Predicting Lemna growth based on climate change and eutrophication in temperate freshwater drainage ditches

The Somerset Levels and Moors, UK is an area of high conservation value, including nationally and internationally protected wetland sites. Duckweed (Lemna) mats in the Somerset Levels and Moors are increasingly common and are an indication of hyper-eutrophication. Duckweed mats can contribute to increased management burdens and decreases in biodiversity. Research suggests duckweed will thrive in temperate regions as the climate warms. This study investigated the impact of climate warming and eutrophication on duckweed growth in the Somerset Levels and Moors using a previously published model to simulate duckweed growth from the years of 2020–2080. Simulated local climate change projections and adjustments in actual nitrogen and phosphorus levels were used to estimate changes in biomass. Using the simulated data, the model predicted an 83% increase in biomass from the 2020’s to the 2070’s if nutrients do not change. In order to offset the impact of climate change on duckweed biomass, nutrient levels will need to decrease by more than 50% by 2080. Further changes to management practices will likely be necessary to restore healthy ecological function and biodiversity in the area.