It all comes down to population size. To meet demand, both veggies and animals are pumped full of agri-chemicals and fertilisers, or hormones respectively. Of these, agri-chemicals and fertilisers are probably the most damaging, as run-off into the lakes and rivers has been massively damaging to marine wild-life and humans, both animal and vegetable.
(hmmm - don't know many vegetable humans, but you get my drift!)
One thing is certain - the huge growth and use in the last century of processed carbohydrate products (especially sugars) has corresponded almost exactly with the huge rise in diabetes, heart failures and obesity. Basically, the human body has not yet adapted to dealing with them - maybe in a thousand years or so!
However, whether the issue is shortage of resources - land, food, water, minerals, oil, gas , or the impact of potential global warming or cooling, raised water-levels etc - and the associated political implications and conflict these bring, the root cause of them is population growth, and the only realistic solution to any of them is population control. Everything else is trying to apply a sticky plaster to a cut jugular.