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WWF Poland, MGGP Aero, and the Warsaw University of Technology have joined forces to launch an innovative project aimed at assessing the amount of shade cover along rivers and streams in Poland

With the increasing threat of climate change and rising temperatures, trees' shade is vital for the survival of various fish species in Poland's waters. Finding life-giving shade is particularly important for saving salmon, sea trout, brown trout, and grayling from death. The project's objective is to identify the areas where trees need to be planted first to mitigate the impact of rising temperatures on aquatic ecosystems.

As climate change worsens, heatwaves and droughts become more severe, causing significant impacts on urban residents, farmers who lose their crops, and riverside ecosystems. In Poland, many rivers and streams dry up during summers, putting fish populations at risk. Higher air temperatures also increase water temperature, leading to a decrease in dissolved oxygen, which is critical for aquatic life. The presence of trees on riverbanks is vital as they can prevent water from reaching dangerous temperatures for fish.

Cold-loving salmonid fish are particularly vulnerable to unnaturally high water temperatures, and the optimal range for them is between 14-18°C. When the water temperature rises to 23-25°C, various fish species, including brown trout, grayling, young salmon, and migratory trout, die. Grayling are particularly vulnerable to overheating.

High water temperatures also increase the toxicity of pollutants in the water, raising the risk of fish death in overheated rivers. Trees and bushes not only provide shade to the water but also create a natural buffer zone along the river that captures pollutants washed from nearby farmland by rainfall (nitrogen and phosphorus compounds from fertilized fields and pesticides.)

To determine whether Polish rivers have the potential for beneficial shade from riverside trees during hot days, WWF Poland, with pro bono support from MGGP Aero and the Warsaw University of Technology, is conducting a comprehensive assessment of all rivers and streams in Poland. Approximately 200,000 km of watercourses will be analyzed in detail, divided into several-kilometer sections.

„Carrying out this type of analysis on a nationwide scale is a significant conceptual and technical challenge. To calculate the shadow surface cast at noon on the longest day of the year on the river's surface, we will use the National Tree Crown Map developed by our company,” says Łukasz Sławik, Director of the Remote Sensing Department at MGGP Aero.

The project partners have already obtained some initial results.

„The pilot project carried out in the Bóbr river catchment in the Lower Silesian Voivodeship showed that well-developed forests covering at least 75% of the zone along the riverbank are present only on 13% of the river's length," says Prof. Dominik Kopeć, Deputy Director of the Remote Sensing Department at MGGP Aero.

Thanks to the project, it will be possible to identify areas that lack sufficient shade.

„We will develop a model that will allow us to assess to what extent the current shading of the river channel surface deviates from the maximum shading that would occur if both riverbanks were densely forested,” says Prof. Katarzyna Osińska-Skotak from the Faculty of Geodesy and Cartography at the Warsaw University of Technology.

„Necessary analyses and calculations will be performed using a computer cluster that is part of the CENAGIS IT Platform available at our university” – adds Prof. Dariusz Gotlib, also from the Faculty of Geodesy and Cartography at the Warsaw University of Technology.

The issues of the harmful warming in river water has been observed in several countries north of Poland. For example, in Scotland, during the hot summer of 2018, up to 70% of rivers had temperatures exceeding the threshold at which young salmon cannot survive. To prevent the loss of cold-loving species such as salmon, Scotland implemented a water temperature monitoring system and set national priorities for enhancing shading forests along rivers, since only 35% of Scottish rivers have sufficient shading. With the involvement of MGGP Aero and Warsaw University of Technology, detailed maps will be created to illustrate the restoration priorities for the riverside forests of all Polish rivers and streams, similar to the maps developed in Scotland.

„Our collaboration is an excellent example of joint actions taken by non-governmental organizations, companies, and universities that feel co-responsible for the state of the environment in Poland,” says Karolina Kukielska from WWF.

Poland already has grassroots initiatives in place to address excessive heating of water in riverbeds. For instance, on March 25th, the Polish Angling Association, WWF Poland, and the Youth Parliament of the Świętokrzyskie Voivodeship organized a tree-planting campaign that resulted in the planting of 18,000 trees along the banks of regulated rivers in Kielce. However, it's crucial to acknowledge that the enthusiasm and hard work of volunteers alone cannot solve the issue of excessive heating in rivers. What is required is primarily support from a national program aimed at restoring the riverside forests.