The Ministry of Territory, Housing and Ecological Transition of the Government of Catalonia has published the first global map of light pollution in Catalonia, based on an advanced mathematical model that simulates the propagation of artificial light through its physical characteristics at night and the composition of the atmosphere.
The study, which is part of the 2024 night sky quality assessment campaign, has been developed by the Institute of Space Studies of Catalonia (IEEC), with resources and data from Ecological Transition, and with the support of the Institute of Cosmos Sciences of the University of Barcelona (ICCUB). The new map is a step forward in the assessment and management of this type of environmental pollution, which negatively affects biodiversity, the quality of the night sky and people's rest.
600,000 hours of calculation
The map covers for the first time the entire Catalan territory with a resolution of 1 km² and has been generated, among other resources, using a high-precision scientific prediction model that is used internationally. To calculate the brightness of the sky at zenith at more than 32,000 spots in Catalonia, three supercomputers have been used, one of them from the Consorci de Serveis Universitaris de Catalunya (CSUC), with a total of more than 600,000 hours of calculation.
The global night sky brightness map is now publicly available on the Ministry's website and is due to be updated with more accurate data in the coming months, as part of a project that will run until 2026.
The results show that the areas with the highest levels of light pollution are concentrated on the Catalan coast, in the large cities and in the industrial areas of Barcelona, Tarragona, Lleida and Girona, as well as in some rural areas with strong tourist activity in Cerdanya, Seu d'Urgell and Vall d'Aran. On the other hand, the inland areas and the Pyrenees and Pre-Pyrenees, especially those especially protected in terms of light pollution, such as the Montsec area or the Alt Pirineu Natural Park and the Aigüestortes i Estany de Sant Maurici National Park, maintain an excellent quality night sky, with very low light pollution.
More than 1.56 million light points
The new tool provides a more accurate spatial overview of the current light pollution situation and, in the future, will allow assessing how the quality of the night sky might evolve depending on changes in public lighting, new urban developments or the implementation of certain policies for the protection of nocturnal ecosystems.
Unlike other approaches based solely on satellite images, this project has also integrated the public inventory of outdoor lighting in Catalonia, prepared by Ecological Transition, which facilitates a thorough assessment of the effects throughout the territory. Integrating this database has involved including more than 200,000 lamp and luminaire combinations in the model and has been key to characterizing the sources of light emission in detail, with more than 1.56 million points of light.
Sensors throughout the territory
The map is complemented with the data obtained in real time by the Light Pollution Observation Network (XOCL), also in the actions planned in the night sky quality assessment campaign which, for more than 10 years, has been systematically collecting information on its brightness from different points of the territory. This work has made it possible to create a continuous database, which is key for long-term analysis. Once the data collection model has been consolidated, current efforts are focused on maintaining the network, improving its connectivity and extending it with new measurement points.
The network is made up of several fixed sensors installed throughout the territory. These devices record the sky brightness at the zenith and collect data every few minutes, which are automatically sent to a centralised management system that receives, analyses and processes them to assess the quality of the night sky continuously and in real time.
Preserving the most sensitive areas
The map provides extensive information on the state of the natural night environment and is available to professionals in nature conservation, the design of outdoor lighting installations and also to the public. In this way, it is possible to know the areas with the best night sky conditions to preserve them and also to enjoy amateur astronomy and stargazing. For example, when looking for the best places to observe the popular star shower known as the tears of Saint Lawrence, which takes place in mid-August.
Ecological Transition plans to allocate more than €9 million until 2028 to another project to reduce the environmental impact of outdoor lighting in natural areas particularly sensitive to light pollution. This initiative is financed through the Climate Fund, which is funded by 50% of the revenue from the CO₂ tax on vehicle emissions and 20% from the tax on installations that have an impact on the environment.
The project contemplates different actions with the aim of protecting the areas most sensitive to light pollution. At present, the implementation of the action plan for the Serra de Montsant Natural Park, the initial work to protect the Els Ports Natural Park and the participation process to draw up a plan to preserve and promote the Montsec night sky are being carried out.
The actions fall within the framework of the European Nature Restoration Regulation, which states that it will be necessary to implement measures to restore habitats until they are in a good environmental condition and therefore, among others, in good conditions of natural darkness and acoustic quality.
