In nature, if it weren't for the meat eating creatures, the herbivores would literally eat themselves out of house and home. The limiting factor for them would be starvation.

The omnivores and carnivores are part of the balance.

Think of the Galapagos Marine Iguana. With no predators they stripped their island clean of their plant food centuries ago. Then they started eating seaweed to keep from starving.

The next problem was as their numbers increased, all the easy, close to shore seaweed was soon devoured.

Now they have to dive in the cold water as deep as they can for as long as they can hold a breath, take a bite, and get back to the surface before they drown. Since they are cold blooded, then they have to lie on a hot rock to warm their body temperature so they don't die from being too cold.

Their population is now limited by the Iguanas who either can't hold their breath long enough to get deep enough for a bite (then starve to death) or can't warm their body temperature enough to survive the next bite (then die of hypothermia). It's not a good life, it's a daily struggle to get a minimal amount of food, just enough to make it to the next day, which might be any particular Iguana's last because he/she just couldn't get enough food that day.

A world without predators would not be a nice place for a planet of nothing but herbivores. As romantic as the notion of no meat eating might be, in practice at first it would lead to a world of always hungry, tortured animals with the survivors being those who could exist on the least amount of food.

Eventually the planet would be stripped of all green and all the herbivores left would starve to death.

So when I eat that bacon or grass-fed burger, I'm doing the herbivores a favor.

Bob