Veganism is bad for the environment
Agriculture, e.g. growing fruit and veg, actually requires more space than many cow farms or chicken coops. Demand for all-year-round fruit and veg is causing widespread deforestation, which in turn is the leading cause of animal extinction. Veganism would only increase this demand, worsening the situation. Not only are the space requirements unpractical on a large-scale, but they’re also bad for the environment. If you really want to help the environment, then switch to eating locally grown produce and buying meat from farms which treat their animals well, e.g. no battery farming.