When Michael Mack, the chief executive of Syngenta, a Swiss agribusiness giant that makes pesticides and seeds, hears people say that organic food is better for the planet, he has one response: “Au contraire.”

“Organic food is not only not better for the planet,” he said, in an interview at The New York Times building on Tuesday. “It is categorically worse.”

The problem, Mr. Mack said, is that organic farming takes up about 30 percent more land, on average, than non-organic farming for the same yield (though this varies by crop, of course). If the world wants to feed its fast-growing population on existing cropland – and Mr. Mack is clear that he does not want forests chopped down to clear more land for biofuel production, let alone food – then productivity becomes a key factor, he said.

“If the whole planet were to suddenly switch to organic farming tomorrow, it would be an ecological disaster,” he said.

In terms of yields, he continued, organic food is the “productive equivalent of driving an S.U.V.”

Mr. Mack also addressed what he called the “mistaken belief that natural is always better.”

Pesticides that help crops to grow more efficiently in this country, he argued, “have been proven safe and effective and absolutely not harmful to the environment or to humans,” and have been certified as such by the Food and Drug Administration or the Environmental Protection Agency.

The implication of not believing that pesticides are safe, he said, is that you don’t trust the government’s findings.

“Once you go down that path, I don’t know where the guard rails are,” he said.

Mr. Mack dismissed the notion that Syngenta, a company that sold nearly $12 billion of seeds and “crop protection” technologies last year, felt threatened by the organic movement.