Speakers from California, Georgia and Texas outlined their plans for more high-speed rail projects at a conference in Washington, D.C., in May as a growing number of states and cities are looking into ways to bring bullet trains to their communities. 

The 2021 infrastructure law provided up to $12 billion over five years for rail projects outside the Northeast Corridor, which can include new intercity passenger rail service such as high-speed trains.

“The president wants to go faster on rail. He wants more rail to help with the climate and he wants to produce a lot of jobs and he sees high-speed rail as a part of that,” said White House Senior Advisor and Infrastructure Coordinator Mitch Landrieu at the conference.

The nation’s two most prominent high-speed rail projects are the California effort to connect Los Angeles and San Francisco — the first segment of which is under construction — and the proposed Brightline West project between Las Vegas and Southern California. Both are looking to tap the nearly $4.6 billion in federal funds available for the 2022-2023 fiscal years.

But studies and planning are underway for several other projects that participants described at the conference, organized by the US High Speed Rail Association.

Clement Solomon, division director at the Georgia Department of Transportation, said the agency is looking at routes including Atlanta-Charlotte, North Carolina; Atlanta-Savannah, Georgia; and Atlanta-Chattanooga, Tennessee. The Chattanooga project received a final Tier 1 environmental impact statement and record of decision from the Federal Railroad Administration, while the Georgia DOT is conducting a Tier 1 EIS for the Charlotte route, which it hopes will someday connect with high-speed rail lines to Washington, D.C. 

Last year, the Georgia DOT received $8 million in federal funds to begin environmental studies for the Savannah route. “This was a Congressionally-directed spending project that we have embarked on,” Solomon said at the conference.

Texans have been waiting for, and some have fought against, a proposed Dallas-Houston high-speed rail line for nine years, which was to be privately financed. But little has been heard from the company since 2020 and no construction has begun. However, the North Central Texas Council of Governments has done “a lot of high-speed rail planning,” said the organization’s program manager for transportation planning - Metropolitan Transportation Plan, Brendon Wheeler, speaking at the conference. Wheeler said that the council had studied high-speed rail linking Dallas and Fort Worth, Texas, in 2020, and has looked at regional planning for Dallas-Houston and Dallas-San Antonio lines.

Besides the two existing California projects, four cities, the county of Los Angeles and the Los Angeles County Metropolitan Transportation Authority are jointly backing a proposed 54-mile high-speed rail line to connect Palmdale and other high desert cities with the future Brightline West corridor and the California high-speed rail system.

The California State Transportation Agency recently granted $8 million to the High Desert Corridor Joint Powers Agency last year for preliminary engineering and other development activities. “Hopefully by sometime next year … we should be environmentally cleared with a Record of Decision to move forward and get into final design and construction,” said Arthur Sohikian, executive director of the HDC JPA.

In early February, winter weather pummeled Austin, Texas, where “extreme weather” usually refers to sweltering temperatures, not ice storms. More than 100,000 city residents lost power because of the historic weather event, a recent example of why cities need to prepare for a changing climate.

To Katie Coyne, Austin's environmental officer and assistant director of the Watershed Protection Department, climate change adaptations will require rethinking the interplay between the urban environment and what we consider nature: trees, plants and the ecosystems undergirding them.

“Historically, we’ve thought of [environmentalism] as at odds with development [and] urban places,” Coyne said.  “Now there’s a new focus: How do we think about embedding more ecosystem function into our urban core, our suburban neighborhoods, throughout communities?” 

She said that by thinking holistically about urban design, cities could help both their residents and ecosystems thrive.

According to Coyne, Austin approaches “urban nature solutions” in innovative and varied ways. For instance, urban trees reduce rainwater runoff, promote rainwater soil infiltration, provide cooling and shade, and sequester carbon. The city protects different native trees through city ordinances and created a planting prioritization map to center equity in tree planting, as wealthier and whiter parts of the city currently have more of a tree canopy than more diverse and less affluent neighborhoods.

In addition, developers must provide on-site stormwater treatment, in most cases by using nature-based stormwater infrastructure such as bioswales and rain gardens.

Urban nature solutions using green (land-based) and blue (water-based) infrastructure may become more common across the country following the November 2022 White House launch of a road map to “make nature-based solutions a go-to option for fighting climate change.” The initiative aims to increase adoption by easing access to funding and updating federal guidelines and policies, among other efforts.

Advocates for urban nature solutions say that tapping blue and green infrastructure can help cities realize many climate, social and health benefits for their residents.

Costs and benefits  

“Urban nature is an effective climate mitigation tool that can help local governments save energy, reduce emissions and save money,” said Julia Meisel, manager of RMI’s urban nature initiative and one of the authors of a recent report on the topic. “If you’re a local government wanting to pull every lever that you can to meet your climate action or emission reduction goals, we want to make sure that nature is on [your] list,” she said.

Laurian Farrell, North American regional director at the Resilient Cities Network, defines urban nature solutions as “infrastructure that is serving a purpose within a city [with a] foundation that is built on already existing natural functions — either trying to mimic those natural functions or enhance those natural functions — in a way that integrates urban living with nature.” These solutions include street trees, bodies of water, parks, green stormwater infrastructure, urban forests and more.

The Biden administration’s road map and resource guide are the first official federal government supports for nature-based solutions. According to Farrell, the move “sends a really clear message” about the value of these projects. 

The RMI report estimates the price tag of various urban nature solutions as part of a cost-benefit analysis and concludes that annual investment in such solutions must rapidly increase worldwide. Investment in massive climate mitigation strategies can be steep, with RMI suggesting a global investment of $98 billion yearly until 2050. The report also estimates such investments would have average annual net benefits of $2.1 trillion, delivering $59 trillion in total net benefits by 2050.

Urban nature solutions can help cities meet other goals in addition to building urban climate resilience, the RMI report explains. For example, access to nature can improve residents’ physical and mental health, while investing in urban nature solutions can bring green workforce development and training to cities that sorely need jobs.

The best urban nature solutions for a given city depend on the city itself. A city with scorching temperatures in the summer, like Austin, might benefit from cooling solutions, such as planting trees near buildings to reduce ambient temperature and for shade to mitigate energy consumption from air conditioning. Street trees can also encourage people to use their cars less, as walking, biking, or waiting for a bus in a shaded area is much safer than on hot, unshaded asphalt. The RMI report found that increasing Austin’s tree cover to 40% in areas with deficient shade could decrease the number of vehicle miles traveled in the city by more than 19 million over the next 12 years.

Cooling solutions can have a sizable, positive impact on economically and socially marginalized neighborhoods, which tend to be hotter than similar but wealthier neighborhoods due to more buildings and fewer natural resources like trees. (The Biden administration announced an effort last year to create more equitable access to parks and vegetation, in part to address access disparities across race and class.)

Reversing past damage

Some urban nature solutions address rapid urbanization and are “oriented around trying to reverse the mistakes of paving everything,” said David King, an assistant professor at Arizona State University’s School of Geographical Sciences and Urban Planning. For instance, nature-based stormwater infrastructure reduces flooding and water pollution by allowing stormwater to drain slowly through permeable surfaces like rain gardens and bioswales.

King noted that while building requirements may include these stormwater landscaping solutions, the stormwater runoff was created by regulations requiring “enormous parking lots” that increase the need to manage and filter water from impervious asphalt and concrete surfaces.

Examples like these demonstrate the dichotomy between nature and urbanization that urban nature solutions are working to disrupt. RMI’s Meisel said trees are especially valuable when a city is considering where to focus its urban nature efforts. In fact, RMI estimates that 72% of the total value of urban nature is due to street trees and urban forests. 

But a few trees in a parking lot can’t sequester enough carbon to help lower emissions. While a few planted trees can provide sufficient shade to impact human health significantly, lower temperatures and alter transportation decisions, only very dense tree cover has the potential to mitigate pollution, which isn’t possible in some modern cities.

Urban planning experts emphasized that there’s no one-size-fits-all urban nature solution for cities, and finding consensus on the best approach for any one city can also be challenging. King’s home base of Phoenix — the hottest city in the U.S. — currently aims to cover at least 25% of the city with trees. “Is that the best solution?” he asked. “Or is it better to actually remove some of the asphalt and cement [to help] minimize some of the heat problems that we have?”

While each city will confront its own questions when planning urban nature solutions, Meisel calls for cities to “prioritize [urban nature] as much as they prioritize any infrastructure.”

By 2030, electric vertical and takeoff landing (eVTOL) and other passenger-carrying advanced air mobility aircraft could offer many more flights per day than the largest airlines, according to a McKinsey & Company analysis.

“Flying taxis are going to happen,” said Benedikt Kloss, an associate partner in McKinsey’s Frankfurt office, in a company video. “The question for me at the moment is when it’s going to happen — not if.”

Flights will average just 18 minutes, carrying one to six passengers, but frequent takeoffs and landings will require cities, suburbs and retail districts to accommodate new vertiport infrastructure.

American Airlines and United Airlines placed orders for eVTOL aircraft from developers that have yet to fly or certify production aircraft. UAL and Archer Aviation announced planned routes in New York City and Chicago, while Delta Air Lines is an investor in rival Joby Aviation. Other advanced air mobility developers include U.K.-based Vertical Aerospace, Odys Aviation, Lillium and Germany’s Volocopter.

McKinsey estimates that just one advanced air mobility operator could operate 20,000 flights a day in 2030. By comparison, Southwest Airlines, the second-largest carrier in the U.S., averaged roughly 2,900 domestic flights a day in 2021. 

Most eVTOL aircraft would fly short routes between downtowns and nearby airports or cities. According to the Federal Aviation Administration, these electrically-powered aircraft promise to provide more efficient, sustainable and equitable transportation.

But McKinsey warned, “If leaders want to scale the [advanced air mobility] market and not face the limits seen with today’s helicopter transport, they must establish many more ports, as well as more routes among them.”

The consulting firm estimates that a large, dense, high-income city, such as New York or London, would need 85 to 100 takeoff and landing pads, which could be distributed among 20 to 30 vertiports. Medium-size cities such as Atlanta, Dallas or Denver might require 10 to 18 sites with up to 65 total pads.

Last September, the FAA released vertiport design standards that specify safe dimensions for takeoff and landing areas as well as departure and approach paths; guidelines for markings and lighting to aid pilots; and standards for electric charging infrastructure.

In a March interview, Archer Aviation CEO Adam Goldstein described how aircraft would take off from a downtown heliport, fly 10 or 15 minutes to a major airport, fly back and do it all again within the span of an hour. “We’ll start slow. We’ll put tens of planes out there. We’ll go to a bunch of different cities. We’ll start to show that this can work,” he said. 

Archer Aviation and Joby Aviation both anticipate commercial flights beginning in 2025. “I think this is a mode of transportation that will eventually become quite frequently used,” said McKinsey partner Robin Riedel in a company video.

Nearly 350 cities worldwide can now access Google's free Tree Canopy tool, which maps urban tree cover, the tech company announced in a blog post March 29. Previously available in 14 cities, the tool now covers cities including Atlanta and Baltimore.

The tool aims to help cities “understand their current tree coverage and better plan urban forestry initiatives,” according to Google’s blog post. The company plans to expand the tool to thousands more cities this year.

Trees bring city dwellers a slew of benefits: They absorb planet-warming carbon dioxide, can improve people’s mental health, provide shade and cool the surrounding air. But the benefits are not distributed equitably, with lower-income areas often having less tree cover and hotter average temperatures.

Google’s Tree Canopy tool is built with the same underlying information it uses for Google Maps, using machine learning and aerial imagery to estimate how dense a neighborhood's tree cover is. First launched in 2020, Tree Canopy is one of a suite of tools available through the tech giant’s Environmental Insights Explorer, which also provides estimates of greenhouse gas emissions and solar energy potential of buildings in a region. 

“By surfacing environmental information in a robust platform free of charge, we aim to serve decision makers and researchers working on these issues and solutions for cities globally,” Google said. 

Lessons from early adopters

Leaders from Austin, Texas, and Chicago, among the first cities to use the tool, say they found Google’s tree canopy data to be mostly accurate.

The data aligns with information Austin collected itself, said Marc Coudert, the city’s climate resilience and adaptation manager, in an interview. “Satellite data is hard to refute because we notice familiar objects, and we can sort of understand that it's real.”

According to Google, Tree Canopy may not match up with a city’s data due to factors such as the date the aerial imagery was taken, different versions of city boundaries and errors by the company’s machine learning system. 

Austin and Chicago have found the tool most effective to empower and engage community members by connecting them with easily accessible, understandable data, leaders from those cities said.

In Chicago, Tree Canopy helps community “tree ambassadors” focus outreach efforts and quickly identify where they can most productively request trees on behalf of residents, said Raed Mansour, director of environmental innovation at the Chicago Department of Public Health, in an interview. Google’s downloadable tree canopy data can also help community organizations develop programming or apply for grants, he said. 

“If you’re not connecting it to community members, then it’s not a very useful tool,” Austin’s Coudert said. He added that cities should complement the tool with additional sensors in communities to track heat, humidity and air quality.

Coudert advises cities to use the tool as “a public discussion point” while also doing their due diligence to better understand climate change’s health impacts in low-income communities. 

“It's a wonderful tool, but it's not the only tool,” he said.

As tech improves, so can urban tree efforts

A tool like Tree Canopy can be useful for cities to understand how trees are spatially distributed, but it’s not as detailed as a tree inventory, said Jacob Napieralski, a geology professor at the University of Michigan-Dearborn, in an interview. 

A tree inventory includes granular data about each tree, such as its age and species, which can be useful for cities considering species diversity and which trees to plant in the face of climate change, he said. However, tree inventories are often expensive, time-consuming endeavors that require “systematically going through boots on the ground,” Napieralski said. 

New technologies could change how cities obtain information about trees, he said, suggesting they could crowd-source the information through apps that allow users to discover a tree’s species by scanning a leaf. As technologies further improve, cities increasingly will be able to maintain up-to-date information about their trees, he said. 

Tools that allow cities to understand and address tree-related issues should be as common as those that allow them to identify and fix potholes in the road, Napieralski said. “We should have that same sort of responsiveness to trees.”

The number of U.S. jurisdictions adopting building performance standards has nearly doubled since 2020, with legislation enacted in three states and nine localities, according to a report published in May by the nonprofit research organization American Council for an Energy-Efficient Economy.

The report says these regulations, which aim to reduce the carbon footprint of buildings by requiring them to meet certain standards, are a key climate policy and can, in some ways, “be thought of as the existing-building analog” to building energy codes for new construction.

ACEEE Executive Director and report co-author Steven Nadel said in an interview he is “really impressed how much progress there has been made” since the nonprofit published a similar report on building performance standards in 2020. For example, he said, more jurisdictions are creating longer-term plans and recognizing that affordable housing may require special provisions.

It’s not new for states and cities to encourage energy efficiency upgrades in existing buildings, with such programs existing for decades, the report says. 

However, these programs are too weak in the face of climate change, the report continues, noting that at current rates, it will take more than 300 years to complete whole-building retrofits on all homes and apartments and more than five decades to complete retrofits on all commercial buildings. 

Jurisdictions that have enacted building performance standards include Colorado, Maryland and Washington state, as well as cities such as Reno, Nevada; St. Louis and New York City, the report says.

A “key issue” is whether jurisdictions should base standards on buildings’ energy use or greenhouse gas emissions, the report says. They are increasingly turning to the latter, Nadel explained — whereas “virtually all” the standards examined in ACEEE’s 2020 report were energy standards, many more jurisdictions examined in the new report are carbon standards or a combination of carbon and energy standards. 

Leaders have historically shied away from carbon standards in part due to the complexity of determining the exact carbon footprint of energy used by a building, Nadel said. However, cities are starting to determine ways to overcome that barrier by administratively setting a standard number for the carbon footprint of each unit of energy, he said.

“That way, the building owners know, ‘OK, there’s so many pounds of carbon per kilowatt-hour,’ and they can just do it, as opposed to ‘Well, I don’t know what the utility is doing. Why are you putting this on me?’” Nadel said. 

Jurisdictions are also increasingly accounting for the unique challenges building performance standards pose for affordable housing — a nascent issue in 2020, Nadel said. It can be particularly difficult for affordable housing to comply with building performance standards because the buildings tend to be less energy efficient, owners often don’t have the money to improve the buildings and upgrades spur concerns about rent increases, the report notes.

To address these challenges, many jurisdictions have made special allowances for affordable housing, such as delayed compliance deadlines and extra funding and technical assistance. While many building performance standards include exemptions, meaning certain buildings are not subject to the rules, the report says that program implementers generally advised other jurisdictions to limit those cases.

Building owners may be motivated to get ahead of the regulations as an increasing number of cities set long-term goals for building performance standards, Nadel said.

“When I talk to some people I know in the HVAC industry, for example, already in places like New York and Boston, they’re finding that building owners are saying, ‘OK, I know this is coming. When I replace my chiller, when I replace my boiler, that’s going to be the one that’s going to have to meet this long-term standard,’” Nadel said. 

While the report highlights that regulations will be unique to each jurisdiction, it floats the idea of “improved standardization” of building performance standards to reduce the workload associated with these regulations. The report also stresses that jurisdictions implementing or considering building performance standards should consult stakeholders; have adequate staffing; and complement standards with education, financing and technical assistance for building owners.