Light pollution It has gone from being a matter for astronomers to becoming a major environmental, health and economic problem. light pollution maps allow us to understand the scope of this phenomenon. There is growing evidence that artificial light at night alters biological rhythms, alters wildlife behavior and wastes energy, with effects ranging from urban centers to the open sea.
Thanks to networks of citizen science Already with sensors that record wildlife activity throughout the day, we now know that in the most illuminated places birds begin to sing before dawn and prolong their trill after dusk. Although most of the data comes from Europe and North America, the patterns detected suggest a global impact that urgently needs to be studied in more detail in other regions.
What is light pollution and what is its scope?
Artificial light at night (ALAN) includes urban glow or skyglow, street and shop window lighting, and coastal infrastructure spotlights. It is estimated that 80% of the population lives under that diffuse halo and that global illumination grows between 2% and 3% annually, with impacts that reach natural areas that, in theory, should remain dark.
In the marine environment, this glare already affects more than 23% of coastal areas, can spread up to 20 kilometers offshore and penetrate about 20 meters into the water, modifying feeding cycles, migration and reproduction in multiple species.
What the data says about birds
A global analysis based on more than 60 million acoustic recordings Of 583 species, it is documented that diurnal birds begin singing about 18 minutes earlier and maintain it for 32 minutes later in illuminated landscapes, that is, an average prolongation of about 50 minutes in front of dark areas.
The study, supported by satellite nighttime brightness maps and the platform BirdWeather, analyzed 2,6 million observations at dawn and 1,8 million at dusk in more than 7.800 locations. Species with large eyes, open nests or migratory habits showed the most pronounced changes, especially during the breeding season.
There are striking variations by species: in very illuminated areas, the common blackbird can extend its vocal day by nearly two hours, while the redwing advances its first trill by almost an hour. In nocturnal birds, a "shortened" day is not generally observed, but rather a reduction of vocalizations when the environment is very bright.
The functional impact remains to be clarified: the elongation of the edge could translate into sleep deficit, greater stress or lower survival; although in certain contexts more time to feed or a reproductive success slightly higher, which requires further research before generalizing conclusions.
Beyond the song, light also multiplies the risks for migratory birds: in the United States it is estimated that hundreds of millions of birds They crash into buildings every year, attracted or disoriented by the lighting; in Tenerife, more than 100 are rescued annually. 3.500 shearwater chicks in just two weeks, and it is estimated that this figure represents around 60% of the actual falls.
Underwater: turtles, corals, fish and plankton
Artificial night rewrites the sea clock. On urbanized beaches, up to 93% of the offspring of sea turtle is disoriented by the lights, with mortalities which reach 70% when directed inland instead of the brightness of the marine horizon.
On reefs, the presence of ALAN can delay or even inhibit spawning synchronized coral breeding; reductions in fertilization close to zero have been observed 40%, an added blow to ecosystems already stressed by warming and acidification.
Light modifies the behavior of fish and predators: some species avoid illuminated areas and lose opportunities to feeding and breeding, while others take advantage of the glare to hunt more. In illuminated ports, falls of the 25% in prey fish populations and reductions of up to 30% in the survival of juveniles.
Zooplankton, the basis of many food chains, reduces its nocturnal vertical migration up to 60% in light-polluted areas, with cascading effects that promote episodes of blooms toxic algae, associated in the United States with economic losses of nearly $82 million annually.
Policies, financing and technology to dim the glare
The light can be turned off, redirected, or modulated. In Spain, the MITECO has decided to grant aid for 142 millones de euros to modernize the outdoor lighting of 70 municipalities (about 3,9 million inhabitants), with the replacement of 139.300 points of light for more efficient and night sky-friendly technologies.
The projects incorporate warmer spectrum LEDs, telemanagement to program and adjust in real time, and shielded optics that reduce spillage to the sky; the average expected savings exceed 74,1% of energy, with a direct impact on the public bill and on the skyglow reduction.
Notable projects include Zaragoza (9,9 million, centralized lighting control), Seville with its “Smart Lighting Ecity Cartuja” (9,4 million) and Avilés (8,5 million). Iznalloz (Granada) received the best technical rating for the complete replacement with smart LEDs. advanced control system.
The aid covers 100% through loans without interest 10 years (one year grace period). Since 2015, the IDAE has promoted six lines of financing with 1.049 billion euros, which have reached 2.001 municipalities, renewing 1,5 million points; urban lighting consumes about 5.296 GWh/year with a cost of 741 million, so efficiency and responsible design are key to the PNIEC and the +SE Plan.
Citizen science, maps and local actions
The use of supercomputers and advanced models has allowed Catalonia to have its first complete map of light pollution, which identifies maximums on the coast and large urban areas (Barcelona, Tarragona, Girona, Lleida) and preserves skies of high quality in the Pyrenees and protected areas such as Montsec or Aigüestortes.
Community initiatives are growing: in the Sierra del Rincón (Madrid), outreach activities, coordinated blackouts and guided observations have served to raise awareness about the harm of unnecessary light and to enhance the cultural and scientific experience of the night sky.
There are simple and immediately effective measures that homes, businesses and local governments can take to recover the darkness when it is not essential to keep it lit:
- Shielding luminaires and direct the light to the ground, avoiding glare and emission to the sky.
- Choose warm tones (amber or low CCT) and the minimum power required, with timers and sensors.
- Close curtains, turn off signs and shop windows outside of business hours and remove unnecessary decorative spotlights.
- Create “dark zones” in sensitive areas, ecological corridors and coastal stretches.
Accumulating evidence shows that artificial night is reconfiguring behaviors, cycles and ecosystems on land and sea, but also that there are technical tools, public funding and citizen will to tackle it: adjusting spectrums and schedules, redesigning luminaires and planning with criteria of Enviromental health It allows us to recover starry skies, save energy and reduce impacts on wildlife.
