In their natural condition, peatlands rank among the planet’s most important carbon reservoirs. The soil is saturated with water and contains very little oxygen, which slows the breakdown of dead plants. Instead of fully decomposing, plant material builds up layer upon layer over thousands of years, forming deep deposits of peat that lock away carbon for the long term.
The Science Daily news noted that that balance changes when peatlands are drained for farming. Lowering the water table allows oxygen to enter the soil, speeding up microbial activity. As microbes break down the previously preserved plant matter, carbon that has been stored for centuries is released into the atmosphere as carbon dioxide (CO2).
“At the same time, wetter and low-oxygen conditions can increase methane, since the microbes that produce methane thrive when there is almost no oxygen in the soil.”
Nitrous oxide can also increase under certain moisture conditions. When soil is damp but not completely waterlogged, nitrogen breakdown may stop midway, producing nitrous oxide instead of harmless nitrogen gas.
“Because each greenhouse gas reacts differently to changes in water level, one gas can go down while another goes up. That’s why it’s important to look at the overall gas balance,” says Zhao.
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