“No child who ever played beneath a bur oak will forget it.”
– Donald Culross Peattie, A Natural History of North American Trees
At Anita Purves Nature Center in Urbana, Illinois, a volunteer prepares the garden for planting. Across the Saline Branch in Busey Woods, the red, knobby buds of oak trees look like berries. In a few weeks their leaves will unfurl.
Busey Woods is 59-acre fragment of forest in a region that in satellite photos looks like a yellow and green checkerboard of corn and soybean.
The forest here was once over 600 acres in area. Called the Big Grove, in pre-settlement times it covered most of what is now northeastern Urbana. There was a time when many such bur oak groves dotted the prairie.
The Big Grove’s last remnants were almost erased by development in the 1960s. It is now relegated to just Busey Woods and a few ancient, isolated trees around town.
Away from the Saline Branch, deep in the woods, another body of water shimmers. But this water doesn’t flow. Leaf litter blankets the bottom of a large pond. Mosquito larvae float in the water. The pond is crescent-shaped, curving out of sight behind oak and shagbark hickory.
It’s an oxbow lake, the abandoned meander bend of a river.
Rivers don’t just flow downhill. They meander, their horseshoe-shaped bends migrating over time, sediment eroding from the outer curve of a bend and depositing on the inner curve. If one bend migrates into the path of another, the river takes the more straightforward route, cutting a meander bend off from the main channel.
For this reason, a mature river in map view looks like a snake. The river sheds its skin—scars of old meander bends, patched up with mud and vegetation—into the surrounding floodplain. The freshest wounds, still full of water, are the oxbow lakes.
But the oxbow lakes in Busey Woods aren’t natural. In 1909, in accordance with the Midwest’s enthusiasm for straight lines and right angles, the Saline Branch was channelized. Almost 25% of streams in Illinois were straightened in this manner, with the goal of increasing not only the area of farmland but also the speed at which water drains away from the state’s flat, marshy fields.
In Busey Woods, channelization of the Saline Branch cut off its meander bends, creating artificial oxbow lakes.
Rubble litters the bank of one of these lakes. A set of stairs leads to nowhere. Chunks of concrete decorate the low areas of the forest, reminding hikers that 50 years ago, these woods were slated for development.
Now Busey Woods is protected by the Urbana Park District.
Despite its preservation, the landscape here is not separate from the humans around it. Even before European settlement, natives purposefully set fire to the grass to preserve open land. Once an island in a sea of prairie, the forest is now surrounded by suburbs and farms.
Landscapes like this one have spurred a controversial movement in the scientific community; many Earth scientists are in favor of designating a new geologic time period: the Anthropocene.
“Anthropo” means human.
If the Anthropocene Epoch were to become official, it would encompass that small, recent slice of Earth’s history during which humanity has become master sculptor of not only our planet’s landscapes but also its ecosystems and climate.
Some opponents accuse the movement of arrogance: Who are we, to think we can make even a small dent on this sphere of mostly solid rock over 12 thousand kilometers across? Other critics think the Anthropocene is more about pop culture than geology. Some merely object to its human-centric name.
There are many criteria that could define the Age of Humans. Let’s consider just one—dirt.
In its brief tenure on this planet, humanity has literally produced tons of sediment: concrete basements, asphalt rivers, junkyard ore bodies, plastic fossils. Six tons of earth is deliberately moved per person per year on average. Add ten more tons per person for unintentional erosion from farm fields and pastures. That’s over six cubic meters total, or about 20 bathtubs full. When you consider a world packed full of over seven billion people, each year the human race pushes over 100 billion bathtubs full of rock and sediment.
But right now the word “Anthropocene” is more symbolism than science. If it’s real—and a majority of Earth scientists agree it is—when did it begin? At the peak of the Roman Empire? In the early 1800s, when coal sparked the industrial revolution? What about July 16, 1945, the first detonation of a nuclear weapon?
And how will the geologic record preserve humanity’s contribution? A chapter? An aside? A cryptic abbreviation? Will it make it to print at all?
In 2016, at the next International Geological Congress, a group of 37 experts will present their answers to such questions in an attempt to convince their peers that the Anthropocene is more than just a footnote.
What’s on my mind now, though, barely amounts to the stroke of a pen.
I exit the forest, forsaking Busey Woods for my weekend errands. On my drive through town, I pass a 200-year-old bur oak. The tree towers over a small, grassy patch in front of the Natural History Building on Green Street, its limbs stretching out to the sides, casting a shadow over the parking lot.
Down the street, a tower crane breaks the skyline of this small Midwestern town. The construction of new high-rise apartments—the third such building in under two years—is under way.