Joseph Fourier University, Grenoble, France
A geoscientist ponders possible links between erosion and Earth’s climate.
Mountain ranges have been eroding at an increasing rate over the past 60 million years — seemingly in response to a cooling climate. Some researchers have proposed that this higher rate of erosion has increased the rate at which tectonic plates move at Earth’s surface, suggesting that there is a link between Earth’s climate and its tectonics.
As a member of the Earth science community who studies the relationship between these factors, I was interested in findings by Anthony Dosseto of Macquarie University in Sydney, Australia, and his co-authors. They measured the change in the sediment erosion rate over the past 100,000 years, a period that includes the last glacial cycle (A. Dosseto et al. Geology 38, 395–398; 2010). By dating sediments from several locations in the Murrumbidgee River catchment of southeastern Australia, they discovered that the residence time — the length of time for which sediments remain on the landscape before they are eroded away — varied over geological time. The residence time was longer during warmer periods (such as around 100,000 years ago and today) and shorter during colder periods (such as around 15,000 years ago).
The authors interpret this change in residence time as a consequence of variations in vegetation type. The absence of trees in the higher parts of the catchment during cold periods resulted in an increased erosion rate, whereas the eucalyptus forest that was present during the warm periods slowed the erosion rate.
These results provide a rare quantitative estimate of the influence of vegetation and climate on erosion. This link might also be relevant to estimating how the current anthropogenic changes to Earth’s climate and vegetation affect soil erosion.