Authors:

Orhideja Tasevska, PhD, PSI Hydrobiological Institute - Ohrid

Darko Crvenkovski, MA, UNDP North Macedonia

Marijana Milevska, PhD UNDP North Macedonia

Prespa Lake at a Crossroads: Understanding Loss to Drive Recovery

Prespa Lake is one of Europe’s oldest and most unique freshwater ecosystems on the crossroad between North Macedonia, Greece and Albania. The lake is home to rich biodiversity, including species found nowhere else in the world, from the endemic Prespa bleak fish to the freshwater sponge and Juniperus foetidissima (foya forest) on Golem Grad island, Prespa Lake hosts the largest Dalmatian pelican colonies in the world. However, this unique ecosystem has been under increasing pressure. Over the years, Prespa Lake has experienced a significant drop in water levels, changing its shoreline and affecting habitats. Climate change, together with human activities, has accelerated this process, making the lake more vulnerable and fragile.

Today, Prespa Lake is recognized as one of the most important wetlands in the Mediterranean region, however, the lake continues to face serious challenges. 

Studies show that Lake Prespa has already lost more than half of its water volume and nearly 10 meters of water level since the 1950s, mainly due to reduced rainfall, higher temperatures, irrigation water use, and large losses through underground karst channels to Lake Ohrid. This loss has visibly changed the shoreline, turning once sandy areas into dry or muddy land. As the lake gets smaller, pollution becomes more concentrated fertilizer and waste builds up in the water, causing algae to spread and oxygen to disappear. At the same time, shrinking shores and wetlands leave fish, birds, and plants with fewer places to live, nest and survive.

Climate change through rising temperatures, reduced rainfall and increased evaporation combined with water overuse for irrigation, has accelerated this decline, making the lake more fragile. At the same time, significant amounts of water are continuously lost from Prespa Lake through underground karst channels that feed Lake Ohrid, further reducing the lake’s balance and resilience. These pressures highlight the urgent need for better monitoring and sustainable management to ensure that Prespa Lake can recover and be protected for future generations.

In response to these challenges, the European Union is investing €18 million through the EU for Prespa programme to restore Lake Prespa’s ecosystem in line with EU environmental standards. As the main implementing partner, UNDP is leading efforts to improve wastewater and waste systems, protect nature and wildlife, reduce pollution from farming, support sustainable agriculture and tourism, and strengthen cooperation between countries. 

Masters of Lake Science: Hydrobiological Institute Ohrid

Supporting efforts to better understand, monitor, and restore the fragile ecosystem of Lake Prespa, the Hydrobiological Institute Ohrid draws on nine decades of scientific excellence. As a leading institution in lake research in North Macedonia it provides rigorous research, long‑term monitoring and independent expertise that unwrapping complex scientific data into meaningful messages:

“Prespa Lake cannot be assessed through isolated observations or short-term hydrological improvements alone. Periods of increased rainfall and higher water inflow may temporarily alter ecological indicators, but they do not necessarily reflect long-term ecosystem recovery. Only continuous, seasonally consistent scientific monitoring can reveal the real trends within the lake system, distinguish natural fluctuations from genuine ecological restoration, and provide a reliable basis for evidence-based management decisions. In the context of accelerating climate variability and increasing anthropogenic pressures, long-term monitoring is not only a scientific obligation, but an essential safeguard for the future protection and resilience of Prespa Lake,” stated Dr. Orhideja Tasevska from Hydrobiological Institute Ohrid.

Science Discovery: The True Condition of Prespa Lake

Autumn 2025 and spring 2026 were marked by unusually intense and prolonged rainfall in the Prespa region, leading to widespread flooding of rivers, agricultural land, and residential areas around Lake Prespa. Continuous heavy rains in November 2025 caused several rivers to overflow, flooding farmland and settlements and raise concerns about rising water levels along Golema River, one of the lake’s main tributaries. These rainfall events significantly increased surface runoff and river discharge, resulting in a substantial inflow of water into Prespa Lake. Wet conditions persisted into early 2026, with continued rainfall through spring keeping soil saturated and rivers running high. As a result, water levels in Prespa Lake increased significantly during the spring period, reflecting enhanced surface runoff and increased river inflows caused by prolonged and intensive precipitation events, and further demonstrating the sensitivity of the lake system to seasonal and extreme hydrological fluctuations.