urban

Benefits of electric school buses

July 1, 2024 By EarthWise Leave a Comment

There are about half a million school buses in use in the U.S. A large number of them are older, highly polluting diesel buses. There are well-established health and climate benefits of switching from diesel vehicles to electric vehicles but making the switch is expensive. Diesel buses generally cost between $65,000 to $120,000, depending on the type and configuration. Electric buses cost about $250,000 each.

The substantial cost makes it a difficult decision for local, state, and federal officials, particularly since the actual magnitude of the benefits is not well known.

A new study by researchers at Harvard’s T.H. Chan School of Public Health has quantified these benefits. According to the study, replacing each bus may yield up to $247,600 in climate and health benefits. These benefits derive from fewer greenhouse gas emissions and from reduced rates of adult mortality and childhood asthma.

The study compared the amounts of carbon dioxide emitted from diesel bus tailpipes to the emissions associated with generating electricity for the buses and producing their batteries. It also compared how these respective emissions contribute to fine particulate air pollution, which is linked to adult mortality and the onset of childhood asthma. The study concluded that particularly in dense urban settings, the savings incurred from electrifying older school buses easily outweigh the costs of replacing them.

An important question not tackled in the study is how electric school buses impact children’s exposure to in-cabin air pollution while riding the bus. This issue could further inform policy decisions.

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Electric school buses may yield significant health and climate benefits, cost savings

Photo, posted May 9, 2008, courtesy of Christine H. via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The carbon footprint of urban agriculture

March 22, 2024 By EarthWise Leave a Comment

Urban agriculture – essentially farming within a city – has become increasingly popular worldwide. It is intended to make cities and urban food systems more sustainable. There are social and nutritional benefits to urban agriculture, but its carbon footprint has not been widely studied.

There are high-tech, energy-intensive forms of urban agriculture, such as vertical farms and rooftop greenhouses. But most urban farms are decidedly low-tech such as individual gardens managed by single farmers and community gardens managed by small groups of people.

A comprehensive international study led by the University of Michigan calculated the greenhouse gas emissions associated with the materials and activities of urban farms over their operating lives. The emissions, expressed in the quantity of carbon dioxide equivalents produced per serving of food, were then compared to those of foods raised by conventional agriculture.

On average, food produced through urban agriculture emitted six times higher amounts of CO₂per serving than conventionally grown produce.

The study went on to recommend best practices crucial to making low-tech urban agriculture more carbon-competitive with conventional agriculture. These include making use of infrastructure for more extended periods of time, making use of urban waste, and maximizing social and health benefits.

Urban agriculture offers a variety of social, nutritional, and place-based environmental benefits and has its place in future sustainable cities. It is important to implement it in ways that are most beneficial.

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Study finds that urban agriculture must be carefully planned to have climate benefits

Photo, posted July 27, 2016, courtesy of Sandra Cohen-Rose and Colin Rose via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

New York is raising its shoreline

January 18, 2024 By EarthWise Leave a Comment

Superstorm Sandy in 2012 flooded 17% of New York City and caused $19 billion in damage. In its aftermath, plans emerged to create floodwalls, raised elevations, high-capacity drainage, and other infrastructure to protect the city from future Sandy-like events.

Like all large infrastructure projects in densely populated places, the remaking of New York’s shoreline has only moved along in fits and starts. But there has been significant progress.

The East Side Coastal Resiliency (ESCR) project is the largest urban resiliency project currently underway in the United States. The first piece of it – the Asser Levy renovation – was completed in 2022. Over the next three years, the $1.8 billion ESCR will reshape two-and-a-half miles of Lower Manhattan’s shoreline. The ESCR is just one part of a much larger $2.7 billion initiative called the BIG U, which is a series of contiguous flood resilience projects that will create 5.5 miles of new park space specifically designed to protect over 60,000 residents and billions of dollars in real estate against sea level rise and storm surges.

In a time of rising seas and increasingly powerful storms, flood-prone coastal U.S. cities – including Boston, Norfolk, Charleston, Miami, and San Francisco – are moving toward embracing the long-held Dutch concept of “living with water”, which emphasizes infrastructure that can both repel and absorb water while also providing recreational and open space.

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After a Decade of Planning, New York City Is Raising Its Shoreline

Photo, posted November 1, 2012, courtesy of Rachel via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Groundwater loss

December 21, 2023 By EarthWise Leave a Comment

Groundwater is the water found underground in the cracks and spaces in soil, sand, and rock. It is held in aquifers and bubbles up naturally into springs, streams, and rivers, but also is pumped out for use by people. Groundwater provides almost half the drinking water in the U.S. and is a main source of water for agriculture.

The world’s supply of groundwater is steadily declining. The combination of climate change and human population growth is increasingly diminishing groundwater.

A study by the Desert Research Institute published in the journal Nature Communications has mapped the global permanent loss of aquifer storage capacity for the first time. Computer modeling with advanced machine learning techniques has provided a detailed picture of the world’s groundwater situation.

The study found that global aquifer storage capacity is disappearing at a rate of 10 miles a year, about the size of 7,000 Great Pyramids of Giza. The loss of groundwater storage is permanent, forever reducing the amount of water that can be captured and stored because the pumping of groundwater can cause the ground surface above to sink, collapsing the space where water can be stored.

About 75% of this subsidence is occurring over cropland and urban regions. The United States, China, and Iran account for most of the global groundwater storage loss but many other places in the Middle East and Asia are experiencing significant groundwater withdrawal as well.

Most regions of the world do not have monitoring programs for groundwater pumping. The study underscores the need to better understand this issue on a global scale and take appropriate action before it is too late.

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Scientists Map Loss of Groundwater Storage Around the World

Photo, posted August 7, 2015, courtesy of NRCS Oregon via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Global Stilling | Earth Wise

October 20, 2022 By EarthWise Leave a Comment

During the summer of 2021, much of Europe experienced a “wind drought” – wind speeds in many places were about 15% below average. In the UK in particular, winds were unusually calm and wind energy production was dramatically reduced.

Globally, wind speeds have been dropping by about 2.3% per decade since the 1970s. In 2019, however, global average windspeeds actually increased by about 6%. The question is whether a trend of slowing winds – so-called global stilling – is associated with climate change or is just natural variability in action.

Wind results from uneven temperatures in air masses. Much of the world’s wind comes from the difference between the cold air at the poles and the warm air at the tropics. Because the Arctic is warming much faster than the tropics, it is possible that winds will continue to decline around the world.

Another factor people cite is the increase in surface roughness. The number and size of urban buildings continues to increase, which acts as a drag on winds.

Some models predict that wind speeds will decrease over much of the western U.S. and East Coast, but the central U.S. will see an increase. Experts do not all agree about what is happening with global winds. Many believe that the observed changes to date have been within the range of variability. Furthermore, some places have been windier than usual.

All of this really matters for many reasons. Europe is increasingly dependent upon wind power as an alternative to fossil fuels. A 10% drop in wind speed results in a 30% drop in energy generation. Whatever their cause may be, wind droughts cannot be ignored.

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Global ‘Stilling’: Is Climate Change Slowing Down the Wind?

Photo, posted June 28, 2008, courtesy of Patrick Finnegan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Timber Cities | Earth Wise

October 3, 2022 By EarthWise 2 Comments

More than half of the world’s population lives in cities and by 2100, this percentage is predicted to be much higher. This means that more homes will be built with steel and concrete, which both have very large carbon footprints. According to a study by the Potsdam Institute in Germany, housing a growing population in homes made of wood instead could avoid more than 100 billion tons of carbon dioxide emissions over the remainder of the century. This is about 10% of the remaining global carbon budget for staying below the 2-degree Celsius climate target.

The study presents the alternative of housing new urban populations in mid-rise buildings – no more than 4-12 stories high – that are substantially made of wood. Wood is a renewable resource that carries the lowest carbon footprint of any comparable building material. Trees take up CO₂ from the atmosphere to grow. Producing engineered wood releases far less CO₂ than production of concrete and steel and the finished product continues to store carbon.

The study shows that sufficient wood for new mid-rise urban buildings can be produced without a major impact on food production. The wood would come from timber plantations as well as natural forests. The study also looked at biodiversity impacts and ways that ecosystems could be protected while still providing the necessary timber.

Overall, the Potsdam study demonstrates that urban homes made out of wood could play a vital role in climate change mitigation based on their long-term carbon storage potential coupled with the reduced utilization of the carbon-intensive concrete and steel industries.

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Living in timber cities could avoid emissions – without using farmland for wood production

Photo, posted May 24, 2005, courtesy of Stig Anderson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Importance Of City Trees | Earth Wise

January 28, 2022 By EarthWise Leave a Comment

It is well known that green spaces can improve the quality of life and create a better climate in cities. City trees and vegetation can help reduce urban heat island effects by shading buildings and roads, deflecting radiation from the sun, and releasing moisture into the atmosphere. City trees and green spaces have also been proven to increase property values, promote wildlife and plant diversity, reduce noise pollution, and improve human health. But how important are trees and vegetation for producing cleaner air in cities?

According to a new study led by researchers at the University of Gothenburg in Sweden, trees do contribute to cleaner air in cities, but the degree to which they do so varies greatly between different locations.

The research team measured air pollutants across seven urban settings in the city of Gothenburg, and compared them with pollutants on the leaves of deciduous trees. The researchers chose to focus on polycyclic aromatic hydrocarbons (PAHs), which are pollutants generated primarily during the incomplete combustion of organic materials, like coal, oil, and wood.

The results revealed that the pollutants in leaves did increase over time. The researchers were able to show a clear correlation between the level of air pollutants and the concentration of pollutants in leaves.

But at the same time, the researchers discovered that pollution levels varied greatly between measurement sites. For example, the levels of PAHs were seven times higher at the most polluted site (the city’s main bus station) than they were at a location on the periphery of the city.

The research team hopes its findings will be used to help guide the planning of future urban landscapes.

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Trees are important for cleaner air in cities

Photo, posted November 5, 2021, courtesy of Maria Eklind via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Nanoplastics In The Air | Earth Wise

December 17, 2021 By EarthWise Leave a Comment

The world is awash in plastic. Discarded plastic litters our roadways, woodlands, and beaches. It piles up in landfills. Plastic enters the oceans by the millions of tons. And plastic is finding its way even to remote and supposedly pristine parts of the world.

A team of researchers has found nanoplastics at the isolated high-altitude Sonnblick Observatory in the Austrian Alps. This is the first time the particles were found in the area. The researchers were looking for certain organic particles and only found the nanoplastics by chance.

The detected plastic particles were less than 200 nanometers in size, about one hundredth the width of a human hair. It is highly unlikely that such particles originated in remote Alpine areas.

The researchers were looking for organic particles by taking samples of snow or ice, evaporating them, and then burning the residue to detect and analyze the vapors. They described the detection method as essentially like a mechanical nose. In this case, the nose smelled burning plastics in the form of polypropylene and polyethylene terephthalate.

Looking into the issue, the researchers found a strong correlation between high concentrations of nanoplastics and winds coming from the direction of major European cities – especially Frankfurt and the industrial Ruhr area of Germany, but also the Netherlands, Paris, and even London.

Modeling supports the idea that nanoplastics are transported by air from distant urban places. This is particularly worrisome because it means that there are likely hotspots of nanoplastics in our cities and in the air that we are breathing. Plastics appear to be everywhere.

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Nanoplastics found in the Alps, transported by air from Frankfurt, Paris and London

Photo, posted July 1, 2013, courtesy of Robert J. Heath 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.

The Importance Of Urban Green Spaces | Earth Wise

August 10, 2021 By EarthWise Leave a Comment

Projections are that 68% of the global population will be living in cities by 2050. It is therefore not surprising that urban green spaces are critically important for promoting mental and physical well-being.

An international study, published in Science Advances, took soil samples from different types of urban green spaces and comparable neighboring natural ecosystems in 56 cities from 17 countries across six continents.

The study concluded that even roadside plantings contribute a range of important microbial communities that are critical for sustaining productive ecosystems services, such as filtering pollutants and sequestering carbon dioxide.

Parks and gardens constitute most of the open spaces available for recreational activities in cities and play important roles in curbing pollution, reducing noise, and lowering air temperatures.

In addition, human exposure to soil microbes has been shown to be beneficial to human health by promoting effective immunoregulation functions and reducing allergies. The study found that city parks and even roadside plantings support a great variety of different microbes that are different from natural ecosystems.

We think of roadsides as being barren but the vegetation along footpaths and roadsides are important microbial habitats. Some European cities, such as Bern in Switzerland, have instituted policies to protect the natural vegetation along footpaths and roadsides.

The new study is a part of a series of research efforts looking at the important of green spaces for ecosystem health. As the world becomes increasingly urbanized, every bit of greenery in cities and highways is important and is needed for sustaining a healthy environment.

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Every spot of urban green space counts

Photo, posted June 3, 2013, courtesy of Manuel MV via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Residential Gardens And Pollinators | Earth Wise

April 2, 2021 By EarthWise Leave a Comment

A new study led by the University of Bristol in the UK measured for the first time how much nectar is produced in urban areas to gauge the role of residential gardens in providing nutrients for pollinators. They discovered that home gardens accounted for the vast majority of the crucial nutrients for pollinators; in fact, some 85% on average.

The study found that gardens generated a daily average of about a teaspoon of the unique sugar-rich liquid found in flowers which pollinators drink for energy. A teaspoon sounds like very little, but it is enough to feed thousands of bees.

The research examined nectar production in four major UK towns and cities and measured nectar production in nearly 200 species of plants. The results were that the nectar supply in urban landscapes is more diverse than in farmland and nature reserves. In addition, gardens are critical because they produce the most nectar per unit area of land and actually cover the largest area of land in the cities studied. In those cities, nearly a third of the land comprised domestic gardens, which is six times the area of parks and 40 times the area of small green allotments.

The upshot of the research is that home gardeners have a huge role to play in pollinator conservation. Without domestic gardens, there would be far less food for pollinators that include bees, wasps, butterflies, moths, flies, and beetles. Thus, it is important for home gardeners to keep planting nectar-rich flowers, mow lawns less often to let dandelions, clovers, and daisies flourish, avoid harmful pesticides, and avoid covering gardens in paving, decking, or artificial turf.

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Pioneering research reveals gardens are secret powerhouse for pollinators

Photo, posted June 23, 2018, courtesy of Wolfferl via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Even The Common House Sparrow Is Declining | Earth Wise

March 17, 2021 By EarthWise Leave a Comment

According to the first-ever comprehensive assessment of net bird populations published in 2019, nearly three billion birds have disappeared in the United States and Canada since 1970. The study, by researchers from the Cornell University Lab of Ornithology, found that North American bird populations have lost 2.9 billion breeding adults during that timespan. Forests lost one billion birds, and grassland birds declined 53%.

According to a newer study from Cornell University, it appears that even the common house sparrow is declining. In parts of its native range in Europe, house sparrow numbers are down nearly 60%. Researchers from the Cornell Lab of Ornithology sought to clarify the status of the species in the U.S. and Canada by using 21 years of citizen science data collected through its Project Feederwatch program.

Project FeederWatch is a winter-long survey of birds that visit feeders at backyards, nature centers, community areas, and other locales. For the study, which was recently published in the Wilson Journal of Ornithology, the research team reviewed recorded observations of house sparrows during their non-breeding season. These sightings from nearly 12,500 sites were used and cross-referenced with the National Land Cover database to determine whether the U.S. sightings came from rural or urban locations.

From 1995 to 2016, researchers found that Feederwatch sites reporting house sparrows declined 7.5%, and the mean flock sizes declined 22%. House sparrow populations declined in urban areas, but actually remained stable in rural areas.

The researchers say a lack of green space and nesting sites in urban areas are likely factors in the population declines.

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Study finds even the common house sparrow is declining

Nearly 3 Billion Birds Gone

Photo, posted May 14, 2014, courtesy of Jacob Spinks via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Street Trees And Depression | Earth Wise

February 25, 2021 By EarthWise Leave a Comment

**According to a study published in the journal Jama Network Open last fall, the COVID-19 pandemic has tripled the rate of depression in U.S. adults in all demographic groups.**

Previous studies have demonstrated that greenspaces in urban areas can have a positive effect on those people experiencing mental ill health. But most of those studies used self-reporting measures, which makes it difficult to compare results and draw conclusions.

As a result, an interdisciplinary research team from three research organizations in Germany tried to improve upon the work by involving an objective indicator: prescriptions of antidepressants. To figure out whether greenspaces – in this case street trees – could positively influence mental health, the researchers focused on how the number of street trees and their proximity to homes correlated to the number of prescribed antidepressants.

After analyzing data from nearly 10,000 people living in Leipzig, Germany, and combining the findings with data on city street trees, researchers were able to identify an association between antidepressant prescriptions and the number of street trees. The results were controlled for other factors known to be associated with depression, such as employment, gender, age, and body weight.

Having more trees within 100 meters of the home was associated with a reduced risk of being prescribed antidepressants. The association was especially strong for groups of people deprived of street trees.

Street trees in urban cities can not only serve as a nature-based solution for good mental health, but they can also contribute to climate change mitigation and biodiversity conservation.

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Street trees close to the home may reduce the risk of depression

Photo, posted August 17, 2011, courtesy of Aleksandr Zykov via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Lifestyle And Carbon Footprint | Earth Wise

March 23, 2020 By EarthWise Leave a Comment

Many studies have shown, to no great surprise, that affluent lifestyles lead to larger carbon footprints. Households in Switzerland enjoy a high standard of living and a team of researchers there has been studying the consumption and travel habits of Swiss citizens to better understand the impact of various factors on carbon footprint. Key factors include household composition and income, and whether the households are in the city or the countryside – even though, in the end, people’s lifestyles do not differ greatly from one environment to another.

A team of researchers at EPFL’s School of Architecture, Civil and Environmental Engineering analyzed data from Switzerland’s household budget survey for 2008, 2011 and 2014. They combined that data with an environmentally extended input-output analysis to assess households’ carbon footprints by measuring their direct and indirect emissions.

Overall, households in the countryside have larger carbon footprints than those in the city, mainly because they travel more and use more energy in their homes. But urban households have larger carbon footprints than their rural counterparts when it comes to food, clothing, cultural activities and air travel.

A household’s composition directly influences its carbon footprint. A two-person household has the largest per-capita carbon footprint, and it falls as the size of the family grows since many of the same resources are shared by more people.

Income levels play an important role. People consume without much thought because they can afford to and enjoy doing it. But there is a trend towards people becoming more conscious of their levels of consumption and trying to be more responsible in Switzerland. Overall consumption has actually declined over the years studied.

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Our carbon footprint is highly impacted by how we live

Photo, posted December 19, 2017, courtesy of Alexander Kozik via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Reducing Air Pollution With Plants | Earth Wise

January 15, 2020 By EarthWise Leave a Comment

New research by Ohio State University suggests that adding plants and trees to the landscapes near factories and other pollution sources could reduce air pollution by an average of 27%. In addition, the study indicates that, in many cases, plants may be a cheaper option for cleaning the air than more technological approaches.

The study looked at public data on air pollution and vegetation on a county-by-county basis across the lower 48 states. It then calculated what adding additional trees and plants might cost. The calculations included the capacity of current vegetation to mitigate air pollution as well as the effects that restorative planting might have on pollution levels.

In 75% of the counties analyzed, it was cheaper to use plants to mitigate air pollution rather than add technological interventions such as smokestack scrubbers to the sources of pollution. The results varied according to the pollution source. For example, technology is cheaper at cleaning the air near industrial boilers than ecosystem approaches. For the broad manufacturing industry, one approach or the other was favorable, depending on the type of factory.

Adding trees or other plants generally can lower air pollution levels in both urban and rural areas, although success rates depend on a variety of factors including how much land is available to grow new plants and current air quality.

Reducing air pollution is critical to public health. An estimated 4 in 10 people in the U.S. live in areas with poor air quality, leading to health issues including asthma, lung cancer, and heart disease. The study shows that nature should be part of the planning process for industry to deal with air pollution.

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Nature might be better than tech at reducing air pollution

Photo courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Urban Agriculture And Sustainability Goals

November 12, 2019 By EarthWise Leave a Comment

In 2016, the City Council of Phoenix, Arizona adopted eight Environmental Sustainability goals for 2050 that lay out the desired long term requirements in order to become a Sustainable Desert City. Recently, a group of researchers from Arizona State University assessed how urban agriculture can help Phoenix, a desert city of 1.6 million people, meet those sustainability goals.

Using public records and high-resolution satellite imagery, researchers analyzed the potential benefits of growing crops in three types of urban areas in Phoenix: vacant lots, rooftops, and building facades. The study, which was supported by the National Science Foundation and the USDA, estimated that there are 28 square miles (or 5.4% of city space) available for urban agriculture. The data-driven analysis found that 71% of the available areas for urban agriculture would come from existing buildings as opposed to vacant lots.

All this available space for urban agriculture in Phoenix could supply the city with nearly 183,000 tons of fresh produce annually, which would allow for the delivery of fresh fruits and vegetables to all of the city’s existing food deserts. In fact, the city’s own urban-agriculture output could meet 90% of the fresh produce demand that currently exists in Phoenix.

In addition to producing food, rooftop agriculture could also reduce the energy use in buildings by 3% per building per year, and displace more than 55,000 tons of CO2 annually. The use of vacant lots could increase the total Phoenix green space by 17%, and reduce the number of areas lacking green space by 60%.

This study demonstrates the many different ways that urban agriculture can benefit a city.

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Urban agriculture can push the sustainability

Photo, posted May 10, 2011, courtesy of Stephen Zank via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Cooling Down Urban Heat Islands

November 6, 2019 By EarthWise Leave a Comment

Researchers have known about and studied the urban heat island effect for quite some time. Since large cities began to emerge in the 19th century, it has been understood that various aspects of the urban environment lead to warmer temperatures than the surrounding countryside.

Researchers led by a group at Portland State University in Oregon have been utilizing a new way of studying the urban heat island effect. They have used citizen science volunteers in 24 cities around the world to map temperatures in the cities at ground level in great detail using mobile sensors attached to slow-moving vehicles. Previous studies have used data from satellite or stationary sensors. They have learned that the urban heat island effect is more complicated, more varied, and subtler than the earlier data indicated.

They found that there are six things that affect urban heat. Three are living — the volume of the tree canopy, the height of the tree canopy, and the ground level vegetation. Three are human-built — the volume of buildings, the difference in building heights, and the coloring of the buildings.

Buildings can have both negative and positive effects. Tall buildings that cast shade actually lower relative afternoon temperatures, while densely packed shorter buildings, like the big-box stores in suburban areas, lead to hotter afternoon temperatures. The studies show that increasing the difference in building heights in an area creates more air circulation, which has a cooling effect.

The study also showed that urban heat is a social justice issue. Lower-income neighborhoods largely barren of trees have considerably higher temperatures than more affluent, tree-shaded areas.

Such detailed research can be used to guide decisions in urban planning with regard to trees, building heights, and the color and type of surfaces in our urban spaces.

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Can We Turn Down the Temperature on Urban Heat Islands?

Photo, posted July 21, 2009, courtesy of Daniel Dionne via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Electric Buses In Latin America

October 31, 2019 By EarthWise Leave a Comment

Latin America has become increasingly urbanized. In fact, about 80% of the region’s population lives in cities today and by 2050, that figure could climb to 90%. Transportation is the largest and fastest-growing source of energy-related emissions in Latin America and accounts for about a third of all of the region’s carbon dioxide emissions.

Private vehicle ownership is rising in Latin America but at the same time, the region’s rapidly growing cities have increased demand for buses, taxis, and motorcycles. Currently, an estimated 64,000 people die prematurely every year in Latin America and the Caribbean as a result of air pollution, which is mostly caused by transportation emissions.

Given this situation, major cities across Latin America – from Colombia to Argentina – are starting to adopt electric bus fleets. Latin America actually has the highest use of buses per person globally. So, the transition to electric buses is an important step toward meeting climate targets, cutting fuel costs, and improving air quality.

Medellin, Colombia – whose metropolitan area has 3.7 million people – has started to add electric buses to its fleet, the rest of which runs on natural gas. When new units arrive from China later this year, Medellin will have the second largest electric bus fleet in Latin America, after Santiago, Chile.

Worldwide, 425,000 electric buses are in operation, 99% in China. Europe has a couple of thousand while the United States has only 300. But going forward, and especially in Latin America, electric buses are the wave of the future. Estimates are that there will be 1.3 million on the roads by 2040.

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