Ditches are human-made, linear waterways built to serve a variety of purposes, such as draining wetlands, irrigating crops and creating desirable waterfront properties. Previous research revealed that man-made ditches were responsible for emitting 3% of the total global methane emissions from human activities. Now a new study, carried out by ditch experts from the UK, Netherlands, Denmark, Australia and China, has found ditches also emit a significant amount of CO₂ and nitrous oxide, contributing to global warming and climate change.

Photo by ClickerHappy

Using existing data of greenhouse gas emissions from more than 100 ditches in 23 different countries, across all major climate zones, they found ditches emit more CO₂ and nitrous oxide than ponds, lakes and reservoirs, when compared by the same surface area. These high emissions are thought to be a consequence of high nutrient inputs that go into ditches.

The researchers estimated that global ditches cover about 5,353,000 hectares, equivalent to the whole of Costa Rica. Given their extent, ditches therefore make a notable contribution to freshwater greenhouse gas budgets in many countries throughout the world. The researchers estimated that including ditches would increase global freshwater CO₂ emissions by up to 1% and nitrous oxide emissions by up to 9%. While these numbers sound small, when accounting for all three greenhouse gases, emissions from the world’s ditches are nearly equivalent to the UK’s total greenhouse gas emissions in 2023. However, researchers still do not know the true global extent of ditches, and believe they may actually cover a much larger area.

The researchers emphasised solutions do exist, including; installing fences to prevent cattle from entering farm dams; planting more trees along ditch banks; and dredging ditches. However, the solutions will likely only be employed and scaled up once the significance of emissions from ditches is quantified and more widely recognised.