The arithmetic of one person
A person moving from an average high-income omnivorous diet to a plant-based one avoids roughly 800–1,000 kg CO₂e a year, frees around 2,000–3,000 m² of farmland, and removes roughly 25–30 land animals plus a much larger number of aquatic animals from demand each year. Over a normal adult lifetime that is on the order of a thousand animals and tens of tonnes of emissions. These figures are modest against global totals and decisive against the alternative of doing nothing.