An invasive species is spreading through Canada's parks, leaving its mark on the landscape wherever it goes.
The culprit isn't the Asian long-horned beetle or the Baltic water flea ... it's the inukshuk.
The friendly-looking stone structures are multiplying on hiking trails and at campsites across Canada.
This is prompting some park officials to plead with visitors: no more.
Killarney Provincial Park officials placed an ad this summer in the park's newspaper, urging visitors to "stop the invasion" of inukshuks in the Ontario park.
Cairns mark many of the park's hiking trails.
And the proliferation of inukshuks built by well-meaning but clueless people threatens to lead hikers astray, says park superintendent Chuck Miller.
Also, Mr. Miller says his park and others contain archeologically significant quarry sites.
This means that rearranging the rocks could disturb the historical record.
Park workers take down inukshuks wherever they find them, Mr. Miller says. Workers at the nearby French River Visitor Centre dismantled 30 in a single day.
"It is a considerable piece of work for park staff," Mr. Miller says.
The Inuit people use inukshuks as markers to help them navigate the landmark-less terrain above the Arctic Circle.
The artfully arranged stacks of stones also mark good fishing spots, hunting grounds, or other significant places. (Though the Inuit prefer the spelling inuksuk, the common English spelling is inukshuk.)
Non-native people quickly caught on, and inukshuks are popping up across the country, from beaches to roadsides to campsites.
Stacking rocks in a tower can be a pleasant, meditative act, and it comes naturally when you're sitting on a rocky beach or beside a campfire with little else to do but count mosquito bites or sing Kumbaya one more time.
Inukshuks also allow nature-lovers to satisfy the very human desire to proclaim "I was here" in a less invasive way than carving the words on a tree.
In recent years, the inukshuk has assumed symbolic importance as a beacon of friendship and an icon of the first nations and Canada at large.
The government of Canada placed an inukshuk at Juno Beach to honour the spot where Canadian forces landed at Normandy in 1944.
The rock sculpture graces the Nunavut flag, and was chosen as the emblem for the 2010 Winter Olympics in Vancouver.
The Olympic logo stirred up controversy, though, as some native leaders objected to the anthropomorphism of the navigational marker and noted that traditional inukshuks are built in certain locations for specific reasons - not for decoration or marketing.
Park officials' objections to inukshuks are more practical than cultural. Bill Fox, technical services manager for Pacific Rim National Park Reserve in British Columbia, says park workers take down inukshuks left by visitors because they want to keep the park in its natural state.
Some beaches on the Broken Group Islands, particularly, seem to attract the stone stacks.
"We dutifully remove them and hope they don't reappear like mushrooms every year, which they seem to do," Mr. Fox says. "I guess it's mostly boredom, combined with a need to express oneself. But it's just not part of the environment naturally."