People who advocate eating less beef often argue that producing it hurts the environment. Cattle, we are told, have an outsize ecological footprint: They guzzle water, trample plants and soils, and consume precious grains that should be nourishing hungry humans. Lately, critics have blamed bovine burps, flatulence and even breath for climate change.

As a longtime vegetarian and environmental lawyer, I once bought into these claims. But now, after more than a decade of living and working in the business—my husband, Bill, founded...