For most countries around the world, sourcing energy entirely from wind, solar, geothermal, and hydropower by 2050 would reduce their energy needs and costs, improve air quality, and help slow climate change, according to a study in Environmental Science & Technology.
Going vegan is a relatively small difference from going vegetarian, which is a small difference from just drastically cutting back on meat. The big thing is that our current systems are unsustainable for animal rights and the environment and everyone needs to cut back on meat drastically at the least. But I imagine that if you could stop driving a car entirely, that would be a bigger difference than losing a reasonable amount of meat from your diet. Though, cutting back on meat is an important step that all of us can take with much more ease.