The thrill of playing in the mud is apparently hard for some people to resist. Nothing else can explain the frequency with which riders of all-terrain vehicles (ATVs) stray off designated trails to churn pristine wetlands into ugly rutted mudholes.

The continued prevalence of such misbehavior, despite laws enacted five years ago to curb it, was documented in a series of reports this week by Star Tribune staff writers Tom Meersman, David Shaffer and Glenn Howatt. Their accounts should disturb anyone who wants this generation of Minnesotans to leave future ones a legacy of healthy, unspoiled woodlands.

State officials concede that ATVs continue to scar state forests, and that only a fraction of the riders who have caused off-trail damage have been ticketed. About 1,600 warnings and tickets have been issued for natural-resource damage in the past five years, Meersman and Shaffer reported; only 42 offenders since 2003 have been fined more than $200.

That's a paltry number, especially considering the growing popularity of ATV recreation. Minnesota has 264,000 registered all-terrain vehicles, triple the number it had a decade ago.

More enforcers in the woods might help, even though the state conservation officer corps today stands at full complement, 200, after years of being 40 to 50 officers short. But stiffer fines and penalties, including the confiscation of the machines of purposeful offenders, would likely be a more effective deterrent to riders tempted to play in the mud. With 4 million acres of state forests, the chances of errant ATV riders getting caught wouldn't be high even if the number of enforcers were doubled. But make the price of an offense steep -- say, steep enough to pay for repairing the damage they do -- and more mud lovers might think twice before leaving a trail.

Steeper fines would send a needed message: Stripping a parcel of state land down to naked mud isn't harmless fun. It's a serious offense. It destroys existing plants, kills or banishes animals, and alters the habitat for both, in some cases permanently. It disrupts streams, invites erosion and spoils the wilderness experience for others.

The Department of Natural Resources, the agency entrusted to protect this public asset, is in the process of mapping and marking a huge ATV trail and forest road system, expected to be more than 7,700 miles long when completed.

That may beat the anything-goes "system" that existed before 2003. But the Legislature, which ordered this project in the name of environmental protection, ought to ask whether it is getting what it bargained for. Can a trail system so extensive ever be adequately maintained and monitored? Are ATVs being allowed to dominate forest recreation to the detriment of those who prefer quieter pursuits? And with funding for this and other projects coming from ATV registrations and gas taxes, has the state given its enforcement agency a built-in bias in favor of ATV sales and use?

Underlying the establishment of the new trail system, and the DNR's enlistment of ATV club members as volunteer trail monitors, is the hopeful idea that if the four-wheelers are given enough legal room to ride, they will steer clear of off-limits places. The 2009 Legislature needs to confront the reality that so far, those hopes look like wishful thinking.