Climate & Environment

Drone experiment reveals how Greenland ice sheet is changing

Yvaine Ye — Thu, 27 Mar 2025 14:54:06 +0000

Drone experiment reveals how Greenland ice sheet is changing Yvaine Ye Thu, 03/27/2025 - 08:54

Yvaine Ye

For the first time, researchers have collected detailed measurements of water vapor high above the surface of the Greenland ice sheet. Their research, aided by a custom-designed drone, could help scientists improve ice loss calculations in rapidly warming polar regions.

Kevin Rozmiarek (Credit: Hayley Bennett)

“We will be able to understand how water moves in and out of Greenland in the next few years,” said first author Kevin Rozmiarek, a doctoral student at the Institute of Arctic and Alpine Research (INSTAAR) at CU ��Vlog�ƽ��. “As a major freshwater reservoir, we need to understand how Greenland’s environment is going to change in the future.”

The findings were published March 14 in JGR Atmospheres.

According to the National Oceanic and Atmospheric Administration (NOAA), Greenland lost about 55 gigatons of ice and snow between fall 2023 and fall 2024. The island is shedding ice for the 28th year in a row, and scientists estimate that it has lost more than 5 trillion tons of ice since 1992.

The Greenland ice sheet contains about 8% of the planet’s freshwater, and its meltwater could contribute significantly to rising sea levels, changing ocean circulation and ecosystems worldwide.

The majority of ice loss comes from large ice chunks breaking off from glaciers and the melting of surface ice and snow. Sublimation, the process of solids turning into gases without turning into liquids first, may also play a role. Prior studies have suggested that in some parts of Greenland, about 30% of summer surface snow could sublimate to water vapor.

A drone landed on the Greenland snow surface at EastGRIP. (Credit: Ole Zeising/Alfred-Wegener-Institute)

Tracking water in the sky

It is unclear where the water vapor goes, said Rozmiarek, who's also a student in the Department of Geological Sciences. Some might fall back down as snow or recondense on the surface later, but some could leave Greenland’s water system entirely.

Collecting air samples in the Arctic is an expensive and technically challenging task, because it traditionally involves flying a plane to the middle of an ice sheet in harsh weather and carrying air samples back to the laboratory.

Rozmiarek and his team overcame the challenges by loading air sampling equipment on a large drone with a 10-foot wingspan.

Throughout the summer of 2022, the team flew the drone 104 times from the East Greenland Ice-Core Project camp—managed by the University of Copenhagen— in the island’s interior. The drone collected air samples at different heights of up to nearly 5,000 feet above the ground.

The team aimed to look into the type of hydrogen and oxygen atoms in the air’s water vapor. Water molecules from different sources contain distinct combinations of hydrogen and oxygen. Scientists call these variations in isotopes.

A launched drone bound for collecting air samples for isotopic analysis at EastGRIP, Greenland. (Credit: Ole Zeising/Alfred-Wegener-Institute)

“Isotopes are water’s fingerprints. By following these fingerprints, we can trace back to the source where the water vapor came from,” Rozmiarek said. Scientists have collected high-quality data on the source of water in Greenland, including water that flows from the tropics, and the sink, which is the surface snow on the Greenland ice sheet. “But we don’t know much about the isotopic composition of water in motion, which is the vapor between the source and sink,” he added.

When the team compared their drone-based measurements with an existing computer simulation that models the Arctic water cycle, they found the simulation underestimated the amount of precipitation that fell on Greenland. By incorporating the isotopic data observed in the simulation, the model rendered an accurate prediction of how water moves over Greenland.

“It’s really important to be able to predict what’s going to happen to Greenland in the warming world as accurately as possible,” Rozmiarek said. “We demonstrated how useful water vapor isotope data is by successfully improving an existing model.”

Melting ice sheet

About 125,000 years ago, when Earth was warmer than preindustrial levels, Greenland was covered by a significantly smaller ice sheet, and the sea level was as much as 19 feet higher than today. As the planet continues to warm, the Greenland ice sheet could see dramatic changes and even shrink to its size back then, Rozmiarek said.

The Greenland ice sheet contains a massive amount of freshwater, and that water, if leaving the system, could lead to significant increases in global sea level. The United Nations estimated that rising sea levels caused by climate change currently impact 1 billion people worldwide.

Rozmiarek hopes to return to Greenland and other parts of the Arctic to conduct more flights and gather additional data.

“It’s like we just figured out how to discover fingerprints at a crime scene. This is a concrete step forward in understanding where water is going and where it is coming from in this important system at a time when we need it most,” he said.

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A CU ��Vlog�ƽ��-led study measured water vapor in Greenland’s air, collecting data crucial for improving climate models and forecasting Arctic changes.

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A drone landed on the Greenland snow surface at EastGRIP.(Credit: Kevin Rozmiarek/CU ��Vlog�ƽ��)

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A drone landed on the Greenland snow surface at EastGRIP.(Credit: Kevin Rozmiarek/CU ��Vlog�ƽ��)

Wildfires, windstorms and heatwaves: How extreme weather threatens nature's essential services

Yvaine Ye — Mon, 24 Mar 2025 16:19:06 +0000

Wildfires, windstorms and heatwaves: How extreme weather threatens nature's essential services Yvaine Ye Mon, 03/24/2025 - 10:19

Yvaine Ye

How much will strawberry harvests shrink when extreme heat harms pollinators? How much will timber production decline when windstorms flatten forests? How much will recreational value disappear when large wildfires sweep through Colorado’s mountain towns?

These are some critical questions that a new computer simulation, co-developed by a CU ��Vlog�ƽ�� ecologist, can answer. In a paper published March 5 in Nature Ecology & Evolution, researchers presented a model that aims to understand how extreme weather events, worsened by climate change, will affect ecosystems and the benefits they provide to humans.

Laura Dee

Based on the model, a Minnesota forest could lose up to 50% of its timber revenue if a severe windstorm hits.

“With climate change, there’s an urgent need to incorporate the impacts of extreme events like mega-fires and hurricanes have on the benefits nature provides,” said Laura Dee, the paper’s first author and associate professor in the Department of Ecology and Evolutionary Biology. “This research is an important step toward anticipating impacts to ecosystem services so that we can adapt management strategies accordingly.”

Scientists use the term “ecosystem services” or “nature’s contributions to people” to refer to the essential functions that nature provides to support human life and well-being. Tree roots purify water, insects pollinate crops and forests lock away carbon, helping to stabilize the climate. In addition to these tangible benefits, mountains, lakes and oceans offer recreational enjoyment for people and hold cultural significance for communities.

Previous models for predicting how ecosystems respond to climate change tend to assume that changes are steady. For example, a gradual increase in global temperatures of up to 1.5°C. But as climate change makes extreme weather events like wildfires and floods more frequent and severe, the impacts from rapid disturbances have become significant.

Dee and her team developed a new mathematical model that tracks how the probability of an extreme weather event affects certain species and the ecosystem services they provide. The model also incorporates how people value these services.

To show the model’s potential, the team applied it to calculate the possible consequences of extreme windstorms in a mid-latitude forest in northern Minnesota. The model considered how winds have different effects on different tree species, each of which has distinct economic value. For example, thick white cedar trees are more resilient to windstorms than balsam fir trees, but the balsam fir can sell at a higher price.

The model suggested that a windstorm, depending on its intensity, can slash the total timber value of the forest by 23% to 50%. Recreational opportunities like hiking and camping would also take a hit.

Dee said that researchers and land management officials could use the model to evaluate the impacts of any disturbances, from drought to invasive species.

Dee’s research group at CU ��Vlog�ƽ�� studies how prescribed fire strategies, or deliberately burning specific areas under controlled conditions, can reduce wildfire risks in Colorado.

The new model also helps to identify the areas where scientists should prioritize burning to achieve the greatest reduction in fire risk, while also considering other benefits trees provide, such as removing carbon dioxide from the atmosphere and filtering water.

“Nature’s contributions to people have not typically been valued and are usually left out of key decision-making processes when developing land management policies and strategies,” Dee said.

The United Nation’s World Meteorological Organization announced on Tuesday that more than 150 unprecedented extreme weather events struck Earth last year. With disturbances becoming more common, future Gross Domestic Product analyses, for example, should start incorporating the impacts of climate change, Dee added.

“If we fail to consider the growing risks from extreme weather events, we could lose more than we realize,” she said.

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A new model suggests that timber production in Minnesota could decrease by half as windstorms intensify with climate change.

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A forest in Minnesota. (Credit: James St. John/Flickr)

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A forest in Minnesota. (Credit: James St. John/Flickr)

CUriosity: What makes Colorado so windy—and will it stay that way?

Daniel William Strain — Fri, 21 Mar 2025 22:12:10 +0000

CUriosity: What makes Colorado so windy—and will it stay that way? Daniel William… Fri, 03/21/2025 - 16:12

Daniel Strain

In CUriosity, experts across the CU ��Vlog�ƽ�� campus answer pressing questions about humans, our planet and the universe beyond.

This week, meteorologists Andrew Winters and McKenzie Larson weigh in on the question: “What makes Colorado so windy—and will it stay that way?”

Winds swoop over Colorado's Rocky Mountains. (Credit: CC photo by Zach Dischner via Flickr)

Whoosh. This month, a series of windy days went roaring through Colorado’s Front Range. Gusts topped out at more than 80 miles per hour on March 17 in ��Vlog�ƽ�� and caused a few power outages.

It’s not an unusual occurrence for the region in its colder months, said the aptly named meteorologist Andrew Winters. In ��Vlog�ƽ��, locals are no strangers to getting knocked off their bikes by winds that can hit 90 or even 100 miles per hour.

McKenzie Larson installs a precipitation wind shield at the CU ��Vlog�ƽ�� Mountain Research Station at Niwot Ridge in 2023. (Credit: McKenzie Larson)

“You’ll hear people from a lot of places saying, ‘You don’t like the weather, just wait five minutes.’ I think the Front Range has a pretty good claim to being where that’s most true,” said Winters, assistant professor in the Department of Atmospheric and Oceanic Sciences (ATOC) at CU ��Vlog�ƽ��. “We get severe thunderstorms, tornadoes, hail, strong winds. The only phenomenon we don’t get here in Colorado is hurricanes.”

So how does the Front Range’s weather get so blustery—and will it stay that way as the planet’s climate changes?

It’s a topic that McKenzie Larson, a doctoral student in Winters’ lab, is exploring. She’s originally from Florida but earned her bachelor’s and master’s degrees at CU ��Vlog�ƽ��. In the process, she became taken by the state’s more mercurial weather.

“In ��Vlog�ƽ��, our proximity to the Flatirons and complex terrain pose quite a challenge for weather forecasts,” Larson said. “We can get a lot of temperature whiplashes.”

She explained that, in the Front Range, severe winds tend to come in two flavors: chinook and bora winds.

Boras usually arrive just after a cold front snaps through Colorado, while chinooks bring warmer winds. (The gusts on March 17 fell into that warmer category). They both tend to peak in the winter months and both occur when winds arriving from the west slam into the Rocky Mountains.

“Those warmer winds come more often from the southwest or the west,” she said. “The boras, along with the associated the cold fronts, often come from the northwest.”

When that happens, those westerly winds feel the squeeze. The moving air is forced between the tops of the mountains and what meteorologists call a “stable layer” of the atmosphere—a layer where the temperature of the atmosphere increases with altitude rather than decreases, which is more common. Winds pick up speed as they pass between the mountain tops and this stable layer and, by the time they near ��Vlog�ƽ��, are ready to scream downhill.

Previously in CUriosity

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Or read more CUriosity stories here

But will living in Colorado always feel like being in the Wizard of Oz?

That’s not clear, Larson said. She noted that as the state warms, that stable layer above the mountains could climb higher in the atmosphere. Without that lid, winds may not feel as much of a squeeze as they pass over the mountains and could slow down.

Larson and Winters took part in a recent study that unearthed the first hints that such a slowdown may already be happening. The research was led by scientists at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR). The group reported that scientists at NCAR recorded one blast of air in ��Vlog�ƽ�� in 1971 moving at a staggering 147 miles per hour. Today, measurements at roughly the same location rarely exceed 100 miles per hour.

Scientists need to do a lot more research before they can say for sure how climate change could shift Colorado’s erratic winds. But those kinds of questions matter for more than just weather buffs, Winters said. Chinook winds moving east were one of the main factors that made the Marshall Fire in 2021 so devastating for ��Vlog�ƽ�� County.

“Even if winds slow down, these events are still going to happen, and they’re going to happen in an environment that will likely have less wintertime snow cover than in the past,” Winters said. “That could lead to more events like the Marshall Fire, especially when we have more people living closer to the mountains.”

March 2025 has been a gusty month for Colorado's Front Range. Meteorologists Andrew Winters and McKenzie Larson break down what makes the region's weather so mercurial.

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Researchers coin ‘thirstwaves’ as new term for prolonged periods of atmospheric thirst

Megan Maneval — Fri, 21 Mar 2025 13:24:27 +0000

Researchers coin ‘thirstwaves’ as new term for prolonged periods of atmospheric thirst Megan Maneval Fri, 03/21/2025 - 07:24

CIRES

Most people have heard of heatwaves: extended periods of abnormally hot weather. But researchers from CIRES and the University of Idaho have coined a new term to describe extended periods of atmospheric thirst. Studying these ”thirstwaves“ can help farmers better manage their water resources and improve crop yields.

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CIRES hosting international meeting of Arctic researchers

Megan Maneval — Thu, 20 Mar 2025 19:20:00 +0000

CIRES hosting international meeting of Arctic researchers Megan Maneval Thu, 03/20/2025 - 13:20

CIRES

A summit underway at CU ��Vlog�ƽ�� through March 28 is bringing an estimated 800 people from more than 40 countries to plan for the future of the Arctic.

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Small bird, big trick: How a hummingbird chick acts like a caterpillar to survive

Yvaine Ye — Mon, 17 Mar 2025 14:53:18 +0000

Small bird, big trick: How a hummingbird chick acts like a caterpillar to survive Yvaine Ye Mon, 03/17/2025 - 08:53

Yvaine Ye

When Jay Falk and Scott Taylor first saw the white-necked Jacobin hummingbird chick in Panama’s dense rainforest, the bird biologists didn’t know what they were looking at.

A white-necked jacobin hummingbird chick. (Credit: Michael Castaño-Díaz)

The day-old bird, smaller than a pinky finger, had brown fuzz all over its body. When Falk and Taylor walked closer to the nest, the chick began twitching and shaking its head—a behavior they had never seen in birds before.

It turns out the hummingbird might fend off predators by mimicking a poisonous caterpillar that lives in the same region. In a new paper published March 17 in Ecology, Taylor, associate professor in the Department of Ecology and Evolutionary Biology at CU ��Vlog�ƽ��, and his team described this unusual mimicry behavior for the first time in hummingbirds.

“We know so little about what nesting birds do in the tropics,” said Falk, the paper’s first author and postdoctoral fellow in Taylor’s lab. “But if we put more effort into observing the natural world, we might discover these kinds of behavior are very common."

A chance discovery

White-necked jacobin hummingbirds are common in Central and South America. Male birds have shimmering blue and green feathers, while females tend to sport low-key green plumage.

The tropical rainforest is a dangerous place for small birds, said Falk, who’s also a researcher at the Smithsonian Tropical Research Institute. Snakes, monkeys, birds and even insects all prey on them. Prior studies have suggested that bird chicks in the tropics are more likely to be eaten by predators than those in temperate forests.

So how can tiny hummingbird chicks survive? Falk may have stumbled on the answer during a trip to Soberanía National Park in Panama in 2024.

A white-necked jacobin hummingbird was incubating its eggs. (Credit: Michael Castaño-Díaz)

Despite the birds’ frequent visits to Falk’s feeders outside his research station in Panama, Falk had never seen a white-necked jacobin chick or its nest before.

But last March, co-authors Michael Castaño at the Smithsonian Tropical Research Institute and Sebastian Gallan-Giraldo at the University of Antioquia in Colombia discovered a female jacobin hummingbird incubating an egg in its nest, not far from a forest trail. The nest, smaller than Falk’s palm, was made of plant parts to blend in perfectly with the surrounding environment.

Over the following month, the team closely monitored the nest and witnessed a chick hatch from the egg. Unlike most hummingbirds that are born naked, the jacobin chick was covered in long brown feathers, looking nearly identical to the nest material. That’s when the team witnessed the chick’s unusual jerking behavior. Scientists had never reported a similar behavior in any other hummingbird species.

“I started texting a video to people and asking them, ‘What does this look like?’” said Taylor. “And invariably, they said, ‘That looks like a caterpillar.’ It was very exciting.”

On the second day after the egg hatched, the team saw a predatory wasp approach the chick when the mother was away. As the wasp hovered above the nest, the chick started to twitch its body vigorously like it had for the researchers, swinging its head from side to side. A few seconds later, the wasp flew away.

Surviving the tropical rainforest

The jacobin hummingbird chick reminded Falk and Taylor of a paper they came across previously. Another team of researchers reported that a young cinereous mourner, a songbird native to the Amazonian rainforest, might resemble toxic orange caterpillars from the region by having a bright orange coat and waving its head from side to side when disturbed.

Falk and his colleagues looked into other caterpillars in this region of Panama and found that many have similar-looking brown hairs that can give painful stings to predators and even kill them. Some of these caterpillars also shake their heads when they feel threatened, much like the chick.

Scientists refer to this survival strategy of mimicking the defensive signaling of a harmful species as Batesian mimicry. For example, some non-venomous milk snakes have developed a pattern of red, yellow and black coloring similar to that of venomous coral snakes to ward off predators.

“A lot of these really classic examples of Batesian mimicry involve butterflies mimicking other butterflies, or snakes mimicking other snakes. But here, we have a bird potentially mimicking an insect, a vertebrate mimicking an invertebrate,” Taylor said.

While the study described a single observation, the researchers hope to test their theory in the future through experiments like placing artificial chicks with different looks and behaviors in nests to see which are more likely to be attacked by predators. They also hope to encourage birdwatchers and citizen scientists to document more hummingbird nests.

“Our perception of the natural world is very biased by our own thoughts about what could be possible,” Taylor said. “It’s incredible what we can discover, but we really have to think broadly.”

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For the first time, scientists described a hummingbird chick potentially mimicking a poisonous caterpillar to avoid getting eaten.

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The hummingbird chick was covered in long brown feathers. (Credit: Scott Taylor/CU ��Vlog�ƽ��)

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A white-necked jacobin hummingbird chick. (Credit: Scott Taylor/CU ��Vlog�ƽ��)

People of color breathe Denver’s smelliest air

Yvaine Ye — Thu, 13 Mar 2025 15:56:51 +0000

People of color breathe Denver’s smelliest air Yvaine Ye Thu, 03/13/2025 - 09:56

Yvaine Ye

In Denver, people of color and those with lower household incomes are more likely to live in neighborhoods near facilities that emit bad smells, a new CU ��Vlog�ƽ��-led study reported.

For many Denver residents, the city’s crisp mountain air is a perk of living near the Rocky Mountains. But every so often, a gust of wind can carry less welcome scents, like the pungent odor of pet food factories or the skunky smell of marijuana grow houses.

In a paper published Feb. 22 in the Journal of Exposure Science & Environmental Epidemiology, scientists revealed inequality in exposure to Denver’s odor. The research found that while racial minorities and socioeconomically marginalized communities are more likely to be exposed to bad smells, residents in gentrifying neighborhoods file more odor complaints.

If you experience strong environmental odors:

Submit a complaint to the City and County of Denver by phone at 720-913-1311, or email at 311@denvergov.org.

“Our study suggests that there's potentially an underreporting of odor in certain neighborhoods,” said first author Priyanka deSouza, a researcher with CU ��Vlog�ƽ��’s Institute for Behavioral Science and assistant professor at the University of Colorado Denver. “Some residents in these communities that are disproportionally affected by odor may not feel that their voices are being heard.”

Before 2016, Denver, like many cities across the U.S., used an inefficient and archaic way to address odor issues, according to Shelly Miller, the paper’s senior author and professor in the Department of Mechanical Engineering at CU ��Vlog�ƽ��.

Traditionally, when the city received complaints about an odor issue, an odor inspector would go to the site and sniff through an odor measuring device, but these inspections often found nothing. Because odor is very transient, by the time the inspector arrived, the smell might be long gone.

A 1938 map illustrates the redlining of neighborhoods in the City and County of Denver. (Credit: Home Owners' Loan Corporation/Wikimedia Commons)

“Odor is a complex issue. It’s very hard to measure, and it’s subjective. You probably smell things differently than I do, but that doesn’t mean what you’re smelling is any less valid than what I’m smelling,” Miller said.

Miller’s previous studies in odor and air quality, as well as concerns from local communities, prompted the Denver Department of Public Health and Environment to update its air pollution control ordinance in 2016. A new rule requires odor emitting facilities, including pet food factories and marijuana growers, to submit odor control plans if they receive five or more complaints within a 30-day period.

“This updated rule is one of the most innovative odor ordinances of all major cities in the U.S. It’s willing to take action based on community complaints,” deSouza said.

The team mapped out all 265 facilities in Denver that had to submit an odor control plan as of 2023. More than 96% of these facilities were marijuana growers, processors and manufacturers. The rest included pet food manufacturing, oil refining and construction.

They found that malodorous facilities are more often located in historically redlined neighborhoods. After the Great Depression, the U.S. government implemented a racist and discriminatory policy that designated neighborhoods with racial and ethnic minority residents as high-risk, or “red” for mortgage lenders.

In Denver, these neighborhoods are located along the city’s two major interstate highways, I-70 and I-25, and still host a higher percentage of people of color. A prior CU ��Vlog�ƽ�� study revealed that residents in these historically redlined areas are exposed to higher levels of air pollution.

When the team compared the odor facility map to an odor complaint map, they found that neighborhoods more susceptible to odor did not file more complaints than other neighborhoods. Instead, more complaints per population came from older neighborhoods that are transitioning into more modern, wealthier neighborhoods, like River North in Denver’s city center.

It is unclear why gentrification has led to more odor complaints, but it could be that the more privileged feel more empowered to file complaints, the authors said. New residents could also be more sensitive to the city’s smells compared to long-term residents.

“Given that odor complaints are the primary driver for Denver to take action on odor control, I hope our findings could encourage the city to continue working on rebuilding trust with these communities and empower them to use the tool,” deSouza said.

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A new study found racial and socioeconomic disparities in where odor-emitting marijuana grow houses and other malodorous factories are located in Denver and in how communities report these issues.

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Ariel view of Denver. (Credit: Jacob/Adobe Stock)

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How COVID-19 challenged car-centric cities, and what comes next

Yvaine Ye — Wed, 12 Mar 2025 17:08:35 +0000

How COVID-19 challenged car-centric cities, and what comes next Yvaine Ye Wed, 03/12/2025 - 11:08

Yvaine Ye

In February, the city of Denver reopened a segment of a restaurant-lined street in its town center to car traffic. The move ended a five-year experiment that created new space for fresh-air strolling and socializing during the COVID-19 pandemic.

Denver’s Larimer Street was one of hundreds of U.S. streets that opened to bikers and pedestrians during the pandemic, limiting car traffic. These street-focused emergency response measures, billed as “open streets,” “slow streets” or “shared streets,” allowed restaurants to expand their outdoor dining spaces and provide safe spaces for walking or rolling on bikes. Kevin J. Krizek, a professor of environmental design, has researched these measures.

Kevin Krizek

“That was a valuable experiment, allowing cities and residents to see their public spaces in different ways,” Krizek said. “They showed the power of spurring vibrant spaces when people eat outside and brought different forms of society together in these areas.”

But five years later, many of these trial programs have ended as funding, permits and support ran out.

In 2022, ��Vlog�ƽ��, Colorado, reverted a stretch of its West Pearl Street to better accommodate car traffic. In New York City, the number of open street project miles dwindled from 83 to just 20 between 2020 and 2022.

Krizek shared his take about how COVID-19 temporarily changed cities across the United States, what cities learned and why many of these forward leaning programs didn’t last.

How did COVID-19 reshape our cities?

During COVID-19, experimentation with slow or open streets was a big breakthrough. Neighbors saw their public space in new light and leaned on their nearby streets to provide space for walking, riding bikes and meeting people in safe spaces.

Americans often travel to Europe to experience the vibrant outdoor cafes and active street life. COVID allowed them to see the possibility of doing that here and the power of changing streets overnight. That's one of the most valuable lessons COVID taught us: Street space could quickly change and be used for more than moving and storing cars.

Are American cities designed to support pedestrians, bikes and safe public spaces?

No. American cities are mostly designed to maintain the swift movement of cars. If you take an aerial view of the country, roughly a third of our cities are devoted to space owned by the public, and most of that space is devoted to either storing or moving cars.

Coming out of the second industrial revolution in the 1930s, city designers began writing a whole labyrinth of legislative codes to prescribe the width of travel lanes, the turning radii and the length of a green light. All these rules were designed to swiftly move cars.

These outdated codes have become the architectural blueprint for most American cities and continue to be followed.

Children playing on a street in New York City during an open street program. (Credit: Street Lab)

What are the consequences of that design?

In the past decades, cars in the U.S. have become larger, higher, more intimidating and heavier. They are now more dangerous, especially at high speeds.

Cities continue to allow these vehicles to dominate our streets, all in the interest of convenience and economic vitality. But swiftly moving traffic and safe walking are mostly mutually exclusive, particularly around intersections.

Traffic violence has killed more than 40,000 people each year over the past years in this country. That number equals a Boeing 737 plane going down every other day. When a plane crashes, we spend months investigating the cause. But when a car crash happens, we sweep up the carnage as quickly as we can, and we revert the system back to ‘normal’ conditions as quickly as we can. We fail to properly investigate and address the underlying factors that lead to these crashes. We've all become complacent with the risk and the need for speed, assuming there’s little to be done.

How did the public respond to these COVID-era experiments?

Many communities used these street changes as novel experiments. Studies found that, despite the isolation of COVID, people leaned into public spaces, which helped the local community integrate in ways that were previously unfathomable.

Why were they discontinued?

A lot has to do with how we frame the access to key spaces in our communities. Because American cities are designed for cars, many businesses are only accessible by driving there. Such businesses claim that if you diminish that access, you're compromising economic vitality.

That’s mostly an unsupported fear. There’s a slew of studies showing that if a town provides for multiple ways to get there, over time, more people access these businesses using varied modes.

What can individuals do to push for more pedestrian-friendly cities?

We, as a society, collectively accept an enormous amount of risk every time we get in and out of our cars. That risk comes with personal conveniences. We can ask ourselves to better understand the costs of these personal conveniences and to accept better street planning protocol that allows lower speeds and heightens safety on our transportation system.

People who want their cities to become safer and more pedestrian-friendly can approach their city council person and say, ‘We'd like to express our desire to move beyond the existing codes that lock us in.’ Changing existing codes, while challenging, is possible when citizens empower their city councils to think differently and create safer public streets.

CU ��Vlog�ƽ�� Today regularly publishes Q&As with our faculty members weighing in on news topics through the lens of their scholarly expertise and research/creative work. The responses here reflect the knowledge and interpretations of the expert and should not be considered the university position on the issue. All publication content is subject to edits for clarity, brevity and university style guidelines.

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Our sustainability impact by the numbers:

First student-run campus environmental center in the U.S.
No. 11 university for environmental and social impact in the U.S.
First zero-waste major sports stadium in the U.S.

Follow CU ��Vlog�ƽ�� on LinkedIn

Environmental designer Kevin Krizek shares how systemic barriers and status-quo planning have led many cities to revert to car-dominated designs five years after the pandemic.

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Denver opened up several blocks of its Larimer Street to pedestrians and bikes during COVID-19. (Credit: Jacob/Adobe Stock)

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Denver opened up several blocks of its Larimer Street to pedestrians and bikes during COVID-19. (Credit: Jacob/Adobe Stock)

Sea otters help kelp forests recover—but how fast depends on where they are

Megan Maneval — Tue, 04 Mar 2025 19:58:47 +0000

Sea otters help kelp forests recover—but how fast depends on where they are Megan Maneval Tue, 03/04/2025 - 12:58

CIRES

A new modeling method developed by CU ��Vlog�ƽ�� researchers helped scientists understand why kelp forests returned more slowly in Southern California than in British Columbia.

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Institute of Behavioral Science grad student helps farmers balance economic livelihoods, conservation

Megan Maneval — Fri, 28 Feb 2025 15:26:00 +0000

Institute of Behavioral Science grad student helps farmers balance economic livelihoods, conservation Megan Maneval Fri, 02/28/2025 - 08:26

Savannah Lehnert will help cacao farmers in Brazil balance their economic livelihoods with conservation methods, advancing agroforestry conservation in an intensely biodiverse region.

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