Many features of the estuary have been 

 substantially altered by both natural and 

 human disturbances. In the early 1900's, 

 sewage disposal practices led to the dredging of 

 an east-west channel to connect the estuary to 

 an adjacent lagoon. Dikes were later 

 constructed to subdivide that lagoon into three 

 wastewater receiving ponds, which were 

 subsequently abandoned and the dikes breached 

 to improve tidal flushing. Gravel extraction 

 for street and dike construction left isolated 

 ponds within the estuary. Long-term dumping 

 and filling altered most of the peripheral 

 topography, and off-road vehicles denuded 

 many roads and paths. Scars remain 

 throughout the southern half of the estuary 

 from former military, agricultural, and 

 horse-raising activities. Present-day sewage 

 spills from Mexico change the quantity, and 

 certainly the quality, of inflowing waters. 

 More recently, natural flooding in 1980 

 broadened the riverbed and changed its course. 

 Winter storms in 1983 washed the dunes into 

 the main channels and obliterated two salt 

 marsh islands. The estuary closed to tidal 

 flushing in April 1984 and remained nontidal 

 until it was dredged open some eight months 

 later. 



Can any area that has experienced such 

 extensive assaults still be considered a 

 naturally functioning estuary? The closest we 

 can come to answering that question is to 

 compare it with more disturbed systems near 

 Los Angeles and with less disturbed systems in 

 Baja California. Tijuana Estuary ranks with 

 the latter. 



1.4 BIOLOGICAL SIGNIFICANCE 



The presence of several rare and 

 endangered species has focused the attention of 

 resource agencies and environmentalists on 

 Tijuana Estuary. Significant populations of 

 the California least tern (Sterna antillarum 

 browni) and the salt marsh bird's beak 

 (Cordylanthus maritimus ssp. maritimus) 

 remain at Tijuana Estuary. In addition, the 

 State-listed Belding's Savannah sparrow 

 (Passerculus sandwichensis beldingi) nests in 

 the salt marsh. These and other rare and 



threatened species have declined in numbers 

 as their habitats have succumbed to the 

 pressures of development. Their persistence 

 at Tijuana Estuary documents the importance 

 of the area for wildlife. The plight of other 

 species, such as the light-footed clapper rail 

 (Rallus longirostris levipes), illustrates the 

 need to enhance and maintain the area. 



1 .5 PROTECTION EFFORTS 



Public ownership of lands was for many 

 years the main protection against 

 development. In 1971 the California 

 Department of Parks and Recreation acquired 

 U. S. Navy lands in the southwestern portion 

 of the estuary (396 ac = 160 ha) for Border 

 Field State Park. The Navy retained a strip of 

 land (263 ac = 106 ha) through the northern 

 arm of the estuary, which is under its 

 helicopter flight path. 



In 1980 the U. S. Fish and Wildlife 

 Service purchased a large part of the estuary 

 (505 ac = 204 ha) from private owners for 

 protection of endangered species and their 

 habitat. This area became the Tijuana Slough 

 National Wildlife Refuge. 



1 .6 NATIONAL RECOGNITION 



Following an extensive selection and 

 review process (OCZM and CCC 1981), 

 Tijuana Estuary was designated a National 

 Estuarine Sanctuary in 1982. It was later 

 renamed a National Estuarine Research 

 Reserve (NERR). Tijuana Estuary joined 

 Padilla Bay in Washington, South Slough in 

 Oregon, and Elkhorn Slough in central 

 California to become the fourth Pacific Coast 

 NERR. Tijuana Estuary was the nation's 10th 

 NERR. Several attributes made this 

 "southwesternmost estuary" eligible for 

 national recognition. The site was relatively 

 undisturbed for "a region characterized by 

 degraded wetland and estuarine systems" 

 (ibid., p. 44). It was known to support 

 several protected bird species and to be a 



