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Vegetation
The unusual characteristics of the vegetation of the Ebro Delta have no
parallel elsewhere in Catalonia, not only in terms of the sparseness of the
plant communities, but also in terms of the quantitative potential. In the most
recent catalogue there are 515 species.
Areas of salty ground are mainly located at spots where
the delta meets the sea and where salinization is produced by the direct action
of the sea or by the salinity of the water table. The plants growing here have
high concentrations of soda in their tissues to enable them to maintain high
osmotic pressure and so withstand drying. These salty zones often include sand
dunes (known locally as "tores" or "muntells") which are
held together to a greater or lesser degree by vegetation.
In the first stage marram grass (Ammophila arenaria) and spurge (Euphorbia
paralias) establish themselves. Then other species appear: first a ring of Sporolobuspungens
and then above that sea daffodils (Pancratium maritimum) and, in
higher and more mature locations, rest marrow ( Ononis natrix), Thymelaea
hirsuta and Erianthus ravenae. In the northern part of the delta the
rare Limoniastrum monopetalum appears at the last stage.
Reed-beds are to be found over much of the delta in places
where the water table is very high and the land is usually waterlogged. Here the
most characteristic plants include reeds (Phragmites communis and Phragmites
communis isiacus) and large bindweed ( Con volvulus sepium). In
places where the water is deeper and remains for longer periods, sedge (Cladium
mariscus and Carex sp) and reedmace (Thypha sp) are to be
found. The last two species were formerly used to make chair seats, mats,
baskets, etc.
The riverside woods are the only forest community on the
delta. They are to be found along the banks of the Ebro where the land is higher
and water is always available. White poplar groves occupy the higher spots and
willows (Salix alba) the low-lying areas. Other common trees include the
alder, ash, elm and water-willow, as well as subspontaneous species such as
black poplars, eucalyptus, locust trees, plane trees and others like Lonicera
biflora ("lligabosc de riu") which are of particular interest.
Where the influence of the sea is strongest the wood becomes thinner and only
oleanders and tamarisks remain.
There is also spontaneous vegetation in the rice paddies. In
the small, fresh-water ponds known as "ullals", water lilies (Nymphaea
alba) grow alongside pondweed (Potamogeton sp) which causes serious
problems to agriculture since it invades the irrigation canals and even the rice
paddies themselves. In the rice fields, which during the greater part of the
year act as small ponds, we find, in addition to the plants already mentioned,
reedmace (Lemna sp, "llaponet de pato") and bladderwort. Other
species which have been considered the most representative adventitious plants
in the rice-field flora are: Ammania coccinea
("presseguera"), Bergia aquatica and Lindernia dubia
("aufabigueta").
The freshwater pools or ‘Ullals’ along the delta’s
junction with the higher land mass are caused by upsurgence of groundwater
checked by the delta groundwater. This water permeates the karstic limestone on
the inland plateau and flows underground through the limestone to the western
edge of the delta where it rises to form numerous small springs and pools, up to
50m in diameter and 8m deep. The water is clear and relatively constant
in temperature as a result of the continual upwelling. It has a relatively high
salt content (2,000RsIcm) but the pH remains neutral due to a high base ion
content. The Ullals have been greatly modified by human activity and much of
this water is channelled via ditches to irrigate the market garden and fruit
crops that occur in close proximity to this ample supply of fresh water.
Schematic Plan of Habitats on the Delta.
Fauna
The wide range of habitats and the mild, humid climate provide
conditions favourable to many invertebrates. Leeches were once so abundant that
the legs of those working in the rice fields needed to be well protected and
hundreds of thousands of the animals were exported to far-distant places every
year. Some species, such as the hemipteron Naucoris maculatus (know in
the delta as "cutimanya"), have almost disappeared while the
crayfish Pro camba rus sp is on the increase.
Mosquitoes are the most widespread and characteristic insects
of the delta. As a result a systematic fight against malaria, once an endemic
disease in the area, had to be undertaken, starting with the campaign launched
by the Mancomunitat (Catalan regional administration) in 1917. Lepidoptera
include a vast number of species which attack crops. Some are interesting,
however, from the biogeographical point of view like Chilo supressalis, Borbo
zelleri or the various species of the Danaus sp that are very
occasionally observed. Many interesting small species of crustaceans, such
as Apus cancriformis, live in the rice paddies.
With such an extensive range of entomological fauna, predators
are well represented: arachnids like Argiope lobata which inhabit sandy
areas, or many Odonata such as dragonflies (Libellula sp and Calopterix sp).
On summer nights any source of light draws veritable clouds of mayfly (Polymitarcis
virgo).
There are also many varieties of beetle which play a basic role
in the different ecosystems: Hydrophilus ("iaio") in the rice paddies
and their aggressive larvae known as "miquels", Pimeha in sandy zones,
Scarabeus, Anoxia, Amphimalon, Elenophorus, etc.
Among the reptiles and amphibians first mention must go to the
very numerous slow worms and Montpellier snakes. Turtles on the other hand are
rare and stripeless tree frogs (Hyla meridionahis) have almost died out.
Only the marsh frog (Ranaperezi) is still present, but in rapidly
declining numbers. Toads include the common toad and the western spade-foot
toad. The painted frog (Discoglossus pictus) is found here and there throughout
the delta. Sly rogue lizards (Podarcis hispanica) are common everywhere
while the spiny-footed lizard (Acanthodactylus erythrurus) and species
such as the large psammodromus lizard (Psammodromus algirus) scamper
about the beaches. There are few newts but Moorish and Turkish geckos (Tarentola
mauritanica and Hemidactylus turcicus) are found in buildings.
Fish are abundant on account of the important part played by
water in the delta and the various levels of salinity which range from the
insignificant quantities of salt in the small, fairly deep fresh water ponds
("ullals") to sea water, via the areas where the river flows into the
sea. Sturgeon and river lamprey have declined sharply, as have allis and twaite
shad (Alosa sp). On the other hand, new species such as the large-mouth
bass (Micropterus sabmoides), pike (Esox lucius), black bullhead (Ictalurus
melas) and wels (Siburus glanis) have appeared. Aside from these
rather rare species there are other more common fish including ,mullet,
cyprinids and serranids, hundreds of tons of which are caught each year. Eel
fishing is a tradition: 30-50 tonnes of eels and over 5 tonnes of elvers are
netted every year. The coast of the delta has won well-deserved fame for its sea
species, which include gilthead, ombrine, meagre and red mullet.
Owing to the size of the human population of the delta, large
mammals, such as the wild boar and badger, are only to be found occasionally,
but it is known that in days gone by there were red deer and roe deer. A few
rabbits still remain and red foxes are bred. There are still a few commcin
otters, hedgehogs and weasels, while brown rats, water voles, wood mice and
common European white-toothed shrews (Crocidura sp) are very widespread.
The formerly very large pipistrelle bat population has greatly declined.
Birds make up the most striking aspect of the fauna of
the delta and, far from constituting a merely local source of interest, are of
the utmost importance internationally, both in quantity and quality. It is
because of its role as a breeding ground for water fowl, waders and seabirds,
and as a stopping place for winter migrants that the delta has been defined as
an area of great significance in various conventions and has always been
classified in the ‘A’ category, as being in urgent need of protection.
The size of the bird population is particularly obvious in the
autumn months of October and November when the rice has been harvested and the
still waterlogged fields are invaded by many thousands of water birds which are
either migrating through or settling in for the winter. In November 1980 and
1981 over 75,000 ducks were counted in addition to 16,000 coots. The autumn
average is 53,000 ducks and 13,000 coots while in winter there are 26,000 ducks
and 5,000 coots. These figures represent over 90% of the waterfowl that winter
in Catalonia and about 10% of those that winter in the whole Iberian peninsula.
Interesting species are the shoveler duck (Anas clypeata) and
the widgeon (Anas penelope) though the greater part of the flocks is made
up of mallards (Anasplatyrhynchos). Other interesting species are
shelducks (Tadorna tadorna), gadwalls (Anas strepera), teals (Anas
crecca), and pochards (Aythyaferina).
Representatives of other groups of birds include: the marsh
harrier (Circus aeruginosus), short eared owl (Asioflammeus), bittern
(Botaurus stellaris), little bittern (Ixobrychus minutus), night
heron (Nycticorax nycticorax), squacco heron (Ardeola ralloides), cattle
egret (Bubulcus ibis), little egret (Egretta garzetta), grey heron-(Ardea
cinerea), greater flamingo (Phoenicopterus ruber), great crested
grebe (Podiceps cri status) , purple heron (A rdeapurpurea), water
rail (Rallus aquaticus) , Baillon’s crake (Porzanapusilla) ,
coot (Fulica atra), oystercatcher (Haematopus ostralegus), black-winged
stilt (Himantopus himantopus), avocet (Recurvirostra avosetta), collared
pratincole (Glareolapratinicola), slender-billed gull (Larus genei) ,
Audouin’s gull (Larus audouinii), and many others.
The bird population consists of 50,000-100,000 individuals
belonging to about three hundred species, 60% of the total number of species
found in Europe. The local nomenclature comprises some 250 names which makes it
one of the richest in the world.
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