The Art of the Park with Michael Van Valkenburgh

“I don’t see parks as an escape from the city; I see them as an escape in the city, and therefore an essential part of what a city is,” explained landscape architect Michael Van Valkenburgh, FASLA, at The New York Times’ Cities for Tomorrow conference in New York City.

In a Q&A, Van Valkenburgh touched on five parks his firm designed throughout the country and Canada, beginning with his redesign of the landscape of the Jefferson National Expansion Memorial on the St. Louis riverfront, which is home to Eero Saarinen’s famous Gateway Arch.

Here, Van Valkenburgh explains, his team at MVVA incorporated elements of Modernist landscape architect Dan Kiley’s original intention for the site while “creating a series of bridges – physical and metaphorical” to better stitch the previously-isolated 91-acre historic Arch ground with St. Louis

Van Valkenburgh then discussed Maggie Daley Park in Chicago; A Gathering Place for Tulsa, a new park in Oklahoma; and Corktown Commons in Toronto.

And, finally, Van Valkenburgh, a Brooklyn resident, finished his talk on the now-famous Brooklyn Bridge Park, a set of piers once used for maritime industries now turned into a beloved 85-acre park, a project realized after 18 years of planning and design.

Landscape Architecture in the News Highlights (July 1 – 15)

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Manhole in Central Park, NYC / Cole Wilson, via Curbed NY

Sprucing Up Your Garden for Summer, the Tropical Way Vogue, 7/2/17
“Fernando Wong knows how to make a lush, enviable garden. The accomplished landscape architect has done so time and time again for his various private clients.”

Seven of America’s Top New Museums and Monuments The Architect’s Newspaper, 7/4/17
“Last year saw one of the biggest and most publicized museum openings in recent memory: the Smithsonian’s National Museum of African American History and Culture (NMAAHC).”

Why Do Some Graduate Landscape Architects Have a Poor Understanding of Planting? Landscape Architect’s Network, 7/12/17
“In the pursuit of a landscape architecture degree, students have the opportunity to acquire a wealth of knowledge on planting, but as with other subjects there are some students who take this issue more seriously than others.”

The Manhole in the Meadow Curbed NY, 7/12/17
“Standing in the Long Meadow, pondering a manhole cover, I realize that I never look at this significant urban place with the critical eye that I routinely apply to the city around me, and that my neighborhood expanse of greenery is, as it happens, a primary example of engineered nature.”

Lawrence Halprin’s Freeway Park in Seattle to Undergo Wayfinding-focused RenovationThe Architect’s Newspaper, 7/4/17
“The renovations are being undertaken by the Freeway Park Association (FPA)—a nonprofit organization created in 1993 ‘in response to the community’s demand for greater public safety in their aging neighborhood park.'”

Hamptons Homes Blur the Line Between Inside and Out The New York Times, 7/14/17
“Twenty-foot-wide glass walls retract electronically at the tap of a cellphone app at the over-the-top $39.5 million furnished mansion John Kean built last year on four acres in Southampton.”

How Joplin, Missouri, Used Nature to Recover from a Devastating Tornado

I’ve always been struck by the undeniable power of nature. It destroys—as it did on a late Sunday afternoon in May, in Joplin, Missouri, six years ago when an EF5, mile-wide tornado chewed through the city in 38 minutes. It left 161 people dead, 1,150 others injured, countless more traumatized–and the rest of us watching and aching for them all. Aside from the human toll, it also caused billions of dollars in damages, and left thousands of trees decimated, uprooted or maimed.

Joplin was devastated. It needed to recover in every sense—physically, emotionally, spiritually. Many stories have been told in the aftermath of how the city drew together, rose up, and rebuilt.

But one story that’s not been told is about how nature, the thing that brought the destruction, has been the very thing that is bringing much needed emotional recovery to the community. Nature heals too. This is the story we wanted to tell.

When I flew in to Joplin, I gasped as I saw the massive scar in the landscape left by the tornado. It was a mile wide and several miles long. From that perspective high above the city, all that I could see was the destruction. But on the ground, a different picture emerged.

Key community members shared their stories and those of the community. Chris Cotten, head of Parks and Recreation for Joplin, was one of them. I quickly began to see what he saw: hope, hard work, and resilience were everywhere. And then I heard about the butterflies. Many community members told us stories of how the butterflies had saved them. Children told stories of being protected by them–like angels–while the destruction roared around them. I was captivated; but we weren’t the only ones who saw nature as a potential piece of the city’s recovery.

Just after the tornado hit, The New York Times ran a series of haunting images, including ones of Cunningham Park, showing a devastated landscape; mangled trees that had been stripped of their canopies and bark. These caught the eye of Cornell University’s Keith Tidball, who dropped everything to go to Joplin and, in his words, begin planting. A researcher and author, Keith has done some amazing work and spent years studying how nature can be a source of resilience for communities in crisis. He had been working in post-Katrina New Orleans just prior to the tornado.

Keith connected with Chris, and the idea for a healing garden was born. They worked quickly, with the support of the TKF Foundation to assemble a diverse team that included city officials, landscape architects, psychologists, musical therapists and urban planners–and most importantly, the community. Fusing research, design and nature—a healing garden the community named the Butterfly Garden and Overlook opened to the public in May 2014. As former Mayor Melodee Colbert-Kean described to us, it’s a place where children and adults go to feel safe and whole, and to reflect. To recover. The nature effect is real. And our understanding of just how powerful its benefits are continues to grow.

Stories like this one, from Joplin, have much to teach us. Even in the hardest hit places, whether the disaster is natural or man-made, nature can heal and restore—and has the power to unify and rebuild communities in lasting ways.

This guest post is by film maker Alden E. Stoner, who is also a board member of the nonprofit TKF Foundation.

The Hive: An Acoustic Playground Made out of Cardboard Tubes

Jeanne Gang describing The Hive / Dana Davidsen

Spiraling upwards into the grand space of the National Building Museum in Washington, D.C. is the Hive, a trio of domed chambers designed to create unique acoustic experiences. Conceived by Chicago-based architect Jeanne Gang, the Hive towers some 60 feet and is comprised of over 2,500 cardboard tubes. Within its chambers are chimes made out of building materials, like copper pipes and wrenches, and a giant tubulum, an instrument constructed out of pipes of varying sizes that produces warm, surprising sounds.

The Hive / Dana Davidsen

In a tour of the Hive, Gang explained how she used sound to define the space. In the vast expanse of the National Building Museum, “you can’t really hear someone just 10 feet away from you. The sound gets lost, as it does in a big field.”

Within the museum, Gang instead wanted to create an intimate acoustic space. She wanted to recreate the sense of being inside a forest clearing, open but enclosed by trees, where one can sense, acoustically, the bound space as sound waves bounce off trees.

Working with acoustic engineers with Threshhold Sound, Gang and her team accomplished a similar surround sound effect inside the Hive, using catenary structures, painted silver and magenta, to create a full, harmonious timbre.

Inside The Hive / Dana Davidsen

Gang seemed particularly excited about the tubulum. “When everyone plays together, the chamber will be rocking!”

Tubulum / Dana Davidsen

The structures are inspired by both built and natural forms — Gang talked about the oculus of the Pantheon in Rome and mused about pine cones. “We see spirals in nature, too.”

The Hive is open until September 4. Interactive sound experiences will be held on Saturdays. Tickets are $16 for adults and $13 for kids and seniors. Get your tickets in advance.

Are Urban Bats the Future?

Urban bats at Congress Bridge in downtown Austin, Texas / Flickr

The plight of the honeybee has been well-documented since the term colony collapse disorder made its way into news headlines about a decade ago. The phenomena fueled public interest in the health of bee populations, ushering in a new generation of bee-keeping enthusiasts. And justifiably so. Pollinators like bees are essential to our nation’s economy and food supply.

Another, albeit less popular, pollinator is also facing a precipitous population decline. Bats are dying at an alarming rate due to an invasive fungal disease that’s wiping out entire species, and the unlikely savior may be one of their own.

Bats pollinate over 500 species of plants around the world, including cocoa and agave — fans of chocolate and tequila, take note. What’s killing them is called White-Nose Syndrome (WNS), a fungal disease that grows on bats’ skin and wakes them up during hibernation. Repeated waking during the hibernation period depletes winter fat storage and causes starvation. The fungus needs high humidity and low temperatures to survive, typical cave-like conditions.

Millions of bats in North America have died from the disease since it was first documented in a cave in New York in 2007. Now, WNS has spread to 30 U.S. states and five Canadian provinces and is reaching the west coast. Last year, a bat in Washington state tested positive for the disease.

“Populations will likely never return to where they were,” said Amanda Bevan, lead for the Organization for Bat Conservation’s Urban Bat Initiative.

Bats in urban areas are less affected by the disease because they tend to hibernate in man-made structures that stay warmer than caves. And migratory species, like the Hoary Bat, do not spend the same amount of time in caves as bats that hibernate, and therefore have limited interaction with the fungus.

With more opportunity and reduced competition, Bevan says, it’s possible that some of these urban and migratory bats could push into the realms of cave and forest-dwelling bats.

“They are what’s going to be the saving grace for white-nose syndrome,” Bevan said. The Evening Bat, for example, more often found in southern regions of the U.S., has recently been discovered in caves in Wisconsin and Michigan where it’s possible it could help rebuild the states’ cave-dwelling bat populations. This is a relatively new, but potentially promising, phenomena that could help bolster species in decline.

Bevan thinks, given current trends suggesting changing behavior, urban bats are likely to become the majority population.

But there is a significant lack of research on the urban bat, and more broadly, trends in bat populations over time. Migratory bats especially are challenging to track because they are hard to catch multiple times. In absence of robust data, it’s difficult to understand movements and patterns across species.

To date, research has focused largely on cave-dwelling bats, but now ecologists seek a better understanding of bat activity in urbanized landscapes. In 2012, researchers from Fordham University published an acoustic monitoring study of bat activity in the Bronx. The report, which was the first of its kind documenting urban bats in the northeast, found five different species at various sites. A subsequent study reported increased bat activity over green roofs, compared to conventional roofs in the Bronx, indicating green roof provide habitat benefits for bats.

Urban gardeners who want to support their fellow urban-dwelling mammal can create habitats like bat houses and supply pollinator-attracting plants. Plants like milkweed and evening primrose attract night pollinators, like moths – a diet staples for bats. Gardeners can also use plants that bloom late in the day, are scented at night, and have a lighter in color. One of the biggest threats to urban bat populations are pesticides, which can affect a bat’s ability to navigate using echolocation.

Landscape Architecture in the News Highlights (June 16 – 30)

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Shades of Green’s 630-square-foot Pacific Heights rooftop garden / Ive Haugeland

San Francisco Rooftop Terraces That Rise Above It All The San Francisco Chronicle, 6/16/17
“Just in time for summer, three local landscape designers share the San Francisco rooftop terraces they’ve transformed from barren wastelands to inviting urban escapes.”

Planned WWI Memorial Would Harm Historic Park, TCLF ArguesCurbed, 6/20/17
“It shouldn’t be any surprise that The Cultural Landscape Foundation (TCLF) is pushing against the National Park Service’s planned WWI Memorial in Washington, D.C.”

Lack of Coordination on Obama Center, Tiger Woods Golf Course Threatens Jackson Park RedesignThe Chicago Tribune, 6/23/17
“Before he became America’s foremost landscape architect, shaping Chicago’s Jackson and Washington parks as well as New York’s Central Park, Frederick Law Olmsted was a fervent abolitionist.”

Creating a Garden Oasis in the CityThe New York Times, 6/23/17
“Samira Kawash and Roger Cooper bought their Park Slope brownstone five years ago with the idea of giving big dinner parties and enjoying lazy afternoons in the extra-large backyard.”

Highland Park’s First ‘Green’ Stormwater System CompletedThe Pittsburgh Post-Gazette, 6/26/17
“The first, and so far only, green infrastructure solution to flooding in Highland Park’s valleys is completed along Negley Run Boulevard — a 1,100-foot bioswale that will intercept an estimated 600,000 gallons of water running off pavement annually.”

This Is the Landscape Architect Nantucket’s Elite Have on Speed DialArchitectural Digest, 6/27/17
“Neighbors on Nantucket’s eastern end have more than faded red chinos and a desirable zip code in common; many have landscape artist Marty McGowan, too.

Engagement by Design

Staten Island Living Breakwaters Community Meeting / Rebuild by Design

It’s been just over three years since the winners of the Rebuild by Design competition were announced. Since then, there have been almost 400 meetings with communities around each of the seven project sites in the New York metro region. The competition, launched by President Obama’s Hurricane Sandy Rebuilding Task Force, called for large-scale, cross-sector, hybrid solutions to make communities more resilient to future storms.

Long before construction begins, teams in charge of design and implementation are helping community stakeholders visualize the project, the goal being to stimulate dialogue. At each step, community feedback is integrated into plans and designs.

Staff of Rebuild by Design — a research and design organization that was formed after the competition — attended public meetings held by every design team, where they have catalogued the most effective community engagement practices. Engagement by Design, an event put on by the organization at New York University, showcased them:

Living Breakwaters, which was presented by Nans Voron, SCAPE Landscape Architects, and Victoria Cerullo, Living Breakwaters Citizens Advisory Committee, is an innovative project off the coast of Staten Island that will use constructed offshore oyster reefs to attentuate waves in future storms and reduce shoreline erosion. In addition, the project will increase biodiversity and social resiliency by providing educational and stewardship opportunities and increased access to the shoreline.

Living Breakwaters is unusual for an urban landscape design, in that much of it is underwater and over 500 feet offshore. This proved to be a challenge when it came to communicating the project to the public. “Even though we were producing renderings to try to envision the future, at the end of the day it’s still very hard to communicate the experience a boater, a swimmer, or even an oyster will have next to one of the breakwaters,” said Voron.

The team began to use virtual reality (VR) goggles to help the public visualize the project. Voron believes VR offers the opportunity for a more visceral and immersive understanding of the effects of climate change. When classic flood maps fall short in their ability to communicate urgency, VR has the potential to create a deeper emotional impact.

Hoboken, a city hit especially hard by hurricane Sandy, recently released the draft Environmental Impact Statement for an urban water management strategy with four components: Resist, Delay, Retain and Discharge. Most of the Rebuild by Design competition funding is going to the “resist” features, which keep storm surges out of the city. The resist features morph into various forms depending on surroundings, so the team decided to make a flyover animation to give context and scale to this complex infrastructural intervention.

Alexis Taylor, outreach team leader for the New Jersey department of environmental Protection, narrated as a flyover animation of the current preferred design for the urban water management plan played. The animation followed the path of the resist feature through city, as it changed from a berm with a serpentine path and integrated recreational spaces to a floodgate closure and then a way-finding device.

At certain points, Taylor interjected to tell the audience that features had been added or amended based on community recommendations. The absence of a fixed audio narrative for the animation allows anyone presenting it to describe the project in their own voice — whether they are a city official or a Hoboken community member.

All teams admitted the engagement process is not without conflict. Angela Tovar, The Point Community Development Corporation (CDC) in the Bronx, urged project teams to be patient with the “planning fatigue” of community members reticent to participate, especially in under-served communities such as the Bronx. For decades, these communities have been subjected to broken promises by city officials, discriminatory housing policies, and environmental injustices, so promises of improved quality of life can be met with justified skepticism.

For David Kooris, director of Rebuild by Design & national disaster resilience for Connecticut, community engagement is not a necessary evil, but critical to evaluating the progress of the project: “I would be very nervous to follow just the bare minimum standards, and once every few months go to a public hearing not having any idea what people were going to show up and say.” By meeting with the stakeholders in Bridgeport, Connecticut, on a near-weekly basis, “I know what all the issues are. I know the ones we can address and the ones we can’t, and we can tweak the project in response to them.”

“I think the most important thing is to arm people with information,” explained Taylor. “Whether or not they are going to come out in support or opposition is fine, at least we are giving them the tools to communicate.”

This guest post is by Chella Strong, Assoc. ASLA, landscape designer at SWA/Balsley in New York City.

Landscape Architects as Futurists

Delivery robot / Starship Technologies

We learn about landscape architecture through a study of context. Technical courses teach students to see the physical characteristics of a site. We learn to identify slope, follow the point of steepest grade in a trail of mud following a rainstorm, identify ecosystems. Theoretical courses teach students to see the intangible qualities of a site — the implications of design decisions upon usability. We learn about the exciting but unpredictable ways a site may develop and come to be used differently than originally intended.

Forward-thinking landscape architecture practice usually involves re-combining the physical and intangible characteristics of a site. Excellent waterfront and post-industrial redevelopment landscape projects have inspired a generation of landscape architects. “What can this become?” is the question that sets most of us on fire.

We imagine a behemoth dump as a park, breathing life back into a great metropolis. A concrete drainage channel transforms into a living waterway, mixed-use development, and microbreweries springing up like eddies along its length. Disused utility easements become oases for habitat in the most unexpected of urban places. We have also seen an increasing amount of “futuristic” landscapes, with high-tech features, such as interactive light or water, app-enabled components, and more.

But what of the impact of new technologies in our built environment? We have anticipated autonomous vehicles for some time (to little effect in our design decisions), but what of the possibilities of autonomous delivery vehicles, or average urban dweller navigating their day with the aid of a reality-enhancing headset, or the convenience/intrusion of biometric scanning as an Apple Pay-inspired method of negotiating daily life?

Without the human element, landscape architecture is not landscape architecture. Yet humans do not remain static and are now in the process of technology-assisted development. In light of these impending realities, what can landscape architects do to maintain an edge on the design of public spaces?

As a profession of such varied talents and individual specialties, there is a place for landscape architects as futurists. There exist landscape architects as ecologists, living systems designers, food system engineers, and health care amenity designers. Leafing through the ASLA annual meeting presentations is enough to inspire the most dispirited of practitioners with new possibilities.

A “futurist” is “a person who studies the future in order to help people understand, anticipate, prepare for and gain advantage from coming changes,” writes the Association of Professional Futurists (APF). This should resonate with landscape architects.

Whether we study the condition of a breakwater and local weather patterns in order to recommend an appropriate intervention or recommend a green roof or living system at an urban development project to address the urban heat island effect, we are in essence studying current conditions and predicting future trends in order to help people prepare for and gain advantage from coming changes.

A recent string of articles caught my eye. First, from an article on CNBC, April 21st, 2017: Robots are Now Delivering Food in San Francisco. Next, on Eater, May 17th, 2017: San Francisco Declares War on Food Delivery Robots. Also from May 17th, 2017, this time on technology blog Wired: San Francisco Tries to Ban Delivery Robots Before they Flatten Someone’s Toes.

The first article reports the San Francisco robots in question are run by a company called Marble, founded to re-think the “last mile” of the delivery supply chain. Their solution is meant as a step toward relieving vehicular and courier snarls during the final stage of delivery of small packages and items. The article goes on to refer to companies, such as Amazon, Alphabet, and Uber, which have also been investing this facet of the supply chain.

Following initial roll-out of the automated delivery system there was an offended backlash that follows an unanticipated offense, with calls to ban these small robots. The Eater article pegs the issue as one of insufficient policy paired with infrastructure. San Francisco city supervisor Norman Yee told them: “Our streets and our sidewalks are made for people, not robots. This is consistent with how we operate in the city, where we don’t allow bikes or skateboards on sidewalks.” When asked if he thought robots could safely run in a bike lane, Yee agreed it was something to think about: “Maybe in the future there will be robot lanes.”

It’s true that progress in urban policy integrating “last mile” delivery robots across the United States and internationally is being driven by robot companies that lead planning and policy initiatives, which can then result in a narrow definition of a municipality’s approved specifications that apply exclusively to that company’s product.

But the uproar was strange for a few reasons. First, given the city’s location adjacent to Silicon Valley, San Francisco residents and managers should not be unprepared for the introduction of automated systems to perform mundane tasks. Starwood Aloft hotels have been using a mobile automated system to delivery sundry items such as toiletries to hotel guests since 2014. Silicon Valley company Knightscope manufactures security robots which have been roaming buildings and industrial complexes in the Bay area for at least a year prior to deployment of Marble’s food delivery robots.

Second, as a dense West coast city with progressive urban development policies, it is surprising that San Francisco is resisting the benefits of a potentially-advantageous technological advancement. Delivery robots, especially when automated to follow given paths and arrive at specific locations (very possible using satellite mapping technology), represent a potential solution to a number of traffic headaches. The narrow streets of historic cities are often clogged by delivery trucks, a trend which is on the rise. Millennials in particular continue to invest in the convenience of home-delivered groceries, meal plans, clothing sampling services, and Amazon Prime for everything else.

This human behavior pattern has consequences for the health and function of our cities, and the policy and design response must adjust itself dynamically to accommodate such trends.

It is common in conversations with landscape architects and planners to arrive at mutual agreement about the antiquated views of traffic congestion wherein the cyclical solution is to simply add more lanes. Many praise the benefits of multi-modal transportation planning, transit-oriented development, and walkable complete streets to create healthier cities.

We must ask, however, if these views are becoming as antiquated as the automotive-focused interventions we disparage. Don’t we have technologies that can work now, complementing evolving human behavior, to produce a healthier system?

The landscape architect as futurist may be any of us of different professional specialties. We are, at heart, a profession made up of practitioners who study variations of environmental context and human influence. We have the opportunity to look to the future in order to help people understand, anticipate, prepare for and gain advantage from coming changes.

Our lifetimes will see dynamic shifts in the way humans co-evolve with technology. It is time for landscape architects to look creatively upon these changes, and ask with a futurist’s eye: what can this become?

This guest op-ed is by Alison Kelly, ASLA, LEED AP ND, a landscape designer at O’Dell Engineering in Modesto, California. She has presented on culture, landscape, and learning at the Society for Applied Anthropology national conference and the Children’s Outdoor Environments professional practice network (PPN) at the ASLA Annual Meeting.

Inside the Garden, and Mind, of Peter Marino

The Garden of Peter Marino / Rizzoli USA

Peter Marino’s garden is about as unexpected as you would expect from the celebrity architect, whose name has become synonymous with high-end fashion lines like Chanel and Luis Vuitton. The Garden of Peter Marino offers a look inside the designer’s sprawling 12-acre Hamptons property, where over the course of two decades he has carefully curated a series of gardens that blend formal landscape elements with unexpected details.

The Garden of Peter Marino, azaleas / Jason Schmidt via Rizzoli USA

Marino organizes his garden by color. But he also agrees with a friend’s assessment that he’s created a network of outdoor rooms, which are home to his 42-piece collection of Italian artists Claude and Francois-Xavier Lalanne’s surreal, cast-iron sculptures. Spread after spread reveal a pristine, manicured garden dotted with art, often placed to interact with the plants. In lieu of a masterplan, these photographs of the sculptures orient the transitions between colors.

The Garden of Peter Marino/ Jason Schmidt, Artwork: 2017 ARS, NY, ADAGP, Paris

But perhaps equally as interesting as the images is the book’s insight into Marino’s design process, which is both thorough and technical, and random and personal. Sometimes, he goes to great lengths to explain the layers and spacing of planting, where at other times, he states unqualified preferences: “I don’t care for yellow flowers mixed with other colors, so I planted them all together in what I intended to be one big explosion of yellow.” He will detail his plant choices with Latin names and variety, and in the same paragraph use phrases like “mad amounts” to account for the density of hydrangeas.

The Garden of Peter Marino, yellow garden / Jason Schmidt via Rizzoli USA

Marino also gets personal. He describes the whimsical forest section of the estate as “Harry Potter-esque,” imagined for his daughter.

The Garden of Peter Marino woods / Jason Schmidt via Rizzoli USA

The Zelkova trees in this section of the garden date back to the Civil War, he was told by an arborist. One was among 16 trees lost in Hurricane Sandy. “I was devastated,” Marino writes. “But nature has a way of doing its thing, which is why I will never really consider any garden as ‘finished.’”

The Garden of Peter Marino / Manolo Yllera via Rizzoli USA

These moments, coupled with the photos, offer an absorbing visual essay of a decades-long pursuit of an architect designing a home for his art in the unpredictable medium of the garden.

Renewable Energy Is Soaring, but Debate Rages on Far It Can Take Us

Wind farm in Guazhou, China / Carlos Barria, Reuters via National Geographic

Renewable energy is gaining momentum. Within a quarter of a century, one third of global electricity generation will be supplied by wind and solar, according to a report from Bloomberg Renewable Energy Finance (BNEF) released this month.

BNEF, which produces long-term forecasts on the global energy sector, says wind and solar will make up nearly half of installed capacity and 34 percent of electricity generation globally by 2040, a significant increase from today’s 12 percent and 5 percent respectively. The plunging cost of renewable energy is making it cheaper than coal generation in many countries. The cost of solar photovoltaic (PV) panels will fall by 66 percent and onshore wind, by 47 percent. The report predicts a $7.4 trillion investment, approximately $400 billion per year, in new renewable energy generation globally by 2040.

Meanwhile, the United States just hit a renewable energy milestone. Last week, the Energy Information Administration (EIA) announced for the first time wind and solar made up over 10 percent of the nation’s electricity generation in the month of March.

This record-breaking share was aided by low demand, common in the spring and fall months, longer days with more sunlight, also typical of spring months, and higher winds in parts of the country like Texas and Oklahoma. Wind and solar will likely hit double-digits again in April before dipping in the summer.

Some experts argue the U.S. could run solely on renewable energy by mid-century – and that’s caused some controversy among the scientific community.

Last week, a group of over 20 researchers published a paper in the Proceedings of the National Academy of Sciences (PNAS) assessing the feasibility of that 100 percent target. The assessment is a response to a 2015 paper, also published by PNAS and led by Mark Jacobson, a professor at Stanford University, which argued that wind, solar, and hydroelectric power could meet U.S. electricity needs affordably and without risk to grid stability between 2050 and 2055.

Jacobson’s report has been both popular and contentious. It has been supported by many environmental organizations and touted by public figures, like former presidential candidate and U.S senator Bernie Sanders.

Now, researchers led by Christopher Clack, founder of Vibrant Clean Energy, are taking issue with Jacobson’s paper, arguing this week in PNAS that its analysis “involved errors, inappropriate methods, and implausible assumptions.” The rebuttal contends that Jacobson’s paper does not make a sufficient argument against previous analysis holding that a diverse set of technologies beyond wind, solar, and hydroelectric power are needed in the transition to a low-carbon future, and that a target of 80 percent is more feasible renewable power generation goal.

Jacobson fired back with a counter response, also published in PNAS, and in an interview with the MIT Technology Review, he called into question his critics’ motives. “They’re either nuclear advocates or carbon sequestration advocates or fossil-fuels advocates,” Jacobson told the online publication. “They don’t like the fact that we’re getting a lot of attention, so they’re trying to diminish our work.”

Those questioning a fully renewable-power U.S. electricity system say some nuclear and carbon capture and storage as well as continued use of some fossil fuel-based sources are also needed, because of the intermittent nature of wind, solar, and hydroelectric power, and, as of yet, there is insufficient storage capacity.

The Trump administration is among critics who say a large-scale conversion to renewable energy could be destabilizing to the U.S. electric grid. Energy Secretary Rick Perry is expected to release a report in the next month reviewing federal regulations to determine whether policies supporting renewable energy, like the Obama-era Clean Power Plan, have made the national electricity grid less reliable. Anticipating the department of energy analysis, two industry organizations released their own report this week, finding that wind and solar have not threatened the reliability of the grid.

It’s no secret President Trump supports the coal industry. Earlier this month he announced plans to withdraw the U.S. from the Paris climate accord, making good on a promise he reiterated throughout his White House bid and isolating the U.S. from the 194 other countries supporting global carbon reduction efforts. Previously, he ordered Environmental Protection Agency (EPA) administrator Scott Pruitt to scrap the Clean Power Plan, which was expected to reduce power sector emissions by 32 percent below 2005 levels by 2030.

Regardless, the U.S. will come close to achieving those power sector emission reductions even without the federal policy. According to the BNEF report, the U.S. is expected to reduce emissions by 30 percent below 2005 levels by 2030. And renewable energy sources are giving coal and fossil fuels a run for its money. The BNEF report also predicts that by 2040 coal consumption will have dropped 51 percent and be replaced by cheaper renewables and natural gas.