File under, "What did you expect?"

Actions do indeed have consequences:

The dozens of public works officials, municipal engineers, conservation agents and others who crowded into a meeting room here one recent morning needed help. Property in their towns was flooding, they said. Culverts were clogged. Septic tanks were being overwhelmed.

"We have a huge problem," said David Pavlik, an engineer for the town of Lexington, where dams built by beavers have sent water flooding into the town's sanitary sewers. "We trapped them," he said. "We breached their dam. Nothing works. We are looking for long-term solutions."

Back in the day it was decided by someone (someone far more caring, nuanced and insightful than any NP reader) decided to do something:

He is not alone in his dismay, and it is not just beavers. Around the nation, decades of environmental regulation, conservation efforts and changing land use have brought many species, like beavers, so far back from the brink that they are viewed as nuisances. As Stuart Pimm, a conservation ecologist at Duke University, put it, "We are finding they are inconvenient."

In Florida, alligators were once nearly wiped out by hunters; today the state maintains a roster of trappers who remove thousands of nuisance gators each year. The pesticide DDT once left the Pelican State, Louisiana, bereft of the birds; today wildlife organizations say fishermen must guard their bait and catches from the birds. In California, warnings about marauding mountain lions are posted on hiking trails.

There were tens and maybe hundreds of millions of beavers in North America before it was settled by Europeans, whose craze for beaver hats is often cited as motivating much of the exploration of the continent. But by 1900 their numbers had been reduced to about 100,000, almost all of them in Canada. As farming faded and the forests reclaimed much of their lost ground, Castor canadensis made a spectacular comeback. Today there are believed to be 10 million to 15 million of the animals in North America, and they are regarded as pests in much of their range.

You wanted it, you got it, now deal with it.