Lakes and ditches cause a large share of the total emissions of methane, a greenhouse gas, in the Netherlands (estimated to be around 16%). Unfortunately, climate change amplifies this problem, because emissions of methane increase rapidly as water warms up. This happens especially in nutrient-rich water, where a lot of organic matter is present on the bottom that microorganisms convert into methane via the process of decay.
Free-floating aquatic plants (such as duckweed) and algae benefit the most from climate change, because they grow near the surface and so are the first to take advantage of the higher temperatures and higher CO2 concentrations in the air. Meanwhile, the increasingly heavy rainfall is causing even more fertiliser to leach from farmland into the surface water.
However, in water where submerged plants predominate rather than free-floating plants, emissions increase much more slowly as the water warms up, researchers from Radboud University, the Netherlands Institute of Ecology (NIOO-KNAW), Wageningen University and IGB Berlin have revealed. They made their discovery by simulating Dutch waters in large tanks containing either mainly algae, free-floating plants or submerged plants. Half of the tanks were warmed by four °C, anticipating the expected degree of climate warming by the end of this century.