The Ecology of Tijuana Estuary, California: An Estuarine Profile

footed clapper rails; the pickleweed-dominated
areas are important to gelding'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 contributes substantially to
the primary productivity base that supports
estuarine food chains.
prog.) need to be incorporated into planning for
trails. The initial plans for identifying and marking
specific foot paths (Dobbin Associates 1985)
should be implemented with one exception. The
construction of a bridge that would open to traffic
the salt marsh west of the inland lagoon should be
reevaluated. The ecological communities and
endangered species that will be affected by
increased human use have not yet recovered from
past traffic and denudation.
Recent disturbances have reduced the natural
diversity of plant communities; cordgrass
populations have declined drastically; annual
pickleweed, sea-blite, and Jaumea carnosa have
also declined. The marsh vegetation is convert~ng
to the pickleweed-dominated community that
characterizes the region's lagoonal wetlands.
These events affect salt marsh animals, as
indtcated by the loss of the light-footed clapper rail
population. It dropped from about 40 pairs to zero,
and at mesent, onlv two individuals are known to
occur in the entlre estuary In addition, the
endangered salt marsh bird's beak IS h~ghly
vulnerable because of ~ts locatron adjacent to
urban development. Among the threats to ~ts
hab~tat are trampling, filling, and (along Seacoast
Drive) ornamental piantings. An annual, salt marsh
bird's beak IS conspicuous only durlng the spring
and summer, making enforcement of the
Endangered Species Act d~fficuit if the species'
habitat disappears when plant are present only as
seeds, there is llttle evidence that a "taking" of an
endangered specles (as prohibited by the Act) has
occurred
c. Salt pannes. The natural values of salt
pannes are not often recognized, and, in many
wetlands, proposals are made to convert them to
other uses. During both the wet and dry phases,
salt pannes are important areas for insects,
including rove beetles and mudflat tiger beetles,
When inundated, the areas serve as feeding
grounds for migrant and resident birds. Species
associated with the intertidal salt marsh and the
transition to upland also use these areas.
Lack of quantitative information about their
habitat value is thus a management problem.
Another continuing problem in salt pannes is the
compaction of soils caused by vehicle and foot
traffic. In the southern part of the estuary, a horse
track that was abandoned in the 1960's still has
soils that appear too dense for colonization by
burrowing insects and too dense or too saline for
vegetation reestablishment.
We recommend that research be initiated to
quantify the communities of organisms that use salt
pannes throughout the annual cycle of wet and dry
condit~ons, and that compacted and noncompacted
Overall. the habitat management goal should be areas be further, on the
to restore the natural diversity of ecological
work of Nordby (1984) Methods of
comrnunlties " the Intertidal marsh reaeratlng the soils that are effective, but not too
dredging to maintain good flushing Is the disruptlve, should be developed An
usual recommended procedure, there IS concern
approach with several alternative treatments IS
that too much dredging will not allow recovery of
these populations. The hydrological plan
recommended
(Williams.
in prog.) will be done w~th ecological ~nput to
evaluate alternatives. Studies are ~n progress at d Brackfsh marsh Areas that have reduced
PERL to provide management recommendations for salinltles throughout most of the year are currently
recovery of cordgrass and annual plckleweed malntained by rainfall and urban runoff Although
Olrecl disturbances, such as trampl~ng and filling artlficlal In this sense, they do support an
must be prevented Qn a limited basis, plants such ecosystem with species native to the area
as salt marsh bird's beak should be grown from Elsewhere in the reglon, brackish marshes are
seed at PERL as a gene bank and to provide valued for their augmentation of habrtat for
materral for exper~mental work. F~nally, the salt p~p~lati~n~ of clapper rails, black-necked stilt,
marsh mon~torirrg program that began in 1979 snowy egrets, and other birds They also Increase
needs to be funded on a permanent basis
habitat d~versity at the estuary and attract species
that would not otherwise occur there (e.g, red-
The potential conflict between resource
management attd vrsttor access needs to be
confronted, wrth clear prrorrtles developed Access The management problem assoc~ated with
to salt marsh habitats needs to be carefully brackish marsh is thelr potential expansion at the
controlled to protect resources, but vrsltors may not expense of saline wetlands. With increased
be satisfied with views from a dlstance Data on freshwater runoff, soils are leached of salts, and
responses of birds to disturbance (e.g., White, in the brack~sh marsh species d~splace those of the
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