The United Nations Special Envoy for Water Affairs, Retno Marsudi, has warned that the quality of global lake ecosystems has deteriorated sharply since the 1970s, with biodiversity suffering a dramatic decline.

According to Retno, animal and plant species in lakes have decreased by 85 percent over the past 50 years, despite lakes providing 87 percent of the world’s supply of fresh water.

She said the UN’s World Lake Day, commemorated every August 27, should serve as a reminder to address the urgent challenges facing lakes in a continuous and coordinated way.

“If lake degradation continues, by 2050 the quality of lake ecosystems will decline by 20 percent,” Retno said in her remarks at the National Coordination Meeting on Indonesia’s Lake Rescue in Jakarta on Wednesday, October 1, 2025.

Indonesian Environment Minister Hanif Faisol Nurofiq added that 15 national priority lakes are already in poor condition, facing problems ranging from environmental degradation that increases sediment levels to aquaculture with floating net cages and the introduction of invasive species disrupting ecosystems.

“Twelve ministries fully support the effort to save priority lakes, but so far this support has been limited to administrative measures. Physically, what have we actually done? Not much,” Hanif said.

The 15 lakes designated as national priorities include Toba, Singkarak, and Maninjau in Sumatra; Rawa Pening and Rawa Danau in Java; Batur in Bali; Tondano, Limboto, Poso, Tempe, and Matano in Sulawesi; the Mahakam Cascade and Sentarum in Kalimantan; and Sentani in Papua.

Hanif also noted that some well-intentioned activities, such as ceremonial fish releases during lake celebrations, have unintentionally worsened the problem by introducing invasive species. Meanwhile, mounting waste from tourism activities has added to the pressures on Indonesia’s lakes.

The Environment Ministry is preparing to hold a coordination meeting next month with 12 related ministries to strengthen physical action and accelerate efforts to restore the country’s most threatened lakes.