NEW YORK — Barry Commoner, a founder of modern ecology and one of its most provocative thinkers and mobilizers, died Sunday in Manhattan. He was 95. His wife, Lisa Feiner, confirmed his death.

Dr. Commoner was a leader among a generation of scientist-activists who recognized the toxic consequences of America’s post-World War II technology boom and one of the first to stir the national ­debate over the public’s right to comprehend the risks and make decisions about them.

Raised in Brooklyn during the Depression and trained as a biologist at Columbia and Harvard, he came armed with a combination of scientific expertise and leftist zeal. His work on the global effects of radioactive fallout, which included documenting concentrations of strontium 90 in the baby teeth of thousands of children, contributed materially to the adoption of the Nuclear Test Ban Treaty of 1963.

From there it was a natural progression to a range of environmental and social issues that kept him happily in the limelight as a speaker and an author through the 1960s and ’70s, and led to a wobbly run for president in 1980.

In 1970, the year of the first Earth Day, Time magazine put Dr. Commoner on its cover and called him the Paul Revere of Ecology. He was by no means the only one sounding alarms; the movement was well underway by then. But he was arguably the most peripatetic in his efforts to make environmentalism a people’s political cause.

Dr. Commoner was an imposing professorial figure, with a strong face, heavy eyeglasses, black eyebrows, and a thick head of hair that turned pure white. He was much in demand as a speaker and a debater, especially on college campuses, where he helped supply a generation of activists with a framework that made the science of ecology accessible.

His four informal rules of ecology were catchy enough to print on a T-shirt and take to the street: Every­thing Is Connected to Everything Else. Everything Must Go Somewhere. Nature Knows Best. There Is No Such Thing as a Free Lunch.

Although the rules were plain enough, the thinking behind them required leaps of faith. Dr. ­Commoner’s overarching concern was not ecology as such but rather a radical ideal of social justice in which everything was indeed connected to everything else. Like some other left-leaning dissenters of his time, he believed that environmental pollution, war, and racial and sexual inequality needed to be addressed as related issues of a central problem. Having been grounded, as an undergraduate, in Marxist theory, he saw his main target as capitalist ‘‘systems of production’’ in industry, agriculture, energy, and transportation that emphasized profits and technological progress with little regard for consequences: greenhouse gases, nonbiodegradable materials, and synthetic fertilizers and toxic wastes that leached into the water supply.

He insisted that the future of the planet depended on industry’s learning not to make messes, rather than on trying to clean them up. It followed, by his logic, that scientists in the service of industry could not merely invent a new process or product and then wash their hands of moral responsibility for the side effects. He was a lifelong opponent of nuclear power because of its radioactive waste; he scorned the idea of pollution credit swaps because after all, he said, an industry would have to be fouling the environment in the first place to be rewarded by such a program

He was concerned that the integrity of American science had been compromised: first by the government’s emphasis on supporting physics at the expense of other fields during the development of nuclear weapons, and second by the growing privatization of research, in which pure science took a back seat to projects that held short-range promise of marketable technologies.

But although he had a record of achievement as a cellular biologist, he was seen primarily as the advocate for a politics that relatively few considered practicable or desirable. Among other positions, he advocated forgiveness of all Third World debt, which he said would decrease poverty and ­despair and act as a natural curb on population growth.

His platform did not get him very far in the 1980 presidential race, which he entered as the head of his Citizens’ Party. He won only about 234,000 votes as Ronald Reagan swept to victory. Dr. ­Commoner conceded that he would not have made a very good president. Still, he was angry that questions he had raised had generated so little interest. His favorite moment of the campaign, he recalled many years later, was when a reporter asked, ‘‘Dr. Commoner, are you a serious candidate, or are you just running on the issues?’’