Roads and airstrips across the Western Arctic are sagging, cracking and washing away as climate change slowly melts the permafrost beneath them.
And as engineers try to adapt transportation networks and buildings to warmer weather, some say the consequences of doing nothing are already apparent just a short drive out of Yellowknife.
''It literally looks like an earthquake zone,'' says Northwest Territories transportation planner Jayleen Philps about an old stretch of Highway 4.
Maintenance on the 700-metre section stopped after a new road was built around it in 1999.
Now, cracks in the asphalt can swallow a fist and the shoulders have washed away. The surface, parts of which have sunk by more than a metre, is more roller-coaster than road.
''It gives you a vision of the amount of maintenance that would be required,'' says Philps.
Research suggests climate change is occurring up to three times faster in the North than anywhere else on the globe. The northwest corner of the N.W.T. is heating up especially quickly.
Those warmer temperatures threaten permafrost, the permanently frozen subsoil water that is widespread across all three territories and the northern reaches of most provinces.
It can provide a stable base for roads and homes, but that stability is lost once the permafrost melts.
In Yellowknife, an insulating liner had to be installed four metres under a 100-metre section of runway with a history of sagging.
In Inuvik, freezing rain that used to fall as snow has caused a tenfold increase in the volume of de-icer and gravel used at the airport.
Workers have had to terrace embankments along the Dempster Highway south of Inuvik to keep sections from collapsing. Even then, the roadbed has been sinking and new construction includes insulation under the asphalt.
Portions of the road from Yellowknife to Fort Providence have been abandoned and rebuilt over more stable permafrost.
The season for ice bridges and ice roads - crucial to industry for moving in supplies - has shrunk from an average 75 days before 1996 to about 47 days.
Transport Canada says 42 airports in the zone are likely to be most affected.
And a soon-to-be-released study funded by Natural Resources Canada suggests six N.W.T. communities, mostly in the Mackenzie Delta, are highly vulnerable to infrastructure damage from melting permafrost. Another 18 communities are moderately vulnerable.
''It's fairly widespread,'' says Philps.
Her department, together with three federal departments, is just starting to look at the cost.
''It's a horrendous investment,'' says Heather Auld of Environment Canada, who gave a presentation on climate change and infrastructure in April at a conference in Montreal.
The problem becomes even more acute as the N.W.T. prepares for massive industrial development - much of it likely to be concentrated in the Mackenzie Delta, the area most affected by climate change.
Federal officials say changes to Canada's building code are probably needed, despite the extra costs involved.
''It's a fast way of getting action,'' says Auld. ''If you ask people to voluntarily consider climate change, economics rule.''
Aining Zhang of Natural Resources Canada agrees.
''There is a need to change the building code to make it more resistant to thermal flux,'' she says. ''It is one of the things that we are trying to make happen.''
There are, as yet, no clear-cut examples of buildings sinking. The Arctic is generally hard on structures of all kinds and failures are impossible to blame on single causes.
But Auld says it's just a matter of time before what's happening to roads starts happening to homes.
''Some buildings may end up . . . condemned,'' she adds. ''After a point, it becomes a safety issue.''
Climate change has become a fact of life, says Philps.
''We're considering climate change in all of our planning and construction.''
