My first thought would be that humans are probably the reason why culling needs to happen in the first place, but then again I guess stuff like this can happen without human interference, too? I'd love for a biologist to chime in here.
Here's the way I'd explain it in brief. There is almost nowhere left that can be considered a truly natural ecosystem. We've changed our environment so much, in so many ways, that such a thing essentially doesn't exist anymore in places like North America.
Note that I don't just mean the obvious things like pollution and global warming. Roads, damns, cities, crops, telephone lines, etc. etc. Animals and plants rarely can just settle into a natural balance, even if you're talking about a 40,000 acre forest or something. These lands have to be actively managed. And that
definitely includes culling invasive species.
Around here, coyotes are a huge problem. In fact, we don't even quite know the scale of it, though we have been studying it. We know they have reduced the numbers of several species, though. They have heavily preyed on whitetail dear. We used to think they just ate fawns, but now we know they attack adults as well. They also eat rabbits, turtles, and other small animals.
And before the 1960s, there wasn't a coyote in the state. We're taking them at a rate of about 40,000 a year, and it's not enough. In fact, DNR instituted a bounty on them a couple of years ago.
One thing a recent Warnell study looked at was how they even get here. How they move around. Up above, when listing how humans have changed the landscape, I mentioned telephone lines. Well, that was a major culprit. We discovered they like to travel along the cuts made to put up power lines. And that gets them around quite well. If it weren't for roads, powerlines, acres of crops, etc. we wouldn't have coyote here at all, and they wouldn't be killing the natural species that live here.
And coyotes are just one example. Don't even get me started on cogongrass. Fuck cogongrass. It accidentally arrived as a seed in a packing container from Japan in 1911. Shouldn't even be on this continent. Now, it has spread to several states. Estimates are something like 1.5
million acres.