Content uploaded by Afrah Saad Al-Mahfadi
Author content
All content in this area was uploaded by Afrah Saad Al-Mahfadi on Dec 08, 2020
Content may be subject to copyright.
Afrah Saad Al-MAhfAdi & Mohamed dAkki
Research Team on the Management of Wetlands, Zoology Department, Scientic Initute, Mohammed V University of Rabat, Ibn Battota
Street, BP 703, Rabat, Morocco. *(afrahalmahfadi@gmail.com)
Abract. Day after day, the wetlands of arid regions reveal new secrets about their importance, in terms of biodiversity as well as functions
and services. Yemen, a mountainous country surrounded by seas and a desert, has a ora and fauna heritage shaped by both African, Asian
and Palearctic inuences, and by a pronounced insularity that has enriched it with endemic forms of world intere. However, this biodiversity
has ill not received the attention it deserves, in terms of conservation. This lack prompted us to carry out a general diagnosis of the Yemeni
wetlands, providing the essential scientic elements allowing to initiate a suainable use rategy of these ecosyems. This diagnosis focuses
r on the main factors that control the functioning of these wetlands, then on the characteriics of these, presented for each type, according to
a usual classication scheme. While relating the richness already discovered in the seas and islands, this article provides arguments in favor of
the originality of the euarine and uvial ecosyems. The creation of a geodatabase, using satellite data (digital elevation model, precipitation,
thematic images) has made it possible to illurate the high density of the river network in Yemen, which is juied by the census of some 450
euaries, identied along a 2,500 km long coa. This base was enriched by cartographic inventories (in particular those of hydraulic dams
and towns and villages), reconructed from bibliographic and unpublished information, which also gives often non-cartographic information
on the diribution of habitat types (especially marine). The riking features of these ecosyems are highlighted through arguments borrowed
especially from orography, climate and human pressures. These are very old, but their recent increase is alarming, due to the rapid growth of
the population and of its needs in agricultural and urban, even indurial, water and space. Urgent solutions are essential to improve and protect
wetlands in Yemen, arting with research likely to lead to a complete classication and inventory of these ecosyems, but also to a better
characterization of their originalities and their functioning and of the pressures they undergo.
Key words: wetland, ecology, human pressures, conservation, GIS, Yemen.
Résumé. Jour après jour, les zones humides des régions arides révèlent de nouveaux secrets sur leur importance, tant au niveau de leur
biodiversité que de leurs fonctions et services. Le Yémen, pays montagneux encerclé par des mers et un désert, possède un héritage oriique
et fauniique façonné par des inuences à la fois africaines, asiatiques et paléarctiques, et par une insularité prononcée qui l’a enrichi de
formes endémiques d’intérêt mondial. Pourtant, cette biodiversité n’a toujours pas reçu l’attention qu’elle mérite, en termes de conservation. Ce
manque nous a incités à réaliser un diagnoic général des zones humides de ce pays, qui fournit les éléments scientiques essentiels permettant
d’initier une ratégie d’utilisation durable de ces écosyèmes. Ce diagnoic porte dans un premier temps sur les principaux facteurs qui
contrôlent le fonctionnement de ces zones humides, puis sur les caractériiques de celles-ci, présentées pour chaque type, selon un schéma
de classication usuel. Tout en relatant les richesses déjà découvertes dans les mers et les îles, cet article donne les arguments en faveur de
l’originalité des écosyèmes euariens et uviaux. La conitution d’une base de données géospatiale, à partir de données satellitaires (modèle
numérique de terrain, précipitations, images thématiques) a permis d’illurer la forte densité du réseau uvial du Yémen, laquelle e juiée
par le recensement de quelque 450 euaires, identiés le long d’une côte longue de 2500 km. Cette base a été enrichie par des inventaires
cartographiques (notamment ceux des barrages hydrauliques et des villes et villages), reconitués à partir de sources bibliographiques et
inédites, lesquelles donnent aussi des informations souvent non cartographiques sur la diribution des types d’habitats (surtout marins).
Les traits marquants de ces écosyèmes sont mis en exergue via des arguments empruntés surtout à l’orographie, au climat et aux pressions
humaines. Celles-ci sont très anciennes, mais leur augmentation récente e alarmante, en raison de la croissance rapide de la population et
de ses besoins en eau et en espace agricole et urbain, voire induriel. Des solutions urgentes pour améliorer et protéger les zones humides au
Yémen sont indispensables, à commencer par les recherches susceptibles d’aboutir à une classication et un inventaire complets de ces milieux,
mais aussi à une meilleure caractérisation de leurs originalités et leur fonctionnement et des pressions qu’elles subissent.
Mots clés: zones humides, écologie, pressions humaines, conservation, SIG, Yémen.
INTRODUCTION
Wetlands are well known as rich reservoirs of biodiversity
and as sources of socioeconomic services and of knowledge
(Stuip et al. 2002, MEA 2005, Bruland 2008, Erwin 2008
and McCartney et al. 2010). However, these ecosyems are
exposed to continuous loss, mainly in arid regions (Sheppard
et al. 1992, O’Connor & Crowe 2005 and Duy 2006), due
to human expansion, whose needs in terms of land and water
are continuously growing. These losses are eimated at 50%
since 1900 (Davidson 2014), and have been amplied by
climate change and recurrent droughts (Barnard & Thuiller
2008, Elasha 2010 and Crooks et al. 2011). Therefore, wetland
protection and reoration become highly prior in national
policies (Hushulong 2012, Parry et al. 2007 and Erwin 2008),
more especially in arid countries. These rategies mu
be based on a solid knowledge of these ecosyems, more
especially of their main functional characteriics.
In Yemen, a mountainous country extending on 527,970
km², wetlands are supposed to hold a rich biodiversity due to
their high variety and to the original context of their genesis
e-ISSN : 1114-6834
Bulletin de l’Institut Scientique, Rabat, Section Science de la vie , 2020, n° 42, 31-42
Scientic elements for a Yemeni wetland conservation rategy:
overview of the main factors explaining the diversity and characteriics of wetlands
Éléments scientiques pour une ratégie de conservation des zones humides du Yémen:
aperçu des principaux facteurs expliquant la diversité et les caractériiques des zones humides
32 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
and evolution (variable orographic and climate situations,
long coaline overlapping three dierent seas, high number of
islands, etc.). This richness is well marked by the biogeographic
situation of this country at the transition zone between three
major domains (Afrotropical, Oriental and Palearctic) and on
major routes of waterbird migrations. Besides these aspects,
the Yemeni wetlands evolved in an insular context, since they
belong to a mountainous area surrounded by seas and desert
and to a high number of islands dispersed in a semi-closed sea.
This evolution explains the high rate of endemism highlighted
in dierent Yemeni wetlands.
In Yemen, wetlands are endorsing heavy and rapid
degradations (EPA 2009, Al-Mahfadi & Dakki 2019),
whereas they provide mo of the survival resources to the
population. In order to design a good conservation rategy for
these wetlands, we gather in this article the mo signicant
information necessary to provide a good underanding of the
conguration and the sensitivity of these ecosyems.
MATERIAL AND METHODS
This article was essentially based on satellite and
published data, supported by our unpublished eld knowledge
of the Yemeni wetlands and by interviewing research and
adminirative competencies.
Mapping
Mapping of the natural context concerns essentially
orography, hydrography, geology and rainfall, which play
a decisive role in wetland conguration. This work was
accomplished, using GIS tools (ArcGIS) and Remote Data,
mainly the Digital Elevation Model (DEM) of the country,
extracted from ASTER GDEMV2 (Advanced Spaceborne
Thermal Emission and Reection Radiometer) and the
rainfall satellite data for the period 1981-2014 extracted from
CHIRPSV2 (Climate Hazards Group InfraRed Precipitation
with Station data). Data were compiled and assembled by
watersheds, with the knowledge that wetlands conguration is
mainly dened by their watershed characteriics. In addition
to natural factors, major human activities (e.g. damming and
agriculture) are evocated and discussed, in a way to and out
their hiorical and actual impacts on wetland characteriics.
Field knowledge and interviews
Although unnoticed in the article, intensive work on
wetland identication and location allowed an overview of
exiing wetland types in the country and an eimate of their
representativity. This inventory was mainly focused on coaal
and marine wetlands but also on articial reservoirs, knowing
that lacurine wetlands are quite absent in the country.
Considering our eld knowledge and observations, they
concern more than fourteen wetlands, which are moly on the
coa, in addition to some mountainous rivers. Moreover, the
remote and eld data were reinforced through interviews with
academicians in the Faculty of Agriculture (Environmental
Department) and adminirators in dierent initutions:
Directorate of Irrigation and Dams (DID), Environmental
Protection Authority (EPA), Regional Organization for the
Conservation of the Environment of the Red Sea and Gulf of
Aden (PERSGA), Food and Agricultural Organization (FAO),
the Ramsar Convention, etc.
RESULTS
Main factors conguring Yemeni wetlands
Using GIS tools and satellite resources, we provide
the mo useful information for a good underanding of
the abundance, the diversity and the classication of the
Yemeni wetlands. In addition to some classical results, this
analysis highlighted some originalities that should be taken
in account in designing an eventual conservation rategy of
these ecosyems or in planning researches or inventories or
monitoring programs on wetlands.
Oro-hydrographic context: a mountainous country with a
dense river network
The simplied oro-hydrographic map of Yemen (Fig. 1),
generated from a DEM, shows a mountainous country, with
highe altitudes (over 2,000 meters) in its weern and
South-weern sides, including the highe mountain of the
Arabian Peninsula (Jabal Al-Nabi Shu’ayb, at 3,666 meters).
Further ea, the mountains fall away in progressive eps
to the North-Ea (Rub’a Al-Khali) and the Ea, through a
large plateau, where altitudes are around 700-1,000 meters.
In the Mountain Massif, slightly parallel to the Red Sea,
landscapes are marked by eep slopes and deep valleys, with
relatively frequent volcanic craters. This topography plays
in favor or a dense riverine network, mainly permanent and
semi-temporary, whereas these ecosyems are intermittent
or ephemeral in the large eaern Plateau and Desert areas.
Plains are diributed along the weern and Southern coas
of the country and along its northern boundary with Oman.
They are relatively narrow (less than 30 km wide), slightly
sloppy, with highe altitudes around 200 meters. They are
also dominated by alluvial landscapes (EPA 2004b) with
several large and dry valleys.
Marine context: high representativity of coaal and island
ecosyems
The 2,500-km coaline of Yemen belongs to three dierent
seas (Red Sea, Golf of Aden and Arabian Sea) with dierent
hydrological and ecological conditions. The use of satellite
images with some exiing maps revealed a coaal landscape
dominated by long rocky clis with variable height, and a
minimum of 450 euaries, which corroborates with the high
number of watersheds. The weern and south-weern margins
of the country, overlooked by high mountains, show several
large euaries, mo of them being often separated from the
sea by natural sediment dams. Between these euaries exi
also many small river mouths, with coaal small watersheds
that occasionally ow, whereas these rivers mouths are often
separated from the sea with sediment thresholds. These two
kinds of euaries exi also on the Arabian Sea side, but this
coa has the particularity to receive the large euary in the
country, generated by Wadi Hadramawt, which drains the
large watershed of the Arabian Peninsula.
Yemen is also well known for its numerous islands
(more than 186), mo of which (more than 112 volcanic
islands) being in the Red Sea. These reliefs enrich the marine
environment in shallow rocky habitats occupied by very rich
communities, whereas their terrerial biodiversity is highly
marked by endemism, which has been clearly demonrated in
the bigge islands (Tardelli & Baldini 2000 and RAP 2004),
as Socotra (3625 km²) in the Arabian Sea and Kamran (108
km²) in the Red Sea.
Geological context: basic data explaining ecological
diversity and endemism
Geology can aect wetland diversity and abundance through
dierent aspects (petrography, permeability, hiory, etc.),
besides its determinism of the orography and the hydrology.
A simplied geological map of Yemen (Fig. 2) drawn
according to an exiing scheme (Van der Gun & Ahmed
1995), shows a relatively high petrographic diversity. The
main rocky outcrops date from the Mesozoic and continues
33
Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
until now (Geukens 1966); the basement of this cover, which
ushes in limited mountainous areas, consis of Precambrian
impermeable cryalline rocks (amphibolite’s, migmatites,
gneiss and granite), Cambrian sandones and Permian shale.
Until the middle of the Mesozoic, Yemen remained attached
to the African continent, before being immersed from Jurassic
to Cretaceous, when great limeone series were generated,
conituting a large part of the high mountainous outcrops.
In the middle of the Tertiary, tectonic movements led to
the opening of the Red Sea and the Gulf of Aden and to the
overelevation of the Yemeni mountains, simultaneously to
an intense volcanic activity (basaltic deposits), that marked
a large part of the weern mountain relief. The exiing
limeone series were surmounted by Tertiary widespread
river deposits (sandone) and by Paleocene deposits (thick
layer of limeone) that form the Jawl plateau in the eaern
half of the country.
During the Quaternary, the volcanic activity resumed locally
in the weern half of the country. During the wet quaternary
periods (e.g. la glaciation), an intensive erosion happened
in mountains, creating remarkable deep valleys and abundant
alluvial sediments that conructed the main coaal plains
and the platforms of Rub-Al-Khali and Hadramawt valley
(Mohammed et al. 2018).
From this hiory, it could be concluded that both mountainous
and coaal wetlands exied in Yemen since the Tertiary
and their actual biodiversity survived under the Quaternary
climate oscillations. The impermeable cryalline subratum
is generally favorable to groundwater oring, mainly
during the Quaternary wet periods, and to springs and rivers
abundance. During the Cenozoic, the inland wetlands have
evolved in insular environment (country between seas and
desert), which generates numerous endemic forms among
aquatic biodiversity, as well as in islands.
Climate: a determinant factor of the hydrology ress in
wetlands
Yemen lies within the sub-tropical climatic and the
northern retches of the tropical zone (Elasha 2010). It is
submitted to the monsoon regime, with two rainfall seasons
(March-May and July-September), separated by a dry season
(October to February), with some irregular precipitations in
the weern mountains (Fig. 3).
Annual rainfall, calculated using satellite data for
the period 1981-2014, varies from We to Ea between
1500 mm/year, mainly recorded in the high mountainous
dirict of Ibb, and less than 100 mm/year in the eaern and
northern deserts (Fig. 4). Mo of the country, including
medium altitude slopes, is under more or less dry climate (Van
der Gun & Ahmed 1995). The rainfall trend, as illurated by
four watershed examples chosen in dierent regions (Fig. 5),
is slightly negative, characterized by high interannual
uctuations and frequent droughts.
In concordance with the sunshine duration (6-9 hours/
day), the evapotranspiration rate is regularly high, with large
spatial variation (NBSAPY 2005): 1500-2500 mm/year in the
weern mountains and 1800-2700 mm/year in the coaal
zones and foothills, whereas higher values (2000-3500 mm/
year) are recorded in inland arid areas.
Given this climate, inland wetlands should be frequently
submitted to hydrologic ress during a large part of the year
(EPA 2004b). Therefore, intermittent wadis and ponds are
predominant and very few and small lakes are known in the
volcanic crater of Bir Ali in Balhaf area of the Arabian Sea
as well as on Al Zubair Group in the Red Sea. Due to the
recent droughts and the high number of articial dams, the
river waters generally do not reach the sea, in the sense that
their low courses are ooded only after violent rain showers.
Therefore, mo of the euarine ecosyems are intermittently
open/closed (sensu Whiteld 1992), due to sediment barriers
Figure 1. Oro-hydrography and main geographical regions of Yemen.
34 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Figure 2. Simplied geological Map of Yemen (Van der Gun & Ahmed 1995).
Figure 3. Monthly variation of precipitations in Yemen (Hadramawt watershed).
35
Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Figure 5. Rainfall trend in Yemen: annual average precipitations (1981-2014) in four rivers.
Figure 4. Spatial diribution of the annual rainfall in Yemen.
36 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
mainly built by sea and wing dynamics, and behave like North-
African euarine gueltas (Dakki et al. 2020), as brackish to
hypersaline agnant water.
Human context: heavy pressures on wetlands, amplied by
frequent droughts
Human activities conitute a key issue in conservation
rategies, since they play a decisive role in wetland loss,
more especially in arid emerging countries that know a rapid
increase of their population, while recurrent droughts deplete
their water resources. In Yemen, the population increased
ve-times between 1955 and 2019 (Fig. 6); its growth rate
regiered between 2014 (CSO 2014) and 2016 (Worldmeters
2019) is 3.2% (i.e. 26.25 to 27.58 million), with alarming
values in major cities, which have absorbed large numbers of
rural emigrants. The average population density is about 55.6
people/km² (CSO 2014), with large spatial variation (e.g. 1.1
and 388 people/km2 respectively in Almahra and Ibb regions).
This explosive growth means a high increase of both water
demand and pollution; however, the decit between available
resources and consumption is continuously increasing, i.e.
400,000 m3 in 1990 and 900,000 m3 in 2000 (Ward et al. 2000).
In this arid agricultural country, thousands of water
derivations have been managed for millennia along the
riverbanks and from springs; their increasing number often
dry up the riverbeds on long diances. Damming was also a
traditional approach in this country, as illurated by the old
Ma’rib dam, but the increased water demand has forced the
government to adopt and intensied damming politics. The
number of dams has increased concomitantly to recurrent
droughts, from 60 in 1970 to 240 in 1990 (Charbonnier 2009),
exceeding now more than 600 dams (MAI 2016), mainly
concentrated in the weern highlands of the country.
Similarly, the groundwater exploitation has led to their
rapid depletion, mainly in the weern part of the country
where the great majority of the population resides (NWRA
2005). The decrease of the water table level was eimated
between 1.0 and 3.0 meters/year in Al-Hodidah, Ta’iz and
Amran regions, but in Sana’a region, it reached 6-8 m/year.
Recently, the water extraction was extended to fossil deep
aquifers, which have been also depleted in some zones, such
as Amran and Ta’iz basins, after what agriculture has been
opped.
This evolution is ecologically translated into a recurrent
hydrologic ress in all wetlands depending from riverine
waters, mo of them being frequently dried, sometime for
several years. As mo of the human agglomerations are
close to rivers (Fig. 7), water pollution is ill increasing due
to continuous growing of urban euents and to dierent
development poles. Being the nal recipient of watersheds,
euarine wetlands are certainly suering from all these
impacts.
Status of the major wetland types present in Yemen
Considering the former description, we mu conclude
that wetlands are relatively diversied in Yemen, despite the
aridity of this country. This diversity is presented hereafter,
through a simplied classication borrowed from the
Ramsar Convention scheme (Navid 1989), where all factors
described above are reected. However, this presentation is
moly focused on their characteriics, representativity and
diribution in the country.
Coaal and marine wetlands
As formerly explained, Yemen coaline is 2,500 km long
and belongs to three dierent seas, with dierent sizes, hydro-
sedimentary dynamics and ecological factors: (1) the Arabian
Sea, which is largely open on the Pacic Ocean and its coaal
wetlands are submitted to its high hydrodynamics; (2) the
Gulf of Aden, where salinity increases from Ea (35.5 mg/l)
to We (37.5 mg/l) and the coaal wetlands are inuenced
by upwellings (surface waters relatively cold); and (3) the
Southern Red Sea, which width decreases from the North
(270 Km) to the Bab Al-Mandeb retch (20 Km). This latter
regulates the water exchange between this sea and Gulf of
Aden, isolating the Red Sea ora and fauna from the other
marine communities and enriching them in endemic forms
(EPA 2009).
Figure 6. Yemen population growth during 1955-2020 period (Worldmeters 2019).
37
Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Figure 7. Superposition between human habitat and hydrographic network, an illuration of human pressures on wetlands
(e.g. Wadi Al Mahiam).
Coaal open waters
Considering the former introduction, tidal and subtidal
shallow waters in the three seas dier by their hydrodynamics,
with clear decrease of the tide amplitude, depth and bottom
slope from the Arabian Sea to the Red Sea.
Coaal beaches
These ecosyems include sediment coaal lands, at
or slightly sloping, submitted to sea tides and waves; they
slightly vary in pace, mainly in relation with the coa slope
the tide amplitude and the orm waves. In the weern half
of the country and Socotra, mo of the coaline is close to
foothills and its beaches are more or less narrow and sloping,
frequently enriched with coarse sediments (gravel, pebbles
and blocks), mainly when they are close to river mouths. Pure
sandy beaches are relatively rare, but more frequent on the
Arabian Sea coa.
Sea clis
These habitats correspond to vertical or sub vertical coaal
lands, beaten by sea waves and spray. These landscapes,
with variable height (generally exceeding 20 meters), have
remarkable length, although they are frequently interrupted
by euaries. High sea clis play an important ecological role,
mainly as refuges for particular forms of ora and fauna; this
importance is amplied in Yemen by the high rate of endemic
species (Sheppard et al. 1992).
Euarine syems
These habitats correspond to sea inlets (lagoons and river
mouths), relatively sheltered from marine hydrodynamics and
more or less fed with inland waters. As the country is mainly
mountainous, it holds a dense river network that generated
more than 450 euaries. Considering their extension, 89 %
of them have an area of less than 50 ha; the remaining 47
euaries that exceeds 50 ha are mainly in the Red Sea (43%)
and the Gulf of Aden (36%). Sixteen euaries exceed 200 ha
and are also on the Red Sea side, and only three of them are on
the Gulf of Aden or the Arabian Sea coas. This latter receives
the large euary (555 ha) in the country, Wadi Hadramawt
(or Almasilah). The morphology of euaries reects the
impact of large oods that happened during pa wet periods,
including the Holocene. Actually, the riverbeds are frequently
dried up for several weeks or months, even for several years,
and mo of the river mouths took the form of a anding water
pond. Therefore, they can be classied as intermittently open/
closed euaries (Whiteld 1992), due to sediment obacles
built between the sea and the river by marine hydrodynamics,
sometime supplied by wind. However, the river oods
transport coarse materials, enriching the euarine subrate
with gravels and pebbles, even in blocks, which contribute to
consolidating the sediment dam. Outside of these oods, the
ponds will be enriched with ne materials, including organic
matter produced by biological processes, more especially in
Red Sea inlets. Sandy habitats seem to be more abundant
in the eaern half of the country (about 115 euaries of the
Arabian Sea).
This functioning scheme was well described in similar arid
zones, as in North Africa (Dakki et al. 2020), where they are
named ‘euarine gueltas’, in Southern Asia (Ranasinghe &
Pattiaratchi 2003), Auralia (Roy et al. 2001), New Zealand
(Lill et al. 2012) and more especially in South Africa, where
they conitute more than 70% of the euaries (Perissinotto et
al. 2010, etc.) and beneted from abundant udied (Nozais et
al. 2005, James et al. 2007, Snow & Taljaard 2007, Taljaard
et al. 2009, Whiteld et al. 2012, Tweddle & Froneman 2015,
Scharler et al. 2020, etc.).
Lagoons are intended here as sea inlets that are not fully
open to the sea and receive few inland waters. The whole
information used in this udy is based on satellite images
and punctual eld visits, noting that the ecological udies
dedicated to these ecosyems (EPA 2009) concern mainly
Kalnsia and Ditwah lagoons on Socotra coa and the Mocha
Lagoon in Ta’iz region (Red Sea). These ecosyems are
38 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
mainly represented on the Red Sea coa, where 26 inlets
could be identied as lagoons, the two other seas show only
six small inlets, the large one (Almahra-Arwet) having a
maximum surface of 65 ha. Some large shores, developed in
the Gulf of Aden and the Arabian Sea coas, show on their
inland side a sebkha like landscape, which dries out seasonally
and form va salty ats, with scattered halophytic plants or
blue-green algal crus (EPA 2013).
Islands
These small lands entirely surrounded by sea waters, are
particularly numerous along the Yemen coas, about 186
islands (Al-Najar et al. 2008). The bigge Islands in the
Red Sea are Zugur groups (120 km²), Kamaran (108 km²)
and Big Hanish (65 km²), Socotra is however the large
Yemeni island on the southern margin of Arabian Sea (3,549
km²). It holds diverse ecosyems, including terrerial
habitats, and a rich ora and fauna, with high endemism rate
(Tardelli & Baldini 2000, Al-Saghier 2002b …). Islands are
ecologically remarkable by their coaal and marine habitats
(clis, beaches, mangroves and coral beds), which are treated
separately in this article.
Mangroves and Seagrass
These tropical sea-coa formations are common in the Red
Sea, where they were identied in more than 130 km of coas;
they are organized in discontinuous belts, with some large
formations in the north-weern coa of Yemen (e. g. Midi
to Alluhayah). More to the South (e.g. Al-Urj to Al-Hodidah
or Bab Al-Mandab areas), these habitats are organized in
well conserved thin belts around islets, but sometimes highly
fragmented into small patches. Furthermore, the seagrass
diribution is quite-continuous along the Red Sea coa
(Barratt et al. 1987), while they are rare in the Gulf of Aden
and the Arabian Sea.
Coral reefs/beds
These habitats make the Red Sea among the mo famous
coral areas in the world, both by their diversity, in terms of
number of species and communities, and by their extension.
This sea contains about 260 species of hermatypic corals,
organized in large but discontinuous patches (Kemp 2000
and Sheppard et al. 1992). In Socotra Island, coral reefs are
remarkable, while they are relatively rare in the Gulf of Aden.
In addition to its high richness, the Yemeni Coral fauna is
mainly remarkable with its high rate of endemism both in
Socotra and the Red Sea (Sheppard et al. 1992).
Inland wetlands
River (Wadi) syems
This category includes all types of running waters,
the local term Wadi refers to ‘surface drainage channels
essentially characterized by intermittent ow’ (Hall et al.
2008). These ecosyems are very widespread in Yemen, due
to its mountainous reliefs (more than 450 watersheds). Mo
of them belong to nine wide watersheds, draining the weern
mountains and southern slopes. The appreciable rainfall at
these highlands ensures some regular ow to the mountainous
wadis, but these acquire intermittent regime when moving
downream, taking then the form of a chain of separate ponds.
Their waters arrive to the sea or to the desert only during high
oods (NBSAPY 2005), which oods carry a great quantity
of alluvial deposits, with variable sizes, allowing agriculture
on hillside terraces and riparian farms, even in high altitudes.
Surface water temperature, as a highly determinant
ecological factor in the longitudinal organization of river
communities, have been poorly udied, but punctual
measures show high values: i.e. 27 to 35°C (exceptionally
40°C) at dry season between elevations of 230 m and 1254 m
(Minissale et al. 2007). These values translate a determinant
role of insolation combined to ow lowering in warm running
waters. Consequently, as demonrated in other dry lands
(e.g. Dakki 1987), the Yemeni river communities are exposed
during dry seasons to extreme thermal conditions in addition
to the severe hydrologic ress.
The global warming, expressed in Yemen by frequent
droughts, generates heavy loss in running water’s
biodiversity. On another hand, the riverine natural vegetation
was dramatically deroyed in medium altitudes, due to the
excessive occupation of the riverbanks. In the mountains, as
well as in the plains, dams contribute to this regression by
drying these riverbanks for long periods. However, vegetation
is ill relatively abundant at several canyons, that have been
dug during the Quaternary pluvial periods (i.e. Hadramawt,
Ayhaft, Dirhur, Al-Guedam north of Sana’a) and continue to
deepen with violent oods. Because of their inaccessibility,
canyons therefore play a signicant role as reservoirs for
aquatic biodiversity (Scholte 1992).
Springs
These small habitats correspond generally to groundwater
emergencies, characterized by a low thermal amplitude and
low concentration of organic matter. They are abundant in
the weern highlands and are responsible for the permanent
and semi-permanent ow of some torrents. Mo of these
habitats have been transformed in a way to facilitate their
use for drinking and irrigation. Thermal springs are relatively
widespread in the weern mountains and the southern
littoral; at lea 65 sites are known, moly in the Tertiary
and Quaternary volcanic areas (Kamra 2006 and Al Kubati
et al. 2017). Their water temperature ranges between 40°C
and 96°C (Minissale et al. 2007), giving them low chance
to hold living communities, except some endemic phreatic
invertebrates. The other springs, considered in geological
literature as cold, have hot waters (30-35°C), in the sense
that they are very selective of living communities. The lowe
temperatures measured in springs and wells (21-27°C) are
favorable to subtropical thermophilic fauna rather than to the
Palearctic one (Dakki 1987 and Abd El-Mageed et al. 2013).
Lakes and ponds
In Yemen, freshwater lakes are practically absent, mainly
because of the scarcity of large natural depressions and the
dominance of the arid climate. However, intermittent pools
are signicantly frequent, as a consequence of the dry climate
and intensive evaporation. The crater lake of Bir Ali near the
coaal village of Bir Ali, is the only natural permanent lake;
its brackish water reaches 28°C in dry season, indicating no
volcanic inuence (Mohammed et al. 2018).
Articial wetlands
Throughout hiory, wetlands of Yemen as well as in
other arid countries, have provided essential services to the
local populations, thus their management and transformation
date back to thousands of years. The traditional uses of these
ecosyems were moly suainable, in the sense that they
generate soft modications. However, the recent exponential
increase of the population intensies the use of ecosyems
with modern techniques that led to their deep transformation.
39
Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Articial reservoirs
It includes large articial reservoirs and small ponds, mainly
created for agriculture, domeic use and aquifer recharge.
According to the Miniry of Agriculture and Irrigation, 615
dams have been conructed in the upper lands until 2015,
with dierent sizes and objectives. Mo of the dams are in the
weern and central parts of the country, where more than 77%
of the population lives. It should be reminded that Yemen has
a long hiory in river damming and its ancient civilizations
(like Ma’in, Saba and Himyar, which exied before the 12th
century BCE) were mainly dependent of the great dam of
Ma’rib, in such a way that their civilization disappeared when
this dam collapsed. The new Ma’rib reservoir has a capacity
of 400 million m3, while the others reservoirs have a total
capacity of 62.5 million m3 (MAI 2013). This means a very
high domination of small reservoirs that are relatively benec
at lea in terms of recharging supercial aquifers (FAO
1997). Mo of these reservoirs have small extension and are
in deep valleys; therefore, their capacity to hold waterbirds is
supposed to be relatively low (Al-Safadi 1995); many other
reservoirs are exposed to intense insolation, which is highly
favorable to evaporation and to eutrophication with frequent
algae blooms (Charbonnier 2009).
Oases
These ecosyems, highly important in dierent
international conventions, are considered as articial because
of their absolute domination by human habitats and activities.
In Yemen, as in other dry and desert countries, oases take
place on large river banks that benet from renewable
fertile soils (provided by the river) and from both surface
and underground waters, making them as key agricultural
lands. Oases have been managed for millennia; however,
their vegetation and hydrological regime have recently been
deroyed and depleted. In Yemen, mo of the cities were
originally in oases, as well as numerous villages that are
actually growing up. However, the luxurious vegetation of
oases, generally articial and dominated by palm trees, oers
very attractive habitats to breeding and migrating birds. The
presence of large oases in Yemen, both at foothills and in
mountains, amplies this role (Almhab & Busu 2011).
Sewage wetlands
Waewater treatment arted only recently in Yemen,
and less than twenty sewage ations have been created, but
this number is expected to increase. Some famous treatment
areas (as Ta’iz, Aden, Dhamar …) created large mud pans
and marshes where several species of ora and fauna exi,
including waterbirds. For example, sewage ponds in Aden
including inter-tidal mudats and a retch of sandy beach and
salt pans, are considered as important wetlands especially for
migrant birds (e.g. Shobrak et al. 2003).
Channels
These articial wetlands are very abundant, but small
and traditionally concentrated in mountainous valleys, where
they ensure domeic waters and more especially irrigation
water for small agricultural terraces (Mohammed et al. 2018).
Nevertheless, some large channels exi, mainly located in
Coaal areas, the mo popular one being in Mukalla city.
Salt pans
In Yemen, salt exploitation played an appreciable role in
improving local people income, particularly on sea borders.
Several salt pans were managed on the coas of the Red Sea
and the Gulf of Aden, the mo famous salt production being
in the Al-Hodidah region (mainly Alsaleif coa). However,
salt pans are progressively abandoned since the 1990s and
their number is decreasing in the whole country (Al-Najar
et al. 2008), reducing their function as habitats for migrant,
wintering and breeding waterbirds.
Several euarine habitats were transformed, at lea
partly, in saltpans that are treated here as articial ecosyems,
although their area has been accounted in the euaries.
DISCUSSION: MAJOR ORIGINALITIES OF
YEMEN WETLANDS
The r major output of this overview concerns the high
diversity and abundance of the Yemen wetlands, which have
been demonrated and juied. This result, unexpected in an
arid country that evolves as a large island, is mainly explained
by the diversity of orographic and marine situations and by
the country’s position at the crossroads of three biogeographic
regions. Indeed, hundreds of wetlands have been identied,
dominantly in riverine, marine and coaal domains, while
lacurine syems are quasi-absent.
Rivers hold, as well as in other arid zones, a high number
of permanent puddles, named gueltas in North-Africa (Dakki
et al. 2020), which hydrology is rongly linked to large oods
that alternate with long droughts. These habitats extend to the
river mouths, as these are in majority intermittently open/
closed euaries (Whiteld 1992, Whiteld et al. 2012).
This udy focused also on the remarkable endemism that
gives a high patrimonial importance to the ora and fauna of
the country. Several udies focused on endemism in islands
and in the Red Sea, but this aspect remains unudied in
running waters and springs, habitats as endemism hotbeds in
arid zones (e.g. Dakki 1987). Indeed, the country evolves at
lea since the early Quaternary in insular context, amplied
since the Arabian Desert appears.
In addition, Yemen is located in a major crossroads of
bird migration between Eaern Europe and Weern Asia to
the North and Eaern Africa to the South. The data on this
aspect are ill relatively poor (Porter 1993, Shobrak 2003, Al-
Obaid et al. 2017), but the habitat composition of the coaal
wetlands and articial reservoirs permit to suppose that they
conitute determinant aging habitats for a high number of
waterbirds.
Despite this importance, the Yemen wetlands undergo
heavy human impacts. In fact, this country hiorically
conituted a land of agriculture and shing, mainly thanks
to its river waters and seas. These were widely used since
millennia, but this use became recently unsuainable because
of an exponential population growth, combined with frequent
droughts, political inabilities and a conservation policy
context very lacunar.
The precipitation trend is until now clearly negative and
don’t seem improving in the near future; this means that the
water scarcity is the major challenge that will face an eventual
conservation rategy for wetlands. Actually, river damming
and derivation and groundwater pumping are highly prior in
facing this scarcity, but they transformed hundreds of river
sectors, including euaries, and impoverished their aquatic
biodiversity.
CONCLUSION
The present article oers a large overview of the wetland
diversity and characteriics in Yemen, and describes the
natural and human factors that determine these characteriics,
including dysfunctions. Facing the great rarity of academic
udies, this work was achieved mainly thanks to satellite
data, technical reports and unpublished information.
40 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
With this overview, it becomes easy to launch a national
wetlands’ inventory, as a major ep in the assessment of
their patrimonial values, their services and their dysfunctions
and in planning their management, whether for conservation
purposes or for suainable use.
Compared to the whole Arabian Peninsula, Yemen shows
the highe richness in wetlands and should therefore play a
major role in conserving the regional aquatic biodiversity.
This role is essential especially because of the originality
(in terms of richness in endemics) of its ora and fauna. It is
therefore clear that a high priority should be given to wetland
conservation in this country. Indeed, despite their great value,
these ecosyems beneted from poor conservation eorts
(Harvey 1999, Shobrak et al. 2003, Al-Sagheir 2002b …) and
few biological udies (i.e. Almhab & Busu 2011, Al-Safadi
1991, 1992, 1995), meanwhile they remain under heavy
human and natural pressures.
In the actual political context, marked by inabilities
that amplify poverty and juify more water use, a wetland
conservation rategy has few chances to emerge, and even
less for being implemented, only with national initiatives.
It is to say that international organizations are called to give
more attention to these wetlands and to help in gathering and
publishing scientic data and in conserving habitats.
The poverty of the ecological knowledge on Yemen
wetlands is another challenge that the country has to meet, for
improving the conservation processes, mainly in inland water
ecosyems. We are convinced that their aquatic communities
will reveal many great surprises, mainly their relationships
with European, African and Asian communities.
Abbreviations
GIS: Geological Information Syem, MEA: Millennium
Ecosyem Assessment, EPA: Environmental Protection Authority,
DEM: Digital Elevation Model, DID: Directorate of Irrigation and
Dams, MAI: Miniry of Agricultural and Irrigation, NWRA: National
Water Resources Authority, PERSGA: Regional Organization for the
Conservation of the Environment of the Red Sea and Gulf of Aden,
FAO: Food and Agricultural Organization, CSO: Central Statiical
Organization.
ACKNOWLEDGMENT
The authors are grateful to all Yemen’s experts in the Miniry
of Environment, the Miniry of Agriculture, the Faculty of
Engineering, the Environmental and Water Centre and the Research
Authority for providing precious Available at data. We would like
to thank also for their help the members of the Research Unit for
Wetlands Management at the Scientic Initute.
REFERENCES
Abd El-Mageed A, El-Kamel A., Abbady A. et al., 2013. Natural
radioactivity of ground and hot spring water in some areas in
Yemen. Desalination, 321, 28-31. https://doi.org/10.1016/j.
desal.2011.11.022
Al Kubati M. Al Qraa Fahd, Mattash M. et al., 2017. Geothermic
characters of the mo promising geothermal led for power
generation in republic of Yemen. International Journal of
Scientic & Technology Research, 6, 55-63.
Almhab A. & Busu I. 2011. The approaches for oasis desert
vegetation information abraction based on medium-resolution
Landsat TM image: A case udy in desert wadi Hadramut,
Yemen. Faculty of Geoinformation Science and Engineering,
University of Technology, Malaysia, 1-5.
Al-Najar A., Aldeeb A. & Ahmed A., 2008. Geological and Tourism
Study for Coaal Areas in Yemen. PHD Thesis, Aswan
University, Egypt, 1-427. [Original version in Arabic].
Al-Obaid S., Samraoui B., Thomas J., El-Serehy H.A., Alfarhan
A.H., Schneider W., O’Connell M., 2017. An overview of
wetlands of Saudi Arabia: Values, threats, and perspectives.
Ambio, 46, 98–108.
Al-Safadi M.M., 1991. Freshwater macrofauna of agnant waters in
Yemen Arab Republic. Hydrobiologia, 210, 203-208.
Al-Safadi M.M., 1992. Freshwater shes of Yemen. Proceedings of
the Egyptian Academy of Sciences, 42, 265-271.
Al-Safadi M.M., 1995. A pilot udy of lake Ma’rib, Yemen.
Hydrobiologia, 315, 203-209.
Al-Saghier O. 2002b. Survey for the Breeding Seabirds in Red Sea
of the Republic of Yemen. PERSGA Report. Jeddah, 1-35.
Barnard P. & Thuiller W., 2008. Introduction Global change and
biodiversity: Future challenges. Biology Letters 4, 553-555.
Barratt L., Dawson-Shepherd A., Ormand, R. et al. 1987. Yemen
Arab Republic Marine Conservation Survey. Volume 1,
Diribution of habitats and species along the YAR coaline,
IUCN, Red Sea and Gulf of Aden Environmental Programme/
TMRU, UK, 1-23.
Bruland G.L., 2008. Coaal wetlands: function and role in reducing
impact of land-based management. Natural Resources and
Environmental Management Department, University of Hawaii
Manoa, USA. 1-39. Available at: http://www.ctahr.hawaii.
edu/brulandg/publications/CWM_Chapter04.pdf [Accessed:
February 7th2016].
Charbonnier J., 2009. Dams in the weern mountains of Yemen:
a Himyarite model of water management. Proceedings of the
Seminar for Arabian Studies, 39, 81-94.
CHIRPS. 2015. Climate Hazards Group. UC Santa Barbara.
Available at: http://chg.geog.Uc sb.edu/data/chirps/ [Accessed
April 21th 2016].
Crooks S., Herr, D., Tamelander J. et al. 2011. Mitigating Climate
Change through Reoration and Management of Coaal
Wetlands and Near-shore Marine Ecosyems: Challenges
and Opportunities. Environment Department Paper 121,
World Bank, Washington DC, 1-47. Available at: http://
siteresources.worldbank.org/ENVIRONMENT/Resources/
MtgtnCCthruMgtofCoaalWetlands.pdf [Accessed: June 14th
2015].
CSO (Central Statiical Organization), 2014. Central Statiical
Organization Yearbook 2014. Miniry of Planning, Yemen,
1-127. [Original version in Arabic].
Dakki M., 1987. Ecosyèmes d’eau courante du haut Sebou
(Moyen Atlas): études typologiques et analyses écologique et
biogéographique des principaux peuplements entomologiques.
Travaux de l’Initut Scientique, Rabat, Série Zoologie, 42,
1-99.
Dakki M., El Fellah B. & Qninba A. 2020. Rivers’ natural
reservoirs: new inputs to the classication of Mediterranean
and Saharan wetlands. Bulletin de l’Initut Scientique, Rabat,
Série Sciences de la Vie , 1-14.
Davidson N.C., 2014. How much wetland has the world lo?
Long-term and recent trends in global wetland area. CSIRO
Publishing. Marine and Freshwater Research, 65, 10, 936-941.
Available at: http://dx. doi.org/10. 1071/MF14173 [Accessed:
September 18th 2018].
Duy, J.E., 2006. Biodiversity and the functioning of seagrass
ecosyems. Marine Ecology Progress Series, 311, 233-250.
41
Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Elasha B.O. 2010. Mapping of Climate Change Threats and Human
Development Impacts in the Arab Region. UNDP, Regional
Bureau for Arab States, Arab Human Development Report,
Research Paper Series, 1-49.
EPA (Environmental Protection Authority), 2004. Fir National
Report to the Convention on Biological Diversity. Miniry of
Water and Environment, Yemen, 1-88.
EPA (Environmental Protection Authority), 2009. The 4th National
Report: Assessing Progress towards the 2010 Target - The 4th
National CBD Report. Miniry of Water and Environment,
Yemen, 1-100.
EPA (Environmental Protection Authority), 2013. Yemen’s Second
National Communication under the United Nations Framework
Convention on Climate Change. Environmental Protection
Authority, Yemen, 1-68.
Erwin K., 2008. Wetlands and global climate change: the role of
wetland reoration in a changing world. Wetlands Ecology
Management, 17, 71-84. Available at: https://www.wetlands.
org/wp-content/uploads/2015/11/Wetlands-and-Global-
Climate-Change. pdf. [Accessed: October23th 2015].
FAO (Food Agricultural Organization), 1997. Irrigation in the Near
Ea Region in Figures, FAO , Rome, 1-320. Available at: http://
www.fao.org/documents/show_cdr.asp?url_le=/ docrep/
W4356E/w4356e0z.htm [Accessed October 24th 2015].
Geukens, F., 1966. Geology of the Arabian Peninsula, Yemen: U.
S. Department of the interior ewartl. UDALL, Secretary
Geological survey. B1-B22. Available at: https://pubs.usgs.gov/
pp/0560b/report.pdf [Accessed September 13th 2018].
Hall M, Al-Khulaidi A.W. & Miller A.G. et al. 2008. Arabia’s La
Fores under Threat. Plant Biodiversity and Conservation in
the Valley Fore of Jabal Bura’a (Yemen). Edinburgh Journal
of Botany, 65, 113–135.
Harvey D. 1999. Wildlife conservation initiatives in Yemen. Al-
bab, Available at: https://al-bab.com/wildlife-conservation-
initiatives-yemen [Accessed: May 18th 2019].
Hushulong Q. 2012. The problems of wetlands in our country and
the researches. International Conference on Future Electrical
Power and Energy Syems. Energy Procedia, 17, 462-466.
James N.C., Cowley P.D., Whiteld A.K. & Lamberth S.J. 2007.
Fish communities in temporarily open/closed euaries from the
warm -and cool- temperate regions of South Africa: A review.
Reviews in Fish Biology & Fisheries, 17, 565-580.
Kamra A.A., 2006. Yemen Geothermal Resources. GRC Transactions,
30, 637-642. Available at: http://pubs.geothermal-library.org/
lib/grc/1025103.pdf [Accessed: June 11th 2017].
Kemp, J.M. 2000. Zoogeography of coral reef shes of the Gulf of
Aden. Fauna of Arabia, 18, 293-321.
Lill A.W.T., Closs G.P., Schallenberg M. & Savage C. (2012).
Impact of berm breaching on hyperbenthic macroinvertebrate
communities in intermittently closed euaries. Euaries and
Coas, 35, 155-168.
MAI (Miniry of Agricultural and Irrigation), 2013. Annual Report.
Yemen. 1-78. [Original version in Arabic].
MAI (Miniry of Agricultural and Irrigation), 2016. Annual Report.
Yemen. 1-56. [Original version in Arabic]
McCartney M., Rebelo L-M., Senaratna Sellamuttu S. et al., 2011.
Wetlands, agriculture and poverty reduction. IWMI Research
Report, International Water Management Initute, Colombo,
137, 26 pp. DOI: 10.5337/2010.230.
MEA (Millennium Ecosyem Assessment), 2005. Ecosyems and
Human Well-being: Wetlands and Water-Synthesis. World
Resources Initute, Washington DC, 67 pp. Available at: https://
www.Millennium-assessment. org/documents/document. 356.
aspx.pdf [Accessed: Augu 13th 2016].
Minissale A., Mattash M.A., Vaselli O., et al., 2007. Thermal springs,
fumaroles and gas vents of continental Yemen: Their relation
with active tectonics, regional hydrology and the country’s
geothermal potential. Applied Geochemiry, 22, 799–820.
Mohammed M., Frenzel P., Keyser D. et al., 2018. A humid
early Holocene in Yemen interpreted from palaeoecology
and taxonomy of freshwater oracods. Journal of
Micropalaeontology, 37, 167-180. Available at: https://doi.
org/10. 5194/jm-37-167-2018 [Accessed: September16th 2018].
Navid D., 1989. The international law of migratory species: The
Ramsar Convention. Natural Resources Journal, 29, 1001-1016,
Available at: http://digitalrepository.unm.edu/cgi/viewcontent.
cgi?article=2481&context=nrj [Accessed: March 23th 2015].
NBSAPY 2005. National Biodiversity Strategy and Action Plan for
Yemen. UNDP/GEF/IUCN YEM/96/G31, Miniry of Water and
Environment, Yemen, 70 pp. Available at: https://www.cbd.int/
doc/world/ye/ye-nbsap-01-en. pdf [Accessed June 14th 2015].
Nozais C., Perissinotto R. & Tita G. 2005. Seasonal dynamics of
meiofauna in a South African temporarily open/closed euary
(Mdloti Euary, Indian Ocean). Euarine, Coaal and Shelf
Science, 62, 325-338.
NWRA (National Water Resources Authority), 2005. Annual Report.
Miniry of Water and Environment. Yemen, 49 pp.
O’Connor N. & Crowe T., 2005. Biodiversity Loss and Ecosyem
Functioning: Diinguishing Between Number and Identity of
Species. Ecology, Ecological Society of America, 86, 7, 1783-
1796.
Parry M.L., Canziani O.F., Palutikof J.P., van der Linden
P.J. & Hanson C.E. (Eds.), 2007. Climate Change 2007:
Impacts, Adaptation and Vulnerability. Contribution of
Working Group II to the Fourth Assessment Report of
the IPCC, Cambridge University Press, 811 pp. Available
at: https://www.ipcc.ch/pdf/assessment-report/ar4/wg2/
ar4_wg2_full_report.pdf [Accessed: May 14th 2015].
Perissinotto R., Stretch D.D. & Whiteld A.K. et al. 2010.
Ecosyem functioning of temporary open/closed euaries in
South Africa. In Crane J.R. & Solomon A.E. (Eds). Euaries:
Types, movement patterns and climatical impacts. Nova Science
Publishers, New York, ISBN 978-1-60876-859-2. 69 pp.
Porter R. 1993. Birds of Yemen. Al-Bab, https://al-bab.com/birds-
yemen
Ranasinghe R. & Pattiaratchi C. 2003. The seasonal closure of tidal
inlets: causes and eects. Coaal Engineering Journal, 45, 4,
601-627.
RAP (Rural Access Program). 2004. Draft Sectoral Environmental
Assessment. SHEBA Engineering Services, Sana’a, 165 pp.
Roy P.S., Williams R.J. & Jones A.R. et al. 2001. Structure and
function of south-ea Auralian euaries. Euarine, Coaal
and Shelf Science, 53, 351-384.
Scharler U.M., Lechman K., Radebe T. et al. 2020. Eects of
prolonged mouth closure in a temporarily open/closed euary:
a summary of the responses of invertebrate communities in
the uMdloti Euary, South Africa. African Journal of Aquatic
Science, 45, 1, 1-10. DOI: 10.2989/16085914.2019.1689911.
Scholte P. 1992. The birds of Wadi Rima, a permanently owing
mountain wadi in weern Yemen. Sandgrouse, 14, 2, 93-108.
42 Al-Mahfadi & Dakki - Scientic elements for a Yemeni wetland conservation rategy
Sheppard C.R.C., Price A.R.G. & Roberts C.M. 1992.
Marine ecology of the Arabian Region: patterns and
processes in extreme tropical environments. Academic
Press, London, 359 pp.
Shobrak M., Alsuhaibany A. & Al-Saghier O. 2003. Regional atus
of breeding seabirds in the Red Sea and the Gulf of Aden.
PERSGA Report, 74 pp.
Snow G.C. & Taljaard S. 2007. Water quality in South African
temporarily open/closed euaries: a conceptual model. African
Journal of Aquatic Science, 32, 2, 99-111.
Stuip M.A., Baker C.J. & Ooerberg W. 2002. The Socio-economics
of Wetlands. Wetlands International and RIZA, The Netherlands,
28 pp.
Taljaard S., Van Niekerk L. & Joubert W. 2009. Extension of a
qualitative model on nutrient cycling and transformation
to include microtidal euaries on wave-dominated coas:
Southern hemisphere perspective. Euarine, Coaal and Shelf
Science, 85, 407-421.
Tardelli M. & Baldini R. 2000. Botanical Report on the Island of
Socotra (Yemen). Portugaliae Acta Biologica, 19, 443-453.
Tweddle G.P. & Froneman P.W. 2015. Inuence of mouth atus on
population ructure of Southern African endemic euarine-
spawning ichthyofauna in a temperate, temporarily open/closed
euary. African Journal of Aquatic Science, 40, 2, 221-225.
DOI: 10.2989/16085914.2015.1051940.
Van der Gun J. & Ahmed A. 1995. The water resources of Yemen.
a summary and dige of available at information. WRY35
Technical Report, Miniry of Oil and Mineral Resources,
Sana’a, Yemen. 106 pp. Available at: https://www.researchgate.
net/publication/282665864 [Accessed: March 10th 2014].
Ward C., Ueda S. & McPhail A. 2000. Water Resources Management
in Yemen. CDR_H2O_0112. World Bank, 39 pp. Available at:
http://siteresources.worldbank.org/INTYEMEN/Overview
/20150274/YE-Water. pdf [Accessed: March 4th 2014].
Whiteld A.K. 1992. A characterization of Southern African
euarine syems. South African Journal of Aquatic Science,
18, ½, 89-103.
Whiteld A.K., Bate G.C. & Adams J.B. et al. 2012. A review of the
ecology and management of temporarily open/closed euaries
in South Africa, with particular emphasis on river ow and
mouth ate as primary drivers of these syems. African Journal
of Marine Science, 34, 163-180.
Worldmeters, 2019. Yemen’s Population from 1955-2050. Dadax.
Available at: https://worldpopulationreview.com/countries/
yemen-population [Accessed: April 9th 2019].
Manuscrit reçu le 04/06/2020
Version révisée acceptée le 28/10/2020
Version nale reçue le 12/11/2020
Mise en ligne le 13/11/2020