Wild invasive pigs are wreaking havoc on North American ecosystems, a new report warns.

"Feral swine cause major damage to property, agriculture (crops and livestock), native species and ecosystems, and cultural and historic resources," Gail Keirn, a public affairs specialist with the National Wildlife Research Center, told PLOS ONE.

The National Wildlife Research Center, NWRC, is the research arm of the Wildlife Services program, part of the Animal and Plant Health Inspection Service, a USDA agency.

"This invasive species also threatens the health of people, wildlife, pets, and other domestic animals," Keirn said. "As feral swine populations continue to expand across the country, these damages, costs, and risks will only keep rising."

According to the new report, $1.5 billion is spent in the United States each year to repair and prevent damage done by wild pigs.

Researchers say that number is likely to rise as wild pig populations continue to grow and spread through the United States. It is estimated that roughly 6 million invasive wild pigs currently inhabit the U.S. They're found in 35 states.

Researchers at NWRC used wild pig data collected between 1982 and 2012 to plot the widening ranges of wild pigs and to predict their territorial expansion moving forward.

The largest wild pig populations are found in the south, but a team of scientists led by Nathan Snow found the pigs have been moving northward at a clip of 4 to 8 miles per year. In 30 to 50 years, Snow and his colleagues predict, wild pigs could be found living in all 50 states and every county in the country. Their conquest could happen even quicker if population introduced into Canada continue to move southward.

Wild pigs reproduce quickly and often, eat nearly anything and can survive in a variety of habitats. They also have no natural predators.

Feral pigs, or razorbacks, were first established in the 1500s, when colonists brought over wild and domesticated pigs for food. Some escaped, founding small feral populations. The Eurasian wild boar, or Russian wild boar, Sus scrofa, was introduced to the United States in the 19th century for hunting purposes. Today, wild invasive pigs consist of a combination of feral pigs, pure wild boars and hybrids of the two.