<p>Using plants and trees in a unique way, Singapore officials opened <a href="http://www.gardensbythebay.com.sg/en/home.html">Gardens by the Bay</a> this year. The 11-million-square foot (1-million-square-meter) complex—the size of nearly 250 U.S. football fields—aims to curb the heat island effect while bringing botanical bliss to urbanites.</p><p>The centerpiece of Gardens by the Bay is a glass atrium that houses approximately 220,000 types of vegetation, or 80 percent of the world’s plant species, according to Singapore's National Parks Board.</p><p>Outside the menagerie of plants is a grove of 18 “supertrees”— vertical gardens up to 164 feet (50 meters) tall that capture rainwater, filter exhaust, and are capped with solar panels that provide enough energy to light up the trees at night.</p><p>The heat island effect occurs in cityscapes characterized by pavement, asphalt, and concrete—all materials that can absorb warmth. The annual mean temperature of a city with one million people or more can be up to 5.4°F (3°C) warmer than surrounding rural areas, according to the <a href="http://www.epa.gov/hiri/">U.S. Environmental Protection Agency</a> (EPA). The effects cascade as summertime peak energy demands rise along with air conditioning costs and greenhouse gas emissions.</p><p>(Test your A/C acumen with our quiz: <a href="http://environment.nationalgeographic.com/environment/energy/great-energy-challenge/air-conditioning-quiz/">What You Don't Know About Air Conditioning</a>.)</p><p>The value of vegetation in urban areas goes beyond cooling and shade. City plantings can also help improve air and water quality through filtering mechanisms.</p><p>A new study in the journal <em><a href="http://pubs.acs.org/journal/esthag/">Environmental Science &amp; Technology</a></em> shows that grass, ivy, and other urban plantings, in addition to trees, can reduce levels of nitrogen dioxide and particulate matter by as much as 40 and 60 percent respectively. Both are pollutants that are potentially harmful to human health.</p><p>(Read more about the water quality benefits of vegetation in National Geographic News’ “<a href="http://news.nationalgeographic.com/news/2012/06/120606/philadelphia-storm-water-runoff/">Philadelphia Cleans Up Storm Water With Innovative Program</a>.”)</p><p><em>—Tasha Eichenseher</em></p>

City Forest, Singapore

Using plants and trees in a unique way, Singapore officials opened Gardens by the Bay this year. The 11-million-square foot (1-million-square-meter) complex—the size of nearly 250 U.S. football fields—aims to curb the heat island effect while bringing botanical bliss to urbanites.

The centerpiece of Gardens by the Bay is a glass atrium that houses approximately 220,000 types of vegetation, or 80 percent of the world’s plant species, according to Singapore's National Parks Board.

Outside the menagerie of plants is a grove of 18 “supertrees”— vertical gardens up to 164 feet (50 meters) tall that capture rainwater, filter exhaust, and are capped with solar panels that provide enough energy to light up the trees at night.

The heat island effect occurs in cityscapes characterized by pavement, asphalt, and concrete—all materials that can absorb warmth. The annual mean temperature of a city with one million people or more can be up to 5.4°F (3°C) warmer than surrounding rural areas, according to the U.S. Environmental Protection Agency (EPA). The effects cascade as summertime peak energy demands rise along with air conditioning costs and greenhouse gas emissions.

(Test your A/C acumen with our quiz: What You Don't Know About Air Conditioning.)

The value of vegetation in urban areas goes beyond cooling and shade. City plantings can also help improve air and water quality through filtering mechanisms.

A new study in the journal Environmental Science & Technology shows that grass, ivy, and other urban plantings, in addition to trees, can reduce levels of nitrogen dioxide and particulate matter by as much as 40 and 60 percent respectively. Both are pollutants that are potentially harmful to human health.

(Read more about the water quality benefits of vegetation in National Geographic News’ “Philadelphia Cleans Up Storm Water With Innovative Program.”)

—Tasha Eichenseher

Photograph by Wong Maye-E, AP

Pictures: 10 Green-Tech City Solutions for Beating the Heat

From a solar mansion in China to a floating farm in New York, green buildings are sprouting up in cities around the world. Among their many benefits are curbing fossil-fuel use and reducing the urban heat island effect.

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