Quantifying the Impact of Light Pollution on Sea Turtle Nesting Using Ground-Based Imagery

Patterns of light pollution on sea turtle nesting beaches in the Egyptian Red Sea

We examined the probability of past sea turtle nesting as a function of light intensity and patterns of temporal changes of light along nesting beaches in the Egyptian Red Sea. Beaches had a lower probability of past sea turtle nesting as light intensity increased. Light has been significantly increasing on mainland nesting beaches between 1992 and 2021 except for temporary declines. Island beaches historically had lower light pollution, but there was a sudden increase of light starting in 2014 that continued through 2021, except for the precipitous decline in 2020 during the Covid 19 pandemic. Light pollution on past nesting beaches has now approached levels that may be too polluted and discourage nesting. The impacts of the increased light pollution on nesting density and hatchling survival of hawksbill, Eretmochelys imbricata, and green turtles, Chelonia mydas, is likely negative.

Increase of nesting habitat suitability for green turtles in a warming Mediterranean Sea

Climate change is reshaping global ecosystems at an unprecedented rate, with major impacts on biodiversity. Therefore, understanding how organisms can withstand change is key to identify priority conservation objectives. Marine ectotherms are being extremely impacted because their biology and phenology are directly related to temperature. Among these species, sea turtles are particularly problematic because they roam over both marine and terrestrial habitats throughout their life cycles. Focusing on green turtles (Chelonia mydas) in the Mediterranean Sea, we investigated the future potential changes of nesting grounds through time, assuming that marine turtles would shift their nesting locations. We modeled the current distribution of nesting grounds including both terrestrial and marine variables, and we projected the potential nesting distribution across the Mediterranean basin under alternative future greenhouse gas emission scenario (2000-2100). Our models show an increase in nesting probability in the western Mediterranean Sea, irrespective of the climate scenario we consider. Contrary to what is found in most global change studies, the worse the climate change scenario, the more suitable areas for green turtles will potentially increase. The most important predictors were anthropogenic variables, which negatively affect nesting probability, and sea surface temperature, positively linked to nesting probability, up to a maximum of 24-25 °C. The importance of the western Mediterranean beaches as potential nesting areas for sea turtles in the near future clearly call for a proactive conservation and management effort, focusing on monitoring actions (to document the potential range expansion) and threat detection.

Skyglow relieves a crepuscular bird from visual constraints on being active

Artificial light at night significantly alters the predictability of the natural light cycles that most animals use as an essential Zeitgeber for daily activity. Direct light has well-documented local impacts on activity patterns of diurnal and nocturnal organisms. However, artificial light at night also contributes to an indirect illumination of the night sky, called skyglow, which is rapidly increasing. The consequences of this wide-spread form of artificial night light on the behaviour of animals remain poorly understood, with only a few studies performed under controlled (laboratory) conditions. Using animal-borne activity loggers, we investigated daily and seasonal flight activity of a free-living crepuscular bird species in response to nocturnal light conditions at sites differing dramatically in exposure to skyglow. We find that flight activity of European Nightjars (Caprimulgus europaeus) during moonless periods of the night is four times higher in Belgium (high skyglow exposure) than in sub-tropical Africa and two times higher than in Mongolia (near-pristine skies). Moreover, clouds darken the sky under natural conditions, but skyglow can strongly increase local sky brightness on overcast nights. As a result, we find that nightjars' response to cloud cover is reversed between Belgium and sub-tropical Africa and between Belgium and Mongolia. This supports the hypothesis that cloudy nights reduce individual flight activity in a pristine environment, but increase it when the sky is artificially lit. Our study shows that in the absence of direct light pollution, anthropogenic changes in sky brightness relieve nightjars from visual constraints on being active. Individuals adapt daily activities to artificial night-sky brightness, allowing them more time to fly than conspecifics living under natural light cycles. This modification of the nocturnal timescape likely affects behavioural processes of most crepuscular and nocturnal species, but its implications for population dynamics and interspecific interactions remain to be investigated.

Exploring the construction of urban artificial light ecology: a systematic review and the future prospects of light pollution

Artificial light at night (ALAN) is rapidly growing and expanding globally, posing threats to ecological safety. Urban light pollution prevention and control are moving toward urban artificial light ecology construction. To clarify the need for light ecology construction, this work analyzes 1690 articles on ALAN and light pollution and 604 on ecological light pollution from 1998 to 2022. The development process and thematic evolution of light pollution research are combed through, the historical inevitability of artificial light ecology construction is excavated, and the ecological risks of light pollution to typical animals are summarized. The results show that international research has advanced to the ecological risk factors of light pollution and the related stress mechanisms, the quantification, prediction, and pre-warning by multiple technical means, and the translation of light pollution research outcomes to prevention and control practices. While Chinese scholars have begun to pay attention to the ecological risks of light pollution, the evaluation indicators and prevention and control measures remain primarily based on human-centered needs. Therefore, a more integrated demand-side framework of light ecology construction that comprehensively considers multiple risk receptors is further constructed. Given the development trend in China, we clarified the consistency of the ecological effect of landscape lighting with landsense ecology and the consistency of light ecological risk prevention and control with the concept of One Health. Ultimately, landsense light ecology is proposed based on the "One Health" concept. This work is expected to provide a reference and inspiration for future construction of urban artificial light ecology.

The effects of light pollution on migratory animal behavior

Light pollution is a global threat to biodiversity, especially migratory organisms, some of which traverse hemispheric scales. Research on light pollution has grown significantly over the past decades, but our review of migratory organisms demonstrates gaps in our understanding, particularly beyond migratory birds. Research across spatial scales reveals the multifaceted effects of artificial light on migratory species, ranging from local and regional to macroscale impacts. These threats extend beyond species that are active at night - broadening the scope of this threat. Emerging tools for measuring light pollution and its impacts, as well as ecological forecasting techniques, present new pathways for conservation, including transdisciplinary approaches.

X,Y, and Z: A bird's eye view on light pollution

The global increase in light pollution is being viewed with growing concern, as it has been reported to have negative effects ranging from the individual to the ecosystem level.Unlike movement on the ground, flying and swimming allows vertical motion. Here, we demonstrate that flight altitude change is crucial to the perception and susceptibility of artificial light at night of air-borne organisms. Because air-borne species can propagate through the airspace and easily across ecotones, effects might not be small-scale. Therefore, we propose including airspace as a vital habitat in the concept of ecological light pollution.The interplay between flight altitude and the effects of light pollution may not only be crucial for understanding flying species but may also provide valuable insights into the mechanisms of responses to artificial light at night in general.

Pervasiveness of biological impacts of artificial light at night

Artificial light at night (ALAN) and its associated biological impacts have regularly been characterized as predominantly urban issues. Although far from trivial, this would imply that these impacts only affect ecosystems that are already heavily modified by humans and are relatively limited in their spatial extent, at least as compared with some key anthropogenic pressures on the environment that attract much more scientific and public attention, such as climate change or plastic pollution. However, there are a number of reasons to believe that ALAN and its impacts are more pervasive, and therefore need to be viewed from a broader geographic perspective rather than an essentially urban one. Here we address, in turn, 11 key issues when considering the degree of spatial pervasiveness of the biological impacts of ALAN. First, the global extent of ALAN is likely itself commonly underestimated, as a consequence of limitations of available remote sensing data sources and how these are processed. Second and third, more isolated (rural) and mobile (e.g., vehicle headlight) sources of ALAN may have both very widespread and important biological influences. Fourth and fifth, the occurrence and impacts of ALAN in marine systems and other remote settings, need much greater consideration. Sixth, seventh, and eighth, there is growing evidence for important biological impacts of ALAN at low light levels, from skyglow, and over long distances (because of the altitudes from which it may be viewed by some organisms), all of which would increase the areas over which impacts are occurring. Ninth and tenth, ALAN may exert indirect biological effects that may further expand these areas, because it has a landscape ecology (modifying movement and dispersal and so hence with effects beyond the direct extent of ALAN), and because ALAN interacts with other anthropogenic pressures on the environment. Finally, ALAN is not stable, but increasing rapidly in global extent, and shifting toward wavelengths of light that often have greater biological impacts.