Two Canadian Cities could be under water in 100 years or less.

As the earth warms, Arctic and Antarctic ice sheets melt and sea levels rise steadily  just a third of a centimetre a year or so, but it adding up, and it isn’t slowing down.

What will our shorelines look like by the year 2100 depends on how much the climate warms, whether air pollution goes on unchecked or reduces, on whether the West Antarctic ice sheet has begun an unstoppable collapse.But even under the most cautious scenarios, the shapes of coastal cities will change.

275 million people live below five metres above sea level, and 60 million within a metre around the world.But some communities on both of Canada’s salt-water coasts will start to feel the effects of rising sea levels, maps produced by Climate Central, a scientific non-profit based in New Jersey, predict.

Below are the two places in Canada, thousands of miles apart, that will see serious challenges and questions about the value of land that may have expensive answers as the century unfolds.

1. Richmond and Delta, B.C.

Even the most conservative flood maps show Richmond, Delta and parts of rural Abbotsford and Coquitlam permanently underwater by 2100.

But it’s not going to look like that, predicts earth sciences professor John Clague, who teaches earth sciences at Simon Fraser University.“It ignores the social reality that we protect areas like that from flooding and inundation, which has to be taken into account when we assess the risk that people face from sea level rise.”Too many people live in the area and there’s nowhere else for them to go.Instead, he argues, we are eventually going to be forced to spend billions of dollars on a massive system of flood defences.

He adds, My guess is that we will spend $10 billion, given what’s at stake on that surface. The alternative is to abandon it.”

2. The Tantramar Marsh, New Brunswick

In the 17th century, Acadian settlers in the Maritimes built aboiteaux, earth dams designed to keep the tides out of marshland and turn it into productive farms. One area they settled was the Tantramar Marsh at the top of the Bay of Fundy, between modern-day Sackville, N.B. and Amherst, N.S.By the end of the century, however, the highway, the marsh (and much of the town of Sackville) may be permanently underwater. Humans may not have taken the land from the sea, in the long run; rather, we borrowed it for a while.

Mount Allison University geography professor David Lieske warns, “$45 billion of trade passes through that corridor.Stuff from the port of Halifax passes through our region. It also includes rail, it includes tractor-trailer traffic and just people commuting between Nova Scotia and New Brunswick, and PEI too, because that corridor is all kind of interconnected.”

Possible solutions include raising the dykes, moving the highway and rail line to a much higher and more massive causeway, or moving the land transport links between Nova Scotia and New Brunswick well to the north, to higher ground.With the right combination of conditions, storms would combine with higher sea levels and the Bay of Fundy’s enormous tides to create sudden, serious flooding, Lieske says.

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