pavement

How to make cities cooler

March 26, 2024 By EarthWise Leave a Comment

In cities, the air, surface, and soil temperatures are almost always warmer than in rural areas. This is known as the urban heat island effect. Urban heat islands occur when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat.

Urban planners around the world have been researching ways to reduce the effects of heat in cities. For example, trees, green roofs, and vegetation can help reduce urban heat island effects by shading building surfaces, deflecting radiation from the sun, and releasing moisture into the atmosphere.

A new study led by researchers from the University of Surrey in the U.K. has analyzed how well various green spaces and waterways are able to cool down cities. The study, which was recently published in the journal The Innovation, found that wetlands, parks, and even botanical gardens are among the best ways to keep cities cool.

In fact, the researchers found that botanical gardens can cool city air by a whopping 9°F during heatwaves on average. Wetlands can cool city air by 8.5°F on average, followed by rain gardens at 8.1°F, green walls at 7.4°F, street trees at 6.8°F, city farms at 6.3°F, city parks at 5.8°F, and reservoirs and playgrounds at 5.2°F.

The researchers also found that cities can unlock even greater benefits by connecting green spaces into green corridors. Greening projects can also help remove carbon emissions and prevent flooding.

The research team hopes its findings will help urban planners design more resilient cities.

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Wetlands, parks and even botanical gardens among the best ways to cool cities during heatwaves

Photo, posted April 25, 2022, courtesy of Catherine Poh Huay Tan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Sponging up a river

March 20, 2024 By EarthWise Leave a Comment

During the first week of February, an atmospheric river dumped enormous amounts of rain on Southern California. Over the course of four days, Los Angeles received 9 inches of rain. The average annual rainfall in the city is only 14 inches.

But Los Angeles was not the site of a flooding disaster because the city has spent years preparing for this type of deluge by becoming a “sponge city.” By installing lots of green spaces and shallow basins with porous soil, Los Angeles was able to soak up 8.6 billion gallons of water during the storm, enough to meet the water needs of 100,000 people for a year.

Cities covered with impermeable concrete sidewalks and paved areas make storm-related flooding worse because they are unable to absorb water. Instead, the water flows into drains and overwhelms infrastructure.

Natural materials like dirt and plants take in water from storms and can filter it into underground aquifer that cities can then tap into, especially during droughts. Adding green spaces to cities has many other benefits beyond the ability to absorb large amounts of rainwater.

The so-called sponge-city movement is catching on in many other places. Philadelphia is revamping its water systems in a 25-year project that includes green spaces to absorb stormwater runoff. In China, the government has spent more than a decade adding spongy elements to dozens of cities around the country.

Sponge cities are part of a broader effort to combine modern engineering techniques with natural systems. This is known as green-gray infrastructure. Nature knows what it is doing when it comes to flood control as well as to pollution control.

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‘Spongy’ LA Soaked Up Tons of Water From Atmospheric River

Photo, posted December 28, 2011, courtesy of Ron Reiring via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Prospects For Floating Solar | Earth Wise

October 10, 2022 By EarthWise Leave a Comment

Countries are trying to figure out how to get enough energy from solar and wind generation to completely decarbonize their economies. According to some estimates, nations might have to devote between half a percent and five percent of their land area to solar panels to get the job done. Half a percent is about the amount of the U.S. that is covered by paved roads. While there is lots of open land in many parts of the country, covering it with solar panels might not be acceptable to farmers, conservationists, or other interested parties.

One way to deploy more solar panels without using up land is the use of floating solar panels. Floating photovoltaic systems – also known as floatovoltaics – are becoming increasingly common, especially in Asia. This year, China installed one of the largest floatovoltaic systems in the world on a reservoir near the city of Dezhou.

Floating solar panels stay cooler and run more efficiently than those on land. The panels also help prevent evaporation from their watery homes and the shading they provide also help to minimize algal blooms. Solar installations on reservoirs generally puts them near cities, making it easier to feed power into urban grids.

On the other hand, floating solar systems need to be able to withstand water and waves and are generally more expensive to build than land-based systems.

At present, the installed global capacity of floating solar is only about 3 gigawatts, compared with more than 700 gigawatts of land-based systems. However, reservoirs around the world collectively cover an area about the size of France. Covering just 10 percent of them with floating solar could produce as much power as all the fossil-fuel plants in operation worldwide.

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Solar Takes a Swim

Photo, posted March 7, 2019, courtesy of Hedgerow INC via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Soaring Heat And Inner-City Neighborhoods | Earth Wise

August 31, 2021 By EarthWise Leave a Comment

The record-breaking heatwaves this summer have exposed the special vulnerability inner cities have to the effects of summer heat. Climate change has exacerbated and supercharged heatwaves, as was seen in Seattle and Portland in late June.

Urban cores can be 10 degrees or more warmer than the surrounding countryside. The urban heat island effect is a result of how cities are built, with so much pavement, so many buildings, and not enough trees. On top of this, decades of disinvestment in neighborhoods where people of color live have left them especially vulnerable to heat as their homes are not able to cope with it.

In New York City, some residents of Hunts Point in the Bronx keep lists of neighbors they check on to help keep the most vulnerable alive during heat waves. The city has subsidized 74,000 air conditioners for low-income, elderly residents, and is spending millions to plant trees. In Phoenix, the hottest big city in the country, officials are working to develop new models for cooler public housing and cooling for streets and pedestrian corridors.

A study, published in 2020, looked at the linkage between higher heat island temperatures and past practices of redlining, where home loans and insurance were unavailable to people in neighborhoods of color. In 94 of 108 communities studied, the formerly redlined neighborhoods had higher surface temperatures.

Cities are confronted with two heat problems: emergencies that require immediate action to save lives, and long-term issues related to combating soaring temperatures in heat islands strengthened by global warming. In many cases, cities are not prepared for either problem. Dealing with and adapting to heat is essential to the long-term viability and quality of life in our cities.

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A Triple Whammy Has Left Many Inner-City Neighborhoods Highly Vulnerable to Soaring Temperatures

Photo, posted May 27, 2014, courtesy of Dan DeLuca via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Bee Friendly Amsterdam

February 11, 2019 By EarthWise Leave a Comment

Scientists around the world have been sounding the alarm for years about the decline of bees and other pollinators that are crucial to the growth of crops. One place where this trend has been bucked is in Amsterdam. The diversity of wild bee and honeybee species in the Dutch capital has actually increased by 45% since 2000.

The city attributes this success to creating bee-friendly environments including the installation of so-called insect hotels. There has also been a ban on the use of chemical pesticides on public land.

Four years ago, Amsterdam set a goal to convert half of all public green spaces to native plants including species that produce flowers and fruits that provide nourishment for bees. Developers in Amsterdam are encouraged to install green roofs on new buildings which reduce reliance on heating and cooling systems and also create habitat for wildlife.

Residents can request to have a 16-inch strip of pavement adjacent to their homes removed in order to plant shrubs, flowers or climbing vines. When a new highway was built in the area in 2015, local activists planted wildflowers along the sides of the road that otherwise would have been left with only gravel or grass. This practice has spread to other major routes and along dikes and railways and is referred to as the Honey Highway.

All of these efforts seem to be having a positive effect. An initial survey was conducted in 2000 to establish a baseline. A 2015 survey of pollinators found 21 bee species not previously documented in the city. The rest of the Netherlands has not done as well, and the Dutch government has recently introduced a pollinator strategy to revive bees, butterflies and other insects crucial to the country’s food crop.

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Bees are dying at an alarming rate. Amsterdam may have the answer.

Photo, posted December 28, 2006, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.