Honestly I've come to the conclusion that most "things" are more intelligent ( or even just worthy of moral worth ) than we usually give them credit for.
This is partially why most veganism arguments that try and say that we shouldn't kill and eat animals and instead we should kill and eat plants usually fall on deaf ears for me just because it makes an implicit assumption that plant life is worth less than animal life ( I'm not saying this is not true but that is the exact same argument meat eaters make with animals. )
There are other reasons why veganism is good for the planet however ( like it being easier to sustain and lower carbon emissions ) but I think that it is better to come at this whole situation with the attitude of how do we live in harmony with the life around us whether that be human, animal, plant, etc.
That is why in my third paragraph I mentioned that it was easier to sustain in the long term.
In my view this just feels like justifying a less deadly mass killing for a more deadly mass killing. They both have their consequences.
For example I think it is just as bad that due to our consumerist society we have to over harvest the land that we work on and grow plants in ways that make them more vulnerable to disease and other things that they would be less susceptible to if we didn't try to optimize their production. This is something that wouldn't change if we all suddenly became vegan we would also need to change our culture of consumption.
And this is why again my argument is not that we should just try and find an optimal utilitarian equation of how many lives are worth killing to sustain society but instead find a way to live that doesn't over exploit the ecosystem that we live in and doesn't go out of its way to do unnecessary harm to life.