Monitoring Natura 2000's Night Brightness

Light pollution, while less well-known, has a significant impact on biodiversity and human health. It disrupts natural behaviors and cycles, particularly affecting nocturnal wildlife and protected seabirds in urban areas and Natura 2000 sites. The LIFE Natura@night project aims to reduce light pollution in the Madeira, Azores, and Canary Islands archipelagos, specifically targeting its effects on EU-protected seabirds such as Cory's Shearwater and the Madeiran Storm-petrel. By collaborating with local authorities and communities, the project will implement efficient, wildlife-friendly lighting solutions, promoting better resource management and contributing to climate change mitigation. Key objectives include raising awareness about the impacts of light pollution and showcasing the benefits of reducing it. One of the project's critical goals is to map and monitor light pollution in selected Natura 2000 sites in Macaronesia.

The geographical region where project LIFE Natura@night intervention areas sit is in the Macaronesian region, a biodiversity hotspot formed by four archipelagos in the Atlantic that belong to Portugal (Madeira and Azores) and Spain (Canary Islands). They have a volcanic origin, creating an abrupt topography and relatively stable climates, which, in turn, became home to a rich biodiversity that includes multiple endemic species. Consequently, this region is highly interested in preserving environmental and biodiversity efforts.

One of the key tools used in this project is the identification of Natura 2000 areas, which serve as the primary reference for our actions. These areas are focused on three directives: the Birds Directive (A), the Habitat Directive (B), and both directives combined (C). The first step was to select sample sites within each protected area, irrespective of the specific directive, location, or landscape characteristics. The second step involved identifying the potential darkest zones within the Natura 2000 site, considering site accessibility. Additional factors considered included road access to the sites and the type and density of vegetation present.

The municipalities selected for the LIFE Natura@night project included Santa Cruz da Graciosa and Corvo from Azores; Santana, Machico, Santa Cruz, Funchal and Câmara de Lobos from Madeira; Mogán and Buenavista del Norte from Gran Canaria and Tenerife.

The Natura 2000 sites within these municipalities are Costa e Caldeirão, Ilhéu de Baixo - Ilha Graciosa, Ponta Branca - Ilha Graciosa, and Ilhéu da Praia - Ilha Graciosa from Azores; Cabo Girão, Caniço de Baixo, Machico, Pico do Facho, Porto Novo, Ilhéu da Viúva, Pináculo, Maciço Montanhoso Central da Ilha da Madeira, Ilhas Desertas, Ponta de S. Lourenço, and Laurissilva da Madeira from Madeira: El Nublo, El Nublo II, Macizo de Tauro II, Macizo de Tauro, Ojeda, Inagua and Pajonales and Teno from Gran Canaria and Tenerife.

For full access to the general map for selected Natura 2000 sites, click on this  link .

With the idea to capture change over time, three periods were used, first between 19:00 and 21:00; second, from 22:00 to 00:00; and third, from 01:00 to 02:00. The reasoning for these three sets is based on documented bird activity and trying to capture abnormalities in the same activity. The first measurement occured when our subjects are more active before sleep, and the last two occurred during the most influential time of urban lights at night.

A DSLR camera was used for photogrammetry. To reduce capture errors and increase efficiency, two approaches were used. First, a fish eye lens at a zoom of 8mm was used to capture the firmaments from the horizon to the zenith. Secondly, at a zoom of 15mm, the camera was pointed towards the horizon (horizontally balanced) and snapped pictures of each one of the cardinal points, giving us a 360-degree view and revealing more details in the landscape.

Following this, a photometer or "Telescope Encode Sky Sensor" (TAS,  https://tess.stars4all.eu/ ) with a field of view of 20 degrees and a spectral response from 400 to 750 nm was set up, which automatically takes information from the zenith to the horizon. Data were downloaded and plotted to identify areas with higher brightness levels. Such brightness levels were set for “absolute brightness,” which creates a 17 to 22 mab/arcs^2 plot; while scores went over and below those limits, it was set like that to develop comparable plots. In each sampling location, the TAS and camera were set on a tripod towards the zenith at 1.8 m if the terrain allowed it.

The photography products served as a reference to compare brightness plots generated by the TAS, helping to construct a visual and qualitative description of the landscape from where the data was collected.

The analysis of night brightness across the Natura 2000 sites yielded several key observations. The study shows that high-altitude locations in Madeira, such as Pico de Areeiro, Pico Ruivo, Ribeiro Frio, and Ribeiro Bonito, generally have lower brightness levels, with scores ranging between 20 and 22 mab/arcs^2. This aligns with expectations, as these areas are farther from coastal populations. In contrast, lower-altitude coastal Natura 2000 sites, like Porto Novo and Machico, experience higher levels of light pollution, with scores dropping to 14 mab/arcs^2 due to their proximity to population centers. Nevertheless, some coastal sites, including Cabo Girao and Pinaculo, are shielded from urban light by natural features such as cliffs.

In Mogan, Gran Canaria, some locations appeared dark in photographs despite brightness measurements being unexpectedly high due to moonlight during sampling. This underscores the necessity of distinguishing between natural and artificial light sources for accurate readings. Urban light was detectable on the horizon in most areas of Gran Canaria, except for Macizo de Tauro II and Nublo, which were the darkest locations.

In the Azores, frequent fog and rain made brightness measurements challenging. The TAS device sometimes reported higher brightness levels, despite the presence of dark photographic evidence. Although the sensitivity of the equipment to humidity affected some of the readings, the data showed that most Natura 2000 sites remained predominantly dark. However, artificial light could disrupt the navigation of species that rely on stars. On Corvo Island, the unique topography ensures that most of its coast is free from artificial light. The bird colonies near the ocean cliffs experience very dark conditions, with brightness scores around 22 mab/arcs^2. Conditions varied in Santa Cruz da Graciosa: Ponta Branca was mostly dark, while Ilheu da Praia and Caparacho exhibited influences from urban and public lighting, respectively.