It is the largest positive impact a single person can have on the environment. Kurzgesagt video with the analysis.
As a vegetarian for decades, it’s also cheaper, often healthier, and isn’t difficult at all once you find some new recipes you like. You also don’t need to switch all at once. Ease into it by cooking one vegetarian meal a week and then increase it as you find ones you like.
Here’s another video just on that!