Photo by Dr. Xenopolous
Photo by Professor Marguerite Xenopoulos

A new Trent study suggests that there is a correlation between human activity and the amount of old carbons being dumped in the Earth’s rivers, showing correlation between areas with high population densities and land use as associated with humans.

The study, titled “Increased mobilization of aged carbon to rivers by human disturbance”, links the age of the carbon in global rivers to human activity by analyzing the carbon deposits through the use of carbon radioisotope technology.

The research paper is co-authored by Professor Marguerite Xenopoulos from Trent University, Professor David Butman from the University of Washington, Professor Rebecca Barnes from Colorado College, Dr. Henry Wilson, Research scientist with Agriculture and Agri-Foods Canada, and Professor Peter Raymond from Yale University.

“The knowledge that we are changing the modern carbon cycle through human activity is important to have,” Professor Marguerite Xenopoulos told Arthur. “It is yet another proof that human activities are continually damaging the environment.”

She explained the “mobilization of aged carbon in to rivers” means that there is lots of old carbon stored in the soil, which is a part of the Earth’s stable carbon cycle.

Some of this carbon laterally transfers into rivers in order to be processed by bacteria but the rest of it eventually forms the soil and stays there. What humans are doing is disrupting the carbon within the soil and incorporating it into the modern carbon cycle.

When humans start injecting older carbon in to the modern cycle, it results in a negative feedback loop for climate warming, says Professor Xenopoulos, because this adds a little bit more to what humans are already producing. Furthermore, this old carbon is something that is usually not measured during climate change assessment, thus it is potentially a missing link.

Dr. Henry Wilson, the research scientist who co-authored the study told Arthur over email that there are several main hypotheses for the trend observed toward mobilization of older carbon in human altered landscapes. He further explained how each has different environmental implications and suggested different possibilities for management based on their findings.

The first is that human activities are exposing soil organic matter that was previously protected in carbon sink areas from leaching. This is due to historical loss of topsoil and exposure of lower soil horizons to processes such as weathering, drainage of low lying carbon rich areas, and subsurface drainage, to name just a few, he explained.

The finding has allowed them to understand the importance of building soil organic matter (SOM) through management practices that return carbon to the soil and suggest the restoration of natural drainage pathways, wetlands, and riparian areas to negate the sustained source of old SOM loss created by export with water.

An alternative explanation is that old carbon is originating from a small amount of very old carbon in pesticides or fertilizers. It indicates the presence of organic contaminants and necessitates further research to identify the type and source. However this explanation is less probable given the relatively large amount of fossil material that would be needed to create the carbon radioisotopes observed, but needs to be considered nonetheless, said Dr. Wilson.

Thirdly, human activities tend to occur on fertile and well drained soils and that these soils naturally have an older organic matter signature. To that end, he said that it calls for additional research to define whether activities on these soils are speeding the export of older organic matter with runoff or if rates are in line with those expected under native vegetation.

“Overall the paper lays out an important pattern, a conceptual framework for the potential causes, and the need for further research to better define the mechanisms by which our activities on the landscape may be impacting SOM and its transport downstream,” stated Wilson.

Meanwhile, the findings of this study is a indication that the results from the global climate assessment can be more severe that what it is said to be.