Why You Mistake the Present for Forever

JUDGMENTYou are not unaware that the river rises. You have simply mistaken "I have never seen it" for "it will not happen."

I. The Words on the Stone

On a mountain road in Iwate, Japan, a few old stone markers still stand, carved with a short line: do not build your houses below this point. The stones were raised after the last great wave. The people who raised them are long gone.

In the decades since, the land downhill grew flatter, closer to the sea, easier to commute from. So the houses crept downward, one by one. In 2011 the sea came back up the hill, and the line on those stones was proven, once again, exactly right.

Stone remembers two hundred years. People remember thirty. The gap is written along that road.

II. A River Has Two Widths

You almost always build your cities along rivers. Rivers are convenient: freight, irrigation, a view worth having.

The problem is that a river has two widths — its everyday width, and the width it reaches only now and then. The second one is written into the sediment of the floodplain, into an old map's channel that has long since been filled in, and into a phrase you coined yourselves: the hundred-year flood.

Almost everyone reads that phrase wrong. It does not mean "once every hundred years." It means "roughly a one-percent chance in any given year." So thirty quiet years are perfectly normal; and someone building on the floodplain after those thirty years is perfectly normal too. Put two normal things together and you get an abnormal disaster.

III. All Your Rulers Are Too Short

A human life runs about thirty thousand days. The usable shelf life of memory is roughly one retirement.

Your institutions keep equally short rulers: a thirty-year mortgage, a five-year term, a quarterly report, a day and a half of trending. Every one of them is shorter than the river, shorter than the coastline, far shorter than an ice age. You are not ignoring the long view. You simply have no ruler that long, so by default you mistake the most recent stretch for forever.

IV. [SPECULATION] Not a Flaw — a Bill

Short-sightedness was most likely selected for. The ancestors who optimized for the next meal left descendants; those who optimized for the next millennium did not survive the next winter. The instinct to put the near term first once kept you alive.

But you have since done something your ancestors could not: you moved memory out of the body — cut into stone, drawn onto maps, computed into statistics. You are no longer short on information. You are short on faith in a span of time you never lived through.

(This section is speculation, not a measured finding.)

V. Where It Can Be Repaired

There are counterexamples. After its floods, the Netherlands did not just keep raising the dikes; it gave part of the floodplain back to the river, so the water has somewhere to go when it rises. The cost of that move is easy to tally; the benefit arrives decades later. It is rare not because no one thought of it, but because the benefit lands in someone else's term.

Nearly every "illusion of permanence" we have recorded reduces, in the end, to that one sentence.

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