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Recently my seven-year-old daughter and I were exploring the beach near our Toronto home when we made what was – for us – an exciting find. Strewn among the pebbles in a little hollow just beyond the water's edge was a rich cache of beach glass.Known as "mermaid's tears" by those with a poetic bent, beach glass is simply broken glass that has been tumbled by the waves until it is rounded and etched. In any other setting, it would be an annoying reminder that people are thoughtless enough to leave their smashed bottles lying around. But beaches don't care if people are thinking or not.

Like prospectors hitting the motherlode we stuffed our pockets with beach glass and brought it home. A couple of weeks later, my daughter led my wife back to the same spot to get more, but came up empty. The little hollow was gone and the beach glass too, presumably relocated by the restless waves.

And that is the fundamental truth about beaches. We flock to them every summer, attracted by their timeless, relaxing quality. Yet a beach is anything but timeless. It is a temporary landscape, a heaving battleground always in transition and frequently on the move.

We would be wise not to overlook this reality as we plan for a future in which many beaches, because of climate change, are likely to migrate from their present locations – if not vanish altogether. Admittedly, this is a relatively recent concern. For most of human history, we've used beaches mainly as transportation corridors. They gave our prehistoric ancestors easy passage as they migrated around the globe. Later, they served as entry points for invading armies. Wave action notwithstanding, Walmer Beach in Kent looks very much today as it did in 55 B.C., when Julius Caesar came ashore.

Our relationship with beaches began to change in the late 18th century, when Britain's upper classes discovered France's Côte d'Azur. By 1801, newspapers were advertising a U.S. seaside resort at Cape May, N.J., notes Duke University geologist Orrin Pilkey and his co-authors in The World's Beaches. As the Industrial Revolution ramped up, the need to escape "modern life" caught on. My beach neighbourhood began as a vacation spot for Torontonians soon after Confederation.

What's different about this kind of interaction is that it involves infrastructure – boardwalks, amusement parks, condos and more. And with it comes the implicit assumption that beaches, once parcelled, packaged and sold as a commodity, stay put.


I did not grow up a beach person. As a teenager, when it came to the outdoors, I preferred a walk in the woods. I didn't see the point in lying around on the hot sand with the rest of the crowd. It seemed mindless.

It was my children who opened my mind and made the beach the backdrop for some of our favourite family moments. When you're two, nothing beats the prospect of an endless sandbox, together with the irresistible but somewhat scary, boundary-crossing sensation that goes with extending a bare toe into the lapping waves. At Old Orchard Beach in Maine, on Cape Cod and in Clearwater, Fla., I watched my children engage with the sand and surf, and soon I was drawn in.

The waves are a big part of it. Each time they gather up and break on the sloping shore, the outcome is a little different. Waves are cyclic but not exactly repeating. They are irregular but not exactly random.

This puts them in a mental sweet spot perfectly tailored to hypnotize the mind. If each wave were exactly like the one before, the predictability would bore us. Waves generated by machines in indoor water parks feel like that. They're functional but uninspiring. Yet when a phenomenon is too complicated to follow, it becomes perceptual noise. Without the hint of a pattern, the mind moves on.

Waves at the beach take us to that creative place halfway between order and chaos. Their semi-regulars pulses offer just the right amount of stimulation to keep the brain in train while leaving room for other thoughts to bubble up from the subconscious. And so the beach becomes our catalyst for reflection and a mental as well as a physical experience.

Seaside sources of energy

But waves also define a beach just as it defines our experience of it. It is the energy carried by the waves and dissipated over a sloping shoreline that keeps unconsolidated sediment – which could be sand, shells, pebbles or large rocks – stirred up enough to give a beach it characteristic form and behaviour.

By the 1950s, W. Armstrong Price, a coastal geologist at Texas A&M University, was classifying beaches by the energy in their waves. In Prof. Price's system, low-energy beaches typically have waves less than a foot (30 centimetres) tall. High-energy beaches are those with waves more than 2 feet (60 centimetres) tall and moderate energy beaches are in between. This dynamic approach to thinking about beaches begins to explaining how and why they change.

Energy translates into mobility for the individual grain or stones that make up beach sediment. They are border dwellers – still part of the land but not entirely committed to it. Inherently we recognize this whenever we pick up a colourful pebble on the beach. Like us, it's there as a traveller, on an individual journey that could be entirely different from that of its neighbours.

The individuality extends to the smallest scale, and is beautifully captured in the work of U.S. photographer Gary Greenberg. A medical researcher by training who turned to micro-imaging, he is best known for his compelling highly magnified photos of beach sand, which show the striking variety in each grain. The work is a vivid reminder that the individual character of beaches – no two are alike – begins with the raw material they are made from, which ranges from jet black fragments of hardened lava to bleached-white bits of shell or coral. (The brown colour we typically associate with sand is mainly due to natural staining by iron oxide – a.k.a. rust.)

What happens next depends on the precise nature of the physical forces acting on the beach. The formula is simple: A beach is created where land and water do battle. But in true Shakespearean fashion, it's a third party, the wind, that motivates the conflict.

The three-way interaction is common enough that as much as one-third of the world's coastlines could be made up of beaches – enough to reach the moon – according to an estimate by Eric Bird of the University of Melbourne's School of Land and Environment.

But in cosmic terms, a beach must be among the rarest of landforms. The spacecraft sent to explore the other worlds of our solar system have found canyons, volcanoes, deserts and glaciers in abundance. But, so far, only on Saturn's giant moon Titan, have we seen something that resembles a beach.

Titan is cloaked in a nitrogen atmosphere that is denser than Earth's and has temperatures frigid enough for methane gas to condense and fall like rain. The methane forms seasonal lakes, which lap up on icy shores as winds blow across the frozen landscape.

On the shore of one such lake (coincidentally named Ontario Lacus after the body of water that sits at the end of my street), NASA's Cassini spacecraft in 2009 spotted what seems to be a line of beachfront. But instead of water waves breaking on rocks, it would have been formed by methane waves breaking on chunks of ice so cold they're as hard as rock. Scientists are already dreaming about an amphibious probe that may some day cruise up to such an otherworldly beach.

Back on Earth, what happens to the world's ocean beaches over the coming decades and centuries may create a much greater technical challenge. The challenge is well documented in The Attacking Ocean , a new book in which British-born anthropologist Brian Fagan points out that 15,000 years ago the oceans of the world were about 120 metres lower than they are today. The beaches of this distant past are now largely submerged, often many kilometres off shore.

In the intervening time, beaches moved inland, sweeping across long-forgotten territories such as Doggerland – today's North Sea. It was once a grassy plain where paleolithic hunters felled antelope and bison. Their weapons and the bones of their prey are still pulled up in fishing nets today. The stretch between Alaska and Siberia was dry land, too, allowing humans to populate North America.

The cause of this dramatic sea-level rise was the melting of glaciers and vast continental ice sheets that began at the end of the last ice age. In some cases, the change was remarkably rapid. In central Canada, a giant freshwater lake formed that encompassed far more territory than all of today's Great Lakes combined.

When a larger barrier of ice gave way some 8,000 years ago, the water drained rapidly through the St. Lawrence and coastlines around the world accelerated their retreat.

The process continued, shaping human patterns of settlement and development in ways that we are still trying to piece together. Around 5500 B.C., the Black Sea was a freshwater lake, and its banks the likely site of a thriving population on the threshold of recorded history. Then the rising waters of the Mediterranean broke through the Bosphorus and flooded the region, erasing what may have been one of civilization's launching pads in a matter of weeks.

Beware the rising damp

The ice age is long gone, but sea level is rising again and that means more changes are in store for us at the beach. A study published last week in the Proceedings of the National Academy of Sciences projects 2.3 metres of sea-level rise for every degree Celsius that the atmosphere warms. And given current rates of fossil-fuel consumption, a global temperature rise of more than two degrees would not surprise most climate scientists. It will take time for the melting ice to catch up. The rising waters won't happen overnight, but as the study points out, we're already committed to a whole new shoreline.

In an early era, this would not have mattered much. Humans can usually move fast enough to stay out of the ocean's way, just as the nomadic hunters of Doggerland did. The difference is that now we're heavily invested in life at the beach.

What that means for our favourite haunts will vary. Freshwater beaches will not be affected by sea-level rise, although changing water levels in many lakes are another anticipated outcome of climate change.

At the seaside, experts suggest that low-lying cities and harbours will receive most of our attention and resources because of their commercial importance. Beach resort areas, despite the millions in property value they represent, may have to be abandoned, or at least engage in a laborious, strategic retreat.

In a recent piece for Rolling Stone magazine entitled "Goodbye Miami," writer Jeff Goodell paints a vivid picture of what awaits one of the world's more celebritized beaches and the city that stands beside it. "Miami embodies the central technological myth of our time," he writes. "That nature can only be tamed but made irrelevant."

The facts suggest otherwise.

After thousands of years of witnessing nature do battle at the beach, it seems we're destined to join the fray – in effect, because we have neglected the warning signs of a changing climate.

But beaches don't care what humans do.