biostudies-literatureFeng LNIEHS NIH HHS631-644https://www.ebi.ac.uk/biostudies/studies/S-EPMC11849997biostudies-literatureUnknown5(9)Harmful algal blooms can produce toxins that pose threats to aquatic ecosystems and human health. In this Review, we outline the global trends in harmful algal bloom occurrence and explore the drivers, future trajectories and potential mitigation strategies. Globally, harmful algal bloom occurrence has risen since the 1980s, including a 44% increase from the 2000s to 2010s, especially in Asia and Africa. Enhanced nutrient pollution owing to urbanization, wastewater discharge and agricultural expansion are key drivers of these increases. In contrast, changes have been less substantial in high-income regions such as North America, Europe and Oceania, where policies to mitigate nutrient pollution have stabilized bloom occurrences since the 1970s. However, since the 1990s, climate warming and Nature reviews. Earth & environmentHarmful algal blooms in inland waters.PMC11849997P01 ES028939Chen NFeng LZheng CWang YHou XKuster TQu FPaerl HWQin BfalseHarmful algal blooms in inland waters.Harmful algal blooms can produce toxins that pose threats to aquatic ecosystems and human health. In this Review, we outline the global trends in harmful algal bloom occurrence and explore the drivers, future trajectories and potential mitigation strategies. Globally, harmful algal bloom occurrence has risen since the 1980s, including a 44% increase from the 2000s to 2010s, especially in Asia and Africa. Enhanced nutrient pollution owing to urbanization, wastewater discharge and agricultural expansion are key drivers of these increases. In contrast, changes have been less substantial in high-income regions such as North America, Europe and Oceania, where policies to mitigate nutrient pollution have stabilized bloom occurrences since the 1970s. However, since the 1990s, climate warming and 2024-01-01T00:00:00Z2024 Sep2025-04-18T21:19:00.666Z2025-04-07T09:15:42.313ZS-EPMC118499973999594710.1038/s43017-024-00578-2