buddha himself was said
to have attained enlightenment.

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Religious reverence slowed farmer’s 
axes and even led the city

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to plant additional trees in urban parks.

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Initially, Uruk’s expansion worked well.

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But without trees to filter their water 
supply,

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Uruk’s irrigation system 
became contaminated.

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Evaporating water left mineral deposits,

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which rendered the soil 
too salty for agriculture.

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Conversely, Anuradhapura’s irrigation 
system was designed to work

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in concert with the surrounding forest.

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Their city eventually grew to more than 
twice Uruk’s population,

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and today, Anuradhapura still cares for 
a tree planted over 2,000 years ago.

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We may think of nature as being 
unconnected to our urban spaces,

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but trees have always been an essential
part of successful cities.

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Trees act like a natural sponge, absorbing
storm water runoff

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before releasing it back into
the atmosphere.

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The webs of their roots protect against 
mudslides

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while allowing soil to retain water and
filter out toxins.

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Roots help prevent floods,

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while reducing the need for storm 
drains and water treatment plants.

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Their porous leaves purify the air by 
trapping carbon and other pollutants,

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making them essential in the 
fight against climate change.

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Humanity has been uncovering these 
arboreal benefits for centuries.

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But trees aren’t just crucial to the 
health of a city’s infrastructure;

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they play a vital role in the health of 
its citizens as well.

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In the 1870’s, Manhattan had few trees 
outside the island’s parks.

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Without trees to provide shade, buildings
absorbed up to nine times more solar radiation

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during deadly summer heat waves.

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Combined with the period’s poor 
sanitation standards,

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the oppressive heat made the city a 
breeding ground for bacteria like cholera.

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In modern day Hong Kong, tall skyscrapers
and underground infrastructure

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make it difficult for trees to grow.

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This contributes to the city’s dangerously
poor air quality,

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which can cause bronchitis and diminished
lung function.

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Trees affect our mental health as well.

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Research indicates that the presence 
of green foliage increases attention spans

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and decreases stress levels.

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It’s even been shown that hospital 
patients with views of brick walls

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recover more slowly than 
those with views of trees.

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Fortunately, many cities 
are full of views like this –

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and that’s no accident.

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As early as the 18th century,

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city planners began to embrace the 
importance of urban trees.

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In 1733, Colonel James Oglethorpe 
planned the city of Savannah, Georgia

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to ensure that no neighborhood was 
more than a 2-minute walk from a park.

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After World War II, Copenhagen directed 
all new development along five arteries –

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each sandwiched between a park.

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This layout increased the city’s 
resilience

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to pollution and natural disasters.

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And urban trees don’t just benefit people.

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Portland’s Forest Park preserves the 
region’s natural biodiversity,

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making the city home to various 
local plants,

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112 bird species, and 62 
species of mammals.

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No city is more committed to trees 
than Singapore.

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Since 1967, Singapore’s government
has planted over 1.2 million trees,

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including those within 50-meter tall 
vertical gardens called supertrees.

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These structures sustain themselves 
and nearby conservatories

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with solar energy and collected rainwater.

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Trees and vegetation currently cover 
over 50% of Singapore’s landmass,

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reducing the need for air conditioning

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and encouraging low-pollution 
transportation.

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By 2050, it’s estimated that over 65% of
the world will be living in cities.

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City planners can lay an eco-friendly
foundation,

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but it’s up to the people who live in 
these urban forests

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to make them homes for more than humans.