Environmental Engineering Reference
In-Depth Information
Laguncularia racemosa, Rhizophora harrisonii and Rhizo-
phora racemosa The open lagoons tend to be dominated by R.
racemosa, while closed lagoons with an elevated salinity
harbour A. germinans, C. erectus, L. racemosa and A. aure-
rum (UNEP 2007 ).
Ghana's mangrove ecosystems are tremendously valu-
able, providing ecosystem services such as carbon seques-
tration, protection from storms, floods, erosion, provision of
timber and nontimber forest products, processing of waste
and nutrient pollution, aquaculture and agriculture support
and habitat for aquatic and terrestrial species. In the lower
Volta area, the total estimated value, including mangrove-
related harvesting for fish smoking or house roofing
(US$340/ha) and contribution to marine fisheries (US$165/
ha), is over US$500/ha, with total country estimates of well
over US$6,000,000/year. These values do not include all the
other mangrove ecosystem services (e.g. erosion control,
trapping of pollutants and provision of biomass for the
detritivore food chain) (Gordon et al. 2009 ). Yet, as in many
other parts of the world, short-term development needs are
undermining long-term mangrove health and survival.
Between 1980 and 2006, the mangrove area in Ghana fell
from 181 to 137 km 2 representing a loss of 24 % (UNEP
2007 ; Ajonina et al. 2008 ).
Economic mechanisms have the potential to tip the
balance towards restoration, maintenance and protection of
mangrove forests. The need for proper valuation of man-
grove ecosystem services underpins such mechanisms,
including the establishment of any realistic payment for
ecosystem services (PES) schemes in any given mangrove
or wetland habitat. The objective of this study was to assess
the types and conditions of mangroves and associated
ecosystem services (e.g. carbon sequestration, wood col-
lection and tourism) in the field for use in feasibility
assessment for PES schemes in the mangroves and wetlands
in Greater Amanzule and surrounding areas in coastal
Western Region of Ghana. This study provides an analysis
of the types of mangroves and wetlands, their status and
distribution in the coastal Western Region; gathers infor-
mation about the uses and governance of these wetlands;
and provides insights into the use of information gathered in
feasibility
areas of the Western Region (Fig. 1 ). The catchment of the
wetland lies within the Western Evergreen Forest zone of
Ghana. It covers an area of approximately 100 square km
and lies within latitudes 453 0 and 446 0 north and longitude
200 0 and 205 0 west, 360 km west of Accra. The mangrove
areas lie within the Greater Amanzule region in the Jomoro
district, Ellembelle, Nzema east and Ahanta west districts of
the Western Region.
Biophysical Environment
The region lies in the equatorial climate zone characterized
by moderate temperatures. About 75 % of the land area falls
within Ghana's high forest zone. The area is characterized
by high rainfall with a double maximum and peaks in May-
June and October-November each year. The average annual
rainfall is 1,600 mm with the relative humidity being
87.5 %, at a mean annual temperature of 26 C. There is a
short dry season (December-March) during which a south-
westerly directional wind is experienced with slight Har-
mattan conditions.
The soil is predominantly Forest Oxysols and Forest
Ochrosols-Oxysols intergrades. Its hydrology is driven by
six streams, one lake, the Amanzule freshwater lake and one
outlet to the sea. The area is subject to seasonal flooding.
The Amanzule wetlands is a relatively pristine complex
consisting of a freshwater lake, forest, grasslands and rivers.
It has the most extensive remaining stand of intact swamp
forest in Ghana. These extensive swamps are outside the
mangrove areas. Swamps cover about 70 % of the area and
associated with a dense hydrological network. Within the
area, there is still some logging of an important swamp
forest species—Lophira alata (ironwood)—for charcoal.
The Amanzule wetlands is the only known swamp forest in
Ghana and the best example of swamp forest characterized
with black humic water. Some 70 % of the site is covered
by swamp forest making accessibility difficult, hence con-
tributing to its unspoiled nature. The area has a rich bio-
diversity and in terms of flora: 33 % of the 237 species of
plants identified are endemic to the wetland. Notable spe-
cies include raffia palm and ironwood (L. alata). Faunal
reports (GWS 2003 ) estimate 27 species of mammals,
including black-and-white colobus, mona and spot-nosed
monkeys; forest squirrels; and Red River hog. Twenty-six
species of reptiles and amphibians, including the slender-
snouted crocodile and the dwarf crocodile, green mambas
and black forest cobra, and 26 species of fish have been
recorded. The wetland is relatively rich in indigenous avi-
fauna and also hosts various migrant species. Over 105
species of birds were recorded in an inventory, 65 of which
are of global and national conservation interest. The area is
classified as an Important Bird Area (IBA) (Birdlife Inter-
national 2007 ), and it meets the criteria for designation as a
wetland
assessments of
the
potential
for
PES
in
the
mangroves and wetlands in the region.
Methods
Site Description
Location of the Survey Area
The survey area lies within the Amanzule wetlands, which
is a community-owned wetland with no official conserva-
tion status in the eastern and western Nzema traditional
of
international
importance
under
the
Ramsar
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