Floral Diversity of South-Western Nigeria Coastal Environments

Floral Diversity of South-Western Nigeria Coastal Environments

Journal Sci. Res. Dev., 2008 / 2009, Vol. 11, 9 – 20
Floral Diversity of South-Western Nigeria Coastal Environments
Olusola H. Adekanmbi,* Ogundipe O. T. and Olowokudejo J. D.
Department of Botany and Microbiology,
University of Lagos, Lagos, Nigeria.
ABSTRACT
Mangrove communities in 8 localities in Lagos State viz: Atlas Cove, 5 Cowrie Creek,
Maroko, Berger De Motz, Palaver Island, Bayeku, Majidun, and University of Lagos
Beach were sampled quantitatively with respect to their flora diversity. Absolute count
and relative percentages of the vegetation were estimated. The first sampling site
Atlas Cove has its vegetation relatively well preserved, 5 Cowrie is devoid of typical
mangrove vegetation, Maroko swamp has been taken over by grasses, Berger De
Motz has sandy substratum, high energy wave and rip of any typical mangrove
species, Bayeku and Majidun still preserve the relics of their biodiversity, while
mangrove is still relatively well preserved in the vicinity of University of Lagos lagoon
and Palaver Island. The importance of having wetland reserves is highlighted.
Key words: mangrove, degradation, natural environment, flora diversity, transect.
INTRODUCTION
The Nigerian coastline is made up of swampy ground separated by fresh or brackish
lagoons and a network of creeks. The typical mangrove swamp forest develops on
the muddy banks of these creeks where the water is brackish and the number of
species is limited by their tolerance to specific environmental condition (Olowokudejo,
1975).
The mangrove swamp forest typified by the Niger Delta is characterized by three
species of Rhizophora, which are Rhizophora harrizoni, R, mangle and R. racemosa.
Cohabiting with Rhizophora are two other less abundant mangroves, Avincennia
germinans and Laguncularia racemosa as well as the salt-water fern, Acrostichum
aureum (Sowunmi, 1981a & b). Behind the mangrove swamp is a zone of freshwater
swamp inhabited by freshwater species such as Symphonia globulifera, Cleistopholis
patens, Nymphae lotus, Ipomoea spp., Vossia cuspidata and other grasses. Also
found in the freshwater zone are the floating communities of Pistia stratiotes, Lemna
and Salvinia among others.
Associated with the swamp vegetation, but by the
edge mainly near the seaboard, where the seawater is undiluted is a strand
vegetation of shrubs and herbs, such as Barteria nigritiana, Hibiscus tiliaceus, and
Ipomoea pes-caprae (Keay, 1949; Lawson, 1966).
Corresponding author. E-mail: [email protected]
10
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
The mangrove forest occurs on muddy intertidal substrates, making it habitable for
birds and other living organisms by stabilising the silt-rich soil and holding it together
by a mat of mangrove rootlets forming a thick felt raft of peaty texture. The
subsequent breaking down of the raft in addition to deposition of coarse detritus and
of leafy woody material results in something nearly resembling a normal soil of the
hinterland (Chapman, 1979; Tomlinson, 1986). In this way the mangrove forest
advances slowly outward, leaving dry land behind. Mangroves are highly productive
biotopes and as such, support a vibrant, rich and endemic wildlife that include the
enormous variety of crabs, ducks, geese and immense varieties of sea life in the food
webs (Odum and Herald, 1975; Nwafor, 2006). Wild birds also stop over at the
mangroves during migration (Erarome, 2005). If properly managed, mangroves can
provide timber for construction, charcoal for energy, food for livestock and fish for
local consumption among others.
This paper discusses the value of swamps, the peculiar flora species found in
specific parts of the Lagos coastal area and importance of conserving these
biodiversities.
MATERIALS AND METHODS
A comprehensive quantitative vegetation analysis of eight lagoonal communities:
Palaver Island, Atlas Cove, 5 Cowrie creek, Maroko, Bayeku, Berger De Motz,
University of Lagos Beach, and Majidun were carried out. Eight belt transects of 50
metres long and 6 metres wide placed at every fifth yard were examined for each
sample site. A list of all the species present in each mangrove community was
compiled. Species frequency was numerically estimated in 10 quadrats within these
transects and the percentage of the total flora was calculated. Vegetation cover of
species present in each transect was also estimated by assigning each species to
one of six categories: Dominant - largest and most abundant sp., Very abundant with the greatest percentage cover but not ecologically dominating other plants,
Abundant - numerous or widespread, Frequent -modest numbers but soon seen,
Occassional -in small number and not found in all transects, Rare -found only singly
and scarcely and absent from most samples following Killick, 1967. Visual
photographs of the various mangrove communities were taken.
RESULTS
All plants species present at each sampling site, their frequency and the percentage
occurrence are presented in Tables 1. Table 2 and 3 shows a list of woody and
herbaceous species common to five or six localities. A total of 56 plant species
analogue to 29 families were recorded for all the 8 sampled vegetation communities.
Visual photographs of some of the sampled communities are shown in Plate 1-6.
Floral Diversity of South-Western Nigeria Coaster Environments
11
Vegetation Description
Atlas Cove
Mangrove here is relatively well preserved dominated by Avicennia germinans (6.9%)
and Laguncularia racemosa (6.3%). Rhizophora racemosa (5.9%) and Alchornea
cordifolia (5.6%) were very abundant occurring in an almost undisturbed manner.
Casuarina equisetifolia (2.5%) and Terminalia catappa (1%) were other abundant
tree species recorded in this mangrove community. Occurring frequently were shrubs
such as Agave sisalana (3.8%), Dalbergia ecastaphyllum (2.7%), Drepanocarpus
lunatus (2%) and the fern Acrostichum aureum (2.8%). Phoenix reclinata (2.1%),
Cocos nucifera (1.8%), Azadiracta indica (1.4%) and Hibiscus tiliaceus (1.1%) were
found occurring together occasionally. Paspalum vaginatum (9.1%), Portulacaceae
(8.8%) and Rhynchospora corymbosa (2.1%) were abundant.
5 Cowrie Creek
This community is almost completely devoid of vegetation except occasional stands
of Casuarina equisetifolia (7.89%), Terminalia catappa (5.26%), and sparse
occurrence of grasses.
Chromolina odorata (7.89%) were frequent. The
indiscriminate cutting, grazing and sand filing has obliterated any sign of the original
mangrove vegetation.
12
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
3
4
5
6
7
8
9
3
8
42
48
33
Rhizophoraceae
47
52
43
Euphorbiaceae
Combretace ae
Casuarinaceae
40
7
18
Malvaceae
Fabanaceae
8
19
Fabanaceae
14
Adiantaceae
Aracaceae
Aracaceae
Meliaceae
Agaveceae
Pontedereriaceae
Nymphaceae
Aracaceae
Poaceae
Portulacaceae
Cyperaceae
20
13
15
10
27
Aracaceae
Compositae
Combretace ae
Poaceae
12
16
22
49
8
12
8
13
4
26
M a ji d u n co m m u ni ty %
U n i ve rs i ty o f L a go s %
Be rg e r D e m o tz %
M o b a, M a ro k o %
0.00
0.00
5.00
13.33
0.00
6.67
0.00
0.00
32.21
22.15
17.45
0.00
T ot al
5 c o w ri e c re ek %
0.00
0.00
At la s C o ve %
75.00
28.19
40
58
240
19.58
0.00
0.00
0.00
21.67
17.92
16.67
24.17
28
5
103
34
70
38.83
20.59
25.71
0.00
23.53
17.14
0.00
23.53
18.57
0.00
17.65
0.00
0.00
0.00
10.00
0.00
0.00
0.00
33.98
0.00
28.57
27.18
14.71
0.00
8 100.00
77 24.68
0.00
0.00
0.00
0.00
0.00
0.00
0.00
32.47
0.00
23.38
0.00
19.48
0.00
0.00
20
25
18
15
19
12
8
5
12
38
49
4
29
15
13
11
32
64
48
46
34
15
60
149
35
6
7
M aj i d u n c o m m u n i ty
Ba ye ku
45
Avicenniaceae
U ni v er si ty o f La g o s
P al a ve r s ou t h
M o b a , M a ro k o
B er g er D e m o tz
A tl as Co v e
Taxa
Combretace ae
B ay ek u %
2
racemosa
Avicennia
germinans.
Rhizo phora
racemosa
Alchorn ea cordifo lia
Terminalia ca ta ppa
Ca suarina
equisetifolia
Hib iscus tiliaceus,
Dalbergia
ecastaphyllum
Drepano ca pus
P a la v er s o u th %
Species
1 Laguncularia
5 co w r ie cr ee k
V e g e tat io n C om m i n iti e s
Table 1: showing the complete floristic list and vegetation taxa with its
vegetation percentages
23.33
0.00
0.00
25.00
0.00
0.00
31.67
20.00
127 15.75
18 72.22
48 31.25
19 52.63
27 100.00
94
0.00
61
0.00
57
0.00
302 21.52
63 100.00
55 27.27
60
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
12.58
0.00
0.00
0.00
0.00
0.00
47.37
0.00
0.00
0.00
0.00
19.87
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
13.91
0.00
45.45
6.30
27.78
0.00
0.00
0.00
0.00
0.00
0.00
3.97
0.00
0.00
9.45
0.00
0.00
0.00
0.00
15.96
0.00
0.00
6.29
0.00
0.00
29.92
0.00
8.33
0.00
0.00
15.96
21.31
19.30
10.60
0.00
27.27
38.58
0.00
60.42
0.00
0.00
68.09
78.69
80.70
11.26
0.00
0.00
12 100.00
56 28.57
22 100.00
155 31.61
0.00
21.43
0.00
20.00
0.00
17.86
0.00
23.23
0.00
0.00
0.00
25.16
0.00
7.14
0.00
0.00
0.00
0.00
0.00
0.00
0.00
10.71
0.00
0.00
0.00
14.29
0.00
0.00
lunatus
10
11
12
13
14
15
16
17
18
20
21
22
23
24
25
26
27
28
29
30
31
32
34
35
36
37
38
40
41
42
43
44
45
46
47
48
49
Acrostichu m aureum
Co co s nucifera
Phoenix reclina ta
Aza diracta indica
Agave sisa la na
Eicch ornia cra ssip es
Nymphae lotus
Pistia stra tiotes
Paspalum vag in atu m
Portu la ca cea e
Rhynchospora
corymbosa.
Elais guinensis
Ch rom olin a o dorata
Combretum sp
Paspalum
scrob iculatum
Panicum subalbidum
Andropogo n sp.
Asystasia gang en tica
Typha au stra lis
Scleria depressa
Kyllin ga erecta
Cyperus esculentus
Centro sem a
pubesens
Ipo moea aqu atica
Saccha rum
officinaru m
Symphon ia
globulifera
Alstonia co ngensis
Cyperus javanicus
Vossia cuspidate
Bambusa vu lg aris
Luffa cylin drical
Mimosa invisa
Poaceae
Raph ia finifera
Ludwigia sp .
Willo w p la nt
Cytosperm a
sensgalense
9
15
65
63
15
38
60
42
12
25
12
10
31
36
19
15
4
6
8
39
45
53
Poaceae
Poaceae
Acantaceae
Typhaceae
Cyperaceae
Cyperaceae
Cyperaceae
Papilionaceae
38
65
33
39
24
39
21
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
100.00
100.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
100.00
100.00
100.00
100.00
100.00
100.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
35.56
62.50
0.00
37.50
16
5
3
45
8
0.00
0.00
0.00
0.00
0.00
0.00
46.67
0.00
17.78
0.00
0.00
0.00
Guttiferae
6
2
8
0.00
0.00
0.00
0.00
0.00
0.00
75.00
25.00
Apocynaceae
Apocynaceae
Cyperaceae
Poaceae
Poaceae
Mimosaceae
Poaceae
Aracaceae
Onagraceae
7
7
80
87
17
36
35
39
26
36
26
39
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
43.59
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
56.41
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
33.33
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
100.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
100.00
100.00
100.00
66.67
100.00
0.00
100.00
100.00
100.00
100.00
Convolvulaceae
Poaceae
12
17
8
45
53
38
65
33
39
24
39
80
87
17
24
35
22
26
36
26
39
Floral Diversity of South-Western Nigeria Coaster Environments
13
Table 2: Woody Species Common to Five or More Localities
1.
2.
3.
4.
5.
6.
7.
8.
Species
Family
Habit
Laguncularia racemosa
Terminalia catappa Linn
Casuarina equisetifolia Linn
Cocos nucifera
Azadiracta indica A. Juss
Avicennia germinans
Conocarpus erectus
Rhizophora racemosa G.F.W. Mey
Combretaceae
Combretaceae
Casuarinaceae
Aracaceae
Meliaceae
Combretaceae
Combretaceae
Rhizophoraceae
Tree
Tree
Tree
Tree
Tree
Tree
Woody
Woody
Table 3: Herbaceous Species, Climbers and Grasses Common to Five or More
Localities
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Species
Family
Habit
Phoenix reclinata
Chromolina odorata Linn
Mimosa invisa Mart
Chromolina odorata Linn, King
& Robinson Mart
Conocarpus erectus
Paspalum vaginatum Sw
Paspalum scrobitulatum Linn
Andropogun sp
Panicum subalbidum Kunth
Scleria depressa Willd
Paspalum vaginatum
Scleria depressa Willd
Aracaceae
Compositae
Mimosaceae
Herbaceous
Herbaceous
Herbaceous
Compositae
Cucurbitaceae
Poaceae
Poceae
Poaceae
Poaceae
Cyperaceae
Cyperaceae
Cyperaceae
Herbaceous
Shrub
Grass
Grass
Grass
Grass
Sedge
Sedge
Sedge
Moba, Maroko Swamp
This swamp community has been taken over by grasses due to urbanization and
reclamation. As a result grasses such as Paspalum (25%) and Andropogon (22%)
species were found dominating. Panicum subalbidum (1.9%) were very abundant
reaching about eight feet high. Tree species occurring frequently are Casuarina
equisetifolia (5.4%), Azadiracta indica (3.8%), and Terminalia catappa (3.3%).
14
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
Berger De Motz
This community has sandy substratum and high-energy wave. It is rip of any typical
mangrove species as the natural environment has been adversely modified. Grasses
including Typha australi (11%), Paspalum and sedges such as Kyllinga erecta
(6.7%), Scleria depressa (5.7%), Rhynchospora corymbosa (4.3%) and Cyperus
esculentus (4.1%) are dominant here. Very abundant are Centrosema pubesens
(6.7%) and Asystasia gangetica (6.5%). Drepanocarpus lunatus (2.6%) and Ipomoea
aquatica (2.1%) are also abundant.
Palaver Island
This community is relatively undisturbed by developers except the influx of solid
waste. Rhizophora racemosa (19%) is found dominating; next to this in abundance
are the very mature Avicennia germinans (17%) reaching about 5 feet in girth and
about 50 feet in height. Dalbergia ecastaphyllum (8.9%) were quite abundant. The
saltwater fern Acrostichum aureum (2.8%), Ipomoea aquatica (2.8%), Casuarina
equisetifolia (2.5%) and Cocos nucifera (1.8%) are frequent.
Bayeku Community
The mangrove floral of this community is dominated by Rhizophora racemosa (13%).
Very abundant is Avicennia germinans (10%) and Dalbergia ecastaphyllum (5.6%).
Paspalum vaginatum (5.9%), Eicchornia crassipes (4%), Acrostichum aureum (3.7%)
were frequently counted. Laguncularia racemosa (2.5%) recorded only occasional
occurrence.
Majidun Community
Dominant in this fringing mangrove lining creeks with fresh water incursion are the
sedges Vossia cuspidata (7.13%), Cyperus javanicus (0.98%) and Rhynchospora
corymbosa (2.62%). Rhizophora racemosa (4.75%) is found occurring together with
Alchornea cordifolia (2.29%) at some sampled sites. Very abundant here are,
Nymphae lotus (8.03%), Eicchornia crassipes (6.88%), Pistia stratiotes (6.22%) and
Acrostichum aureum (4.01%). Mimosa invisa (2.87%), Raphia finifera (2.13%) and
Ludwigia species (2.95%) are abundant. Other frequently occurring species are
Phoenix reclinata (2.38%), Ipomoe aquatica (1.64%), Paspalum scrobiculatum
(1.64%), Bambusa vulgaris (1.39%), and Drepanocarpus lunatus (0.98%). Agave
sisalana (0.82%), Terminalia catappa (0.41%) and Cocos nucifera (0.33%) are
frequent.
University of Lagos Community
Mangrove in the vicinity of University of Lagos is still relatively well preserved with
diverse species. A very visibly dominant species in this community is Rhizophora
racemosa (6.8%), Salt water fern Acrostichum aureum (6.4%) is very abundant.
Other important components of this community occurring in abundance are
Alchornea cordifolia (5.9%), Avicennia germinans (4.4%), Casuarina equisetifolia
(3.4%), Drepanocarpus lunatus (3.2%), Ipomoea aquatica (2.7%), and Dalbergia
ecastaphyllum (2.5%). Paspalum vaginatum (5.4%), Pistia stratiotes (3.6%),
Rhynchospora corymbosa (2.5%), as well as species of Agave sisalana (0.8%) and
Floral Diversity of South-Western Nigeria Coaster Environments
15
Phoenix reclinata (0.7%) were frequently encountered in the samples. Tree species
such as Alstonia congensis (1.2%), Symphonia globulifera (1%), and Terminalia
catappa (0.3%), were occasionally seen. Eicchornia crassipes (2.5%) and Nymphae
lotus (2.2%) recorded rare occurrence showing incursion of freshwater.
Fig. 1: A Mangrove Habitat. Majidun, Lagos, Nigeria.
16
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
Fig. 2: Hibiscus tiliaceaus (Malvaceae) . Atlas Cove, Nigeria.
Fig. 3: Laguncularia racemosa (Combretaceae). Atlas Cove, Lagos. Nigeria.
Floral Diversity of South-Western Nigeria Coaster Environments
17
Fig 4: Rhizophora racemosa (Rhizophoraceae) at low tide. Bayeku, Lagos. Nigeria.
Fig. 5: Fringing mangroves lining creeks through fresh and salt water. Majidun,
Lagos. Nigeria
18
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
Fig. 6: Avicennia germinans (Avicenniaceae). University of Lagos, Lagos. Nigeria.
DISCUSSION AND CONCLUSION
The floristic list shows that the floral composition of the Lagos lagoon is diverse. On
the sandy beaches are found plants like Elaeis guinnensis, Casuarina equisetifolia,
Terminalia catappa, Hibiscus tiliaceus among others. Towards the sea, on shallow
shore, there are submerged grasses with scattered mangrove seedlings in the
shallowest parts. Much of the southwestern Nigerian coast is made up of the open
type lagoon and its therefore influenced by the tide. The typical mangrove species
such as Rhizophora racemosa, Avicennia germinans and Laguncularia racemosa are
well represented. These species typical of the mangrove are found relatively well
preserved at Atlas Cove, Bayeku, Majidun, University of Lagos and Palaver Island
vegetation communities. The remaining sampled sites 5 Cowrie Creek, Maroko and
Berger De Motz are completely devoid of typical swamp flora but replaced by
occasional stands of Terminalia catappa, Casuarina equisetifolia, and grasses due to
urbanization and reclamation.
The largest mangrove stand in Nigeria is found in the Niger Delta and this work has
established that the Lagos lagoon swamp flora communities are comparable to that
of the Niger Delta. The coastal vegetation performs many important ecological roles.
It filters nutrients, stabilize lagoon shores, provide protection for commercially
important fish, help in the continuous formation of soil, and serve as an important
migratory point for birds. The coastal vegetation protects the shoreline from being
Floral Diversity of South-Western Nigeria Coaster Environments
19
washed away in storms. The roots and trunks break the force of the waves, and the
leaves and branches reduce the effects of the wind and rain (UNESCO, 1992). The
trees species of the mangrove are useful, for example mangrove wood is often
collected as firewood, the willow plant is used in crafting furniture and other
household amenities, and many plants of the mangrove have medicinal uses. The
coast around the southwestern part of Nigeria constitutes one of the most fascinating
resources in tropical Africa and it indeed is a center of biodiversity (Plate 1-6) (FAO,
2001). It is therefore recommended that some portions of the
studied wetlands where typical wetland flora are well preserved and yet undisturbed
be prepared and conserved as reserves.
20
Olusola H. A,* Ogundipe O. T. and Olowokudejo J. D.
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