Kilroy was here

Here’s your weekly Science Matters column by David Suzuki with Faisal Moola.

Well, it seems we’ve finally done it. Humanity has finally made its mark – our own little place in history.


Even if we, as a species, snuff ourselves out now, the next
hyper-intelligent creature that emerges from the muck, or one that
finds our little planet drifting through space, will know that we were
here. Millions of years from now, a scientist with six arms will be
sifting through compressed layers of our collective detritus and ponder
the most compelling question about our era: Who the heck was Britney
Spears?

You see – it seems that we’ve entered a new epoch: a period of
geological time usually reserved for distinguishing between massive
periods of change on the planet. In this case we’ve moved from the era
that geologists call the Holocene, which has been this relatively
stable period since the last ice age 10-12,000 years ago, to the
Anthropocene – a time when human activities have become the dominating
force of change on the planet.

Changing epochs is not like changing your socks. In scientific
terms, this is a big deal. Epochs tend to be delineated by periods of
upheaval. Think ice ages and mass extinctions. When Nobel-prize winning
chemist Dr. Paul Krutzen brought up the idea back in 2000 and again in
2002, it was still considered pretty radical and somewhat impetuous for
our little species to have its own epoch.

But a team of scientists writing in a new paper in the journal GSA
Today, published by the Geological Society of America, now argues that
it’s becoming increasingly difficult to deny humanity’s growing
influence on a planetary scale. In their paper, they examine the case
for change and conclude that it’s time to accept the obvious – we are
in the Anthropocene.

According to the researchers, just about every natural process on
the planet now bears a human signature. For example, if you look at the
soils, humans are now the dominant force behind changes to physical
sedimentation. Dramatic increases in erosion from agriculture, road and
urban development, and dams have pushed people to be the largest
producer of sediment by an order of magnitude over nature.

If you look at the air, humans are rapidly changing the composition
of the atmosphere by burning vast amounts of oil, coal and gas. As a
result, carbon dioxide levels are one-third higher now than they were
200 years ago – higher, in fact, than they have been in the past
900,000 years – and they are expected to double this century.

If you look at life on the planet, human activities are causing the
extinction of many species – possibly leading to a “major extinction
event” that rivals others, such as the demise of the dinosaurs. Humans
are also rapidly replacing vast areas of natural vegetation with
agricultural crops. As the researchers point out: “These effects are
permanent, as future evolution will take place from surviving (and
frequently anthropogenically relocated) stocks.”

If you look at the oceans, sea levels have risen slightly due to
melting ice and thermal expansion (water expands as it warms) and these
levels are expected to continue to rise through the century. Our oceans
are also noticeably more acidic now, again due to the human release of
so much carbon into the atmosphere, with “potentially severe effects in
both benthic (especially coral reef) and planktonic settings,”
according to the researchers.

So, there you have it, the case for the Anthropocene. We’ve done it.
We’ve written our name on the wall. We’re the king of the hill, lord of
the sandbox. We’re now the most powerful force of change on the planet
– so much that we actually get our own epoch. A pretty big
responsibility for a naked ape that emerged on the plains of Africa
only 150,000 years ago.

So what now, little human? What now?

Take David Suzuki’s Nature Challenge and learn more at www.davidsuzuki.org.

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