I hope the vegan diet helps your health issues, but it *really* isn't going to save the world. Agriculture is super destructive to whole ecosystems. It destroys habitats, is killing out species of animals and insects, & leads to desertification particularly in poor nations that produce a lot of trendy foods that have been popularised by vegans (I'm looking at you quinoa). If it's a personal moral or health decision, that's cool, but please don't perpetuate the idea it'll save the environment.
Actually, the number one biggest cause of environmental problems is land use for animal feed crops, not for humans. I highly recommend you watch Cowspiracy as a starting point. Or hit up Mic the Vegan’s youtube channel. This video specifically addressing the myth you mentioned: [x]