How are the Mediterranean islands polluted by artificial light at night?
Graphical abstract
Introduction
The Mediterranean is considered a World Biodiversity Hotspot because of the significant reservoir of endemics and the fact that many are threatened with extinction (Myers et al., 2000). Its local flora is rich containing about 24000–25000 species with a high degree of endemism, up to 63.5% (Greuter, 1991; Heywood, 2002). The local fauna is also characterized by its richness and its high level of endemism. There are 298 species (of which 38 are endemic) of mammals (Temple and Cuttelod, 2009), 534 species of birds including 63 endemics (Blondel et al., 2010), 299 species (117 endemics) of reptiles (Cox et al., 2006), 109 species (54 endemics) of amphibians (Cox et al., 2006), 622 species (280 endemics) of freshwater fish (The Critical Ecosystem Partnership Fund, 2017), and 600 species of marine fish with approximately 74 endemic species (Abdul Malak et al., 2011). Invertebrates are highly diverse in the Mediterranean region: anthozoans are represented by 151 species (Coll et al., 2010) with approximately 26 endemic species amongst them (del Mar Otero et al., 2017); freshwater mollusks account for 629 species, including 384 endemic species (The Critical Ecosystem Partnership Fund, 2017); there are 61 species of damselflies and 104 species of dragonflies, 23 of them are endemic (Riservato et al., 2009); 463 species of butterflies (98 endemic species) (Numa et al., 2016); about 580 species of dung beetles occur in the region, of which approximately 150 are endemic; at least 576 species of saproxylic beetles represented here with approximately 338 endemic species (The Critical Ecosystem Partnership Fund, 2017). This rich and unique biodiversity has been formed to a large extent due to island isolation over a long period of time in the Mediterranean (Blondel et al., 2010; Greuter, 2001; Thompson, 2005). As a result, the flora of Sicily has 305 species of vascular plants, with 11.3% being endemic, the flora of Crete – 165 species or 10.1% being endemic, the flora of Sardinia – 61 species of which 5.4% are endemic, and the flora of Corsica – 131 species with 4.5% being endemic (Junikka et al., 2006). Therefore, the islands have special value to this region; many of them belonging to the ten Mediterranean Basin hotspots based on plant endemism and richness (Medail and Quezel, 1999). However, there is a very strong anthropogenic influence on natural ecosystems, which is causing biodiversity loss in the Mediterranean (Coll et al., 2010; Greuter, 1991). Though the human impact on the Mediterranean islands, from early prehistoric settlements through antiquity to the Middle Ages, has been profound, the situation has been changing for the worse in the last few decades; the speed of deterioration of natural habitats has increased exponentially (Greuter, 2001). Moreover, new threats are appearing. One of these is ecological light pollution which is increasing rapidly on a global scale (Kyba et al., 2017). This has already been documented for the Mediterranean (Bennie et al., 2015b; Caruana et al., 2020; Peregrym et al., 2020a).
While the impact of artificial light at night (ALAN) is being ignored by decision-makers at local and national levels, as well as by related organizations and even by some scientists, the problem becomes more dangerous for ecosystems, species, and human health (Abraham et al., 2019; Dominoni et al., 2020; Falchi, 2018; Schroer and Hölker, 2017). However, the fact that 80% of the world and more than 99% of U.S. and European populations live under light-polluted skies shocks (Falchi et al., 2016). In addition, its consequences are deep and serious, because they have a significant influence on reproduction, navigation, behavior, foraging, habitat selection, communication, and social interactions of all living organisms. There is, already, a lot of published data about the ALAN and sky glow affecting plants (Bennie et al., 2018; Brelsford and Robson, 2018; ffrench-Constant et al., 2016; Giavi et al., 2020; Knop et al., 2017; and others), invertebrates (Ayalon et al., 2019; Davies et al., 2012; Grubisic et al., 2018; Macgregor et al., 2017; Owens et al., 2019; Underwood et al., 2017; van Grunsven et al., 2018; and others), and vertebrates (Grubisic et al., 2019; Schroer and Hölker, 2017; Touzot et al., 2020; and others), including humans (Cho et al., 2015; Dominoni et al., 2016; Johnson and Munshi-South, 2017; and others). Consequently, cascading effects with unpredictable results appear in terrestrial and water ecosystems (Bennie et al., 2015a; Bolton et al., 2017; Davies et al., 2020; Depledge et al., 2010; Garratt et al., 2019; Hölker et al., 2015; Maggi et al., 2020; Navarro-Barranco and Hughes, 2015; Perkin et al., 2011; Russo et al., 2019; Sanders et al., 2015; Sanders and Gaston, 2018; Spoelstra et al., 2015). Besides, ALAN can be a driver of evolution across urban-rural landscapes (Hopkins et al., 2018).
In considering the described situation where the Mediterranean islands are natural habitats for many unique species, and the ALAN impact increase on them, it was decided to estimate the strength of the impact of artificial light at night in these territories.
Section snippets
Material and methods
This research covers the Mediterranean Sea and its islands. However, our investigation has mostly been focused on the fifteen islands with the largest areas (Sicily (Italy), Sardinia (Italy), Cyprus (the Republic of Cyprus), Corsica (France), Crete (Greece), Euboea (Greece), Majorca (Spain), Lesbos (Greece), Rhodes (Greece), Chios (Greece), Kefalonia (Greece), Menorca (Spain), Corfu (Greece), Ibiza (Spain), Djerba (Tunisia)) (Fig. 1), as well as on islands with total area more than 0.01 km2
Results
The Mediterranean Sea occupies about 2,510,000 km2 (Salah and Boxer, 2019), but absolutely dark skies at night cover only 1,167,567 km2 or 46.61% of this territory. There are 4 dark sky refugia (Fig. 1): Western (313,593 km2), Adriatic (331 km2), Aegean (12,448 km2), and Eastern (841,195 km2). ALAN pollutes the remaining parts of this marine area.
We have established that there are only 49 non-polluted or partly non-polluted islands in the Mediterranean Sea. The total area is 118.67 km2, and the
Discussion
As seen from our results and data for the Maltese archipelago studied by Caruana et al. (2020) with other methodology, the largest part of the maritime areas of the Mediterranean Sea as well as all islands, exclude 49 mentioned ones, are polluted by ALAN at the present time. However, at the moment our calculated data shows a static situation for the fifteen biggest Mediterranean islands from the New World Atlas of Artificial Sky Brightness publication (Falchi et al., 2016). Taking into account
Conclusion
Thus, we have adequately documented the fact that ALAN heavily pollutes the fifteen largest Mediterranean islands that are habitats for many endemic and rare species, and these islands do not have any plots with zero-level of light pollution. Also it has been found that the level of light pollution of the islands correlates with their human population density. Nevertheless, less than half of the marine area of the Mediterranean Sea is covered by completely dark skies at night, though this total
Funding
The research has been carried out in the framework of the project EFOP-3.6.2-16-2017-00014 “Development of an international scientific and research environment in the field of study of light pollution".
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
Authors are most grateful to a team of researchers led by Fabio Falchi (Light Pollution Science and Technology Institute, Italy) who provided the kmz layer “The New World Atlas of Artificial Sky Brightness” prepared as a result of their project - https://cires.colorado.edu/Artificial-light, as well as to Julia Jones (NGO “Flowers of Crete”, UK)" for linguistic editing. Also we thank three anonymous reviewers for their helpful comments on the earlier versions of the manuscript.
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2022, Journal for Nature ConservationCitation Excerpt :Unlike national parks in hilly mountains, those in coastal regions have long been used by people. Many harbors, shipyards, and fishing villages exist near those parks, which contaminated inside the national parks in coastal regions by light pollution (Caruana et al., 2020; Korea National Park Research Institute, 2019; Peregrym, Kónya et al., 2020). Light pollution in the national parks has a seasonal pattern with highest mean nighttime radiances in winter (January) and lowest in summer (August) (Fig. 3).