Unchecked populations of feral pigs have overrun rural areas, damaged cropland, ruined entire swaths of rainforests and nearly wiped out endangered birds. The question is: Can they be stopped?

A few months ago, our household was one of several hundred in the city of Everett, Wash., that was targeted for installation of a backflow valve in the outgoing sewer line. The valve is a six-inch, hard plastic flap that prevents stormwater — and everything else that travels through a sewer line — from flowing backwards up into one’s basement, laundry tubs, and toilets.

That would not be a good thing, as you might imagine.

The city hired a specialized contractor to dig down to the sewer line, cut through the pipe and install the valve. But 24 hours later, he returned because there was some leakage seeping up through the ground.

Turns out that a rat had crawled through the main sewer line from the street — probably from some nearby storm drain — squeezed through 120 feet of the discharge pipe and proceeded to gnaw through the half-inch-thick piece of plastic.

You gotta admire the tenacity, and the destructive capability, of an animal that has adapted to its proximity to humans arguably better than any species on Earth.

At the same time, I don’t want rats gnawing their way into my household plumbing!

Yes, their survival instincts are formidable, but rats are pests. Vermin that aren’t welcome inside anyone’s home.

Or on their land.

Which brings us to the growing problem of feral pigs.

A comprehensive report in Scientific American titled, “Can Wild Pigs Ravaging the U.S. Be Stopped?” noted that two years ago, the estimated population of wild pigs now exceeds five million animals, all busy devouring crops and damaging rural habitats in some 40 states.

The growth of the feral pig population — and its expansion into dozens of states beyond the original concentration in the South — was rapid, and unexpected.

“If you look at maps of pig distribution from the [1980s], there’s a lot of pigs, but primarily in Florida and Texas,” Stephen Ditchkoff, an Auburn University wildlife ecologist, was quoted in the report. “Today, populations in the Southeast have exploded. In the Midwest and the North, it’s grown to be a significant problem.”

How did it happen? Ditchkoff said he believes that “sportsmen” transported the pigs out of the South so they could hunt them on their land.

Beyond mere management

Although wild pigs are but one of numerous invasive species that cause all sorts of problems for agriculture, they tend to be left out of the earnest conversations about the urgency of implementing “humane” methods of population control when it comes to cuter, friendlier (and native) wildlife, such as deer.

Yet while a combination of increased food sources, thanks to widespread farming, and a dearth of predators, thanks to the near-extinction of wolves and other predators, has allowed the populations of many species of deer to explode across the Midwest, the Northeast and the Mid-Atlantic states, the damage they do is often confined to suburban shrubbery and highway accidents. Such events are traumatic for those involved, but don’t cause significant environmental destruction.

Not true with wild pigs.

According to USDA estimates, wild pigs cause more than $1.5 billion in damages and control costs annually, primarily to farmers. But it doesn’t stop with damaged crops and pastures.

Feral pigs travel in herds, and are incredibly efficient at digging up fields, creating shallow mud pits in pastures and trampling riparian areas around water sources. In Texas along, USDA estimated, some 2.6 million wild pigs in Texas cause $500 million in damage each year, damaging farm fields, destroying fences and killing fish in streams with their manure.

The problem is even worse in our 50th state. The agency’s Hawaiian Forest Bird Recovery Plan stressed “an immediate need for an aggressive strategy of feral pig eradication” to support efforts to protect habitat improvements, maintain re-forestation and plantings of endangered native plants.

Perhaps the biggest challenge in Hawaii is the threat that feral pigs pose to The Islands’ endangered and native bird populations. The wild pigs there have been called by ecologists “the most destructive force in native forests” other than land development. The pigs have overgrazed the rainforest, churning up the forest floor in search of earthworms and edible roots.

Without predators or any wildlife competitors, feral populations have rapidly multiply: a single breeding pair and their offspring can produce 15,000 pigs in just five years. Perhaps the worst part is that mosquitos breed in the muddy wallows the pigs create, and they spread deadly parasites to which most native Hawaiian birds have no resistance.

Things have gotten so out of hand that the U.S. Fish and Wildlife Service is spending more than $500,000 this year to try to identify effective eradication techniques for feral pigs.

And that’s in addition to all the traditional methods of hunting, trapping and poisoning feral herds.

As far as insisting on “natural” or “humane” methods of population control we’re way past that.

The goal with feral pigs is eradication, not management.

There are plenty of animal advocates who vehemently object to such programs.

And most of them are safely ensconced in urban areas far removed from the on-the-ground destruction feral pigs are wreaking on the very environment these same activists profess to cherish.

But just as Nature often does, protecting the health of an ecosystem requires that wildlife occasionally must be destroyed. □

Dan Murphy is a food-industry journalist and commentator