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• Fossil-fuelled development results in rising trends of algal blooms in 91 % of lakes. • Sustainable development results in declining trends of algal blooms in 63 % of lakes. • Future trends in algal blooms for 2050 are significantly attributed to nutrients. • Climate change points to being unfavourable for lakes, exacerbating algal blooms. • Our new model system could aid in promoting effective lake management policies. Lakes are fundamental to society and nature, yet they are currently exposed to excessive nutrients and climate change, resulting in algal blooms. In the future, this may change, but how and where still needs more scientific attention. Here, we explore future trends in algal blooms in lakes globally for >3500 ‘representative lakes’ for the year 2050, considering the attribution of both nutrient and climate factors. We soft-coupled a process-based lake ecosystem model (PCLake+) with a watershed nutrient model (MARINA-Multi) to assess trends in algal blooms in terms of the Trophic State Index for chlorophyll- a (TSI-Chl a ). Globally between 2010 and 2050, we show a rising trend in algal blooms under fossil-fuelled development (TSI-Chl a increase in 91 % of lakes) and a declining trend under sustainable development (TSI-Chl a decrease in 63 % of lakes). These changes are significantly attributed to nutrients. While not always significant, climate change attributions point to being unfavourable for lakes in 2050, exacerbating lake water quality. Our study stresses prioritising responsible nutrient and climate management on policy agendas. This implies that the future of algal blooms in lakes is in our hands.
Tigli et al. (Mon,) studied this question.