[myshpa]

> large amounts of artificial fertilisers

Sure, but also pesti/herbicides.

> without artificial fertiliser you need to have animals to produce fertiliser

Or compost / nitrogen fixing / companion plants.

> But removing all animal products would be counter productive

There are people practicing it for decades pretty well without animal inputs.

Syntropic agriculture (Ernst Götsch), natural farming (Masanobu Fukuoka), veganic farming, permaculture, hydroponics, animal-free biodynamic farming, etc.

It's not a necessity.