Three coasts, fifty-two thousand islands, and the fresh-water myth

Hopewell Rocks, New Brunswick, at low tide. Chantal Doucet is 38, Acadian, a park interpreter, and right now she is standing on the floor of the Bay of Fundy, at the foot of rock towers with trees on top. Twice a day she tells visitors the same thing. Come back in six hours, and where you are standing will be under more than ten metres of salt water.

So here's the question. What shape is Canada's edge? Three oceans, one enormous bay, tens of thousands of islands, and the highest tides in the country. How does one map hold all of that?

Statistics Canada puts the coastline at 243,042 kilometres, measured on the Atlas of Canada's maps and including the shores of more than 52,000 islands. You will see smaller numbers elsewhere. A coastline gets longer the closer you look, so any figure only means something with its map scale attached. Ours is the longest in the world at any scale, on the Pacific, the Arctic and the Atlantic.

Most of those islands are in the Arctic Archipelago, north of the mainland. Atlas of Canada figures: Baffin Island, 507,451 square kilometres, the biggest; then Victoria Island and Ellesmere, each around 200,000. Baffin alone is bigger than the island of Newfoundland, Nova Scotia, New Brunswick and Prince Edward Island put together.

And Hudson Bay, that huge notch in the middle of the map, is not a lake. It is salt water, an arm of the ocean, one of the five basins our rivers drain into. Then Fundy. Statistics Canada gives the Bay of Fundy a mean large tide of 16.1 metres, the highest in Canada. Parks Canada explains why: resonance plus the shape of the bay, like pushing a swing at the right moment.

Find it on the map. This is a Natural Earth map of Canada with latitude and longitude every ten degrees. Find the line marked 80 north, then look above it for the tip of Ellesmere Island: Cape Columbia, our northernmost point, just past 83 degrees north. At the bottom: Middle Island in Lake Erie, near 41 and a half. Statistics Canada says they are 4,634 kilometres apart.

Let's change one fact. Straighten the Bay of Fundy into a wide, open bay with no funnel and no natural rhythm. The ocean's pulse would arrive and simply spread out. The tide would be an ordinary Atlantic tide, a metre or two, not sixteen. No mud flats to the horizon, no towers carved by water, and no job for Chantal, because nobody walks the ocean floor where the ocean never leaves.

The mistake people make is saying Canada has 20 per cent of the world's fresh water. What Ottawa actually publishes today is 7 per cent, of the water that renews each year, for half of one per cent of the world's people. The 20 is the water sitting in our lakes, most of it left behind by the ice age. That is a stock, not an income.

Here's the rule, in one breath. Three oceans, one salt bay, the longest coastline at any scale, and seven per cent of the world's renewable fresh water.

This week, look up today's tide table for the Canadian coast nearest you, on the Fisheries and Oceans Canada website, and find the range: the difference between high water and low. If you are far inland, pick Saint John, New Brunswick, and watch the numbers swing through the day. Then compare them with Fundy's sixteen.

Next time, why Vancouver isn't Winnipeg: oceans, mountains, latitude and lakes, and how to make sense of a climate graph.