Monitoring Peruvian Guano Harvesting

The Peruvian coast represents one of the largest and most productive upwelling systems in the world at times supporting populations of 30-40 million seabirds, more than 20 species of cetaceans as well as sea lions, fur seals, and the southern hemisphere equivalent of our sea otter, the marine otter.   The combination of the abundant seabirds, offshore islands, and a lack of precipitation means that these islands become mountains of seabird excrement or guano. 

As the world's best and most concentrated organic fertilizer, this guano has been harvested commercially for over 150 years and was even used by pre-Colombian Native Americans to support their agricultural production.  The commercial collection of guano is a unique opportunity to exploit a natural resource with little impact on the marine resources.  It also represents a great shot in the arm for Peruvian agriculture and for the Peruvian economy as a source of foreign exchange while at the same time encouraging the responsible management of the fishery that supports the millions of seabirds. 

The islands are currently harvested every 7-10 years by up to several hundred laborers who are hired by the Peruvian Government and visit the islands between the guano birds' breeding seasons.  This careful scheduling effectively reduces the impact on the three main guano producing species, the Peruvian Booby, the Peruvian Pelican, and the Guanay Cormorant, but there are several other species that are potentially threatened by the presence of these guano harvesters - especially the endangered Humboldt Penguin and the Peruvian Diving Petrel.  

We monitored five islands being harvested this year to evaluate the impacts of the harvest, suggest options for reducing those impacts, and determine if the guano can be harvested in a manner that results in a substantial net benefit for the marine resources of Peru.