Lakes and coastal areas appear to recovery slowly and incompletely from eutrophication

What is it about?

We combined the results of 89 studies from around the world about how lakes and coastal areas recover from reduced nitrogen and phosphorus inputs. We found that while aquatic ecosystems can improve, recovery can take decades or longer. But aquatic ecosystems rarely returned to conditions prior to eutrophication. We also found that not all aquatic ecosystems showed improvement, possible due to other factors, like climate change. Nitrogen and phosphorus are critical for life; they are also important fertilizers used in agriculture. Nitrogen and phosphorus from farm land and sewage treatment can leak to the environment and have a fertilizing effect (called eutrophication) on water bodies. Eutrophication can contaminate drinking water, cause harmful algal blooms, reduce water clarity, and change the composition of aquatic animal and plant communities.

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Why is it important?

Eutrophication occurs globally. It is important to understand how lakes and coastal areas recover from reduced nitrogen and phosphorus inputs in order to develop effective policies. Many previous studies compare progress against eutrophic conditions, so we don't know the degree or rate of improvement. Our study was important because we compare recovery progress to restoration targets, which are often defined as the conditions prior to eutrophication. Our results suggest that long term monitoring is needed to better understand the timescales for recovery from eutrophication. Also, policies should consider that recovery could be slow and partial.

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