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Natural history of the Coast

By Ulrich Zanabria Alarcón, MSc in Biology

The Arequipa region has the longest coastline in all of Peru, running approximately 480 km (298 mi.) through three provinces bordering the Pacific Ocean: Caravelí, Camaná, and Islay. Arequipa’s coastal strip consists of an onshore area between 0 and 1,000 meters (0 to 3,280 feet) above sea level, marking the boundaries of the coastal lomas ecosystem and featuring uneven terrain with a hill system known as a “coastal cordillera”; and an offshore part that stretches five nautical miles from the coast or the edge of the continental shelf (200 m (656 ft.) deep). The onshore area belongs to the Pacific desert ecoregion, while the offshore area is part of the Humboldt Current cold-water ecoregion.


The climate on Arequipa’s coast is arid and semi-hot in summer, and humid with low precipitation in the winter. The annual average temperature is 19º C (66º F). The weather here is influenced by the Humboldt Current, with its temperate waters ranging from 15º to 17º C (59º to 63º F) in the summer and 13º to 14º C (55º to 57º F) in the winter. The sea along Arequipa’s coast includes upwelling areas, where the cold water, low in oxygen and high in nutrients, rises to the surface very close to the coastline at depths of less than 100 m (328 ft.). Upwelling is essential for the development of phytoplankton and aquatic plant life, creating the bases for the exceptional productivity that has made the region’s marine environment rich in biomass and diversity. This upwelling occurs near Atico, in the province of Caravelí, and Mollendo, in the province of Islay.

These characteristics allow for a wide variety of environments, including flatlands, dry basins, coastal valleys, wetlands, ravines, cliffs, inlets, capes, small islands, and both sand and pebble beaches. All these environments are home to an immense diversity of species.

The onshore areas with the greatest diversity of species are mainly the coastal fog oases such as the Lomas de Atiquipa, and wetlands such as the Lagunas de Mejía National Sanctuary, both of which are protected natural areas. Together, they are home to over one hundred species of flora, two hundred species of birds, twenty-seven species of mammals, and thirteen species of amphibians and reptiles.

On the coastal sand and pebble beaches, as well as the strip of ocean just off the coast, we find seventeen species of marine mammals, of which fourteen are cetaceans; two species of reptiles; thirty species of macroalgae; approximately eighty species of coastal fish; and over one hundred eighty species of marine macro invertebrates, including mollusks, crustaceans, echinoderms, coelenterates, annelids, and other groups.

There are around twenty threatened species that live on or in the ocean here, including birds, mammals, and reptiles, as well as fourteen species of cetaceans.

The sandy beaches feature an incredible concentration and abundance of species, including Pacific mole crabs and others for which the region has long been renowned, such as macha clams. These areas are important sites for artisanal fisherman thanks to schools of fish such as the corvina, lorna drum, and Peruvian banded croaker, who flock here in search of food.

The pebble beaches and rocky sea bottom are home to an impressive biodiversity of marine species, offering a perfect site for numerous sessile invertebrates to forge communities. Here, marine algae form veritable meadows under the sea. These habitats are unique, hosting species that use them for a range of purposes, whether it be shelter, reproduction, food, or colonizing. Among other species, we find Chilean abalone, limpets, sea urchins, and octopi, as well as fish such as the sargo or white seabream, Peruvian sea bass, two types of sea chub known as the chino and the negrillo, and more.

The wealth of species inhabiting the rocky sea bottom makes this an exceptional place for scuba diving and snorkeling. With the chance to observe all these species in their native habitat, underwater photography is an excellent choice of activity. This way, we can enjoy them without causing them harm or placing them in danger of extinction. Marine species should only be caught and removed by properly licensed artisanal fishermen with a formally established business, respecting closed seasons and all commercial minimum sizes. When visiting the beach, avoid bringing single-use plastics, which can be extremely dangerous to marine fauna.