Folks,
The following is from Daily Observer. Conicidentally I just completed a
paper that address the subject in broad terms. I do hope that the
government do not see the Pirang problem as an isolated case or the
conclusion of my paper as an overstatement. The fact is building a city
state in the Gambia without holistic land use planning could be
devastating to the environment. For those interested, please read the on.
Malanding Jaiteh
Salt intrusion destroys 200 farms in Pirang
By Lamin Dibba
Mar 14, 2005, 07:55
Salt intrusion in Pirang has affected swampy land for rice cultivation
measuring 4km long and 500m wide in which about 200 rice fields were
destroyed as well as the village mango, orange and coconut orchards.
Reports indicated that the cause of the intrusion was due to the impact
caused by the operation of the Scan Gambia Shrimp Farming Company in the
village during the past ten years, as they used to pump saline water
into their ponds.
Rice cultivation is one of the main farming activities of women in
Pirang. For the past five years, the cultivation of rice has declined by
25 per cent. Local measures have been taken to protect the rice fields
from the salt intrusion to no avail.
A rice plot is normally 20 to 25 hecters and a household can own at most
7 or 8 plots which can yield up to 20 bags of rice per plot. Wells
situated 1km from Scan Gambia farms have also turned salty. The gardens
which replaced the village forest, are sources of income for both men
and women. They were all destroyed by the salt intrusion.
The Alkalolu of Pirang and Berending raised concern to the Daily
Observer for immediate help to rescue the village from the "current
devastating situation".
© Copyright 2003 by Observer Company
Consequences of landscape change in western Gambia between 1986 and 1999.
Malanding S. JAITEH
Center for International Earth Science Information Network (CIESIN),
Columbia University, 61 Route 9W, Palisades, NY 10964 USA
Abstract
Western Gambia, occupying an area of 730 sq (6.8% of the total land
area) is home to 670,000 (49% of total population). Fueled by decline in
agricultural productivity and increased poverty in central and eastern
Gambia, and changes in economic activities (availability of modern
amenities and employment opportunities) in and around the City of
Banjul, the region has since 1983, witnessed its population increase
from 250,000 to 670,000 in 2003.
This paper examines the type and extent of land use and land cover
change as well as the biophysical and socioeconomic consequences in the
regions five districts during the period 1986 and 1999. Landsat TM/ ETM+
data from 1986 and 1999 were classified into bare ground and builtup
(BGB), Cropland and Fallow with isolated trees and shrubs (CAF),
woodland, water and mangrove cover types. Post-classification change
analysis was performed to quantify the amount and direction of land
cover transitions within each of five administrative districts. Spatial
pattern analysis was performed on the 1986 and 1999 land cover maps and
a selection of landscape indices were used to assess changes in the
structure and composition of the landscapes.
Between 1986 and 1999, land use change in the region was dominated by
increase in bare ground and builtup areas (217%) at the expense of
cropland and fallow (24% loss) and woodland cover classes (45% loss). In
Kombo North bare ground and builtup area grew 467% (35.9% average annual
growth rate) while Kanifing Municipal Council lost over 75% of its 1986
cropland and fallow areas.
Although the benefits of urbanization include increase in land values,
development of robust real estate market, expansion of modern amenities
such as piped water, electricity and healthcare services to large number
of people across a relatively small geographic area, negative impacts
include cropland loss (as much as 75% in Kanifing Municipal Council),
with 73% reduction in natural habitats (73%), loss of biodiversity and
alteration of ground and surface hydrology.
Introduction
Human-induced land cover change can have a substantial impact on the
structure and composition of natural landscapes as well as the various
biogeochemical processes that depend on them. At global level, human
influence including the conversion of natural landscapes to croplands,
forest plantations, pasture, and urbanization influence over 80% of the
earth's land surface outside the Antarctica (Sanderson et al 2002); with
the loss of 1.2 billion ha of forests and woodland; appropriating
between 32% and 55% of terrestrial net primary production (Rojstaczer et
al 2001; Imhoff et al 2004); accelerated extinction rates (Tilman et al
1994) and causing changes in local and regional hydrology (Ziegler et al
2004).
In the Gambia, urbanization, agricultural development (extensification
and intensification of cropland and livestock management) and
uncontrolled wildfires have decreased woodland cover from 60% in 1950 to
8% in 1993 (Ludwig and Bojang 1998). Over the past 100 years habitat
loss has been attributed to local extinction of a number of important
wildlife species including the elephant, giraffe, lion, leopard, 12
species of antelope, and unknown number of reptiles, birds and
amphibians species (GoTG 1999). Declined in plant species richness and
stocking levels have declined in many of the remaining woodlands (Ludwig
and Bojang 1998).
This paper examines the spatial patterns, biophysical and socioeconomic
consequences of land use change in western Gambia between 1986 and 1999.
Land use land cover maps derived remotely sensed Landsat TM imagery from
1986 and 1999 were analyzed within a geographic information system (GIS)
to identify the type, extent and distribution of land use change across
the region. Changes in landscape patterns during the time period were
analyzed by comparing a set of landscape indices generated from the two
cover maps. The changes are discussed in context of population change,
and the consequences for habitat and species diversity, hydrology, and
environmental sustainability in the Gambia.
Underlying Causes and Proximate sources of land use change in western
Gambia
Land use change is the result of interactions of complex interrelated
set of underlying socioeconomic drivers of land use, proximate
determinants of land use and biophysical attributes of the land (Forman
1987; Risser et al. 1984; Turner et al. 1990, Turner and Meyer 1994,
Lambin et al. 2001). Human population pressure, economic development,
technological change and policy are some of the underlying drivers of
land use change (Turner 1989; Stern et al. 1992; NRC 1999). Proximate
causes are those human activities that directly affect land cover
(Turner et al. 1993). Conversions of woodland to cropland, expansion of
infrastructure and conversion of croplands to settlements are few
examples of proximate causes of land use change (Turner et al. 1990;
Geist and Lambin 2001).
Since 1963 Gambia has witnessed dramatic change in the size and
distribution of its population. Between 1963 and 2003, the population of
the Gambia increased from 360,000 (a population density of 36 persons
per sq km) to 1,364,000 (130 persons per sq km). From 1983 to 2003 the
population grew at an average annual rate of 3.4%. Western Gambia with
its moderate climate and relatively higher economic opportunities as a
result of proximity to the City of Banjul saw its population grew from
234,698 in 1983 to 670,435 in 2003.
Between 1963 and 1983, Kanifing Municipal Council formally Kombo St Mary
Division experienced the largest population increase from 27,000 to
101,500. This rate of growth continued throughout the 1990s with the
population in reaching 228,000 in 1993 and 322,000 in 2003. By mid-1990s
congestion in Kanifing Municipal Council prompted expansion of
settlements into neighboring districts. Between 1993 and 2003 population
of Kombo North more than doubled from 80,478 to 166,351. Similarly, the
population of Kombo South and Kombo Central districts increased by 58%
and 50% respectively during the 10-year period.
At the time of independence in 1965, the capital city, Banjul was the
only urban center in the Gambia. Availability of modern amenities like,
schools, healthcare, commerce and jobs led to a rapid influx of people
from rural areas. Efforts to reduce overcrowding in Banjul and promote
economic growth in the suburbs led to a series of policy measures. In
addition to expanding electricity, piped water and public transportation
system in Kanifing Municipal Council, Kombo North and Kombo Central,
successive government encouraged the establishment of housing estates in
Kanifing, Bakoteh, Kotu and Brusubi as well as re-zoning of the entire
coastline as a Tourism Development Area.
The creation of a Tourism Development Area, TDA along the 40 km
coastline and the housing schemes led to a "Land Rush" in the area.
Driven by the desire to live next to the sea in the neighborhood of
hotels and modern amenities, the affluent segment of the population
began buying home gardens and orchards for construction of residential
and commercial buildings.
Results
Land Use Change
Land use change in western Gambia is characterized by conversion of
woodlands, croplands and fallow areas into bareground and builtup, BGB
areas (Fig. 4). During the 13-year period, BGB increased from 8585 ha to
27,190ha (217 percent) while area under woodland, cropland and fallow
(CAF) decreased by 24% and 45% respectively. This pattern is consistent
in all 5 districts with Kombo North experiencing the largest increase in
BGB cover from 1688 ha to 9568 hectares (467%) about 14.3 annual rate of
increase and more than twice the rate of population growth in the
district. In all districts cropland area was the most affected by BGB
increase. Across the region, 53% of all BGB areas in 1999 were croplands
and fallow in 1986 with this proportion increasing to 56% and 57% in
Kombo North and Kombo Central respectively.
<>Cropland and fallow with isolated trees and shrubs (CAF) cover
experienced the largest net loss, 45% of the 1986 area for the whole
region. Kanifing Municipal Council and Kombo North district saw the
highest rate of cropland loss, about 75% and 53% respectively. About 77%
of all CAF conversion in western Gambia and 89% in Kombo North district
went to BGB cover. Total woodland cover in the region decreased by 25%
(-2.2% per year). Rate of woodland loss vary among districts with Kombo
South recording the lowest decline, 14% (-1.4% per year) compared to 73%
Kanifing Municipal Council (-9.5% per year). For the entire region,
equal amounts of woodland cover were converted to BGB and CAF, 48% and
49% respectively, although this proportion change 58: 40 in Kombo
Central and 43:54in Kombo South.
Despite the 25% decrease in woodland cover, 80% of all woodland areas in
1999 were woodland in 1986 with 15% from regrowth of abandoned croplands
and fallow (CAF) cover. This is consistent with the fact that fewer
croplands and fallows are being allowed to revert back to woodland. The
retention rate, the proportion of cover class that did not change
between 1986 and 1999, was highest in mangrove (85%) followed by
bareground and builtup cover (69%).
Landscape structure
Spatial analyses results show changes in landscape structure across all
districts in western Gambia to be dominated by increase in PLAND and
AREA_MN of urban land use (bareground and builtup areas) and decrease in
both PLAND and AREA_MN for cropland and fallow and woodland classes
(Table 10). PLAND of urban areas increased from 11% to 41% with mean
patch area (AREA_MN) increasing from 12ha and 18ha. This increase
confirms consolidation of urban builtup resulting in an increase in mean
patch size and as the mean patch size increases the proportion of the
land use class that are of interior condition (at least 100 meters from
the edge) CPLAND also increased.
In Kanifing the core proportion of bareground and builtup cover class
grew from 1.6% to 52.9% of the total landscape area. Woodland and CAF
covers were increasingly fragmented during the 13-yr period as evidenced
by an increase in number of patches, decrease in both mean patch size
and core proportion, CPLAND. CPLAND for woodland class has decreased in
all districts, from 62% to 44% for the entire region and both Banjul and
Kanifing have lost all interior woodland areas. In all districts
bareground area consolidated into Mean core area, CORE_MN for bareground
builtup class increased from 11ha to 50ha.
Discussion
Western Gambia, occupying less than 7% of the total land area, is home
to 49% of the country's population. Fuelled by mild climate and
increased economic opportunities presented by proximity to the City of
Banjul, the region's population has between 1983 and 2003, increased
from 290,000 to 670,000. Using land cover maps derived from 1986 and
1999 Landsat TM imagery, we estimate that permanent settlement
(bareground and builtup areas) increased by 217% at the expense of
woodland, cropland and fallow (Cropland and fallow with Isolated Trees
and Shrubs, CAF) cover classes.
Overall Kombo North saw the highest increase in permanent settlement,
476%, nearly 10 times the rate of population increase in the district.
The difference between the rate of increase in bareground and builtup
cover class and that of actual population increase is attributed to land
acquisition by absentee land owners living outside the district. Also
the district is the site of several government supported housing
schemes. The biophysical and socioeconomic consequences of these changes
include habitat and species loss, changes in local hydrology, loss of
agricultural productivity increased in soil erosion.
Conversion of woodland to impervious surfaces reduces rainfall
infiltration, dry season streamflow as well as increase storm runoff
during the rainy season (Van der Weert, 1994; Ziegler et al 2004). Many
of the perennial streams in Kanifing Municipal Area and Kombo North
districts are now dry riverbeds or buildup areas and loss of wetland
ecosystems in these areas have to reduced the presence of many resident
and migratory species that depend on them for breeding or feeding or
resting.
Habitat loss is the number main cause of loss of species diversity in
the Gambia (GoTG 1999). The Abuko Nature Reserve, occupying only 105ha
is last remaining protected old-growth gallery forest in the whole of
western Gambia. Of more 270 species recorded in the reserve, four
species of monkeys, maxwell's duiker, two species of Genets, bushbuck,
sitatunga, the spotted hyena, the Nile and Dwarf Crocodile are all
locally outside the park with many other species like Nile and Boscs
Monitor, Ngama Lizard, various skinks and geckos, African Rock Python,
Royal Puff Adder, Black Necked Cobra and Green Mamba close to
extinction. The woodland cover includes seasonal moist forest, gallery
forest and dry woodland savannah habitat types, has the largest
concentration of land species.
Our results show that not only did total area of woodland decreased over
the 13-year period but mean patch size has become smaller and patches
have become more isolated. More importantly average core area (woodland
area more than 100 meters from other cover types) decreased more than
50% in all districts and non-existent in the Whole of Greater Banjul
Area. The total area of gazetted protected forest and national parks in
western Gambia is 2850 ha (3.9% of total area). Of these more than 1900
ha (67%) are forest plantations managed for timber production with
remaining 900 ha, managed as natural forest parks or wildlife
sanctuaries. Abuko Nature Reserve and Tanjeh Bird Reserve the two nature
reserves occupy a total of 730 ha. While these areas provide sanctuary
for many of species in the short-term, their long-term viability as
sanctuaries is doubtful because of their small size and increased
isolation from other habitats. More importantly there is increasing
evidence that stocking levels and species richness in many woodland area
including protected areas have significantly declined over the past 20
years. Ludwig and Bojang (1998) reported significant decline in the
number of important forest tree species from many parts of western
Gambia including Khaya senegalensis, Bombax bonopozense, Ceiba
pentandra, Parinaria excelsa. In addition to loss of habitats woodland
loss the region has directly affected the availability and price of
fuelwood, the primary source of domestic energy. Un-authorized
woodcutting in forest parks like Salagi, Furuyar and Nyambai has reduced
many of these to scrublands.
Relatively mild temperatures and high rainfall make western Gambia the
country's main fruits and vegetable producing area. Increased
urbanization in Kanifing Municipal Council effectively eliminated
orchards and market gardens in many parts of the district. The city of
Serre Kunda, which until 1970s was known for its mango groves, has lost
all its mango trees to buildings and pavement. Similarly, fruit orchards
and cassava fields in Kombo North, Kombo Central and Kombo South are
systematically being converted to buildings resulting to loss of
livelihood for many subsistence farmers in the region.
Western Gambia depends exclusively on well water for all its domestic
and industrial use. Until the 1990s local hand-dug wells were the main
source of portable water with a few boreholes developed in Kombo North
to supply water to Banjul and surrounding. Increased withdrawal to
provide piped water to rapidly growing population has led to overall
lowering of the water table, drying up streams and hand-dug wells across
the region. Also, the expansion of impervious surfaces that characterize
builtup areas reduces the amount of groundwater and surface water
recharge, a phenomenon that is blamed for increased saltwater intrusion
from the Atlantic into the groundwater system.
Regardless of the ultimate causes increase urbanization in western
Gambia at the cost of fertile cropland, diverse and rich woodlands are
occurring rapidly. At current rates all the woodland and cropland in
western Gambia will be lost before the end of this decade well before
the impacts on biodiversity, water quality and overdevelopment are felt.
These conversions are significant in that the changes are permanent and
the loss irreversible. The current study although simplified in many
ways should serve as a wakeup call for the government and people of the
Gambia regarding the fate of dwindling land resources in the face of
uncertain climate patterns and increased and uncontrolled urban sprawl.
To the effect it will be prudent for the government to declare 5 to 10
moratorium on settlements in the region so as to give time for the
development of a rational urban planning mechanism.
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