Environmental Science
Why peatland drainage accelerates carbon dioxide emissions
Quick fact
When peatlands are drained, they can release up to 30 tonnes of carbon dioxide per hectare per year—equivalent to the annual emissions of about six cars.
Why this is interesting
Did you know that draining a swamp can turn it from a giant carbon sponge into a carbon emitter? Peatlands store twice as much carbon as all the world's forests combined—so why does draining them release that carbon as CO2?
Read the full explanation
Understanding Why peatland drainage accelerates carbon dioxide emissions
Imagine a peatland as a giant sponge made of partially decayed plants, soaked with water. Because the ground is waterlogged, oxygen is scarce, so the bacteria and fungi that break down dead plants can't work efficiently. The peat accumulates over thousands of years, locking carbon away. When people drain the peatland by digging ditches or lowering the water table, the sponge dries out. Now oxygen can penetrate the peat, and the same microbes spring into action, rapidly decomposing the organic matter. The carbon that was stored for millennia is released back into the atmosphere as carbon dioxide (CO2). This turns a natural carbon sink into a significant source of greenhouse gases.
A deeper explanation
The key mechanism is oxygen exposure. Peat is composed of organic matter that accumulates because the waterlogged conditions inhibit aerobic decomposition. When the water table is high, the peat below is saturated, and any oxygen that diffuses into the top layer is quickly consumed by microbes. Below that thin aerobic layer, conditions are anaerobic, and microbes that break down organic matter without oxygen are far less efficient, leaving most of the carbon intact. Drainage lowers the water table, increasing the thickness of the aerobic layer. Oxygen now penetrates deep into the peat, enabling aerobic bacteria and fungi to decompose the organic matter at a much faster rate. This aerobic decomposition converts the stored carbon into CO2, which is released to the atmosphere. The rate of decomposition is also influenced by temperature and peat quality, but the fundamental switch from anaerobic to aerobic conditions is the primary driver of the accelerated CO2 emissions.