A bird droppings biodiversity paradise – the Guano Islands and Capes National Reserve System, Peru

The Guano Islands and Capes National Reserve System, Peru

Islas Ballestas

The Guano Islands and Capes National Reserve System in Peru represents an important network of MPAs, full of history and biodiversity. Before the invention of synthetic fertilizers, guano from bird droppings was an essential agricultural fertilizer.  Peru was the biggest producer in the world, due to the large nesting bird populations of the Humboldt, or Peruvian, Current and the arid climate´s ability to preserve the guano.  After over-exploitation, the government took over management and sustainably managed guano production for 100 years, monitoring the bird populations and rotating guano extraction through the islands every few years.  In order to augment the populations of sea birds, walls were built around isolated capes to restrict access and movement of people near nesting areas.

In December of 2009, the islands and capes that had been managed by the Ministry of Agriculture (AGRORURAL) were established as the first MPA network in South America under the administration of the Ministry of Environment.  The islands are now under the supervision of the protected areas agency (SERNANP), while AGRORUAL maintains authority for sustainable guano extraction with prior approval under SERNANP´s management plan and consideration of environmental components.  The objectives of the network include not only conserving the bird populations, but also maintaining the important biological diversity of the Humboldt Current that occurs around the islands.  Other entities that collaborate on management include the Ministry of Production, responsible for fisheries resources, IMARPE, the marine scientific investigation entity, and the Coast Guard (DICAPI) for enforcement.

Though the islands are uninhabited by humans, with the exception of the guards, they are also an important reminder of an era in Peru’s history. Guano extraction, for export as fertilizer to Europe and North America, was crucial to the Peruvian economy during the 19th and early 20th century. The Guanay Cormorant and the environment off Peru produce the best guano in the world, which was so highly valued that two wars were fought over possession of the islands.  While the invention of synthetic fertilizers decreased the demand and led to an end of the “boom” years of guano mining, guano extraction for domestic and international uses still takes place at sustainable levels since the fertilizer can be used in organic markets.  The islands all feature buildings, small stone walls, and trails that serve as relics from the “boom” years of guano mining, and are a significant part of Peru´s history.

View photos of the reserve

Size and Location

The reserve is made up of 22 islands and 11 capes along the entire coast of Peru and covers an area of 140,833 ha of islands, coastline, and ocean.  Each island and cape serves as a national reserve, but all are managed together as a system.  The islands are located in the Humboldt Current, an important upwelling zone that is rich in nutrients and supports one of the world´s largest fisheries: the Peruvian anchovy. As such, it is also a fundamental zone for the sea birds, marine mammals, and fish that feed on these forage species.

 Flora and Fauna

The islands are refuges for large populations of important seabirds.  The primary guano-producing birds are the Peruvian Pelican (Pelecanus thagus), Guanay Cormorant (Phalacrocorax bougainvillii), and Peruvian Booby (Sula variegata). The average population of seabirds on the islands in 2011 was 4.2 million, down from the historic levels of 53 million in the late 19th century. Other seabirds on the islands include the Blue-footed Boobies (Sula nebouxii), Red-legged Cormorant (Phalacrocorax gaimardi), Inca Tern (Larosterna inca), Kelp Gull (Larus dominicanus), Band-tailed Gull (Larus belcheri), Franklin´s Gull (Leucophaeus pipixcan), and Grey Gull (Leucophaeus modestus), as well as the northernmost range of the Humboldt Penguin (Spheniscus humboldtri-IUCN vulnerable).  The islands are also essential breeding zones for marine mammals such as the South American Sea Lion (Otaria byronia) and the Marine Otter (Lontra felina-IUCN endangered). Other species pass through the waters around the islands, such as whales, dolphins, and sea turtles.

The rocky areas and kelp forests around the island are also populated by many fish and invertebrate species. And many species such as mackerel and other migratory species migrate through the waters of the reserve system.


One of the principal threats to the biodiversity of the islands an industrial anchovy fishery, which competes with the seabirds for prey. Anchovies make up the majority of seabird´s diets, and the industrial fishery has put pressure on the stock.  In fact, seabird populations and guano production have declined greatly since the start of the industrial anchovy fishery in the 1950s. 

Climate change also poses a serious threat to the biodiversity that depends on the Humboldt Current. Many economic and ecological functions are dependent on this upwelling zone.  Studies of historical trends in seabird populations show declines in El Niño years, with certain years of the El Niño phenomenon, such as that of 1982/83 resulting in drastic declines. El Niño often impacts the range and availability of anchovy, and thus impacts all of the fauna in the area that feed on them.  The likelihood of more extreme weather events or oscillations escalates the pressures on these populations in an increasingly changing climate. 

In addition, unsustainable activities like local fishing, bird hunting, and unregulated tourism pose threats to the islands.  The recently formed reserve is currently developing a top-down management Master Plan in a participatory manner, and has initiated involvement with local stakeholders, primarily the artisanal fishing community, in order to promote sustainable fisheries and tourism.

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