Reptile diversity and composition at urban-rural edge zones along the Mediterranean coastal dunes of Israel

The land where the city meets the wild is rarely a quiet boundary. In ecology, this meeting place is known as an edge zone, a place where the rigid order of human development presses against the fluid rhythms of nature. These zones are often messy and mixed, hosting a strange blend of creatures that can tolerate the noise and lights of a city alongside those that require the deep silence of the natural world. While the heart of a city is often too harsh for many animals, surviving the transition from a paved street to a sandy dune is a different challenge entirely. Reptiles, the cold-blooded lizards and snakes that rely on the sun and the texture of the ground, are particularly sensitive to these changes. They act as living barometers for the health of an ecosystem; if the delicate balance of a habitat shifts, these animals often feel it first. Understanding how the creeping edge of a town alters the community of reptiles living in coastal dunes is not just a matter of cataloging species, but of seeing how human expansion reshapes the very fabric of life in these fragile environments.

Along the Mediterranean coast of Israel, a team of researchers set out to measure exactly how this urban edge affects the reptiles living in the sand dunes. They focused on four distinct settlements: two large cities, Ashdod and Ashkelon, and two smaller rural communities, Caesarea and Zikim. All four sit right on the border of nature reserves, creating a perfect laboratory to observe the transition from wild dunes to human influence. The researchers chose these locations because the sand itself is consistent, originating from the same source and carried north by ocean currents, meaning any differences they found would likely be due to the nearby settlements rather than the soil itself. They divided their study area into three specific types of terrain. First, there were the shifting far dunes, the wild, moving sands located deep within the reserves, far from any houses. Second, there were the semi-fixed far dunes, where vegetation has begun to hold the sand in place, still distant from the towns. Finally, there were the semi-fixed near dunes, the same type of stabilized sand but located right up against the borders of the settlements.

To understand what was happening in these different zones, the team spent six years, sampling every two years during the summer and early autumn. They did not rely on a single method to find the animals, knowing that some reptiles are shy, some are fast, and some leave no trace unless you know exactly what to look for. Instead, they used a combination of three techniques at thirty-six fixed plots across the four sites. They buried plastic cups in the sand to catch any small creatures that wandered in, they smoothed out long trails in the sand to look for footprints left overnight, and they walked the plots with their eyes open, scanning for active lizards, snakes, or signs like shed skins and droppings. This careful, multi-layered approach allowed them to build a complete picture of which species were present and how active they were in each location.

The results revealed a clear and significant story about how the city changes the desert. When the researchers looked at the total number of different reptile species, they found that the count remained surprisingly stable whether the dunes were near a city or deep in the wild. The variety of life did not simply vanish as the urban edge approached. However, the identity of the animals changed dramatically. The dunes near the settlements were dominated by generalist species—reptiles that are adaptable, tough, and comfortable living in disturbed environments. In contrast, the wild, shifting dunes far from the cities were home to a different cast of characters: specialists that depend entirely on the specific conditions of the moving sand. These sand-dwelling specialists, which include certain lizards and snakes that have evolved to thrive in the open, shifting substrate, became much less common as the distance to the city decreased.

One of the most striking findings was the disappearance of three specific sand-specialist species from the Caesarea area entirely. The lizard Acanthodactylus scutellatus and two snakes, Lytorhynchus diadema and Spalerosophis diadema, were found in the wilder dunes but were absent from the sands near the town. Meanwhile, generalist species like the lizard Chalcides ocellatus and the snake Psammophis schokari increased in numbers in the semi-fixed dunes near the settlements. The data showed that proximity to urban areas significantly reduced the abundance of the native sand-dwelling reptiles while promoting the dominance of these adaptable generalists. It was not that the reptiles were gone; rather, the community had been restructured. The unique, specialized creatures that define the health of the coastal dune ecosystem were being pushed out, replaced by a few hardy species that can survive the noise, the lights, and the foot traffic of human activity.

This shift suggests that the urban edge acts as a filter, allowing only the most tolerant species to pass through while blocking the more sensitive ones. The reasons for this are likely a combination of factors associated with city life: the crushing weight of off-road vehicles, the constant disturbance of hikers, artificial lights that confuse nocturnal animals, and the presence of domestic predators. The researchers noted that the specialized reptiles, which rely on open, sandy ground and specific micro-habitats, are the first to suffer when these conditions are altered. The generalists, however, can exploit a wider range of resources and conditions, allowing them to thrive even as the natural habitat degrades. This means that simply counting the number of species in an area can be misleading; a dune near a city might still have a high number of reptiles, but it has lost its ecological soul, becoming a place for the common and the adaptable rather than the rare and the specialized.

The implications of these findings extend beyond a single stretch of coastline. Coastal dunes are among the most disturbed environments on Earth, with over half of the human population living near them. The study highlights that the loss of specialized reptile communities is a direct consequence of urban expansion and recreational pressure. If conservation efforts focus only on maintaining the total number of species, they may miss the subtle but critical erosion of habitat quality that drives away the most vulnerable animals. Protecting these ecosystems requires more than just setting aside land; it demands managing the edge zones where the city meets the wild, limiting intensive recreational activities, and preserving the connectivity of the dunes so that the specialized species can continue to find the specific conditions they need to survive. The desert is not just a backdrop for human development; it is a living system that responds to our presence, and in the case of Israel's coastal dunes, the response is a quiet but profound reshuffling of life.