Wastewater inflows are now being 

 managed. Collection and diversion of sewage 

 flows will correct most of the problems 

 associated with dry-season inflows. Tidal 

 restoration should improve the situation 

 further, if increased tidal flows and stronger 

 currents can remove at least some of the 

 materials that have accumulated in the river 

 channel over the past decade. 



6.3.4 Habitat Management 



Decades of disturbance to the estuary and 

 its watershed have substantially altered the 

 environmental factors that control habitats. 

 The physiographic and hydrologic conditions 

 that led to the pre-1900 ecological 

 communities have been irreversibly changed. 

 Since 1900, some communities have been lost 

 entirely (e.g., woody beach vegetation), and 

 other new ones have developed (e.g., brackish 

 ponds and marshes). With the recently 

 accelerated sedimentation rates and the threat 

 of greatly altered streamflows, it is no longer 

 possible to recommend passive habitat 

 management of Tijuana Estuary. Careful, 

 well-planned management procedures are 

 required to insure that the recognized values 

 of Tijuana Estuary are maintained. 



Several management recommendations 

 follow from the habitat values identified in 

 Chapter 3. The overall management goal 

 should be to maintain the natural variety of 

 habitats (Zedler 1984), recognizing that 

 increasing the area of any one habitat type 

 should not reduce habitat for another. Single- 

 species management is not desirable, because 

 procedures that might benefit one species 

 might negatively affect another. We list here 

 the recognized values of each habitat type, 

 identify management problems, and suggest 

 management objectives. 



• Transition from upland to wetland. This 

 is a diminishing habitat in southern 

 California; it is valued for its rarity, its 

 function as a buffer between wetlands and 

 urbanized areas, and as a foraging ground for 

 bird species. Habitats that are transitional 

 between wetland and upland now will be the 

 wetlands of the future, as sea level continues 



to rise. Hence, a broad transition zone is 

 needed to insure persistence of this fringing 

 community and the high marsh below it. 

 Species of concern include sensitive birds 

 (e.g., short-eared owls, black-shouldered 

 kites) and the horned lizard. The latter have 

 been collected for pets and reduced to 

 extremely low numbers. Frankenia palmeri 

 is a potential member of the habitat, but it has 

 not been recorded at Tijuana Estuary. 



The generic problem facing the transition 

 habitat is urban encroachment, which occurs 

 as fill, trash disposal, trampling, and 

 invasion by dogs and cats. Associated impacts 

 are invasions by exotic weeds and altered 

 densities of native animals. 



Recommended management objectives are 

 to remove fill, control visitor access, 

 revegetate unofficial trails, control dumping 

 of trash, control feral and domestic animals, 

 control exotic plants, and plant native 

 perennials that are likely to have occurred in 

 this habitat. Suitable plants to consider 

 include lemonadeberry, laurel sumac, box- 

 thorn, and native succulents. Ideal locations 

 for transition restoration projects are the 

 slope at the corner of Imperial Beach 

 Boulevard and Third Street, the abandoned 

 gravel mounds near the gravel pit ponds, and 

 abandoned agricultural lands along the 

 periphery of the 495-acre restoration 

 project. 



• Salt marsh. The most widely valued 

 attribute of the salt marsh is the habitat it 

 provides for rare and endangered species. The 

 cordgrass-dominated marsh is nesting and 

 foraging habitat for the light-footed clapper 

 rails; the pickleweed-dominated areas are 

 important to Belding's Savannah sparrows; 

 and the upper marsh is the sole habitat for 

 salt marsh bird's beak. In addition, the marsh 

 is essential to a variety of other organisms, 

 including nonendangered birds, insects and 

 invertebrates, as a place to feed, seek cover, 

 and reproduce. Overall, the salt marsh 

 vascular plants and algal mats contribute 

 substantially to the primary productivity 

 base that supports estuarine food chains. 



We know that nontidal conditions can 

 reduce the natural diversity of plant 



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