Vegan for the environment.
Animal agriculture is the most destructive industry on the planet.
Livestock farming causes more environmental damage than mining, driving an SUV, rail or air transport.
Animal agriculture is the leading cause of species extinction, ocean dead zones, water pollution, and habitat destruction.
A World Watch report showed that 51% of greenhouse gas emissions worldwide can be attributed to animal agriculture, land clearing for livestock, by-products and animal transportation. 
Animal agriculture’s destructive environmental impacts include animal gas emissions, nitrous oxide from animal waste, deforestation for farmland and stock feed and subsequent species extinction. Livestock covers 41% of the planet’s land  and has resulted in devastating habitat destruction and consequent extinction of hundreds of species.
47.9% of New Zealand’s greenhouse gas emissions are from agriculture. This is largely due to methane from cows, which is 28 times worse for global warming than carbon dioxide:
Animal agriculture causes pollution
Climate change is not the only environmental disaster caused by livestock farming.
Up to $10.7 billion is needed to remove nitrates (created by dairy farming) from drinking water, $3.1 billion to counteract greenhouse gas emissions and $611 million to respond to soil compaction, a serious environmental issue which inhibits infiltration, plant growth and thus productivity.
Over 75% of soils under dairying are badly affected by compaction, and river quality New Zealand-wide has declined tragically, significantly worsened by intensive farming. 29% more nitrogen was leached into soils from agriculture in 2012 than 1990, mainly due to more dairy cattle and nitrogen fertiliser.
Excess nitrogen ends up in groundwater, rivers and lakes, which causes growth of harmful periphyton that restricts river flows, blocks irrigation and water supply intakes, and suffocates riverbed habitats. Nearly 50% of rivers in New Zealand are significantly degraded.
The Manawatu river is one of the most polluted in the world. Most of the Waikato’s rivers and streams are unsafe to swim in, with approximately 90% of pollution being caused by rural runoff from dairy farms and other pasture. National Minister Nick Smith considers water pollution to be an environmental issue second only to climate change in importance.
The 16,000 pigs in an intensive operation cause as much effluent as a city of 23,000 people, and this is largely untreated. Reids piggery in Carterton (owners of the Premier Bacon brand) were convicted for dumping what essentially amounted to raw sewage into waterways.
We are in the midst of the largest mass extinction in 65 million years. 
Animal agriculture is responsible for 91% of Amazon destruction and is the cause of 80% of all globally threatened bird and mammal species, largely due to deforestation for livestock feed or grazing.
Habitat destruction is the leading cause of extinction especially in a recognised “biodiversity hotspot” like New Zealand. Thanks to our insatiable demand for animal flesh, the once diverse lowland forest that covered the Hauraki Plains, the Horowhenua and other places, have become a sea of pasture, dotted with livestock, as far as the eye can see.
Environmentalists are concerned over the damage caused by possums, but it was no marsupial that felled thousands of hectares of bush for the sake of a livestock monoculture.