Light Pollution Measurements in Ribeira dos Socorridos

In light of the  LIFE Pterodroma 4 Future program , we have been working on measurements of Artificial Light at Night (ALAN) in important habitats of the Pterodroma species. One of these habitats is the Ribeira dos Socorridos in the municipality of Câmara de Lobos, Madeira. This story will tell you more about this location, it's importance and the work we did.

One of the focus areas for the Pterodroma4Future programme is the valley between the villages Câmara de Lobos and Curral das Freiras, both part of the municipality of Câmara de Lobos. A natural boundary separates the municipality of Funchal from the municipality of Câmara de Lobos, namely the Ribeira dos Socorridos. 

The Pterodroma4Future programme works on the conservation of the two endemic bird species inhabiting the islands of Madeira and the islands of Desertas, the Freira da Madeira (Pterodroma Madeira) and the Freira do Bugio (Pterodroma Bugio).

The area of study in this case is specifically important for the Freira da Madeira as they use the valley to travel from and to the sea. Thus, the valley functions as a wildlife corridor, connecting the two important habitats of the bird, the sea and the inland mountain peaks. Alongside the importance of the corridor for the Freira, it is also an important habitat for several other plant and animal species, including the Manta (Buteo buteo).

The most emblematic bird species present in the valley is the Freira da Madeira (Pterodroma madeira), a seabird belonging to the order Procellariiformes. The bird has gray/blackish wings, a white body and a faded gray feather pattern on the head reminiscent of the veil of a nun (hence the name ‘freira’, portuguese for ‘nun’).

This bird species is classified under the ‘Endangered’ category of the  IUCN Red List . The main threats to the Freira da Madeira include the introduction of invasive species, wildfires and human disturbances (including ALAN).

The breeding areas of the Freira are the high peaks of the mountains inland and they prefer to nest on rocky surfaces. Outside of the breeding seasons, the Freira’s migrate to more southern regions in search of food, which mainly consists of fish and small squid. Migration areas include the region of Cape Verde, the central Atlantic equatorial waters and the Brazil current.

To hear Freira da Madeira vocalisations,  click here .

ALAN is one of the factors that threatens the well-being of the Freira da Madeira and other organisms in the region. Research has shown that ALAN can disorient birds because they can not properly use the natural night sky with its stars and moon to navigate, they instead get distracted by all the lights coming from human infrastructures.

For more information about the impacts of ALAN on biodiversity and human health,  click here .

It is important to understand the current levels of ALAN in this area as it could inform future policies to protect nature.

There are several measurement points for the Pterodroma4Future program, as can be seen on the map above. Five of these point are located in the Ribeira dos Socorridos.

The work involves walking into the river, finding an appropriate measurement location and setting up the equipment needed to take the measurements, doing the measurements and then walking back (in the dark). We used a camera with a normal and fish eye lense to take pictures of the area surrounding the measurement point and a special application called a Telescope Encode Sky Sensor (or TAS) that can objectively quantify the light pollution.

We also performed two surveys for each point to note down the conditions under which the measurements were taken, as they could impact the results. These conditions include among others the humidity, the moon phase and the cloud coverage. In the map above, you can see the survey data by clicking on the points.

We are currently working on gathering all the data from the different measurement points. The mapping software of ArcGIS pro helps us to make a visual representation of the state of light pollution.