Complejo Lagunar Ojo de Liebre -
Guerrero Negro

Ecology and Conservation

An expanded Site Profile for Ojo de Liebre - Guerrero Negro will be available soon!

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Guerrero Negro

The area of study is found in the western half of Mexico’s Baja California Peninsula, in the Sebastian Vizcaino Bay. Three large bodies of water are located in this bay: Manuela Lagoon (600 hectares), Ojo de Liebre Lagoon (57,100 hectares), and Guerrero Negro Lagoon (21,100 hectares). This lagoon complex is next to the El Vizcaíno desert. The region’s climate is arid, with winter rains that usually do not exceed 100 millimeters per year. The predominate vegetation is xerophilic matorral and is, in general, low and dispersed. The average annual temperature ranges between 18 and 22 degrees Centigrade.

The Salt-mining Business at the Site

To the east of Oje de Liebre Lagoon is the Guerrero Negro salt mine, run by Exportadora de Sal, S.A. de C.V. This is the largest salt-mining business in the world, which bases its production on the solar and wind evaporation of saltwater. Its average annual production is 7 million tons. The salt mine is 51 percent owned by the Mexican Federal Government and 49 percent owned by a private Japanese company, Mitsubishi. The production process involves pumping saltwater to concentration areas that encompass 30,000 hectares; however, it has been observed that only 20,102 hectares are being used by birds. The primary areas (S-1A and A-1) receive water pumped directly from Ojo de Liebre Lagoon, with salinity similar to that of mid-sea (3.5-3.8 %), whereas the salinity in the last concentration areas reach 25 %. The areas are separated by a series of dikes, and the salinity within each area is maintained at a constant. The brine resulting from the evaporation process is pumped to a series of crystallization vessels, where it continues the process. Once most of the water has evaporated, the salt precipitates and is harvested. In general, the birds don’t use the crystallization vessels nor the concentration areas with the greatest salinity (areas 10 to 13). The salt mine, for the most part, presents substrates that are sandy and muddy, and not subjected to the regimen of the sea. However, it’s possible to present slight variations in the substrates’ levels, due to the activity of the pump, which intensifies in the summer.

The Human Population
Some 15 kilometers north of the salt mine is the town of Guerrero Negro, which has a population of approximately 12,000 inhabitants. The economy of this place revolves around three activities: fishing in the Ojo de Liebre Lagoon , ecotourism (particularly gray-whale watching), and salt extraction. Exportadora de Sal directly employs an average of 1,000 people.

The Birds
The Guerrero Negro salt mine constitutes a high-quality, artificial habitat and therefore is of great importance for migratory and resident birds. The WHSRN site is used by at least 100,000 shorebirds throughout the year, making it a site of international importance. The maximum abundance at Guerrero Negro is actually 110,500 shorebirds. The most numerous species are: red-necked phalarope (Phalaropus lobatus; 58,000 birds), western sandpiper (Calidris mauri; 26,000), dunlin (Calidris alpina;13,000), dowitchers (Limnodromus spp.; 12,000), and marbled godwit (Limosa fedoa; 5,400). Recently, (2005-2006) important numbers of red knots (Calidris canutus) were observed using the salt mine, presumably the subspecies C. c. roselaari; the maximum observed was 3,000 individuals, which corresponds to 15% of this subspecies’ estimated total population. Additionally, at least 10 species (see Special Information section) nest at the salt mine; among those that stand out is the California least tern (Sternula antillarum browni), a species categorized as in danger of extinction.

Management and Protection
The area concessioned to Exportadora de Sal receives effective and permanent surveillance by the company, and access to the area is restricted. This prevents any type of physical alteration to the environment used by birds, as well as any extraction of organisms (fish, shrimp, Artemia, etc.) that the birds feed upon. Additionally, the area is within the El Vizcaino Biosphere Reserve, where the only potential threats to the site would be those arising from problems related to land tenure--and conflicts have already arisen between the ejidatarios and the salt mine company with respect to prices, which should be resolved through the temporary occupation of land agreement.

Given that an indispensable requirement for adequate salt production is the maintaining of stable conditions, a management plan is not necessary as long as the salt mine remains in operation.

Research
As part of a program for researching birds’ use of the region in general, to date continuous studies (monthly censuses) have been carried out since 2004. Additionally, capture studies also have been conducted, using mist nets, and have focused on two shorebirds species—western sandpiper (Calidris mauri) and red knot (C. canutus).

Listed in the Special Information section is published research that doesn’t directly tackle topics regarding shorebirds and the most relevant results from recent field work. Below is a list, with explanatory comments, of the most relevant studies regarding shorebirds:

• Danemann et al. (2002) described the species composition, variation in abundance, and timing of migration for the shorebirds at the salt mine. They registered 26 species, of which Phalaropus lobatus (58,000) and Calidris mauri (26,000) were the most abundant.
   
• Carmona et al. (2006) determined the abundance of Calidris canutus at the salt mine. The red knot favored one of the first concentration areas (Salitrales 1A). Additionally, the researchers evaluated the effect of sea level on this species’ abundance. The greatest numbers were observed in October 2005 (2,900 birds maximum), which are also the highest ever registered in Mexico.
   
• Morales-Gopar and Carmona (2006) described a new feeding technique of the western sandpiper (Calidris mauri). They encountered the birds “feeding in flight.” This foraging behavior allows the sandpipers to access the marine invertebrates (mainly Artemia spp.) and some insects.
   
• Recently, Arce (in revision) determined the utilization for Calidris mauri in a natural area of Guerrero Negro (a beach on Ojo de Liebre Lagoon) and in an artificial area (a salt-mine concentration area). Arce found that the population structure by gender was 3:1 (male: female); the global population structure by age was 1:1, but distinct between the two wetlands (76% of juveniles at the beach and 76% of adults at the salt mine).
   
• Ayala-Perez (in revision) evaluated the relationship of shorebird abundance with seawater levels at a natural area and at an artificial one. Ayala-Perez registered 25 species of shorebirds using the zone, with Calidris mauri the most abundant at the beach (63%) as well as at the salt mine (46.3%). The birds were more abundant at the salt mine at high seawater levels, and at low levels at the beach. There were seasonal differences; the seawater level affected the birds more during periods of high energetic demands (fall and spring).