Speciesism is a system of thought that humans are superior to non-human animals so we have an inherent right to exploit them. This ideology is at the heart of our detachment from and destruction of the natural world.
It's well-documented that animal agriculture is a top source of greenhouse gas emissions, the largest user of fresh water, and a major cause of wildlife extinction and habitat destruction. Humans and the animals we eat now account for 96% of mammal biomass, with wild animals only accounting for 4%. The same goes for birds, which is one of the main reasons wild bird populations are crashing. Our species has destroyed 83% of wild mammals. The standard American diet of lots of meat, dairy, and eggs is not sustainable for anyone, humans included.