How can they be disputed? It's a fact clear as a day that deforestation in many places is caused by people making room for farmland… that don't produce food for people but fodder for livestock. And livestock has a calorie conversion efficiency much lower than unity. So you need to cut more forest to feed the same number of people. It can also scarcely be disputed that cattle produce large amounts of methane, enough that it's a significant factor in total greenhouse emissions.

There's also no disputing the fact that turning uncultivated land into monocultural farmland is a great cause of biodiversity loss – it's essentially the definition of farmland!