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Venezuela´s Eco Regions

 

Coastal Venezuelan mangroves 

This ecoregion is regarded as one of the most pristine and structurally complex mangrove
forests ecoregions in the Americas; holding forests that reach heights of 35-40 m and form
almost continuous belts, extending through 400 km of coastline. They host a rich avifauna
that includes winter migrants and endangered and vulnerable species, as well as several species of terrestrial and aquatic mammals and reptiles that are deemed as threatened.Subsistence and artisanal fisheries that take
place within or in the proximity of mangrove areas are locally important. Venezuelan
mangroves are specifically protected through a Presidential Decree, but this does not offer
complete protection due to many exceptions. Fortunately, many of this ecoregion's
mangrove forests are within the limits of high-ranking conservation units. The degree
of preservation varies accordingly and also in relation to the extent of isolation from centers
of intense urban, tourist and demographic growth. 

Location and General Description 

Distributed on a narrow latitudinal stripe this mangrove ecoregion’s mangrove
woodland fringe almost 1/4 of the Venezuelan coastline, on the northernmost
extreme of South America stretching from Laguna de Cocinetas in the west, to the
western edge of the Orinoco Delta system in the far east. They cover nearly 5,900
km2, thus ranking as one of the largest mangrove ecoregions in South America
(Conde & Alarcón 1993; Conde & Carmona-Suárez 2002). The main mangrove
stand located on the Atlantic Ocean coast, between the Gulf of Paria and the
Orinoco Delta, annual rainfall exceeds 2,000 mm, freshwater input is steady and
geomorphic conditions are regarded as optimal. These pristine, structurally complex
and extensive mangrove forests reach heights of 35-40 m and form almost
continuous belts, extending through about 400 km of coastline. The rest of the
ecoregion is located on a semi-desert belt along the Caribbean Coast of Venezuela,
mostly in the Gulf of Venezuela and on the central-western and central-eastern
coasts (MARNR 1986). Small stands are also found offshore on many of the
islands. 

Most of the coastal Venezuelan mangrove ecoregion stands are small and only a few surpass 40
km2. These are found in the Gulf of Paria, San Juan River, Limón River- San Carlos Island, Los
Olivitos, Cuare-Morrocoy and in Laguna de Tacarigua. In the insular domain, smaller although
substantial mangrove tracts are found in Los Roques and Las Aves Archipelagos, La Orchila
Island and in Margarita Island. 

Red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans) and white
mangrove (Laguncularia racemosa) are the most common species of mangroves in Venezuela.
A fourth species, the buttonwood mangrove (Conocarpus erectus) is regarded as an
"associate" rather than a "true" mangrove; it appears in mangrove stands located in arid zones.
Some species are less abundant, geographically constrained or their presence is still to be
unquestionably confirmed are R. harrisonii, R. racemosa, A. schaueriana and Pelliciera
rhizophorae. Although locally called mangroves, Thespesia populnea, Calliandra riparia and
Coccoloba uvifera are not mangroves in the strict sense. The chewstick (Symphonia
globulifera), a tree whose leaves resemble those of the genus Rhizophora, was
photo-interpreted as a mangrove, leading to an almost three-fold overestimation of mangrove
coverage in a survey undertaken some 15 years ago, in this ecoregion (Conde & Alarcón 1993). 

In general, the coastal climate is dry tropical for most of the Caribbean strip, with average
temperatures around 27.1°C to 30.6 °C. Scant precipitation is distributed in two distinct periods.
In many localities rainfall rarely exceeds 200 mm each year, although in a few cases it has
reached 800 to 1000 mm due to local climatic variations. In the Atlantic facade, the climate is
more humid and precipitation usually exceeds 1600 mm each year and monthly average
temperatures oscillate between 25 and 27 °C. The Venezuelan Coast is influenced by the action
of the trade winds from the east-northeast and northeast-southwest directions. In some coastal
zones winds can reach very high speeds, such as in Laguna de Cocinetas, where speeds vary
from 50 to 65 km/h, inducing processes of accelerated sedimentation (Conde & Alarcón 1993). It
has been postulated that mangrove development and structural complexity are closely related to
this climatic gradient (Pannier 1986).

In the continental domain of Venezuela, mangroves are confined to two geomorphologic units:
coastal lagoons and alluvial plains. In turn, in the alluvial plains three categories can be
distinguished: 1) those with sedimentary marine deposition, as is the case of Los Olivitos
Swamp, Morrocoy Bay, and Gulf of Paria; 2) Deltaic swamps with marine-fluvial deposition, as
in the San Juan River and the Gulf of Paria; 3) Swamp deltas with predominantly alluvial
sedimentary processes, as in the Orinoco Delta. The characteristic deltaic plains of the oriental
sector have induced a major diversity of landscapes, due to the interaction of microtopographic
and pedological factors, mediated by local characteristics (Pannier 1986; Conde & Alarcón
1993).

Biodiversity Features

Throughout their range, Venezuelan mangroves are associated with various types of
vegetation, ranging from thorn scrub woodlands to coastal evergreen forests. These
various associations host diverse faunal assemblages, which, in turn, might be a
consequence of the variations of nearby vegetation and their proximity to other
pristine ecosystems. Exhaustive lists of the species are meaningless, since they can
vary substantially from forest to forest, however, mention of some species can help in
sketching the importance of mangroves and their diversity. Some of the plant species,
seem to be constantly associated with mangrove forests throughout their distribution
range in the Neotropics. Among them, the fern (Acrostichum aureum) and the
Malvaceae (Hibiscus tileaceus) are the most widespread. These species frequently
form dense belts along the landward edge of mangroves, on more elevated sites and
around dry and saline areas inside mangroves. 

In the desert coastal areas of western Venezuela, mangrove forests are associated with
xerophilous littoral scrubs, and halophilous and psammophilous littoral meadows. Xerophilous
scrubs are characterized by individuals with heights from 0.5 to 5 m. Typical species are Acacia
tortuosa, Bourreria cumanensis, Cercidium praecox, and Hibiscus tiliaceus. Columnar cactus
can also be present. Halophilous meadows appear in brackish depressions of coastal areas,
where Atriplex pentandra, Heterostachya ritteriana, and Sesuvium portulacastrum prevail.
Psammophilous meadows settle on sandy dunes, normally not flooded by the sea and Egletes
postrata, Ipomea pes-caprae, and Sporobolus virginicum are distinctive species (Conde &
Alarcón 1993).

Mangrove forests located at the southwestern margin of Lake Maracaibo merge with tall (30-40
m) partially flooded ombrophilous evergreen forests, where Anacardium excelsum, Cariniana
pyriformis, Ceiba pentandra, and Gustavia hexapetala predominate while the endemics
Rhodospatha perezii and Spathiphyllum perezii are related to the Amazonian flora. Medina &
Barboza (2000) have provided a detailed description of these mangroves and the associated
vegetation. 

Some mangrove stands are close to tropophilous semi-deciduous seasonal forests,
characterized by one or two strata, and heights from 5 to 8 m, with emergent individuals up to
10-12 m. Representative species are Capparis coccolobifolia and C. tenuisiliqua, and the
endemic Apoplanesia cryptantha. Mangroves also flourish near tropophilous basimontane
deciduous forests, with heights from 10 to 15 m, and emergent trees up to 20 m. Bauhinia
megalandra, Bourreria cumanensis, Calliandra caracasana, Erythrina poeppigiana, Hura
crepitans, and Tabebuia billbergii are some of the more abundant species. In some localities,
Capparis coccolobifolia, Diospyros inconstans, Jacquinia revoluta and Maytenus officinale
predominate. 

Since mangrove woodlands lie on the littoral zone, the mangrove fauna comprises elements from
marine and terrestrial habitats. In effect, few species can be considered exclusive inhabitants of
mangroves, although many are most commonly found associated with mangroves, and it is only
in this sense that they can be called mangrove fauna (Lacerda et al. 2001). Most of the animals
to be found in mangroves also appear elsewhere in other coastal ecosystems, and even in areas
hundreds of kilometers from the coastal area, as in the case of the scarlet ibis (Eudocimus
ruber) (Conde & Alarcón 1993), although some endemics have been recorded, such as the
Trochilidae birds (Lepidopyga lilliae and Amazilia tzacatl) the latter being responsible for the
pollination of Pelliciera in Colombia (Lacerda et al. 2001). The presence of a given species
depends on a number of factors, such as rainfall patterns, tides and life cycle stage. Hence the
difficulty of characterizing a "true" mangrove fauna. Whether transient or permanent, the
mangrove fauna is large and diversified. Over 140 species of birds and 220 species of fish and
hundreds of species of terrestrial and marine invertebrates can bring about high diversity
assemblages along mudflats and other intertidal habitats. 

From an ecological perspective, mangroves might be very important, since in barren areas that
otherwise are deprived of any vegetation, such as coastal strips in desertic areas, mangrove
woodlands can offer exceptional opportunities for resting, feeding, sheltering and nursing to
faunal elements. Due to the accelerated destruction of inland forests, mangrove stands have
become important sanctuaries and also could function as stepping-stones in the migratory
routes of various species, that other wise would be confined to small vegetational patches and
thus threatened to extinction. For instance, small populations of the vulnerable American
crocodile, Crocodylus acutus, inhabit mangrove swamps, which have become their main
remaining shelters in Venezuela. 

The inventory of animals that live in or are transiently associated with Venezuelan mangroves is
far from being over. Typical species are considered the yellow warbler (Dendroica petechia),
the bicolored conebill (Conirostrum bicolor), the clapper rail (Rallus longirostris), the
great-tailed grackle (Cassidix mexicanus), the spotted tody-flycatcher (Todirostrum
maculatum), the rufous crab-hawk (Buteogallus aequinoctialis), the crab-eating raccoon
(Procyon cancrivorus), the American crocodile (Crocodylus acutus) and the arboreal snake
(Corallus hortulanus). Yet, some of these species have also been reported in other habitats; for
instance, P. cancrivorus is common in savanna forests, far from mangrove stands, and D.
petechia can be found in grasslands and rain forests. Some invertebrates appear closely related
to mangroves and could be considered typical; for example, the mangrove tree crab (Aratus
pisonii) and the crabs (Goniopsis cruentata and Ucides cordatus), the bivalve (Crassostrea
rhizophorae) and many sponges. 

The avifauna of Venezuelan mangroves has been reasonably inventoried through surveys in
seven mangrove stands. A total of 141 species have been tallied, including resident,
opportunistic and winter migrant species (MARNR, 1986). The highest number in Venezuela (80
species) was totaled in the mangroves of the Orinoco Delta of the Guianan mangroves
ecoregion, while only 26 species have been recorded in the xeric mangroves of Laguna de
Cocinetas. Only four of these species are shared by all these localities: the common egret
(Casmerodius albus), the black vulture (Coragyps atratus), the brown pelican (Pelecanus
occidentalis) and the scarlet ibis (Eudocimus ruber). The latter, an endangered species in
several countries is quite common in Venezuelan mangroves. The Caribbean flamingo
(Phoenicopterus ruber) inhabits many mangrove swamps of Venezuela, where it can reach high
numbers. In 1990, 15,000 individuals were estimated in Los Olivitos Swamp, one of only four
Caribbean localities where this bird nests. The mangrove-bordered Laguna de Tiraya
(Paraguaná Peninsula, State of Falcón) is one of the feeding grounds for large flocks of
flamingos, which nest on the islands north of Venezuela. 

The endemic plain-flanked rail (EN) (Rallus wetmorei) is restricted to brackish lagoons and
mangroves along a small stretch of this ecoregion on Venezuela's north coast (Stattersfield
1998). Other endangered or vulnerable birds that have been observed in mangroves of this
ecoregion are the long-winged harrier (Circus buffoni), the dark-billed cuckoo (Coccizus
melacoriphus), the boat-billed heron (Cochlearius cochlearius), the striped-backed bittern
(Ixobrychus involucris), the masked duck (Oxyura dominica), the red-capped cardinal
(Paroaria gularis migrogenis) and the osprey (Pandion haliaetus), a boreal winter visitor.

Herons, egrets, terns and gulls are very abundant in Venezuelan mangroves. Also, the
magnificent frigatebird (Fregata magnificens), the roseate spoonbill (Ajaia ajaja), the anhinga
(Anhinga anhinga), and the jabiru (Jabiru mycteria) are common. Winter visitors are comprised
of the sandpipers (Calidris mauri and Micropalama himantopus), the blue-winged teal (Anas
discors) and several Nearctic limicolaes. Non-aquatic species can be occasionally observed in
mangroves including the orange-winged parrot (Amazona amazonica), the yellow-headed
parrot (A. ochrocephala), as well as dense populations of macaws such as Ara chloroptera and
A. severa. 

The crab-eating raccoon (Procyon cancrivorus) is one of the most common terrestrial mammals
sighted in these mangroves. Visitors from the surroundings ecoregions include the crab-eating
fox (Cerdocyon thous) and the cottontail rabbit (Sylvilagus floridanus). The spotted paca
(Agouti paca), the kinkajou (Potos flavus), and the Orinoco agouti (Dasyprocta guamara) are
also common. Among larger mammals, the jaguar (Panthera onca), the South American tapir
(Tapirus terrestris), the giant anteater (Myrmecophaga tridactyla), and the ocelot (Felis
pardalis) have been sighted, although their abundance is unknown. The red howler monkey
(Alouatta seniculus) and capuchin monkey (Cebus sp.) have been also observed. In the
waterways, aquatic mammals include the West Indian manatee (Trichechus manatus), the river
dolphin (Sotalia fluviatilis), the Amazon River dolphin (Ina geoffrensis) and the river otter
(Lutra sp.). Several of these species are included on IUCN status protection lists. 

The American crocodile (Crocodylus acutus) inhabits many mangrove swamps. In the San Juan
River, the spectacled caiman (Caiman crocodylus), an endangered species, is common.
Intruding marine species, such as the endangered Atlantic green turtle (Chelonia mydas), are
also sighted. 

Many commercial fishes, which sustain subsistence and artisan fisheries, are associated to
Venezuelan mangroves, including catfishes (Arius herzbergii, Cathorops spixii); snooks
(Centropomus undecimalis, C. ensiferus); mullets (Mugil curema, M. liza); and mojarras
(Diapterus plumieri, D. rhombeus, Gerres cinereus). Crustaceans, such as shrimp Penaeus spp.
and swimming crab Callinectes spp., can also be very important in mangrove-based fisheries
for humans and as a base for the food chain of mangrove ecosystems. 

In some localities of the Venezuelan coast where waters are crystal-clear, a variegate community
of sponges (33 species), tunicates (12), bivalves, and algae, can be found adhered to the
submerged roots of R. mangle (Sutherland 1980; Díaz et al. 1985, 1992; Orihuela et al. 1991). The
mangrove oyster (Crassostrea rhizophorae) used to be one of the most common species in this
community and a high-ranked staple for subsistence fishermen, but nowadays is almost totally
extinct due to overexploitation (Rodríguez & Rojas-Suárez 1995). This fragile ecosystem can be
wiped out due to the re-suspension of sediments (Orihuela et al. 1991) or a combination of low
temperatures and simultaneous plunges of salinity (Laboy et al. 2001).

Current Status 

Although mangrove woodlands have not been systematically monitored, some
evidences suggest dramatic losses during the last decades. In the Vegetation Map of
Venezuela, published in 1960 (Hueck 1960), mangroves are reported for most of
Lake Maracaibo perimeter, whereas their present distribution is more restricted. The
current cover of mangroves in this area has been estimated in 1/10 (Conde &
Alarcón 1993) of that reported by Hueck (1960). In other ecoregions the reduction
is also remarkable. In 1926, Henri Pittier described several mangrove forests where
nowadays only small patches are left. Similarly, in Adícora (State of Falcón),
Cumaná (Sucre), and at Píritu and Unare (Anzoategui), as well as along the coast of
the State of Carabobo, where historical records afford evidence of extensive
mangrove forests (Pittier 1926; Esteves 1980), they have disappeared almost
entirely or only small patches are left. The causes of such deforestation is unknown;
however, it is probable that in some of those areas semi-industrial exploitation was
carried out, or that small-scale extraction levels, to meet local needs, were constant
for decades. However, in a few localities, an inverse process has been observed,
such as in Caño Mánamo (Delta Amacuro), where mangroves have expanded at a
rate of 6 - 7 ha/year since 1965, when a cofferdam was built, leading to the
salinization of the formerly limnetic waters (Colonnello & Medina 1998). 

Mangroves have been specifically protected since 1974 when a Presidential Decree was passed
(Decreto Presidencial N° 110; Gaceta Oficial de la República de Venezuela N° 30.408). This
decree banned the direct destruction of mangroves and those activities that could threaten
them, including discharging of wasted waters, dredging of marine bottoms and dumping.
However, since 1991 a new Presidential Decree allows the option of intervention in those
coastal localities regarded as economically depressed, to allow some destructive activities
—that is, almost the entire Venezuelan coast (Decreto Presidencial N° 1843; Gaceta Oficial de la
República de Venezuela N° 34.819). In this second decree the possibility of intervention of
mangroves, with the administrative authorization of the MARNR as the only requisite, is open
and the need for an Environmental Impact Assessment (EIA) is discretionary. 

However, since Venezuela has an extensive system of protected areas, which embraces nearly
1/3 of its territory, many mangrove stands are within the limits of conservation units, which in
some cases have the rank of national parks and natural monuments (Conde & Alarcón 1993).
Among them, it is worthwhile mentioning Parque Nacional Morrocoy, P. N. Mochima, P. N.
Laguna de Tacarigua, and P. N. Archipiélago de Los Roques.

Types and Severity of Threats 

There is a protracted story of use and abuse of Venezuelan mangroves that at least
dates back to the pre-Columbian times when mangroves where extracted extensively
by the indigenous dwellers in Los Roques Archipelago, 100 km north of the
Venezuelan mainland (Amend 1992; Conde & Alarcón 1993). The exploitation
levels were so intense that mangroves disappeared from some islands. During the
XIX Century's second half, the Curaçoleans also exploited Los Roques mangroves,
mostly R. mangle, to be used as charcoal for the steamship's furnaces, and tannins
from the bark. Charcoal industries were installed in several of these desolate islands
(Amend 1992; Conde & Alarcón 1993). Recent examples of exploitation worth
mentioning follow. Including the extraction of mangrove trees for use as lumber in the
copper mines of Aroa (State of Falcón) by the English company Bolivar Mining
Association in 1930. As well as heavy mangrove extraction at the southern zone of
the Lake Maracaibo (State of Zulia), for exportation to Germany and the USA prior
to the Second World War. Also deforestation occurred during the 50’s, due to the
expansion of coconut plantations and oil exploitation, which affected the Lake
Maracaibo mangroves. Finally cutting of mangroves, for production of firewood and
charcoal, in the Limón River.

Cutting, farming and oil spills have provoked important mortality events in some mangrove
forests in the same area of the ecoregion. Currently, threats vary from one mangrove forest to
another, but, in general, the main impacts are furtive deforestation and more recently habitat
conversion due to urban, tourist and demographic growth, a common trend in countries in the
Caribbean basin (Ellison & Farnsworth 1996). Other activities, which could put extra pressure on
mangroves, are the creation and expansion of saltworks and aquaculture ponds, and oil spills in
the Orinoco Delta, where intense oil prospecting activity has been mounting during recent
years, and although not in this ecoregion is not far along the coast from the Grotto de Paria
(Conde & Alarcón 1993; Conde 2001). The establishment of shrimp farms to meet the consumer
demand for luxury shrimp has been a driving factor of massive mangrove losses in several Latin
American countries such as Ecuador but not in Venezuela where this industry is circumscribed
to a few places. 

In Laguna de Tacarigua, an estuarine coastal lagoon bordered by mangroves, sustained
massive deforestation occurred during 1920, 1927-1931, and 1953-1957. Other substantial
impacts are the detour of the Guapo River’s original course in 1964, that has brought about an
increase in the erosion and sediment transported towards the lagoon, provoking progradations
and, it is presumed, a decrease in fish catches. A compendium of the impacts on this lagoon
includes accumulation of tannins due to changes in the hydrodynamic patterns; dredging with
consequent modification of tidal intrusion patterns; furtive exploitation of crocodiles and
turtles; and overfishing with illegal fishing gear. More recently, resort development has put new
pressures on the mangroves. Exclusion of the western bar of the legal protection regime;
probable use of defoliants; and the alleged scarce interest of governmental entities to enforce
the pertinent laws must be added to the list. The pressures should be subdued, due to its
current National Park status however, during the 80's in the neighboring areas, several resorts
were built (Díaz & Zelwer 1985).

Justification of Ecoregion Delineation

Classification and linework for all mangrove ecoregions in Latin America and the
Caribbean follow the results of a mangrove ecoregion workshop (1994) and
subsequent report (Olson et al. 1996). 


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