Wild animals face overpopulation all the time. You've heard admonitions to spay and neuter your pets? That's because we have a worldwide overpopulation of domestic dogs and cats. In the southern US wild hogs devastate pasture land and forest to the point where in most counties hunters and trappers are encouraged to bag as many of them as possible year-round. Mongooses (introduced to prey on the local snake population) have become pests in Hawaii; it's now a civil violation to offer aid or shelter to a mongoose there.

And it's not just the animal kingdom, either. Kudzu is a very well known vine that's native to Asia. It was brought to the US for the 1876 Centennial Exhibition and it escaped custody. Seriously. Now it's a massively destructive plague on the east coast of the United States, growing faster than it can be cut down, covering everything particularly in the southeast. They call it completely unironically "the vine that ate Georgia".

Long story short, nature is not a steady state. Populations are constantly in flux, waxing and waning. The natural state is not one of balance but one of constant change. Things tip one way and a particular plant scatters its seeds wider than before and the next thing you know the animal that feeds on that plant has had more offspring than before: population boom. The newly expanded population adapts to feed on other plants as well and crops them down to the dirt which opens up a new ecological niche for a different plant and that one spreads like wildfire. A predator catches whiff of the exploded herd and feasts, scavengers lay eggs numbering in the tens of millions, enough bugs hatch to darken the skies … it just goes on and on. Nothing ever stays the same for more than a minute. Everything is changing all the time. We only thing things are consistent because we're here for such a short time.