Download Causes of biodiversity loss in coastal ecosystems

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Causes of biodiversity loss in coastal
ecosystems
Els E. Martens *
Department of Zoology, University of Nairobi, Po. Box 30197, Nairobi, Kenya
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Although far less publicised than loss of biodiversity on land, the loss of marine
genetic, species and ecosystem diversity is a global crisis in its own right. The coastal
strip (the shallow water, the intertidal area and the immediately adjacent land) is
the most vulnerable as well as the most abused marine zone. Coastal ecosystems
are not only an important source for essential products for mankind, including
foods, medicine, raw materials and recreational facilities, but also provide ecologi­
cal services that directly benefit the coastal zone.
Loss of biodiversity in coastal ecosystems has both direct and indirect causes. The
direct mechanisms involved include habitat loss and fragmentation, physical
alteration, over-exploitation, pollution, introduction of alien species and global
climate change. The root causes that drive these proximate threats lie in the high
rate of human population growth, the unsustainable use of natural resources,
economic policies that fail to value the environment and its resources, insufficient
scientific knowledge, and weak legal and institutional systems.
The ever-growing exploitation of the coast and its resources is a reflection of the
steady population increase, especially in coastal zones. Habitats are changed or lost
by accelerating urbanisation, development of tourist facilities, industrial installa­
tions and mariculture. Land-based and upstream activities alter sedimentation and
freshwater input in downstream estuaries and coastal biotopes. Contaminants from
sewage disposal and agricultural runoff are rapidly increasing and areas of eutro­
phication and chemical pollution are expanding. Careless disposal of plastic wastes
not only causes a litter problem but also widespread mortality of marine species.
Exploitation ofliving marine resources may damage habitats and alter food webs,
while mariculture generates its qwn pollution and may upset ecological balances
by the introduction ofalien species. Global atmospheric changes, which may result
in altered rainfall patterns and rising sea-level, have become a matter of growing
concern.
Ie
ns
10.
*
Present address: Kenya Wildlife Service - Netherlands Wetlands Conservation Programme,
P.O. Box 82144, Mombasa, Kenya
69
Causes of biodiversity loss in coastal ecosystems
Biodiversity in marine ecosystems
Although fewer marine than land species have been described, marine ecosystems
are far more diverse than terrestrial ones. Of the 33 extant animal phyla, only 11
occur on land while 32 are found in the seas. The coastal and marine biotopes
host nearly the entire extant diversity of basic animal body plans, and also contain
far greater diversity in body size, from whales to picoplankton, than is found on
land. Further, filter feeders create extra levels in aquatic food chains, which tend
to be more complex than terrestrial ones (Margulis & Schwartz 1988,
WRIIIUCN/UNEP 1992).
Marine biological diversity is for most groups considerably higher in tropical
regions than in cooler waters. Within the tropics, many taxa reach the highest
species diversity in the Indo-West Pacific. Tropical, marine ecosystems also have a
high diversity in functions benefitting people (Dugan 1990, Hamilton & Snedaker
1984, Martens 1992, Saenger et al. 1983, Salm & Clark 1984). The coastal strip is
the most vulnerable and the most abused marine zone.
Several aspects of marine systems complicate the task of conservation. First, coastal
waters and their organisms extend beyond and move between national boundaries.
Second, coastal ecosystems are at the receiving end of drainage from land, and
most wastes eventually concentrate there. Third, reproduction ofmarine organisms
can be very variable in space and time. Fourth, some species require more than
one habitat during development and are threatened by activities in anyone of
them (Dugan 1990, Salm & Clark 1984).
Marine conservation has only become an issue of global concern within the last
20 years (WRIIIUCN/UNEP 1992). Although a relationship between human
population increase and environmental change has long been recognised, attempts
have only recently been made to assess the cumulative impacts of development in
the coastal zone by recording their physical, chemical and biological consequences.
Damages that would be readily observed on land are seldom noticed; wastes just
seem to disappear. Also, there is no tradition of managing marine areas for
conservation as on land. Often pollution of coastal systems originates in the open
seas outside the jurisdiction of states. Because the ocean has been an 'open-access
resource', competitive exploitation has been the norm. This led to regional and
international conventions that impose a framework and laws (e.g. UNEP's Regional Seas Programme and the Convention on the Law of the Sea).
Using resources in the coastal zone requires integrated management (including
both land and water components) and protection of some natural areas, so that the
zone may yield the greatest benefit to present generations without losing its
potential to meet future needs. Preserving genetic diversity is a matter of both
ethics and economic survival. Genetic diversity is needed to sustain and improve
agricultural and fisheries production, to keep future options open, to guard against
harmful environmental change, and to secure the raw material for scientific and
industrial innovation (Salm & Clark 1984).
71
Conservation of biodiversity in Africa
Human activities have dramatically increased the intensity, pace and kind of
environmental changes that lead to habitat loss and pose severe adaptive challenges
to marine organisms. Response to these changes includes drastic declines of many
fisheries and extinction of several species. The loss of species and ecosystems
obscures equally important threats to genetic diversity, which is essential for species
survival in a changing environment.
, ough fewe~
ir filr more
t
I ntrod uction
The coastal waters of many African countries contain some of the world's richest
ecosystems characterised by coral reefs, seagrass meadows, mangrove forests,
estuaries and floodplain swamps. Because of the economic benefits that can be
derived from them, the coastal zones teem with human settlement. Without doubt,
the greatest risk for marine ecosystems is their proximity to such high concentra­
tions of humans.
ine biologil
:ions than in
des diversity
i.
diversity in
4, Martens 1
most vulner:
The tremendous increase in the human population and the intense activities to
meet economic needs have placed an immense pressure on natural resources, and
have led to their misuse or abuse. Anthropogenic destruction of resources, frag­
mentation and change ofhabitats, release ofpollutants, introduction ofalien species
and climate change are now more rapid, intensive and widespread than natural
changes (Dugan 1990, WRIIIUCN/UNEP 1992). Although it has often been
assumed that marine organisms are more resistant to extinction than terrestrial
ones, this assumption only reflects a shorter history of intensive exploitation and
our relative ignorance of the marine realm.
The coastal zones of most nations are subjected to increasing pressures manifested
by a variety of human activities, notably urbanisation, industrialisation, fishing,
coastal aquaculture, mining, waste disposal, oil drilling, shipping traffic and tourism
(Bryceson 1990, Dugan 1990, Martens 1992, Portmann et al. 1989, Saenger et al.
1983, UNEP 1982a-c, 1984a,c, UNESCO 1981, 1986). This mix of water-based
and land-based economic activities has put considerable stress on those coastal
resources that are the very basis of their viability. The fast pace of technological
development and economic activity has not allowed for the evolution of appro­
priate attitudes and structures to minimise the exploitation that poses a threat to
marine biodiversity. On the other hand, the information necessary for proper
resource management has remained inadequate and competing human uses have
often remained unrelated and unplanned. Also, the majority of the population
subsisting in coastal systems are the rural poor, and any change will affect them
first (Dugan 1990, WRIIIUCN/UNEP 1992).
This paper gives an overview of the main causes of biodiversity loss in African
coastal ecosystems.
ral aspects 0
.,crs and their
ond, coastal
.·st
wastes ever.
I:
1 be very vari
habitat duri
~m (Dugan 1S
p
ine conserve
"'Years (WRI!
ulation incre
, only recent
f=oastal zone 1
ages that we
pt to disappe
lServation as c
outside the j
)urce', compe
ernational COJ
mal Seas Progl
I
ling resources
:h land and wa
e may yield
ential to mee
ics and econo
icultural and f
ful environr
ustrial innoval
IJ'
70
di~
cur on land 1
,1st nearly the!
greater divel
d. Further, 6:
be more c
I1IUCN/U
Conse",ation oj biodiversity in Africa
Threats to marine biodiversity
The ways that humans threaten marine biodiversity can be grouped into proximate
threats and root causes; the former are driven by the latter. Concerns may differ
from region to region, reflecting local situations and priorities.
Proximate threats
The main types of human activities that damage marine organisms and ecosystems
are: over-exploitation, physical alterations and habitat loss, pollution, introduction
of alien species, and global climate change (Dugan 1990, UNEP 1982c).
Over-exploitation
Coastal ecosystems are an important source ofessential products for mankind, such
as foods, medicines, raw materials and recreational facilities (Dugan 1990, Martens
1992, Saenger et ai, 1983, Salm & Clark 1984, UNEP 1982a-c, 1984b,c, 1985a,
1989). The ever-growing exploitation of coastal resources is a reflection of the
population increase, the most important root cause for biodiversity loss. Tourist
populations, generally concentrated in few areas, increase the local exploitation
for specific crustaceans such as lobsters, crabs and prawns (Schood & Visser 1991).
In theory, virtually any marine organism, even the slowest-maturing or least fecund
species, could be exploited sustainably as long as no more are taken than reproduction
can replace. However, today's exploiters are numerous and their technologies powerful.
Current fishing activities exceed sustainable yields on a large number of traditional
fishing grounds, especially in coastal areas and on continental shelves (Sanders et ai,
1990). Most commercially valuable marine populations are now over-exploited.
Because most methods used to catch targeted fish and shellfish are unselective, large
numbers of invertebrates, fishes, sea turtles and marine mammals are caught and then
discarded. Dynamite fishing and poisoning are unselective and kill large numbers of
vertebrates that are then not harvested (IUCN 1990, Salvat 1987).
Marine mammals, seabirds, sea turtles and many invertebrate species are also
threatened by direct exploitation. Marine mammals and sea turtles are long-lived,
slow-reproducing organisms whose attractive products make them extremely
vulnerable to over-exploitation. Nesting turtles on the beaches are defenseless and
more readily captured than at sea, while their eggs are easy to collect. Many seabird
species are colonial nesters, making them vulnerable to large-scale egg collection
and hunting (IUCN 1990, Salm & Clark 1984, Wells 1988).
Many marine organisms, including corals, sponges, molluscs, echinoderms, puffer
and trigger fishes, and turtles, are collected widely for curios or jewellery (IUCN
1990, Martens 1992, Wells 1988). The over-fishing ofshallow inshore populations
can have serious local effects on these species and their habitats.
Other over-exploited marine products are stony corals for building material and
mangroves for fuelwood and timber (IUCN, 1990, Hamilton & Snedaker 1984,
Martens 1992, Salm & Clark 1984). These activities have contributed to species
72
declines and ca
Martens 1992, 1
Over-exploitatic
returns but also
trophic relationsl
involving multif
species frequent!
food webs and ~
Physical altera
Because organisl
each place are Cl
conditions are al
the biological co
cleared to make
agriculture (Dug
Not only does SI
but many comme
grounds (Salm II
benthic commur
by the trawling
sediment (Salvat
Upstream defore
load in runoff. Tl
threatens coastal
their feeding or r
turbidity reducin
occurred, longer­
substrate, with COl
ecosystems that f
reefs, are especial
decreases the dive
which leads to a
sustain (Blom 19~
hand, reduction in
due to modificati
coastal ecosystem
shrink and fish pc
~he constant or fn
iiiversity. Dams d
!Valuable coastal h:
''the Senegal and N
I, at their deltas and 1
. in fish catch (Dug.
Causes of biodiversity loss in coastal ecosystems
X:lmate
, differ
fstems
llction
[,such
artens
985a,
)f the
aurist
tation
991).
~cund
ction
erful.
ional
et ai.
'ited.
large
then
rs of
also
red,
lely
and
lird
ion
fer
:N
ms
rld
:4,
es
declines and caused structural damage to the habitats (Dugan 1990, ]accarini &
Martens 1992, Martosubroto & Naamin 1977).
Over-exploitation not only reduces specific populations and causes lower economic
returns but also causes genetic changes in the exploited populations and alters the
trophic relationships among species. Marine organisms are part ofintricate food webs,
involving multiple trophic levels at several spatial and temporal scales. Removal of
species frequently leads to losses of other species and to changes in communities,
food webs and key species (Beddington 1984, McClanahan & Muthiga 1988).
Physical alterations and habitat loss
Because organisms are adapted to specific abiotic environments, the conditions in
each place are crucial in determining the community of species that live there. If
conditions are altered, there will be corresponding changes in the composition of
the biological community. Vast areas ofmangroves, estuaries and beaches have been
cleared to make way for coastal development, industrialisation, aquaculture or
agriculture (Dugan 1990, IUCN 1990, UNEP 1982a,c, 1984b,c, UNESCO 1979).
Not only does such development destroy rich mangrove and estuarine fisheries,
but many commercially valuable species depend on these coastal habitats as nursery
grounds (Salm & Clark 1984, UNEP 1985b). Trawling profoundly disturbs the
benthic communities on the seabed. Disturbance includes physical damage caused
by the trawling gear and reduced photosynthesis caused by resuspension of
sediment (Salvat 1987).
Upstream deforestation and careless agricultural practices increase the sediment
load in runoff. The addition of anthropogenic sediments, especially silts and clays,
threatens coastal systems by smothering or burying marine organisms, clogging
their feeding or respiratory organs, coating photosynthetic surfaces, or increasing
turbidity reducing the light available for photosynthesis. After sedimentation has
occurred, longer-term effects can follow from changes in the particle size of the
substrate, with consequences for the structure of the benthic fauna. Shallow coastal
ecosystems that flourish in clear waters, such as seagrass beds and fringing coral
reefs, are especially vulnerable to siltation. An increase in sedimentation usually
decreases the diver~ity of coral species and the percentage of living coral cover,
which leads to a decline in the diversity and number of fishes that the reef can
sustain (Blom 1985, Giesen & Van der Kerkhof 1984, Salvat 1987). On the other
hand, reduction in sediment and nutrient supply from the altered freshwater inflow,
due to modification of river basins, can have dramatic effects in estuarine and
coastal ecosystems. Deltas and their mangrove, marsh and mudflat communities
shrink and fish populations can decline rapidly. Estuarine ecosystems depend on
the constant or frequent freshwater inputs that determine their productivity and
diversity. Dams change the amount and timing of freshwater input and reduce
valuable coastal habitats (Dubois et ai. 1985, IUCN 1990, UNESCO 1981). On
the Senegal and Nile Rivers, dams reduced the freshwater and sediment discharge
at their deltas and lead to coastal erosion, salt water intrusion and significant decline
in fish catch (Dugan 1990).
73
Conservation of biodiversity in Africa
Other activities causing physical alterations are coastal mining and construction,
mangrove clearing for agriculture and aquaculture, dynamiting of reefs causing
serious beach erosion, and dredging of inshore waters. The negative impacts of
tourism include trampling, boating and anchoring on the coral reefs (Martens
1992).
Pollution
A complex mix of anthropogenic pollutants pose a serious threat to estuaries and
coastal waters. Anthropogenic nutrients enter the coastal waters as runoff from
fertilized agricultural and silvicultural lands, sewage effiuents including domestic
and industrial wastes, dredging, vessels dumping cargo at sea and atmospheric
deposition of air-borne pollutants. Nitrogen and phosphorous are the most
common limiting nutrients in coastal waters and their availability determines
species composition and growth of plants, which in turn affects the entire
ecosystem. In most developing countries, sewage is discharged untreated or only
partially treated into rivers, lagoons and coastal waters via short outfalls, most of
which were installed with little attention to advanced planning. Human sewage
(together with pathogenic organisms) and agricultural runoff (with increasing
amounts ofinorganic fertilizers) are particularly rich in nitrogen and phosphorous,
and form the major source of pollution in coastal waters.
The biological process initiated by such nutrient enrichment--eutrophicationcan have far reaching effects such as: increased primary production, changes in
plant species composition, dense and sometimes toxic algal blooms, changes in
structure ofbenthic communities, and conditions of hypoxia or anoxia (GESAMP
1990, Pearson & Rosenberg 1978, Portmann et ai. 1989, UNEP 1982b). Contamination of inshore waters by sewage also causes serious public health problems
(portmann et ai. 1989). Coral reefs grow only in clear waters with low nutrients.
Nutrient pollution creates algal blooms that cloud the water and limit the sunlight
reaching the corals.
Chemicals, such as trace metals, radionuclides and petroleum residues, become
toxic environmental contaminants when discharged in excessive concentrations.
Many contaminants become associated with sediments and may remain sequestered until resuspended by waves and currents or until sediments are disturbed by
dredging activities. Synthetic compounds are becoming increasingly important
chemical pollutants in the sea. Among the most persistent ones are the chlorinated
hydrocarbon pesticides used in agriculture (PCBs, DDT), dioxins from incinerators and paper mills, organotins (TBT) used as antifoulants, and oil dispersants that
are toxic and cause the oil to sink onto benthic communities (GESAMP 1990).
The main concern for toxic chemicals are the long-term effects as many of them
are persistent in the environment and become concentrated through the trophic
chain. In exposed marine organisms, toxins can cause death, disease, reduced
reproductive success and developmental aberrations.
74
massive side-ef
on oceans a
rbons, accumula1
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peratures may
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lange in intensity
Causes of biodiversity loss in coastal ecosystems
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Communities in contaminated ecosystems have reduced species diversity as more
sensitive species are the first effected and tolerant species, relieved of competition
or predation, proliferate. Crude oil and gas production, although bringing in
important foreign exchange earnings and local employment, have significant
impacts on coastal areas (IUCN 1990, UNEP 1984a). Industrial and domestic solid
wastes are often dumped in mangrove creeks with consequent outflushing of
rubbish and toxic products (GESAMP 1990, Martens 1992). With the increased
use and disposal of plastics, solid wastes are now more than a litter problem as
plastic debris causes widespread mortality in marine species through entanglement
or ingestion (Carr 1987).Because of their strength, buoyancy and durability,plastic
products account for more than 50% of all anthropogenic debris items found at
sea and on coastlines.
Introduction of alien species
Introduced species are responsible for many extinctions, especially on islands
where the indigenous biota usually lack the necessary defensive or competitive
capabilities. Many marine organisms are transported by humans, either intentionally for aquaculture and private collections or accidentally from fouling and
ballast-water of ships. Some of these exotics are now dominant species in coastal
communities where they have replaced native species (Carlton 1989, GESAMP
1990, WRIIIUCN/UNEP 1992).
Global climate change
A massive side-effect of air pollution~lobal warming-may have profound
effects on oceans as greenhouse gases, especially carbon dioxide and chlorofluorocarbons, accumulate in the atmosphere. The greenhouse effect will not only cause
an increase of global temperature but also change the distribution of heat thereby
altering patterns of ocean circulation, precipitation and storm tracks. Warmer
temperatures may also cause a rise in sea level of about 140 cm (estimates range
from 8 to 340 cm) during the next century, due to thermal expansion of the water
itself and the likely melting of icecaps (GESAMP 1990, IOC 1992,
WRIIIUCN/UNEP 1992).
Together, these changes could have serious effects on coastal biodiversity. Rapid
environmental change is a common cause of species impoverishment as it favours
small-bodied rapid-producers over large-bodied long-living organisms. Increase
in water temperature will also affect temperature-dependent processes such as
reproduction and growth. Coral bleaching, due to prolonged higher temperatures,
is becoming a widespread phenomenon and significantly reduces coral growth. As
sea levels rise, coastal erosion and severity offlooding will increase so that coastlines
will recede unless stabilised by dykes or sand influx. Changes in rainfall patterns,
salinity distributions and temperatures will alter rates of delta sedimentation, and
coastal currents and upwelling patterns are likely to shift geographically and
change in intensity.
75
Conservation of biodiversity in Africa
A common consensus is that global warming will make the dry areas drier and wet
areas wetter, bringing about a climate of extremes. Coastal wetlands, being highly
populated, are likely to suffer the most visible impacts as their landward movement
may be hindered by the ever-growing development of coastlines. With the loss of
this coastal fringe, the species it contains will be lost too. Many islands would be
completely submerged if the more extreme projections of sea level rise occur.
Root causes
Biotic impoverishment is an almost inevitable consequence of the ways in which
the human species has used and misused the environment. The main root causes
of biodiversity loss lie in: demographic pressure and unsustainable use of natural
resources; economic policies that fail to value the environment and its resources;
insufficient knowledge and its poor application; weakness in legal and institutional
systems (Dugan 1990, McNeely et ai. 1990, UNEP 1984b, WRIIIUCN/UNEP
1992).
markets. Man
purification, s
Because these
that decide w
et al. 1990). "
degradation 0
Economic pol
radation as th
increase envir
products. Ano
both the use a
often the local
out of plannin
Deficiencies i
Scien tists still
innumerable 0
exists it does r
develop policit
coastal biodive
1992). Except
most marine re
databases on m
policy-makers,
difficulty in coc
jurisdictions an
A final difficul~
resource conSUl
campaigns.
I
Human population growth and unsustainable use of resources
The global human population is quickly rising towards the 6 billion mark. Almost
70% of this population lives near aquatic systems, especially coastal zones. In
countries with high fertility rates, about half of the populations is under 16. The
resulting demographic momentum in coming years, due to this large number of
people reaching their reproductive age, means that the global population will
continue to grow for at least the next half-century. The rates and magnitude of
this growth depend on social and economic measures, especially on economic
development in developing countries (WRIIIUCN/UNEP 1992). As numbers
increase, the consumption of renewable and non-renewable resources has a higher
rate of increase. The recreational use of coastal waters is also increasing, in some
areas representing the major industry. Coastal tourism generally shows peaks in
tourist numbers in certain areas, especially those with high biodiversity such as
coral reefs, and at certain times of the year. High tourist numbers put additional
pressure on coastal biodiversity through excessive food, energy and water consumption, physical alterations of the environment (infrastructural development,
boating, trampling), and cultural alterations (Schoor! & Visser 1991). Ironically, this
environmental degradation and congestion may destroy the main natural assets on
which tourism development is based.
Economic systems and policies that fail to value the environment and its
resources
Conversions of natural systems to farmlands or industrial areas take place due to
the urgent need for economic land use. These developments are often economically and biologically unsound because they are implemented regardless of
sustainability, and because natural habitats are commonly under-valued. There are
several reasons for the mis-valuation of biological resources. Many resources, such
as food, fuelwood and medicinal plants, are consumed directly and never enter
76
J#ak legal an,
Most COuntries:
resources, but ea
or tourism. Eco:
including localciplinary and im
nication and i
developing cour
ments to ensure
(Dugan 1990,!v
legal constraints
fragmented and
grated and regio
biotic communil
Causes of biodiversity loss in coastal ecosystems
nd wet
highly
rement
loss of
,uld be
cur.
which
causes
latural
>Ufces;
Itional
JNEP
I.lmost
les. In
5. The
ber of
n will
Ide of
lOmic
mbers
ligher
some
aks in
Ich as
tional
connent,
y. this
:ts on
its
ue to
omiss of
~e are
such
enter
markets. Many values of coastal biotopes do not have markets, such as water
purification, storm surge protection, and nursery grounds for fisheries products.
Because these are 'free goods' they tend to be ignored in economic calculations
that decide whether such biotopes should be conserved or developed (McNeely
et al. 1990). The result is a systematic bias favouring development and hence
degradation of coastal ecosystems.
Economic policies in many African countries contribute to environmental degradation as the need for foreign exchange earnings often forces countries to
increase environmental exploitation, such as for wood, minerals and marine
products. Another aspect is the inequity in ownership and flow of benefits from
both the use and conservation of biological resources (McNeely et al. 1990). Too
often the local communities, who are dependent on the natural resources, are left
out of planning but in the end pay the price.
Deficiencies in knowledge and its application
Scientists still do not have adequate knowledge of coastal ecosystems and their
innumerable components (Martens & Jaccarini 1990). Even where information
exists it does not flow efficiently to decision-makers, who have often failed to
develop policies that reflect the scientific, economic, social and ethical values of
coastal biodiversity (Dugan 1990, McNeely et al. 1990, WRIIIUCN /UNEP
1992). Except for research on commercially important resources, until recently
most marine research had scientific rather than resource-management goals. Few
databases on marine subjects exist that are accessible or informative enough for
policy-makers, especially on a regional and international scale. An additional
difficulty in coordinating information collection and transfer relates to overlapping
jurisdictions and competition among agencies concerned with marine resources.
A final difficulty is often public reluctance to accept policies that reduce excessive
resource consumption, which shows an urgent need for more public awareness
campaigns.
~ak
legal and institutional systems
Most countries have different institutions that are responsible for managing coastal
resources, but each ofthem focuses on only one aspect such as agriculture, fisheries
or tourism. Ecological realities, however, clearly call for a cross-sectoral approach
including local-community participation. It is only quite recently that multidisciplinary and institutional collaboration has been established to facilitate communication and information exchange among all concerned groups. Many
developing countries lack adequate environmental laws and enforcement instruments to ensure protection of the environment and sustainable use ofits resources
(Dugan 1990, McNeely et al. 1990). Largely because of these institutional and
legal constraints, biodiversity conservation and management has typically been
fragmented and restricted to specific protected areas or species. However, integrated and regional approaches are needed to address the habitat needs of whole
biotic communities in relation to development programmes.
77
Conservation of biodiversity in Africa
Conclusions
Although some coastal ecosystem loss is inevitable and can even benefit man, much
is both detrimental and avoidable. Only by increasing awareness of the value of
coastal ecosystems and designing economic incentives that encourage people to
support conservation, will the rate of biodiversity loss be subsequently reduced.
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Impact of
I
S.T. Kariuki
Egerton University, P.
Deforestatio.n, espe(
adverse environmen
by many people as c
actual uprooting of
farmers tend to upr
and pathogens.
Over-grazing may r,
is a major problem i
vegetation regrowth
alists have been enCi
Deforestation is assc
the industrial couo1
logging in tropical a
so its affect is greate:
countries to lose mt
logged annually in I
and 1980; by 1980 ~
Rural industries (suc
and charcoal bumin
about 1 ha of woodl:
about 0.2-0.3 m 3 oj
industries.
Charcoal productiof
is estimated that 4 t<
preferred by charcc
informal traders use
out of control causin
to have reduced fore
Besides extinction 0
economic consequel
reservoirs, fuelwood
80