“Earthworms play an essential part in determining the green-house-gas balance of soils worldwide, and their influence is expected to grow over the next decades. They are thought to stimulate carbon sequestration in soil aggregates, but also to increase emissions of the main greenhouse gases carbon dioxide and nitrous oxide. Hence, it remains highly controversial whether earthworms predominantly affect soils to act as a net source or sink of greenhouse gases. Here, we provide a quantitative review of the overall effect of earthworms on the soil greenhouse-gas balance. Our results suggest that although earthworms are largely beneficial to soil fertility, they increase net soil greenhouse-gas emissions.”
So reads the abstract from researchers in the Netherlands, the United States and Colombia who looked at the results of over 200 separate experiments from other published studies to explore the role of earthworms in global greenhouse gas emissions.
They discovered that approximately 20% of global carbon dioxide emissions and two-thirds of nitrous oxide emissions came directly from soil due to the large number of natural biological processes that occur in the ground.
The problem is simply this, as earthworms burrow in the soil, they make it more porous. They also interact with the microbes that produce the bulk of carbon dioxide emissions, causing it all to be released into the atmosphere.
As the earthworm population grows so does the planet’s greenhouse gas emissions. An added drawback is that earthworms produce nitrous oxide in their guts. Overall, the science team found that the presence of earthworms in soil increased nitrous oxide emissions by 42% and carbon dioxide emissions by 33%.
The report suggests that although earthworms play an essential part in determining the greenhouse-gas balance of soils worldwide and are largely beneficial to soil fertility they also increase net soil greenhouse-gas emissions.”
The study’s co-author Jan-Willem van Groenigen of Wageningen University in the Netherlands, said that traditional argument has always seemed suspect to him.
“It’s strange to claim on the one hand that earthworms are good for soil fertility by decomposing organic matter in soil, and on the other hand that they increase organic matter in soil,” he said.
Van Groenigen was quick to note that the new study is not the last word on the earthworm question. Scientists, who often refer to earthworms as “ecosystem engineers” in recognition of the role they play in churning soil and improving its drainage, have been slow to understand the little organisms’ role in the carbon cycle.
FULL ARTICLE AVAILABLE AT:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1692.html