Cotton is a big drain on water supplies, so that might be another reason why it's not seen 'as' eco-friendly as some of the other crops available.
I found this website to be pretty helpful, though I'm sure there's others.
I've put it as a tiny url as there is a swear word in the website address. There's also A LOT OF SWEARING in the page I've linked (so, if you don't like swearing, don't go to the page. You will be upset).
But, I think it's a fun way to look at how we can be more eco friendly, so I hope it helps you adopt some more eco-friendly habits. (They even mention eating 'less' meat, which is seemingly more of a trend these days).
My favourite tip, is reducing the amount of water it takes during a shower. I cannot STAND it when people leave the tap running, or when they take a shower for more than 10 minutes every single day.
I also like this calculator-
It can give you hints on how to be as eco-friendly as possible.
Just remember, you don't have to do EVERYTHING. By not eating animals, you're already being very eco-friendly to begin with. Don't fall into the trap of feeling guilty that you don't live in a flat that's completely powered by renewable energies and you only eat food that comes from less than 5KM away. You do what you can.