The race to be the most sustainable fashion brand is on.

When Gabriela Hearst presented her spring 2020 collection at New York Fashion Week, she described it as an “industry first.” The designer celebrated for her cashmere knits was not referring to her latest looks.

Instead, Ms. Hearst said she had produced the first fully carbon-neutral runway show, at a time when scrutiny of the environmental footprint of fashion week has reached fresh heights.

Forty-eight hours later, as the traveling fashion caravan rolled into London, Gucci, the luxury powerhouse, announced that it too is taking greater responsibility for the toll its business takes on the planet.

In a telephone interview, Marco Bizzarri, the chief executive of Gucci, confirmed that Gucci will stage a carbon-neutral runway show during Milan Fashion Week later this month.