Change happens. You can look around our world and see the impact of both natural processes and human activity. Storms cause landslides and even forest fires, which change the structure of the landscape. People dig out dirt and plants to build structures, which can lead to more problems from the storms. Wind, rain, freezing, melting, volcanoes, earthquakes… so many processes affect the world around us, both on a large and small scale, that we struggle to track them.

This is why it’s amazing that scientists have determined that the arrival of Europeans in North America lead to an increase in the erosion rate and the rate of river sediment accumulation by a factor of ten. An international team analyzed 40,000 years of sediment at 126 sites across the continent to find the natural, background rate of erosion. Then they compared those values to the rate from the past 200 years. Humans moved as much material in the past century as would have naturally happened over 700-3000 years.

The work was published last year in Nature Communications, and lead author David Kemp noted: By having this huge compilation [of data] that stretches back many thousands of years, we’re able to contextualize the human impact against that natural geologic variability. It was a surprise to me that the jump was there and that it seemed to be so neatly coincident with European arrival.

You might think the effects would be limited to the east coast of North America, where the first of the European colonists set up shop, so to speak, but the study shows that the impact on the sedimentation rate is seen across the continent. Europeans brought their own techniques for agriculture, animal husbandry, and river management, and literally changed the world around them.

Of course, conservation efforts have the challenge of working against these massive changes to try and restore habitats to a more “natural” condition. The study notes there is good news in that sedimentation rates have been reduced in the last few decades due to those efforts. We as a planet need to do a better job of listening to our planet.

No, really. We need to listen to our planet, and that is what researchers have done in new work presented in the journal Geophysical Research Letters. Researchers listened to rocks by attaching sensors to boulders and monitoring the cracking noises they made due to weathering. They measured any resulting cracks and found that higher rates of fracture growth happened in higher temperatures and wetter air. Not a good sign when we already know we’re dealing with higher temps and bigger storms.

I always think of Doctor Who when we talk about rock erosion. “Water always wins.”

On top of accelerated weathering rates, breaking rocks can release carbon into rivers and oceans. Just what we need, right? And these results aren’t due to huge noticeable cracks in rocks; they come from a process known as subcritical cracking.

Lead author Missy Eppes explained: Subcritical cracking is analogous to the weeks-long growth of a crack on a car windshield, as opposed to the rapid cracking that occurs if you hit the same windshield with a hammer. The crack grows slowly and steadily, with very low forces being applied to that crack.

The team intends to expand their research to more types of rock, and we’ll update when they have more results.

Another result of our wetter atmosphere is the loss of coastal land. Coastlines are fickle to begin with, impacted by wind and wave, and even glaciers. Take Cape Cod, for example.

During the last ice age, the Laurentide Ice Sheet covered North America from eastern Canada down through New England, ending at what is now known as the Outer Lands. As the ice advanced and later retreated, it moved sediment and left behind glacial deposits. The landscape ended up malleable and pockmarked with kettle ponds that became the cranberry bogs of today.Cape Cod was free of ice only 18,000 years ago; the blink of an eye, geologically speaking.

Cape Cod was also home to megafauna like mammoths as well as the Indigenous people that hunted them. But as the ice retreated, it also melted, and the sea levels rose, bit by bit, moving people and animals further inland. The currents around the shore changed, and the spit of land that forms the hook of the Cape formed as sand was moved in new directions. Provincetown, a fishing village that is home to 3000 residents and a huge tourist destination during the summer, was built.

But now the sea levels are rising again and alarmingly, they have risen by 28 centimeters since 1922 and are expected to rise to three meters by the year 2100. Flooding events are already on the rise and a huge nor’easter in 2018 inundated parts of the town. The airport could easily be impacted. Town planners are trying their best to shore up, well, the shore, by moving sand from the hook to the town.

Other parts of the Cape are being left alone to let nature take its course. No one is certain how long that will take. The highest point is only 49 meters in elevation. Some of the lowest points are at eight meters. And with all the uncertainties in climate models, estimates of the timeline for overtopping the Cape are vague at best. Climate change is real, though, and it is impacting real people now.

There is one small silver lining in climate change. One particular species of truffle, the Perigord, looks like it will thrive in wetter, warmer conditions. In new research published in the journal Scientific Reports, researchers reported the results of their research into just how several varieties will respond to climate change, and Perigord is going to do really. Plant now, though, everyone. It takes 5-15 years to establish a truffle orchard and actually harvest truffles.

More Information

Eos articles: river sediment, cracking rocks, Cape Cod, truffles

“The human impact on North American erosion, sediment transfer, and storage in a geologic context,” David B. Kemp, Peter M. Sadler & Veerle Vanacker, 2020 November 26, Nature Communications

“Warmer, Wetter Climates Accelerate Mechanical Weathering in Field Data, Independent of Stress‐Loading,” M.C. Eppes et al., 2020 December 6, Geophysical Research Letters

“Predicted climate change will increase the truffle cultivation potential in central Europe,” Tomáš Čejka et al., 2020 December 4, Scientific Reports