Diana Balmori in 2009. (Margaret Morton/Balmori Associates)

Diana Balmori, a visionary landscape designer who saw her theories of ecologically driven urban design widely adopted in her field, died Nov. 14 in New York City. She was 84.

The cause was lung cancer, said her son Rafael Pelli.

As an academic and author, Ms. Balmori spent much of her career railing against the idea that ­landscape architecture served simply to beautify buildings, ­saying instead that it was the primary ­discipline for addressing the woes of urban development in the 21st century.

Challenges such as climate change, rising sea levels and extreme weather required landscape architects fundamentally to rethink design approaches, she argued. “It wasn’t just about putting nature in the city; the city had to work like nature does,” said her colleague Noemie Lafaurie-Debany.

Ms. Balmori established a New York-based firm — Balmori Associates — that put her theories into practice in high-profile projects around the world. The most famous was the creation of a new federal city in South Korea in Sejong City, 75 miles south of Seoul. Here, Ms. Balmori and her colleagues designed a community of buildings linked by a 2.5-mile-long Sky Park of rooftop gardens and paths.

Diana Balmori worked with Robert Smithson on the Floating Island that traveled around Manhattan. (Balmori Associates)

Other projects include a 15-mile linear park that traverses, in part, New Haven, Conn.; Beale Street Landing Park, several platforms next to the Mississippi River in Memphis; and a green neighborhood that has transformed the old industrial port of Bilbao, Spain.

Ms. Balmori previously worked in the New Haven office of her husband, the architect César Pelli, and continued projects with the firm. She collaborated more recently with her son Rafael Pelli, also an architect with Pelli Clarke Pelli Architects, on the Solaire condominium complex in Battery Park City in Manhattan and Sao Paulo Corporate Towers in Brazil.

In her work, Ms. Balmori stressed that by starting with the landscape rather than the architecture, a city was better equipped to deal not just with ecological challenges but also societal ones. Her concept for the greening of Washington’s 11th Street Bridge over the Anacostia River, for example, was conceived to mitigate neighborhood gentrification, Lafaurie-Debany said. (Her bid was not chosen.)

For younger landscape ­architects and urban planners, Ms. Balmori was a pioneer of ecological design and thinking. Another unrealized project of Ms. Balmori’s was for a large floating island in St. Louis that would have given the city precious river real estate while handling changing river levels.

“I’ve been in the office for 18 years, and I remember at school we were looking at things Diana was already doing,” said Javier Gonzáles-Campaña, who now heads Balmori Associates with Lafaurie-Debany.

They attribute much of Ms. Balmori’s creative originality to her upbringing by artistic parents.

Diana Balmori was born in ­Gijon, Spain, on June 4, 1932. Her mother, Dorothy Ling, was a ­musician from England, and her father, Clemente Hernando Balmori, was a Spanish linguist. The family left for England during the Spanish Civil War and later resettled in Argentina, where the Balmori patriarch taught at the National University of Tucuman. It was there, as a student, that Ms. Balmori met her future husband. With ­Pelli, she emigrated to the United States in 1952.

An overview of land and architecture mixing at an extensive Balmori project in Bilbao, Spain. (Bilbao Ria 2000 /Balmori Associates)

Ms. Balmori earned a doctorate in urban history at the University of California at Los Angeles in 1973 before she and her husband settled on the East Coast. One of her heroes was the pioneering landscape architect Beatrix Farrand, the principal designer of the garden at the Dumbarton Oaks property in Washington. In one of several books written or co-written by Ms. Balmori, she examined the campus designs of Farrand at Yale, Princeton and other universities.

Ms. Balmori was a senior fellow at Dumbarton Oaks and, though not a registered landscape architect, a fellow of the American Society of Landscape Architects. She also taught at the Yale School of Architecture and the School of Forestry and Environmental Studies.

With two colleagues, she co-wrote a book in 1993 railing against what she called America’s “ecologically insane” fixation with lawns. The book, “Redesigning the American Lawn,” was at least 10 years too early to gain notice, she said. She once told an interviewer that “if I had to criticize myself, it’s that I’ve been doing it before the time was right.”

Besides her husband, survivors include two sons, Rafael Pelli and Denis Pelli, both of New York City, and two grandchildren.

Ms. Balmori was also an artist who frequently sketched the skyline around her SoHo office.

One of her favorite collaborations was the creation in 2005 of a floating garden designed in part by the land artist Robert Smithson, which was towed around Manhattan. Another, smaller version was conveyed on the Gowanus Canal in Brooklyn last year.

“She saw landscapes as a ­profound formal art,” Rafael Pelli said. “She saw this dimension of change that’s really unique to that form of art.”

Part of the change is the growth and seasonal cycles of plants, he said, but her work also sought to change how we viewed nature and the built environment. “She was so interested in issues of sustainability and how we think of nature, that there is this other aspect of change,” he said.