Agriculture is the worst of environmental exploitation caused by humans.
1. Agriculture kills all other species of plants, insects and animals for growing a single specie of plant in a vast area. This affects the bio-diversity.
2. Agriculture needs irrigation, fertilizers and pesticides. Irrigation leads to draught, altered river routes, soil erosion and deforestation.
3. Fertilizers and pesticides used in agriculture contaminates the waters and endanger fish life.
4. Insects killed by pesticides are eaten by birds which severely affect their reproductive ability and thus threatening many species of birds.
5. Agriculture releases more than two third of N2O (Nitrous oxide) i.e. nearly 70% of man made N2O. N2O is 200 times potent Green House Gas compared to Carbon-di-oxide and it depletes Ozone layer too. Nobel Prize winning scientist Paul J. Crutzen suggests that the agricultural N2O release may be underestimated.
6. Though the calorie output of meat:grain is 1:4. Cattles consume 4 times veggies to produce the meat supplying the same calories. But wait! Are they consuming wheat and rice? They eat agricultural wastes like hay, grass, weeds etc. Moreover, if these vegetation wastes are left to decompose they too will produce methane.
7. If the cattle are deprived of grazing land and all grazing lands converted in to agricultural lands, two problems arise. First, unlike grasslands, agricultural lands need irrigation, fertilizers and pesticides. Second is the animals will soon disappear from the face of Earth like the tigers and elephants due to food shortage and draught.
8. All the people from the vegetarian lobby relish on butter, milk, cream etc. Anyway they are going to keep cattle. If that is the case, abstaining meat will put extra pressure on the planet and resources. We have to feed cattle only for milk and also people only with grains. Still the cattle will be producing methane.