[philwelch]

Most cattle feed isn't digestible by humans, so it doesn't matter. Replacing grass with more human-edible crops would probably introduce new problems of similar scale.

You might ask, can we just process the grass into something humans can eat? Well, that's what cattle are for.

[telchar]

Better to leave natural habitat on that land rather than clear-cutting forest for grazing land, as happens so much these days and in the past. Better food production efficiency means less forest razed which is a significant win.

[philwelch]

Other forms of agriculture also contribute to deforestation. There are also situations where some grasslands may be suitable for grazing but cannot be sustainably made suitable for crops, and situations where livestock can be fed with byproducts of other agriculture.

Livestock are a central part of traditional agriculture and they're more or less essential for people who want to operate small-scale sustainable farms. It's a complicated issue that too many people enter with ideological presuppositions. Which is not to say current agricultural practices are necessarily perfect.

[telchar]

The important point is that animal agriculture is calorically inefficient, so much more land has to be used than if people could substitute plant-based food sources for animal-based. Much of plant agriculture today is only necessary to feed animals. Some animals could probably still be fed with plant agriculture byproducts if little to no land were directly used only for raising animals, but far fewer than are currently raised.

And many grasslands that cannot be sustainably be used for crops could be returned to wilderness rather than plant agriculture, if we were to increase caloric efficiency of food production. They probably should be, in fact. This doesn't preclude some animals being raised, but if we don't greatly reduce the amount of land used for raising animals, deforestation, desertification and other harms will continue to degrade ecosystems.