HÉNIN-BEAUMONT, France — All of the lighting in the city’s streets and buildings is being changed to environmentally friendly LED bulbs. City workers will come to your house to plant trees — for free — as a natural way to keep cool against the kind of heat waves that swept across Europe over the summer.

Sheep also tend to the grass in one large, city-owned field as an experiment in “eco-grazing.” “Less pollution, less noise, fewer chemicals,” a city sign explained. “One more step forward in protecting our biodiversity.”

No, the policies are not the work of a tree-hugging City Council dominated by the Greens. They are of France’s far-right National Rally, the party whose longstanding, fierce dedication to a single issue — curbing immigration — helped it become France’s main opposition.

Only a few years ago, the party showed little interest in the environment. Its founder, Jean-Marie Le Pen, denied human-driven climate change and dismissed ecology as the “new religion of the bobo,” or bohemian bourgeois.