Environment and Ecology of Reynisfjara

A Volcanic Ecosystem

Reynisfjara exists at the intersection of three powerful natural systems: the volcanic geology of the Mid-Atlantic Ridge, the North Atlantic Ocean, and the subarctic climate of southern Iceland. The ecology here is shaped by extremes — harsh winters, powerful seas, nutrient-rich volcanic soil, and an ocean teeming with cold-water marine life that supports enormous seabird colonies along the coast.

Seabird Colonies

The cliffs surrounding Reynisfjara and the nearby Dyrholaey promontory host significant breeding colonies of several seabird species. These colonies are a major ecological feature of the area and a primary draw for wildlife-interested visitors.

Atlantic Puffin (Fratercula arctica)

Puffins are the signature species of Iceland's southern coast. An estimated 8 to 10 million Atlantic puffins breed in Iceland, representing roughly 60 percent of the global population. The cliffs at Dyrholaey and the grassy slopes above Reynisfjara host a substantial colony. Puffins arrive in mid-April to early May and depart by mid to late August. They nest in burrows dug into the grassy turf atop the sea cliffs, returning to the same burrow year after year.

Puffin populations in Iceland have experienced significant declines since the early 2000s, driven primarily by reduced availability of sand eels (Ammodytes), their primary food source during the breeding season. Warming ocean temperatures have pushed sand eel populations northward and reduced their abundance in traditional Icelandic waters. Breeding success — measured as the percentage of burrows that successfully fledge a chick — has declined markedly, with multiple complete or near-complete breeding failures recorded in southern Iceland colonies over the past two decades.

This decline has led to the puffin being classified as "Vulnerable" on the IUCN Red List since 2015. The traditional Icelandic practice of hunting puffins (a cultural tradition dating back centuries) has been curtailed in response, with many communities voluntarily ceasing or reducing their harvest.

Arctic Tern (Sterna paradisaea)

Arctic terns nest in loose colonies on the low ground near Reynisfjara and across the coastal plains of southern Iceland. These birds undertake the longest migration of any animal — breeding in the Arctic and subarctic during the northern summer, then flying to Antarctic waters for the southern summer, covering roughly 70,000 kilometers annually.

Arctic terns are fiercely defensive of their nesting sites. They will dive-bomb any perceived threat, including humans, striking with their sharp beaks. If you are walking near Reynisfjara in June or July and a small white bird begins screaming and diving at your head, you have wandered too close to a nest. The appropriate response is to change direction and move away. Do not swat at them — they are protected under Icelandic law.

Other Species

The cliffs also support breeding populations of northern fulmar (Fulmarus glacialis), black-legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge), and razorbill (Alca torda). Fulmars are particularly abundant and can be seen riding the updrafts along the cliff face year-round.

Marine Ecology

The waters off Reynisfjara are part of the productive North Atlantic marine ecosystem, where cold Arctic currents meet warmer Atlantic water to create nutrient upwelling that supports rich fisheries and marine life.

The nearshore waters host populations of harbor seal (Phoca vitulina) and grey seal (Halichoerus grypus), though seals are more commonly seen on the sandier, calmer beaches east of Vik rather than at wave-exposed Reynisfjara itself. Minke whales, humpback whales, and white-beaked dolphins frequent the waters off the south coast, though they are not typically visible from the beach.

The intertidal zone at Reynisfjara is relatively impoverished compared to rocky shores in warmer waters. The extreme wave energy, the abrasive basalt sand, and the cold temperatures limit the diversity of organisms that can establish themselves. Mussels, barnacles, and various species of seaweed (kelp and fucoid algae) cling to the basalt outcrops and the base of the sea stacks.

Vegetation and Terrestrial Ecology

The area immediately around Reynisfjara is sparsely vegetated. The beach itself is bare basalt sand, and the slopes above are covered in a patchy mix of mosses, grasses, and low-growing Arctic-alpine plants. Iceland's plant communities are shaped by the volcanic substrate, wind exposure, and the short growing season (roughly May through September).

Key plant communities in the area include:

• Lyme grass (Leymus arenarius): A tough, sand-binding grass found on dunes and sandy margins near the beach. It plays a crucial role in stabilizing coastal deposits.
• Moss heath: Racomitrium lanuginosum (woolly fringe-moss) covers vast areas of Icelandic lava fields, including the older flows near Reynisfjara. These moss carpets take decades to centuries to establish and are extremely fragile — a single footprint can destroy moss cover that took 50 years to grow.
• Arctic thyme (Thymus praecox): A low-growing flowering plant found on well-drained slopes, producing tiny purple flowers in summer.
• Crowberry (Empetrum nigrum): A dwarf shrub common on heathlands throughout Iceland.

There are no trees at Reynisfjara. Iceland was largely deforested during the Norse settlement period (birch forests that once covered 25 to 40 percent of the island were reduced to less than 1 percent), and the south coast is too exposed for natural tree regeneration. Reforestation efforts are underway in more sheltered areas of Iceland but have not reached the immediate Reynisfjara area.

Coastal Erosion

The south coast of Iceland is geologically dynamic, shaped by the competing forces of volcanic deposition and ocean erosion. At Reynisfjara, erosion is an ongoing process:

• The basalt cliffs are eroded by hydraulic action (wave impact forcing water into fractures) and abrasion (sand-laden waves grinding the rock surface).
• Storm waves in winter can remove significant quantities of sand from the beach face, only for calmer summer conditions to redeposit material.
• The Halsanefshellir cave is itself a product of erosion — waves have carved into the base of the basalt cliff, exploiting weaknesses in the columnar jointing.
• The Reynisdrangar sea stacks are remnants of a cliff line that has retreated landward over thousands of years. They stand offshore today because they were more resistant to erosion than the surrounding rock.

The rate of coastal erosion varies. It is not linear — catastrophic volcanic events (like the 1918 Katla eruption) can add kilometers of new coastline in days, while decades of wave action slowly reclaim it. Over geological time, the south coast of Iceland is a shifting, impermanent boundary between land and sea.

Climate Change Impacts

Climate change is affecting the Reynisfjara environment in several measurable ways:

Ocean warming: Sea surface temperatures around Iceland have risen approximately 1 degree Celsius over the past century. This warming drives changes in marine species distribution — sand eels moving northward is the most consequential example, directly impacting puffin breeding success.

Glacier retreat: Myrdalsjoekull, the glacier cap overlying Katla volcano, is losing mass. This has implications for glacial river systems that transport sediment to the coast, potentially altering the sand supply to Reynisfjara over time. It also affects the dynamics of potential future jokulhlaups, as a thinner ice cap may behave differently during a volcanic eruption.

Storm intensification: Climate models project increased storm frequency and intensity in the North Atlantic. More powerful winter storms mean greater wave energy at the coast, accelerated erosion, and potentially more dangerous conditions for visitors.

Species shifts: Warming waters are allowing some temperate marine species to extend their range northward into Icelandic waters, while cold-water species retreat. The long-term ecological implications for the marine food web that supports the seabird colonies are not yet fully understood but are a major focus of ongoing research.

Ocean acidification: Increasing atmospheric CO2 is lowering the pH of the North Atlantic. This affects calcifying organisms (shellfish, certain plankton) at the base of the marine food web. Iceland's cold, CO2-absorbent waters are particularly vulnerable to acidification.

Conservation Status

Reynisfjara falls within the Katla UNESCO Global Geopark, designated in 2011 in recognition of the area's outstanding geological heritage. The geopark designation does not confer strict legal protection (unlike a national park) but commits the managing authority to conservation, education, and sustainable development.

The nearby Dyrholaey promontory is classified as a nature reserve and is closed to all public access from May 1 through June 25 each year to protect nesting seabird colonies, particularly puffins and Arctic terns. This closure is enforced and applies to foot traffic, vehicles, and drones.

At Reynisfjara itself, visitor impact management focuses on keeping foot traffic on established paths, preventing disturbance to nesting birds, and — above all — managing the human safety risk from sneaker waves. The tension between conservation and the economic benefits of tourism is a live issue for the community of Vik and for Icelandic environmental authorities more broadly. Visitor numbers have grown faster than management infrastructure, and the long-term sustainability of current access levels is an open question.

The ecological health of Reynisfjara ultimately depends on forces far beyond local management: the trajectory of ocean temperatures, the health of North Atlantic fish stocks, the behavior of Katla volcano, and the global response to climate change. The beach will endure — it has survived eruptions, glacial floods, and millennia of Atlantic storms. Whether its current ecological richness, particularly the seabird colonies that depend on a functioning marine food web, will endure alongside it is less certain.