Boston's five major candidates for mayor all agree that climate change will continue to challenge and compromise the city's future. The creation of sustainable housing; affordable transit; mitigating rising sea levels; planting more trees and striving for clean air all intersect under the umbrella of what a green city could look like. Acknowledging the problem ties the candidates together. Targeting tangible solutions, however, sets them apart.

Here, as the candidates see them, are Boston's most pressing environmental issues — and how, as mayor, they would tackle them.

Michelle Wu

At-large city councilor Michelle Wu was the first candidate to enter the race — and checks the boxes with a lot of other firsts for environment-focused voters. Last August, she was the first candidate to release a climate plan, a wide-ranging 49-page document dubbed “Boston’s Green New Deal.”

Bostonians will have noticed the inordinate number of 90-plus degree days the city has suffered recently: two weeks' worth. Wu was ahead of the game, noting that Boston is staring at 40 days of intense heat per year by 2030, and an entire summer of sweltering weather by 2070. Sea level rise in Boston Harbor could reach over three feet by then, dramatically more than the 9 inches it jumped in the 20th century.

“How we make decisions right now in the next three to five years is going to determine the future of this city for the next three to five generations,” Wu told GBH News recently. “For me it’s been a very clear priority that climate justice is racial and economic justice.”

Her municipal Green New Deal has earned the support of every environmental group that has endorsed in the mayoral race, and echoes Sen. Ed Markey and New York Rep Alexandria Ocasio-Cortez’s federal version in 2019, which Wu urged the City Council to back.

Wu said her local plan is about big things and small, like accelerating the city’s decarbonization’s deadline from 2050 to 2040 and net-zero municipal buildings by 2024, as well as increasing the tree canopy in Boston and of course, making the T free, a controversial position she’s held for years.

In Environmental League of Massachusetts’ endorsement of Wu, the group said she was Boston’s first elected official to call for a fare-free T in 2019.

“A lot of times we think of transportation as the realm of state government, but city government has a huge bully pulpit and we have a huge area of direct authority as well,” Wu said.

Many progressives say Wu’s thunder was stolen when Janey announced the free 28 Route bus pilot this summer, but Wu only said the effort was the result of activists’ work.

According to Wu, the number of buildings that need to be retrofitted for climate change is at around 86,000, a goal that needs to be met by 2050 — and if Wu has her way, much sooner. She supports passing BERDO 2.0, a City Council proposal that would expand on the late Mayor Tom Menino’s 2013 policy that requires large building owners to report their greenhouse gas emissions to the city. The revamped version, from Council President Pro Tempore Matt O’Malley, would push 15 unit-plus residential buildings and 20,000 square foot and over commercial buildings to become carbon neutral.

If elected, Wu would support increasing financial support to help residents retrofit their own homes. The process of doing that could create jobs for Bostonians, she said.

"Through all of the retrofitting, the infrastructure projects, installing solar panels, fixing our storm water infrastructure to absorb water, we will be able to close the racial wealth gap and then some if we ensure that these jobs are right here for our communities,” said Wu. She’s proposed an Urban Conservation Corps, a workforce training program for young people interested in the environment.

Wu wants to foot the bill by leveraging the city’s triple-A bond rating to issue Green Municipal bonds and by having Boston opt into the state’s Property Assessed Clean Energy Program, which gives building owners access to federal funding to make their spaces more energy efficient, easing the cost of renewable energy conversion by private property owners.

John Barros

While walking through the Newmarket Business District, John Barros expressed concern over the lack of tree canopies in parts of Boston where Black and brown residents live and poor air quality.

Pointing out an idling truck in an area long known as a site for commercial trucks to pick up goods, Barros said he would bolster monitoring of poor air quality and partnering with area businesses to ensure sustainable business practices. The neighborhood — where he grew up — has one of the highest rates of asthma in New England, he said.

“I've often said we need to connect the global warming issue, we need to connect the sea rise issues, the extreme precipitation issues, the heat island issues with these more acute problems that are happening in the neighborhoods of Boston, with these issues that people have been fighting for years,” Barros said.

The former city economic development chief has one of the more detailed climate action plans, with a right-off-the-bat dedication of 20% of Boston’s Capital Budget to climate resiliency — for this year, that would be $660 million.

Experience in planning and executing is what he said sets him apart from other candidates. “I have a track record of implementing. That's what Boston needs now. We've done a lot of planning. It's time to get it done,” said Barros.

He pointed out small things government can do in conjunction with neighborhoods and businesses, like cleaning up streets to improve public health. “I'm very proud of the fact that this street is clean because this business here, this particular trash transfer station, cleans this street multiple times a day. But that wasn't the case before. We had to fight for that,” said Barros.

He also lists the implementation of the citywide plastic bag ban as one of his successes in helping businesses keep their operations environmentally sustainable. Barros uses his seven years on former Mayor Marty Walsh’s cabinet to detail his track record, including the creation and launch of multiple climate action plans.

As mayor, he’d want to enhance programs to help large building owners decarbonize existing buildings — removing their carbon dioxide output — as well as require large and medium-sized buildings to report their annual water and energy use. He’d also ask building owners to create publicly accessible parks on their roofs and fund incentives for out-of-the-box projects.

Barros, like many of the other candidates, wants to expand dedicated bus and bike lanes. He also said the Fairmont commuter line, which runs through the Newmarket Business District, could be electrified to cut down noise and air pollution. As mayor, he would use federal funds to implement overhead electrification.

He wants to use federal infrastructure dollars to build flood barriers at Fort Point Channel and Lewis Mall in East Boston — areas vulnerable to sea level rise.

Kim Janey

In June, Acting Mayor Kim Janey reminded a crowd at Frog Pond that the city has been subject to multiple 90-degree days this summer, leading her to extend cooling center hours.

She believes the city has an opportunity to address climate change with federal dollars, and she wants to bring an equity lens to the process.

“As the first woman mayor and the first Black mayor, I have seen too often how poor people of color are often disproportionately impacted by climate change,” she told GBH News.

Janey says the two largest contributors to emissions are building and transportation, which is why she is supports retrofitting city buildings to make them more energy efficient.

“We've invested $48 million right there alone, and that's just in the last four months as mayor,” she said, adding that she pledges to do more if elected.

On transportation, she supports the electrification of the MBTA’s bus fleet and adding more electric vehicle charging stations around the city for residents. Getting people onto public transit is key, she said, touting the July’s unveiling of the free 28 bus route pilot through Mattapan, Roxbury and Dorchester, some of the lowest-income areas in Boston.

“I'd love to see more people getting on the bus and expand this bus pilot beyond one bus route,” Janey said. She said that while she doesn’t control the MBTA, she’d like to see free fares beyond the three-month pilot, and thinks the city can support the agency by building infrastructure for busses to ride more smoothly. Janey said the crux of the responsibility falls with the state legislature to fund an infrastructure bill.

In the interim, she said she’s invested in short-term programs, like a pilot that gave two-month Blue Bike passes and free Charlie Cards preloaded with $60 to 1,000 people in areas hardest hit by the pandemic.

According to her campaign site, Janey allocated $4 million to the city’s Green Jobs program to get young people connected to employment to help the city become more sustainable.

Janey said Hurricane Henri had her concerned about coastal flooding.

She proposed investing $5 million to study to examine measures that can be taken to reduce coastal flooding on Boston Harbor and an additional $20 million to design and create a “climate resilient” waterfront part on the flood-prone Fort Point Channel in the Fiscal Year 2022-2026 Capital Plan.

Asked why she is the candidate to vote for those concerned about environmental policy issues, Janey said she’s “already leading” with the appointment of Rev. Mariama White-Hammond to the position of Environment, Energy, and Open Spaces Chief, calling her a “renowned environmental justice advocate.”

Janey is an opponent of the planned Eversource substation in East Boston, which is wending its way through a complex approval process.

“As mayor of Boston, I will not remain silent when the people of East Boston are crying out,” she said in May, calling it an issue of environmental justice. “From what I have seen, the substation plan is based on flawed projections and flawed priorities. I urge Eversource to prioritize environmental equity and the wellbeing of East Boston residents over their profits.”

Andrea Campbell

Similar to Janey and Wu, District 4 Councilor Andrea Campbell believes an infusion of federal resources is important to solving environment concerns, and voiced her worry that Mattapan is not often a part of climate resiliency efforts.

Campbell’s plan is structured around environmental justice — making sure low-income residents, people of color, immigrants and those with pre-existing medical conditions and disabilities get to see results while also being involved.

Just 1% of city contracts for construction and professional services go to women and minority-owned companies, a statistic oft cited by Campbell. She’d like to see this grow to include engineering and green job trainings for public school students and professionals.

Part of that would be to expand Roxbury Community College’s Center for Smart Building Technology and connecting students to those jobs.

Campbell said her plan is “specific on how we can actually make sure every single neighborhood in the city of Boston is resilient and prepared, every single neighborhood has access to the jobs in this green economy.”

Campbell said she is concerned over the city commissioning almost 40 different plans related to the environment when less than 10% have been completed.

"We've had a lot of plans for years, but we need to move the timeline up and we need greater investment to operate and to act with a sense of urgency,” she said.

According to her campaign site, Campbell would work with the state government to meet the 100% renewable energy portfolio and carbon neutrality for city operations by 2035, instead of 2050.

She told GBH News she would seek to electrify the city’s school bus fleet and lobby the MBTA to follow suit with the buses that serve Boston.

Similar to Barros, she would follow through on the Fairmont Line’s upgrades and electrification using federal money. As mayor, Campbell would also advocate for the state to transition the commuter rail fare system to one that sets a subway fare for all Boston stops, making it more affordable and green way for people to travel.

Annissa Essaibi George

At-Large City Councilor Annissa Essaibi George thinks climate solutions need to be community and regionally based, and told GBH News that she’s seen “suburban elite who come into the city to try to save us from ourselves.”

Instead, she wants to see “neighborhood-centered action,” citing efforts from Mothers Out Front in East Boston to mitigate the impacts of poor air quality from plane pollution in the neighborhood.

As a former East Boston High School school teacher and softball coach, Essaibi George said she’s seen first-hand the impacts of living under a flight path has on the community.

Citing her time as the council’s education committee chair, she said she would focus on improving infrastructure in school buildings and making sure renovations are green. She said Madison Park Vocational High School in Roxbury is the perfect place to expand learning opportunities to train students for the coming green economy.

Essaibi George she’s seen the impacts of sea level rise and flooding in Dorchester as a resident, and wants to see a regional response for protecting Boston’s entire shoreline.

"We can't leave any inch of our coastline unprotected, so a very collaborative effort, especially in partnership with our neighboring cities and towns, because we can't just simply focus on Boston,” she said. Essaibi George listed a series of potential “mitigations” including lifting buildings up, building a sea gate and reinforcing waterways.

Essaibi George also advocates for investing in green spaces and parks in low-income areas and expanding the city’s tree canopy in communities of color.

Correction: A previous version of this story said that Michelle Wu had received an endorsement from Environment Massachusetts. The group is the Environmental League of Massachusetts.