If the whole world went vegan, ecosystems would collapse
Animal agriculture is itself among the largest drivers of habitat loss and biodiversity decline. Reducing it releases land rather than destabilising ecosystems.
Grazing animals have shaped landscapes for thousands of years, and many habitats we value, from wildflower meadows and heathland to upland pasture, depend on their grazing, trampling and dung to stay open and species-rich. Remove livestock from the whole world at once and those systems would not simply return to some pristine state; they would scrub over, lose the plants, insects and birds adapted to them, and leave huge areas of land with no clear plan or use. A sudden global shift away from animals would unravel ecological relationships that farming has been part of for millennia, and the result would be disruption and loss rather than recovery.
Livestock farming is the leading agricultural driver of deforestation, a major contributor to freshwater eutrophication and marine dead zones, and occupies the majority of agricultural land while supplying a minority of global calories and protein. The ecosystems that currently exist do so despite this, not because of it.
Modelling of large dietary shifts consistently finds substantial reductions in agricultural land requirement, with the released area available for restoration. There are real local complications: some semi-natural grassland habitats in Europe depend on grazing to maintain their current species composition, and abandonment would change them. Those are arguments for managed conservation grazing in specific places, not for the global scale of production as it stands.
Replacing someone's actual position with a weaker, distorted version, then refuting that instead. The original argument is left untouched.
How it applies here: Assumes an abrupt, total and simultaneous global switch, which is not the proposal and not how dietary change occurs.
Inferring that one thing caused another from the fact that they occurred together or one after the other. Correlation and sequence are not causation.
How it applies here: Casts animal agriculture as the thing sustaining ecosystems, reversing the direction of the main documented effect.