He did mention in one of the planet earth 2/3 series how so much of the land is used for farmed animals. And, for the sake of completeness of argument, for restoring what was lost, the challenge is how to raise the standard of living fast enough for people so they give a damn about anything apart from ourselves was THE challenge to combat climate change and global ecological disaster. He specifically mentioned e.g. educating girls and making older-aged societies more propsperous. Prosperous people can make better choices about farmed animals as food.

Modern agriculture, both animal and non-animal versions, are bad for the environment. Artificial fertilizers, replacing forests with farm land, and drainage of wet lands are all heavily contributing to emissions and water pollution, destroying local ecosystems as well as warming the planet. Artificial fertilizers is particular bad since its production uses fossil fuels, has large amount of accidental green house emissions, and causes eutrofiering to the point of areas like the baltic sea becoming basically dead from loss of oxygen. Runoff from farms are also now the primary cause of ecosystem collapse in fresh water lakes.