Agriculture
Agriculture is one of the biggest reasons. While the world's population is increasing, food consumption increases, too.
But this consumption is not just coming from necessity. Big Business companies have the aim to make people eat more.
They use monosodium glutamate and other chemicals to affect the human brain about hunger. This makes people eat more than they need to. The industry is set up in cattle ranches to meet the requests. Latin America is the most affected area by this.