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A review of the threat of oil exploitation to mangrove ecosystem: Insights from Niger Delta, Nigeria


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Mangroves supply various goods and provide invaluable ecological services to humanity. They serve as habitat to different species of fishes, provide a variety of plant products, improve water quality, provide fish and shellfish for local communities, ensure coastal stabilization, provide food chain support for near-shore fisheries, and undertake carbon sequestration. They also serve as source of fuel, medicinal ornaments, and honey for the local population. Despite these socio-economic and environmental benefits of mangroves, its depletion is a continuous practice in the Niger Delta region of Nigeria. This is caused primarily by anthropogenic activities, including over exploitation, oil spills, and crude oil exploratory activities. These activities have destroyed livelihood structures, affected global warming control measures, and affected the coastal system stabilization of the Niger Delta region. This paper reviews existing literature and analysed identified gaps. The review indicated a lack of participatory framework for mangrove conservation in coastal communities in the Niger Delta despite the desperate need given the level of mangrove degradation in the region. In addition, mangrove conservation policies exclude community participation and negates co-management frameworks for mangrove conservation and protection in the region. This paper reviews the impacts of land contamination on mangrove ecosystems and socio-economic activities of local communities in the Niger Delta region of Nigeria. A framework for mangrove conservation in the coastal communities is also proposed, with emphasis on the need to develop the capacity of a critical mass of locals and provide low-to medium-level manpower in mangrove restoration in the Niger Delta region.
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Review Paper
A review of the threat of oil exploitation to mangrove
ecosystem: Insights from Niger Delta, Nigeria
Amarachi Paschaline Onyena, Kabari Sam
Department of Marine Environment and Pollution Control, Faculty of Marine Environmental Management, Nigeria Maritime University,
Okerenkoko, Delta Sate, Nigeria
article info
Article history:
Received 16 October 2019
Received in revised form 8 February 2020
Accepted 9 February 2020
Occupational dislocation
Rural-urban drift
Artisanal rening
Environmental refugees
Climate change
Mangroves supply various goods and provide invaluable ecological services to humanity.
They serve as habitat to different species of shes, provide a variety of plant products,
improve water quality, provide sh and shellsh for local communities, ensure coastal
stabilization, provide food chain support for near-shore sheries, and undertake carbon
sequestration. They also serve as source of fuel, medicinal ornaments, and honey for the
local population. Despite these socio-economic and environmental benets of mangroves,
its depletion is a continuous practice in the Niger Delta region of Nigeria. This is caused
primarily by anthropogenic activities, including over exploitation, oil spills, and crude oil
exploratory activities. These activities have destroyed livelihood structures, affected global
warming control measures, and affected the coastal system stabilization of the Niger Delta
region. This paper reviews existing literature and analysed identied gaps. The review
indicated a lack of participatory framework for mangrove conservation in coastal com-
munities in the Niger Delta despite the desperate need given the level of mangrove
degradation in the region. In addition, mangrove conservation policies exclude community
participation and negates co-management frameworks for mangrove conservation and
protection in the region. This paper reviews the impacts of land contamination on
mangrove ecosystems and socio-economic activities of local communities in the Niger
Delta region of Nigeria. A framework for mangrove conservation in the coastal commu-
nities is also proposed, with emphasis on the need to develop the capacity of a critical
mass of locals and provide low-to medium-level manpower in mangrove restoration in the
Niger Delta region.
©2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND
license (
1. Introduction
Mangroves are salt tolerant and sheltered intertidal forest covering most tropical and subtropical coasts with approxi-
mately 137,760 km
e152,360 km
of the worlds surface (Kainuma et al., 2013) yet are highly endangered coastal forest
ecosystem. Across 123 countries and territories around the globe, a sum of 73 mangrove species and hybrids are dispersed
(Spalding et al., 2010). On thewestern coast of Africa, mangroves extend fromthe coasts of Mauritania to Angola in the Gulf of
Guinea with about a third within the Niger Delta of Nigeria.
*Corresponding author.
E-mail address: (K. Sam).
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Global Ecology and Conservation 22 (2020) e0 0961
Mangroves are trees or large shrubs that have adapted to survive in harsh environmental conditions. Hence, has developed
unique survival features in the face of high salinity, anaerobic and waterlogged soils, and a challenging environment for seed
dispersal and propagation (Spalding et al., 2010). Mangrove ecosystems are a shelter for biological diversity consisting of
diverse aquatic and terrestrial ora and fauna which include mammals (monkeys, antelopes, and manatees), molluscs (bi-
valves, oysters), crustaceans, sh, reptiles and avian species.
Mangroves supply several ecosystem services that add to human wellbeing (Van Bochove et al., 2014 Friess, 2016) and may
be threatened by oil explorations and climate change. Mangroves are natural coastal habitats that buffer coastlines from
erosion and inundation, providing important protective services. Other benets, including nursery grounds for commercially
and recreationally valued species, landing point for migratory birds, ltration of sediment, nutrients and pollutants,
enhancement of coastal sheries, support tourism, protect coastlines (shoreline and seashore protection, stabilization of
coastal and shoreline substrate) against natural disasters such as oods and protection of coastal communities from waves
and extreme weather conditions (FAO, 2007;Mukherjee et al., 2014;Huxham et al., 2015;Barbier, 2016). Livelihoods in many
coastal communities in developing countries such as Nigeria largely depend on the productivity of mangroves and adjacent
alluvial systems. At least, 24 mangrove goods have been identied (Ackah-Baidoo, 2013). It is reported that over 60% of
commercial shes in the Gulf of Guinea breed in the mangroves of the Niger Delta. Thus, an impact on the mangrove of the
Niger Delta affects sh distribution in the Gulf of Guinea. Additionally, cultural services (non-material benets) of mangroves
such as recreation, spiritual enrichment and aesthetic that directly affect the people has been disproportionately impacted.
However, the Niger Delta mangroves are amongst the least studied and the worst degraded globally (Zabbey and Uyi, 2014).
Threats to the regions mangroves include overharvesting for fuel wood, oil spill, dredging, wetland reclamation and nypa
palm invasion. A recent review ofcrude oil impact on mangrove shows that 37% of the global impact had occurred in the Niger
Delta (Duke, 2016).
These benets of the mangrove ecosystem, notwithstanding, the disappearances of the mangroves are having a major
impact on the vulnerability of coastal communities particularly in the developing countries (Spalding et al., 2014). This
vulnerability is a contribution of different stakeholders whose responsibility is either neglected or abandoned. While the
government has the responsibility to set policy goals for the conservation of the mangrove ecosystem, rural communities also
have a role in mangrove ecosystem conservation and this could be achieved through a participatory and co-management
2. Onset of oil exploration
Oil prospecting in Nigeria started in 1908 bythe German Company, Nigeria Bitumen Corporation in the Araromi area of the
present Ondo State (see Fig. 1). Their pioneering effort ended due to the outbreak of the First World War in 1914. In 1937, oil
Fig. 1. Africa showing the Niger Delta region and oil pipeline network (red lines) (Sam et al., 2017). (For interpretation of the references to colour in this gure
legend, the reader is referred to the Web version of this article.)
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e009612
prospecting resumed in Iho, Ikeduru local government area (LGA) in Imo State by Shell DArcy (forerunner of the present Shell
Petroleum Development Company of Nigeria) (Ijeh, 2010). The company was awarded the sole concessionary right covering
the whole territory of Nigeria. Similar to the earliereffort, their activities were again interrupted by the Second World War but
resumed in 1947 and by 1951; they discovered oil but not in commercial quantity at Akata, near Eket (Frynas, 2000). In 1956,
oil was discovered in commercial quantities at Oloibiri (Bayelsa State) in the Niger Delta Area by Shell and commercial
production began in 1958 (Nwilo and Badejo, 2007). In February 1958, Nigeria joined the league of oil producers with
approximately 6000 barrels per day. Following this feat, by 1961, other companies such as Mobil, Chevron (formally Gulf),
Agip, and Safarap (Elf) commenced oil exploration activities on-shore and off-shore areas of Nigeria, and the exploration
rights formally granted shell alone was extended to these new comers.
Today, the Niger Delta region of Nigeria has about 606 oil elds with 355 situated onshore; 251 situated offshore with 5284
drilled oil wells and 7,000 km of oil and gas pipelines (Anifowose, 2008;Onuoha, 2008). Nigeria is the largest oil producer in
Africa and the sixth largest in the world (Bello, 2017), producing an average of 2.2 million barrels per day (Pieprzyk et al.,
2009). For the past three decades and even currently Nigerias economy is heavily dependent on the earnings from the oil
sector. The oil sector contributes over 11% to Nigerias Gross Domestic Product (GDP), 95% of foreign exchange earnings and
83% of total Federal Government revenue and has therefore transformed the Nigerias political economy (NNPC, 2019).
2.1. The Nigerian Niger Delta
Nigeria occupies a total area of 923,768 km
, which consists mainly of land and water with 910,768 km
and 13,000 km
respectively and 92 million ha (Bello, 2017). Nigeria has a total population of 190 million people, with an estimated proven gas
reserve of 202 trillion cubic feet (TCF) and 37.4 billion barrels of proven oil reserves (OPEC, 2019). The Niger Delta is made of
nine states (Fig. 1) and remains the hub of oil and gas production and associated activities in Nigeria (Egwurugwu et al., 2013;
Sam et al., 2017). The Niger Delta region currently has about 13,329 settlements. Out of that number, only 98 are rated as
urban, the rest are scattered rural villages which are mostly cut off from the most basic amenities and infrastructure. The
region also hosts over 800 oil eld communities with over 900 active oil wells and thousands of other oil exploitation
Nigerias mangroves in terms of area covered are the largest in Africa with an estimated 10,515 km
, mostly lining the Niger
Delta coastline. The Niger River Delta is located in the southern part of Nigeria and has vegetation covering a landmass of 7.5
million ha consisting of extensive mangrove forests, brackish swamp forests, and rainforests. The region has abundant sh
resources, widespread forests, and agricultural lands for sustainable agriculture (Ana, 2011;Ukpaka, 2012). The Niger Delta
region of Nigeria has numerous oil elds situated onshore and offshore with over 123 gas aring sites; aring about 17.2
billion cubic metres of natural gas per year in conjunction (Ishisone, 2004), making Nigeria one of the top greenhouse gases
emitters globally (Bello, 2017). Gas aring, exploration, drilling, extraction, transportation and rening of oil in the upstream
and downstream sectors including waste discharge, accidental spills and operational failures, as well as sabotage, oil
bunkering and artisanal rening contribute to serious environmental pollution and destruction of mangroves (Bello, 2017;
Zhang et al., 2019).
3. Impacts of crude oil on mangroves
Mangroves are tidal wetlands and are considered to be the most highlysusceptible marine environments to large scale and
chronic oil spill (Zhang et al., 2019). Signicant amount of crude oil is discharged into coastal environments and these
mangroves are extremely responsive to contamination by oil and industrial waste. For the past 60 years, there have been no
less than 238 major oil spills adjacent to mangrove-dominated shorelines worldwide. These oil spills have accounted for over
5.5 million tonnes of oil released directly, affecting up to more or less 1.94 million ha of mangrove habitat, and have killed at
least 126,000 ha of mangrove ecosystems since 1958 (Sheppard, 2000). Oil exploration in or near mangrove shorelines has
signicant adverse impacts, even on the marine ecosystem (US Fish and Wildlife Services, 2013). Crude oil and their by-
products can destroy mangroves by coating aerial and submerged roots and from direct absorption (Fig. 2). Oil deposits as
marine tar residues are susceptible to mangroves which affects soil chemistry and permeability, leading to death and several
sub-lethal impacts (Duke, 2016). Once oil and marine tar residuesare deposited on or around the mangroves, they particularly
stick themselves to the plant surfaces, adsorbing to oleophilic surfaces of both ora and fauna. Oil coats breathing surfaces of
roots, stems, seedlings, and it contaminates surrounding sediments and their sessile intertidal or burrowing fauna (Zhang
et al., 2019). Also, coatings of oil on the leaves and submerged roots of the mangrove can hinder salt exchange responsible
for mediation of salt tolerance (Hoff, 2010). Crude oil is linked with toxic heavy metals most of which contaminate the soil
through underground deposits, especially Lead and Chromium. Iron is present in abundance in tropical and subtropical
aquifers and is also linked with crude oil deposits (Enujiugha and Nwanna, 2004). The damage of mangroves can also occur
through actions of mechanical abrasion, trampling, or compaction during clean-up or remedial activities can exacerbate
negative environmental impacts (US Fish and Wildlife Services, 2013;Bello, 2017;Zhang et al., 2019).
Oil spill on surface water spreads quickly, some become dissolved in water and may oxidize, and others undergo bacterial
changes and ultimately sink to the bottom. In the process, the sediment is contaminated and thus has a huge effect on biota.
Biodiversity loss and habitats destruction, largely due to top soil degradation are a main adverse effect of oil pollution. Any
region of mangroves that has been damaged by oil is vulnerable to other problems. For example, in the Niger Delta areas
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e00961 3
which are largely affected by oil pollution, mangrove forests have disappeared to the toxicity of oil spills and are being
replaced by noxious non-native Nypa fruticans, commonly known as nypa palms (Bello, 2017). These invasive species possess
a shallow root system that destabilizes the banks along the waterways, further impacting sediment distribution lower in the
delta system. Also, the process of photosynthesis is also impaired as a result of the introduction of phytotoxins into the
environment wherever oil spills occur. Oil spills can cause a variety of damage to marsh vegetation as they may reduce
growth, photosynthetic rate, stem height, density, and above ground biomass, eventually leading to plant death (Bello, 2017).
However, larger, more mature, mangroves exposed to oil only on the exposed root surfaces and sediment could have
survival duration of up to 6 months or more (Zhang et al., 2019). The degree of the impact and damage on the mangroves is
dependent on the concentration of the oil; the lighter the oils are, the more damage they cause and vice versa (Michel and
Rutherford, 2014;Duke, 2016).
Oil spill incidents caused by anthropogenic factors (e.g. activities associated with petroleum exploration, development and
production) are common place in the Niger Delta (Sam et al., 2017;Sam and Zabbey, 2018). Oil spills have detrimental impacts
on the soils and sediments, surface and groundwater, marine environment, terrestrial and aquatic ecosystems in the Niger
Delta. Discharges of petroleum hydrocarbons and petroleumederived waste streams also exacerbate impacts on biota and
widespread environmental degradation (Ite et al., 2013;Sam et al., 2017). Marine wildlife is particularly susceptible to the
toxic effects of oil and is basically far more subjected to it thanthe land-based wildlife. Many of the notable effects occur in the
intertidal zone where large volumes of oil are typically concentrated (Bodkin et al., 2003). The mostly affected are the
sedentary species and benthic organisms. Diverse species have shown different levels of biologic resistance or vulnerability to
contact with oil, with extended exposures resulting to preferential redistribution of populations, with expansion and habitat
redistribution by more resilient biota, reshaping ecosystems (Lee et al., 2015;Zhang et al., 2019).
Most marine oil explorations occur in environmentally sensitive areas, typically either in inland sea basins or offshore on
continental shelves, which are habitats to several benthic organisms in the sea (Kvenvolden and Cooper, 2003). The marine
ecosystems harbor signicant bio-indicator species ranging from microbiological communities, habitat-forming species, the
indispensable mangroves, to seabirds, marine mammals, and invertebrates (TRB and NRC, 2003). Ecological impacts arise
from produced water, drilling uids, cuttings and well treatment chemicals, wash and drainage water, sanitary and domestic
wastes and, spills and leakages.
Terrestrial impacts are caused by physical disturbance (e.g. construction of oil elds), land/soil contaminations caused by
oil spillages and leakages during drilling, and solid waste disposal.
Oil exploration by seismic companies involves surveying, clearing of seismic lines, and massive dynamiting for geological
excavations. The explosion of dynamite in aquatic environments leads to narcotic effects and mortality of sh and other faunal
organisms (Zabbey, 2004). The destabilization of sedimentary materials associated with dynamite shooting increases in
turbidity, blockage of lter feeding apparatuses in benthic (bottom-dwelling) fauna, and reduction of plant photosynthetic
activity due to reduced light penetration. The burying of oil and gas pipelines in the Delta fragments rich ecosystems such as
mangroves (Lonard et al., 2017). Apart from the reduction in habitat area, clearing of pipeline track segregates natural
populations, and fragments ecological systems, which may in turn distort breeding behavior of organisms. Oil coats smoother
mangroves and wetland leading to a more severe condition of hypoxia (Lonard et al., 2017). Crude oil contains toxic com-
ponents which cause outright mortality of plants and animals as well as other sub-lethal damage by interfering with the
functioning of various organ systems of plants and animals. It creates environmental conditions unfavorable for life; for
Fig. 2. Expanse of mangroves degraded by oil spills in a coastal community in the Niger Delta region (CEHRD, 2019).
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e009614
example, oil on water surface forms a layer which prevents oxygen penetration into water bodies, and this in turn leads to
suffocation of certain aquatic organisms (Useh et al., 2017). Crude oil kills plants and animals in the affected area; it also
poisons algae thereby disrupting major food chains thereby decreasing the yield of edible crustaceans. It also coats birds,
impairing their ight or reducing the insulating property of their feathers, thus making the birds more vulnerable to cold. Oil
spills in populace areas frequently wide spread, destroying crops and aquacultures through contamination of the under-
ground water and soils (Abarshi et al., 2017;Olatunji et al., 2018). Oil endangers sh hatcheries in coastal waters and as well
contaminates the esh of commercially valuable sh (Useh et al., 2017). The decrease in dissolved oxygen by bacteria feeding
on the spilled hydrocarbons contributes to the death of sh due to lack of oxygen (Beyer et al., 2016;Useh et al., 2017).
3.1. Cultural effects
The activities of the oil industry have often resulted in a multitude of cultural problems. These include occupational
dislocation, rural-urban drift, unemployment and poor human health (Dauda, 2017;Mugisa, 2016;Matemilola et al., 2018).
The extent of these impacts is particularly important to local communities and indigenous people who may have their
traditional, communal and social values affected (Fentiman and Zabbey, 2015). There are cultural activities often practiced in
coastal communities in the Nigerian Delta that are no longer being undertaken as a result of oil spills. A classic example is the
festive bathing of community members in a river to usher in the New Year. It is a culture and also been believed that taking a
bath in that river will usher the community into a new year of many good tidings, as such, members of such community
consider the culture critical to their prosperityin a new year. This culture is continually being abolished as coastal rivers are
polluted by oil spills and cannot be used for such purposes (CEHRD, 2019). The key impacts been experienced in the Niger
Delta include seismic activities that lead to depletion of arable farm land destroys economic and crops, thus reduces farmers
access to land/food, which renders the areas inhabitable and lead to the exodus of man and animals. Farmers have lost their
lands and are consequently forced to emigrate to other communities in search of livelihood exerting additional pressures on
natural resources in such areas (Omofonmwan and Odia, 2009). A resultant effect is the socio-cultural changes for instance
social structure, organization, and cultural heritage, practices and beliefs, and impacts such as effects on natural resources,
rights of access, and alteration in value system inuenced by foreigners (Mugisa, 2016;Zhang et al., 2019). Lack of planning
strategies may arise due to arising conicts between development and protection, natural resource use, recreational use,
tourism and historical and cultural resource. Oil pollution results to loss of aesthetics value because of unsightly and noisy
facilities and transportation system, due to increased road, air and sea infrastructure and associated effects (e.g. noise, ac-
cident risk, increased maintenance requirements, or change in existing service) occurring in the environment.
3.2. Health effects
Human health impact can be direct effect from changes in ecological processes (e.g., consumption of seafood with bio-
accumulated oil toxins), economic stressors that can alter intermediary processes (e.g., psychological effects of community
decline), loss of major subsistence or export industries (such as through loss of sheries), and effects of the spill causing
human harm outright (e.g., inhalation of aromatic hydrocarbons and other vaporous compounds) (Webler and Lord, 2010).
Oil pollution gives rise to the occurrence of certain ailments in areas that have suffered from oil pollution in Nigeria (Bello,
2017). Direct contact with, or exposure to oil spill material, as well as inhalation of volatile compounds, or physical contact
with crude including consumption of water and oil-contaminated seafood can have serious hazardous health effects on
humans, ranging from nausea and dizziness to carcinogenic effects, central nervous system inhibition and disruption, and
several long-term reproductive, developmental, and carcinogenic effects (Aguilera et al., 2010;Chang et al., 2014). A study of
the psychological implications of over 130 modern disaster situations revealed that technological disasters, such as oil spills,
result in more stress for affected communities than natural disasters (Picou et al., 2004). An example is the Hebei Spirit oil
spill that occurred off the Yellow Sea Coast of South Korea in 2007, releasing 12,547 kl of crude that contaminated 167 km of
shoreline and 13,978 ha of sheries and aquaculture facilities, and which involved clean-up efforts by 563,761 people,
resulting in acute health effects. A year later, around 442 of the most affected rst responders to initial effects of exposure
were analysed to assess the longevity of toxic effects. Symptoms reported include eye symptoms (average of 9.7 months),
headaches (average of 8.4 months), skin symptoms (average of 8.3 months), neurovestibular systems (average of 6.9 months),
respiratory symptoms (average2.1 months), and back pain (average 1.8 months) (Na et al., 2012) in descending order. A
number of those that came in contact with the volatile compounds during the clean-up effort still suffer from all supposed
categories of effects after 12 months, with headaches, eye symptoms, neurovestibular symptoms, respiratory symptoms, skin
symptoms, and back pain, respectively (Na et al., 2012). This is made possible given that spilled oil is reported to have
penetrated food chains and life-supporting systems such as controlled waters in the Niger Delta (Ajai, 2010;Zabbey et al.,
2017;UNEP, 2011). While there is no empirical study demonstrating the health implications of exposure to crude oil in
Nigeria (UNEP, 2011), evidence exist in other countries and this indicates a possibility of similar impacts in Nigeria.
3.3. Economic effect
Given that the local economy of many coastal communities is dependent on shing and farming, an impact on mangroves
should have economic implications on such communities. Degraded mangroves affect local sher men and women whose
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e00961 5
economic wellbeing is dependent on a clean rivers and alluvial soil fertile soil (Zabbey et al., 2017;Ehirim et al., 2018,Fig. 3).
Low catch from shing expedition as a result of polluted rivers (Fig. 3) could lead to economic loss and affects peasant families
whose entire livelihood are dependent on shing.
The economic impacts of mangroves comprise of the immediate costs linked with remediating and responding to oil spill
event and prolonged societal cost incurred by population proximal and/or dependent on spill affected ecosystems (Zhang
et al., 2019). Aside the instantaneous loss of the value of the spilled contents, there is a damage connected with the spill
process (e.g., mechanical failure, ship damage/run ashore) in addition to the direct cleanup costs in attempting to remediate
the oil that was lost. The fate of the oil residue has a large effect in costs (Zhang et al., 2019); this is because oil has different
amounts of interaction with the environment and diverse rates of weathering that inuences their succeeding cleanup. Hence
the volume of oil spilled and the amount of movement or dispersal going on from surface or subsurface currents and the wave
energy determines the cost of cleanups (Vanem et al., 2008). Its interaction with sediment could make it difcult to clean than
material which has remained near the spill location thereby increasing the cost of remediation. The cost of oil spill cleanup
would also depend on whether it has undergone widespread natural weathering processes or has become quickly seques-
tered or entrained within the water column or sediment. The inuence on cost depends if the spills occur near-shore which
indeed have a far greater potential for economic losses and are more expensive to clean than those at sea. Examples are the
non-extended social cost to human society from the ABT Summer spill and the Atlantic Empress spill that released an excess
of 250,000 tonnes of oil in 1979 and 1991 respectively. This was due to their remote spill location was hundreds of miles
offshore (White et al., 2012). During large scale offshore spills, varying costs of US$300,000 per tonne can be used to clean for
long range cleanup as a result of distance needed to travel, compared to small near shore spills that cost US$29,000 per tonne
as at 2010 estimates (Kontovas et al., 2010). Oil spills and their effects can have devastating implications economically for
shing and other marine industries such as tourism and have health implications for people who are tasked with aiding in
relief efforts and those that come into contact with it (Upton, 2011).
3.4. Impacts on livelihood structures
Large areas of the mangrove ecosystem have apparently been destroyed in the Nigerian coastal environment (Fig. 2). Oil
pollution results in the destruction of the Niger Delta traditional local economic support systems of shing and farming .
Farming is the major land use system in Nigeria, especially in the Niger Delta region. The Niger Delta population is highly
reliant on the land and natural resources for their livelihoods, which includes subsistence farming and shing (Chinweze
et al., 2012). As a result, the traditional livelihood of the region is primarily shing and farming. Oil spills degrade most
agricultural lands in the area and has turned hitherto productive areas into wastelands. With increasing soil infertility due to
the destruction of soil micro-organisms, and dwindling agricultural productivity, farmers have been forced to abandon their
land, to seek illegitimate alternative means of livelihood. Hence, once oil spills occur, farmlands and rivers are affected (Sam
et al., 2017). Aquatic life has also been destroyed with the pollution of traditional shing grounds, exacerbating hunger and
poverty in shing communities (Pittock et al., 2018).
Oil spills alter the physico-chemical properties of the soil thereby resulting to loss of soil fertility and subsequent loss or/
and reduced germination and growth of plants, and reduced crop productivity (Onwurah et al., 2007;Tanee and Albert, 2015).
Reduction in crop yield and consequent productivity affects economic benets to communities (Sam et al., 2017). The
Fig. 3. Deserted sh landing site following oil spills.
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e009616
mangroves which serve as an important source of both fuel wood for the indigenous people and a habitat for biodiversity is
now unable to survive the oil toxicity of its habitat (Jack et al., 2016). The result is substantial damage to surface water,
drinking water, sh and other fauna as well as other parts of the mangrove ecosystems which make up most of the envi-
ronment in the Niger Delta zone.
Offshore oil drilling activities are major sources of oil pollution, mainly because of leaking pipes, accidents, ballast water
discharges, and production-water discharges. Drilling also involves the use of heavy metals such as vanadium and nickel, and
contamination of seawater with these metals is known to affect plants and animals. Oil pollution damages coastal resources
and habitats, as well as sheries, reducing catches and incomes (UNEP, 2013). This increases poverty among indigenous
populations and may provide opportunity for local communities to take up illegitimate livelihoods (e.g. artisanal rening)
which are environmentally unsustainable (Sam and Zabbey, 2018).
The effects of oil spillage and acid rain resulting from gas aring have been soil degradation which affects crop yield and
harvest and the migration of shes and bottom dwelling organisms from in-shore or shallow waters into deep-sea. The result
of poor crop yield and reduction in number of seafood caught is food shortage and failure of some families to make adequate
money to meet certain basic needs. In Nigeria, agricultural sector has been rendered unprotable with youths and women
jobless since their local economic support system of shing and farming is no longer sustainable, moreover, this sector
supposed to be one of the largest employer of labour in Nigeria, especially in the Niger-Delta region (Bello, 2017). Considering
the condition of the Ogonis is a signicant example of migration from communities and increase in environmental refugees.
The Ogoni people lived in intimately knitted communities with a subsistent economy providing them with their basic needs
before the economic considerations led to the development intervention of oil exploration which resulted in a compounded
change in the socio-economic landscape of Ogoni. Consequently, most of the Ogoni habitants have migrated to the big cities of
Port-Harcourt, Omoku, Eleme, and many others as a result of unavailability of land for farming and polluted river which
barred shing.
The effects of oil pollution on the people and ecosystems of the Niger Delta and the apparent inability of these risks to be
sufciently mitigated by the Government is reported to have contributed to activities of militancy in the region (Babatunde
et al., 2017;Omokhoa, 2015;Tantua and Kamruzzaman, 2016). Coastal communities in the Niger Delta region whose live-
lihoods dependent on luxuriant mangrove ecosystem and its services (e.g. sheries), and can no longer derive such goods and
services, now engage in oil theft and militancy (Babatunde et al., 2017;Omokhoa, 2015). To earn a living, the youths would
kidnap foreign expatriates and demand huge sums of money for their release (Babatunde et al., 2017;Omokhoa, 2015;Tantua
and Kamruzzaman, 2016).
Notwithstanding such variety in the roles of mangroves, these ecosystems are still often seen as valueless wastelands
available for other uses. Such laxity toward sustaining mangroves is leading to a faster rate of destruction and disappearance
of mangroves in the Nigerian Delta. Considerable loss of the worlds mangrove cover is due to their conversion to other land
uses, such as urban area expansion, industrial development, aquaculture, agricultural development, and charcoal making
nach et al., 2018;Primavera et al., 2019). One of the key challenges facing mangrove conservation is inadequate un-
derstanding of their multiple roles due to poor research, particularly in the areas of climate change mitigation and adaptation
(Primavera et al., 2019).
4. Relevance of mangroves to climate change
The primary source of increasing atmospheric carbon dioxide (CO
) is burning of fossil fuels and thus the main contributor
to carbon dioxide concentrations, as well as emissions related to land use change. Mangroves are one of the most signicant
ecosystems for sequestering carbon and reducing greenhouse gases. The capability of mangroves, sea grasses, and salt
marshes to sequester CO
from the atmosphere is becoming increasingly recognized at an international level (Ray and Jana,
2017;Hori et al., 2019). With the increase of atmospheric CO
concentration, there is a growing public and scientic concern
on the carbon sequestration potentialof various terrestrial ecosystems (Serrano et al., 2019). Mangroves are an important sink
for CO
. This can be enhanced by converting marginal agricultural land to non-agricultural restorative uses such as grassland,
forest or wetland. They could also provide more than 10% of essential dissolved organic carbon that is supplied to the global
ocean from land (IUCN, 2009).
Mangroves can trap not only ne sediment and organic matter but also coarse sediment driven by storm waves to form
special mangrove sediment (Allison et al., 2017). Thus, the sedimentation rate of mangrove is high (Alongi and
Mukhopadhyay, 2015). Besides, the litter productivity is high in Mangroves, which provides more carbon sequestrated in
sediments of mangrove, indicating high below ground carbon sequestration. In CO
sequestration, the burial of mangrove
carbon in sediments elocally or in adjacent systems are considered (Allison et al., 2017).
Mangroves, salt marshes, and sea grasses form much of the earths blue carbon sinks. These coastal vegetation sequester
carbon far more effectively (up to 100 times faster) and more permanently than terrestrial forests (Friess et al., 2016). Further,
studies have shown that mangrove forests store up to ve times more carbon (per hectare) than most other tropical forests
around the world (Friess et al., 2016). This ability of mangroves and other coastal vegetation to store such large amounts of
carbon is, in part, due to the deep, organic rich soils in which they thrive. The entangled root systems of mangroves, which
anchor the plants into underwater sediment, slow down incoming tidal waters, allowing organic and inorganic material to
settle into the sediment surface. The sediments beneath these habitats are characterized by typically low oxygen conditions,
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e00961 7
slowing down the decay process and rates, resulting in much greater amounts of carbon accumulating in the soil. In fact,
mangroves have more carbon in their soil alone than most tropical forests have in all their biomass and soil combined.
Carbon offsets based on the protection and restoration of coastalvegetation could therefore be far more cost effective than
current approaches focused on terrestrial and peat forests, even before taking into consideration the enormous additional
benets to sheries, coastal protection, and the livelihoods of coastal inhabitants. Therefore, deforestation of mangroves
means releasing larger amounts of carbon into the atmosphere. This in turn causes the wet soil to dry up, leading to the
release of even more stored carbon into the atmosphere. Estimates suggest a range of between 150 million to 1 billion tonnes
of CO
that is emitted annually due to the destruction of mangrove forests globally. Thus, at the global scale, coastal wetland
destruction could account for 1e3% of industrial emissions; a number that is on the rise as more and more coastal wetlands
are destroyed every year around the world.
Currently, climatic change coupled with oil exploration activities in the region have negatively impacted on the envi-
ronment. This has resulted in the alteration of habitats, biodiversity loss and pollution of water bodies. Climate change
impacts on the mangroves negatively reducing their quality and thus affect livelihood pattern of households in affected
communities (Primavera et al., 2019).
5. What is needed for effective mangrove conservation regime?
In order for mangroves to be managed effectively, critical frameworks or enabling conditions should be established. Given
the Niger Delta context, we recommend the development of frameworks for mangrove conservation. The framework should
introduce a participatory mechanism that would allow a broad-spectrum of stakeholders contribute to a robust conservation
framework. With this approach to designing a framework, stakeholders at the community level will own the initiative,
support it and participate in the implementation of same, as it will deliver net prot to respective communities. A partici-
patory and co-management approach has been practiced in India, where the government, rural communities and other
stakeholders including the regulators undertake complementary functions for mangrove conservation and protection
(DasGupta and Shaw, 2013).
Fig. 4. Proposed co-management model for mangrove conservation in the Niger Delta region of Nigeria. The framework outlines the roles of different stake-
holders in mangrove conservation. Primarily, coastal communities (the custodians of the mangrove ecosystem), have a responsibility to engage in mangrove
planting, restoration/revegetation of degraded areas, and initiation of local norms that would encourage sustainable management of mangrove ecosystem
particularly mapped protected areas.
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e009618
We also recommend a co-management approach to mangrove conservation. Given that the livelihood of coastal com-
munities largely depends on the mangrove ecosystem, a co-management regime will allow communities to contribute to
effective maintenance of the mangrove ecosystem (Fig. 4). This system has been practiced in the Sundarbans, which
constitute the worlds largest continuous mangrove forest (10,000 km
) located within the river delta system between India
and Bangladesh. The co-management approach provides specic roles and responsibility for different stakeholders, including
coastal communities, in mangrove conservation. The framework ensures coastal communities are principally involved and
allowed to participate in mangrove conservation decision-making processes. Once this is established in Niger Delta coastal
communities as a policy, communities will actively participate in mangrove conservation activities. This has been reported to
achieve a participatory governance system and reduced conicts associated with mangrove forest protection between reg-
ulators and communities (German Cooperation, 2017).
Also necessary is a stringent legal framework that supports and incorporates mangrove management strategies into a
wider planning and policy framework (Ayanlade and Proske, 2016;Babatunde et al., 2017;Udoh, 2016). Such frameworks
need to involve all relevant agencies and stakeholders and extend across all adjacent and connected ecosystems, watersheds
and adjacent waters. If restoration of mangrove is to be achieved, the access and use of mangrove forests and land must be
clearly stated (Babatunde et al., 2017). Where local communities and institutions do not have any legal title to the land other
than traditional de facto rights, local masses are frequently displaced by centralized decisions that lead to the development,
reclamation and clearing of mangrove habitats. Establishments of framework policy and legislation established at national
levels can prevent bit by bit loss and degradation (Ayanlade and Proske, 2016;Udoh, 2016). There should be a total removal of
perverse incentives alongside enablingpolicies and legislation (Babatunde et al., 2017). Extremely low-cost purchase of
mangrove areas for development purposes, tax breaks for the establishment of new aquaculture, and subsidies for shrimp
farmers need to be removed or counterbalanced by introducing positive incentives for restoration and maintenance of
mangrove habitat, and legislation to encourage more sustainable low impact aquaculture, including the rehabilitation of
abandoned ponds. Involving local communities in mangrove conservation efforts is vital to the achievement of any resto-
ration intervention (Sam et al., 2017b;Babatunde et al., 2017). Aquaculture provides economic benets and food security in
many mangrove regions (Numbere, 2018). To attain sustainable aquaculture, a complete accounting of the costs and benets
of the forest itself, its removal and replacement by ponds, and the benets derived from aquaculture during the life of those
ponds should be applied (Ayanlade and Proske, 2016;Udoh, 2016).
Protected areas are a generally used management tool that can help prevent mangrove loss and degradation in specic
locations. They can supply social, economic and environmental benets, through a more sustainable management of re-
sources or indirectly comprehensive protection of ecosystem services (Table 1). Restoration and afforestation are viable and
widely used management options to recover lost or establish new mangrove forest. While avoiding loss remains the lowest
cost and highest benet route to mangrove conservation and sustainable use, mangrove restorationhas been widely practiced
around the world. Incentives need to be created that promote more environmentally responsible behavior and enhance local
livelihoods. This may be particularly important in the near future while perverse incentives are still distorting markets and
payments for ecosystem services are still under development. Mangrove conservation for poverty alleviation may require
Table 1
Mangrove ecosystem goods and services. This Table outlines benets that could be derived mangrove conservation management mechanisms
(Adapted from Ronnback et al., 2007;Brander et al., 2012).
Ecosystem services Ecosystem goods References
Carbon sequestration Fish Ronnback et al. (2007)
Brander et al. (2012)
Fentiman and Zabbey (2015)
Shore protection Shrimps
Water quality regulation Honey
Erosion control Molluscs
Climate regulation Birds and eggs
Habitat and nursery ground Tea
Link to other marine systems Vinegar
Cultural and religious values Firewood
Recreation and tourism Charcoal
Information function Poles, beams, paneling
Boat building
Dye for cloth and nets
Tannis for net preservation
Traditional medicine
Fishing bait (worms)
Raw materials for handicrafts
Fishing boats
Lime from mollusc shells
Insect control
A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e00961 9
Governments to recognize the strong link between mangrove ecosystem degradation and the persistence of poverty in many
rural coastal communities. The destruction and degradation of mangroves has strong socio-economic impacts (Babatunde
et al., 2017). Improved appreciation of the range of values of mangroves may prove useful in making appropriate decisions
for more efcient and sustainable use. Community based poverty reduction programmes are needed where restoration and
management of mangroves is implemented while providing communities with suitable alternatives to mangroves de-
pendency (for domestic consumption and commerce). Successfully applied, these efforts can succeed in improving the
ecological conditions of mangroves as well as the livelihoods of local communities (Ayanlade and Proske, 2016;Udoh, 2016).
5.1. Knowledge gaps and research needs
There are many studies outlining the impacts of mangrove degradation (Fentiman and Zabbey, 2015;Duke, 2016;
Numbere, 2018;Onwurah et al., 2007;Tanee and Albert, 2015), but there is limited explanation on how the impacted
communities could participate in mangrove conservation, even as their livelihoods depend on it.
More pertinent is the poor knowledge of rural community members on the dangers of anthropogenic activities on the
maintenance and sustainability of the mangrove ecosystem. Awareness of the risks posed by some activities (e.g. clearing the
mangrove forest) could enhance communitiesactive participation in the conservation and protection of mangrove forests
(Fentiman and Zabbey, 2015). There is also limited knowledge that socio-cultural aspect of mangrove services should be
considered by policy-makers as an indispensable criterion for confronting the key challenges in mangrove ecosystems
conservation (Fentiman and Zabbey, 2015;Tanee and Albert, 2015). With the increase in the disappearance of mangroves and
destruction of livelihood structures in the Nigerian Niger Delta, there is need for the establishment of community vanguards
to develop a sustainable platform for mangrove revegetation and the stabilization of aquatic ecosystem (Onwuteaka and
Uwagbae, 2016;Vaughn, 2017;Numbere, 2018). Where mangrove conservation strategy is lacking, it will be difcult to
harness the diverse benets of the mangrove ecosystem in the Niger Delta and its global implications, given the nature of
mangrove depletion (Numbere, 2018), without a mangrove ecosystem conservation framework.
6. Conclusion
As the worlds mangroves continue to disappear as a result of human population, development pressures, and oil ex-
plorations in the Niger Delta, it becomes even more important to assess the values of these important systems. Oil spills at
marine ecosystems will have many effects on the mangroves, environment and its ecology which are ultimately dependent on
the type and volume of oil. Understanding the various services mangrove ecosystems provide which include attenuation of
waves and buffer winds, storm protection, maintenance of sheries, nutrient cycling, tourism, recreation, education and
research would trigger us developing better methods of assessing the protective benets of these ecosystems. It is worthy of
note that its disappearance due to human development and oil pollution could have deleterious effects on the ecosystem,
cultural, health and socio-economic values of the affected ecosystem and man. The key to dealing with future oil spill events
in the environment that might in turn affect mangroves include prevention, understanding the effects of oil once it is released
into the environment and the effects of oil on marine biota and ecosystems, as well as structural features such as coastlines
and seaoors.
Therefore, mangrove forest should not be seen as useless areas of vegetation to be cut down indiscriminately for agri-
culture, housing and industrial development but as viable resources to be developed in a suitable manner. In order to raise
awareness of the multiple benets of mangrove ecosystems, there is an opportunity to conduct more research and also focus
more on expanding mangrove areas in participation with local communities and other key stakeholders. Improving the
valuation of the protective service of mangroves, and the other benets provided by these essential habitats, may prove
signicant in these future coastal management decisions and sustainability.
Declaration of competing interest
None of the authors declare any competing or conict of interest.
The authors appreciate the efforts of the anonymous reviews that provided comments and inputs that rened the paper.
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Allison, M.A., Nittrouer, C.A., Ogston, A.S., Mullarney, J.C., Nguyen, T.T., 2017. Sedi-mentation and survival of the Mekong Delta: a case study of decreased
sediment supply and accelerating rates of relative sea level rise. Oceanography, 30(3), 98e109.
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A.P. Onyena, K. Sam / Global Ecology and Conservation 22 (2020) e0096112
... Concerning forests, oil development in highly forested tropical countries has led to widespread deforestation both as a direct factor through oil sector infrastructure but also indirectly through its influence on direct and indirect drivers of deforestation, including agricultural expansion, urbanization, and population growth (Acheampong et al., 2018;Baynard et al., 2013;Finer et al., 2008;Onyena & Sam, 2020;UNEP, 2011b). However, Wunder (2003) provides a counter-argument by concluding that oil development in tropical forest countries (including Gabon, Equatorial Guinea, Ecuador, Venezuela, and Papua New Guinea) has resulted in reduced deforestation overall because of the macroeconomic effects of the oil sector. ...
... Most studies show that oil development across most tropical forested nations typically leads to accelerated deforestation levels in both the short term and long-term. Specifically, oil development activities have been associated with increased access to hitherto isolated forest landscape, which in turn gives way to both direct (agriculture and infrastructure expansion) and indirect drivers (population growth and economic growth policy orientation) of deforestation (Ayanlade et al., 2016;Baynard et al., 2013;Onyena & Sam, 2020;UNEP, 1997UNEP, , 2011a. Initially, these various drivers degrade forest functions by negatively altering forest structure and composition (by reducing canopy stratification, species composition, and increasing fragmentation), however often they lead to total forest removal and replacement with alternative economic production, for example, replacing forests with commercial agriculture as the case was for Ecuador (Baynard et al., 2013;Wasserstrom & Southgate, 2013). ...
... Subsistence agriculture is widespread across the three countries (Ayorinde Akintoye et MWE, 2018a;Oduro et al., 2015;Onyena & Sam, 2020). It is estimated that 51%, 60%, and 80% of the population in Ghana, Nigeria, and Uganda are engaged in subsistence agriculture as their primary employment (MEMD, 2015;NACOP, 2016;UN, 2015). ...
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The development of oil resources in tropical countries is a significant driver of deforestation and its associated loss of biodiversity and ecosystem services. However, empirical research on realizing sustainable forest management amidst the implementation of oil development policies in tropical countries of Sub-Saharan Africa is minimal. This dissertation is organized into three independent chapters. Together, these chapters analyze the policy options for enabling the co-existence of sustainable forest management amidst ongoing oil development activities within oil-rich countries of sub-Saharan Africa collectively. The study adopts a case study methodology of Hoima District in Uganda with an overall theoretical framework of the Forest Transition Theory (FTT). ☐ Chapter 2 of this study applies a Driver Pressure State Impact Response (DPSIR) framework within a single case study methodology to investigate the spatial and temporal deforestation outcomes following the implementation of Uganda’s commercial oil development policy in 2006 within Hoima District. We conclude that the implementation of Uganda’s oil development policy has resulted in significant and observable increases in annual rates of deforestation in Hoima District. Annual deforestation in Hoima District was declining at a rate of -1.9% per year in the period before commercial oil development started (2001-2006). However, this increased to 34% annual forest cover loss after the commencement of oil development (2007-219). We estimated that 202,813 forest hectares were lost between 2007 and 2019, potentially resulting in the loss of 18 tree species from Hoima District. Our study found that high population growth, the expansion, and intensification of subsistence agriculture because of commercial oil development maybe some of the significant deforestation drivers leading to accelerated forest cover loss in Hoima district. In Chapter 3 of this study, we apply the Critical Discourse Analysis (CDA) framework to synthesize 14 years of forest policy discourses in Uganda’s national print media (The Daily Monitor) during oil development in Hoima District. Our results in this Chapter seem to indicate that the top three drivers featured in Uganda’s print media discourse were forest policy failures (57%), infrastructure expansion (14%), agricultural development (8%), and co-joined drivers (8%). Our study also found that peripheral actors had a more robust media standing (52%) than center actors (48%) among the 18 distinct policy actors we identified. Specifically, the most predominant policy actors in shaping print-media discourses on deforestation and oil development were journalists (24%), National Forest Authority (NFA, 24%), and Non-Government Organizations (NGOs, 10%). Overall, our results seem to indicate that Uganda’s policy transition from a traditional paradigm of forest management based on cultural values to a modern paradigm based mainly on scientific forest management has not been beneficial to the sustainable forest management outcomes within the country. There is a clear need for a new forest policy paradigm that could complement modern paradigms of forest elements with beneficial values and other traditional paradigm elements. In Chapter 4, we undertook a comparative assessment of deforestation in three oil-rich countries of Sub-Saharan Africa of Uganda, Ghana, and Nigeria. This Chapter applies a Qualitative Comparative Analysis (QCA) framework through a multi-case study methodology. Our results show that agricultural expansion, increased wood extraction, and population growth drive most deforestation in oil-rich nations. However, the role of infrastructure expansion and forest policy failures were contested drivers of deforestation. Our study finds that the original FTT theory currently applied in most forest policy studies was inadequate as a research tool in assessing the totality of deforestation effects from oil development activities. This preceding observation was mostly so when we considered the long-term and cumulative impacts of deforestation, which are associated with the loss of intangible natural and cultural ecosystem services. Therefore, we proposed the Novel Forest Ecosystem Transition Theory (NFETT) theory, which integrates the loss of natural and cultural ecosystem services alongside forest cover loss within the various forest transitions. Addressing deforestation through the NFETT brings to light various policy options for ensuring the co-existence of oil development activities alongside sustainable forest management. To this end, we recommend that oil-rich countries should, among others; i) internalize costs of deforestation through Payment for Ecosystem Services (PES) policies; ii) improve policy coordination to manage multicausal deforestation drivers; iii) population growth management policies; iv) policies for sustainable agriculture and woodfuel solutions; v) strengthen Sustainable Forest Management considerations in Environmental Impact Assessment (EIA) permitting processes and vi) improving environmental governance through the EITI process. These measures used in combination can go a long way in ensuring the successful co-existence of sustainable forest management during oil development in oil-rich countries of Sub-Saharan Africa.
... Although, the economic impact of oil theft associated with these operations of the illegal refineries and on their host communities are widely reported (Oredein, 2013;Bebeteidoh et al., 2020) only a few independent surveys on the impact of the artisanal refineries on the highly sensitive environment of the Niger Delta are reported e.g. impact on vegetation (Hammadina and Anyanwu, 2012;Asimiea and Omokhua, 2013), soil fungi (Douglas, 2018), aquatic ecosystems (Ndidi et al., 2020), mangroves (Onyena and Sam, 2020). This review paper, therefore, seeks to holistically highlight the effect of illegal refineries on the Niger Delta's ecosystems which is recently exacerbated by the increasing air pollution (black soot) in the Niger Delta environment. ...
... Artisanal refining has caused pollution in many intertidal creeks which have left the mangroves denuded of leaves and stems, leaving roots coated in a bitumenlike substance sometimes 1cm or thicker. Mangroves are a shelter for biological diversity consisting of diverse aquatic and terrestrial flora and fauna which include mammals (monkeys, antelopes, and manatees), mollusks (bivalves, oysters), crustaceans, fish, reptiles, and avian species (Onyena and Sam, 2020). ...
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Crude oil is the major source of revenue in Nigeria with the vast majority of exploration from the Niger Delta. Illegal refining of stolen oil is a major cause of oil spills and comes with steep environmental, economic, and social costs in the region. Oil theft, artisanal refineries, and ecosystem pollution are simultaneously linked. Therefore, the review paper seeks to highlight the effect of illegal refineries on the region's ecosystems currently exacerbated by black soot pollution, the causes of increasing artisanal refineries, the implication of illegal oil destruction, and possible solutions. The review revealed that illegal crude oil refining has a denudating impact on flora and fauna, air, soil, aquatic ecosystems, and the mangroves. Causes of illegal refineries include poverty and low standard of living, the pragmatic collaboration between security authorities and other actors, the relatively low setup cost, and the lackadaisical attitude of oil companies towards the replacement damaged oil facilities. The common practice of burning recovered stolen crude further damages the ecosystem. The need for government agencies, laws, and policies for environmental protection to be active while creating synergy with security outfits to curb the menace and engaging in regular cleanups through phytoremediation are possible solutions. We recommend the following; shutdown of all illegal refineries, stakeholders' synergies to guard against oil pollution and biodiversity loss, environmental education, and youth empowerment through vocational training and cleaning, afforestation, and reforestation of degraded sites.
... reported 134 oil spills in the coastal regions where the NMNRs located from 2000 to 2008. When oil deposits cling to the surface of the mangroves, soil and dependent marine life, it would likely cause death and sub-lethal threats or result in a long lasting impact because oils are difficult to decompose naturally (Onyena and Sam, 2020). This disruption could directly lead to capacity decline in ecosystem services of mangroves, like coastline protection and biodiversity maintenance. ...
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Mangroves are high-productive ecosystems and globally protected. Establishing nature reserves aimed at counteracting the negative effects of anthropogenic activities is one of the most pivotal approaches to conserve mangrove ecosystems. Evaluation of the conservation effectiveness for mangrove nature reserves is thus indispensable for making knowledge-based conservation policies and funding-decisions by government and managers. In this study, using composited Landsat images by the Google Earth Engine cloud platform and object-oriented deep learning classification method, the land cover maps of national mangrove nature reserves (NMNRs) in China were obtained from 1987 to 2019. The systematic evaluation of conservation effectiveness for each NMNR was conducted by landscape metrics and an entropy weight model. Combined with the dynamics in mangrove distribution, human interference intensity, and natural environment change, the driving force factors affecting the conservation effectiveness for NMNRs were investigated. The results show that the total mangrove area in all NMNRs increased 968.6 ha during the study period, a 21.8 % rate of increase. Except for one NMNR with a slight decline, the conservation of remaining NMNRs was considered effective with increase varied from 14.8 % to 87.5 % in the level of protective efficacy. The conservation effectiveness of NMNRs was affected by both anthropogenic and natural factors, while the improvement to the conservation effectiveness was largely attributed to the implementation of protection policies, such as reforestation engineering. Further direct or indirect challenges in mangrove conservation effectiveness, e.g., pollution, natural disasters, and exotic species invasion, still require close attention. This study provides an effective and efficient approach to quantify the conservation effectiveness of mangrove nature reserves, which would facilitate mangrove conservation and management in the future.
... On the contrary, other investigations lack debate in decision-making and the participation of the actors that are part of the socioecological system, providing little understanding of the benefits and ecosystem services some natural areas offer [87,94]. Further, in some regions of the world, conservation policies have excluded the participation of coastal communities and co-management frameworks to preserve mangroves [95]. ...
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Marine-coastal ecosystems are productive and valuable habitats worldwide due to their significant contributions to human wellbeing. However, human activities, limited territorial planning, and unsustainable demand and consumption of natural goods and services put pressure on marine-coastal ecosystems. In this sense, marine-coastal planning is a management tool to contrast these forces because it manages different human activities on the coast and in the oceans over space and time, strengthening political, social, and tourist development and the economy of the territory. Our objective is to propose marine-coastal spatial planning strategies through an ecosystem-based approach for allocating a mangrove and estuarine zone conservation area. The study methodology is: (i) Compilation of information from the study area with an emphasis on regulations and protected areas. (ii) Analysis of human relations with marine-coastal ecosystems. (iii) Mapping and zoning of the conservation area. (iv) Analysis of the strengths, weaknesses, opportunities, threats and threats, weaknesses, opportunities, strengths (SWOT–TWOS) matrix to recommend strategies and guarantee the viability of marine-coastal protection. The results show zoning maps of the sector proposed as a conservation area comprising mangroves and an estuarine zone. It also approaches governance strategies or conservation management measures and protection of the marine-coastal space. Finally, as a recommendation, we propose improvements to the current municipal ordinances, guaranteeing the management and protection of the study area, and furthering achievements in the comprehensive development of land-use planning.
... Mangrove vegetation provides various needs and provides enormous ecological services for the surrounding organisms. Mangroves play a role as a place to live for various types of organisms, improve water quality, maintain beach stability and supply food ingredients, so that they can support the life of Mollusca, several types of fish and crabs (Onyena & Sam 2020).The gastropod community is one of the aquatic organisms that utilize the mangrove area as a place to live. Salim et al (2019) proved that there is a strong relationship between mangrove density and gastropod density (the higher the mangrove density, the higher the gastropod density). ...
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Gastropods are one of the communities that utilize the mangrove ecosystem as their habitat. This study aimed to identify gastropods as well as to analyze the community structure of gastropods and analyze their habitat characteristics, in the mangrove area of Kutang Beach, Lamongan Indonesia. Sampling was conducted during the lowest tide using the quadrant-transect method. The Gastropods were identified based on morphological characters. Community structure was analyzed descriptively and quantitatively, based on seven parameters, namely: density (D), relative abundance (KR%), relative frequency (FR%), importance value index (INP%), diversity index (H'), dominance index (C) and evenness index (E). The results revealed that on the Kutang Beach there were 30 species of gastropods belonging to several families. Littoraria articulata (Littorinidae family) had the highest density, D=1.83 ind m-2 , with a relative abundance of KR=19.88%, a relative frequency of FR=7.59% and an importance value index of INP=27.47%. The diversity index 1<H'<3 was moderate, the low dominance index C<0.5 indicated the absence of dominance between species and the evenness index 0.6<E<1 was high, indicating a relatively balanced distribution between species. Gastropods' habitat characteristics in the mangrove ecosystem were: a sandy mud substrate, a temperature of 29±0.00°C; a pH of 7.86±0.00 and a salinity of 3±0.58‰.
... Findings from various studies indicate that the detection of high concentrations of these hydrocarbons and subsequent acute and chronic exposures by plausible receptors as experienced in the Niger Delta, have adverse ecological and health impacts including risk of cancer, mutagen or teratogen (Davies and Abolude, 2016;Ite et al., 2018). Specifically, oil spills in the Ogoni areas of the Niger Delta impact vegetation (e.g., mangrove plants) and wildlife (e.g., fishes, seabirds) (Linden and Palsson, 2013;Osuagwu and Olaifa, 2018;Onyena and Sam, 2020). Given the nature of traditional livelihoods (primarily farming and fishing) of the local population, and the physico-chemical characteristics of crude oil, the impacts are usually severe affecting public health, food system and livelihoods value chains and the environment (Whyte et al., 2020). ...
Environmental contamination by hydrocarbons has negative effects on human health and other receptors including air, water and land resources. Following a United Nations Environment Programme report in 2011 which concluded that remediation strategies adopted in Nigeria did not meet international best practice, the Nigerian Government is attempting to develop a fit for purpose model of managing oil-contaminated land and wetlands. It has established the Hydrocarbon Pollution Remediation Project (HYPREP) to coordinate the environmental remediation and the restoration of livelihoods of local communities in the Niger Delta, starting with Ogoniland. HYPREP has been implementing the remediation process for more than five years with limited expected sustainable outcomes. It is now 11 years following UNEP’s recommendations for environmental and livelihood restoration in the region. The challenges of effective land remediation and restoration of traditional livelihoods are explored in the context of the Niger Delta, Nigeria’s hub of oil and gas production. The preliminary appraisal indicates that HYPREP operations are bureaucratic, suffering from capacity gaps and a weak stakeholder engagement strategy. Other extant challenges include the slow implementation of recommended emergency measures, corruption and the absence of infrastructure for hazardous materials management. Additionally, HYPREP has not optimized quality assurance by engaging internationally accredited laboratories for chemical analysis of environmental samples. Opportunities exist for HYPREP to learn lessons from other regimes for effective contaminated land management. Roles for different stakeholders working towards sustainable contaminated land management in Ogoniland and the wider Niger Delta are outlined. These recommendations would benefit regions with similar contexts and contaminated land issues.
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Malgré leur importance dans la stabilité et la santé des environnements côtiers, les mangroves sont soumises à des pressions importantes, majoritairement causées par des moteurs anthropiques. Les objectifs sont de mesurer la régression des surfaces de mangrove entre 2007 et 2020 dans l’espace urbain du Grand Libreville (Gabon) et d’identifier les moteurs anthropiques de déforestation. Pour cela, deux méthodes complémentaires ont été appliquées : une analyse de la dynamique de l’occupation du sol de trois sites caractéristiques, à partir d’orthophotos à très haute résolution, fournies par Maxar Technologies, et des observations directes. Ainsi, entre 2007 et 2020, les changements d’occupation du sol à Okala-Angondjé, Lowé et Igoumié sont surtout marqués par la progression du bâti et son empiètement sur la végétation. Tous les sites ont connu des régressions nettes de mangrove : 35,6 hectares à Okala-Angondjé, 46,9 hectares à Lowé et 36,6 hectares à Igoumié, donnant lieu à un taux de déforestation global de 0,8% par an. Les reculs d’origine anthropique y représentent 57% des régressions à Okala-Angondjé, 96% à la rivière Lowé et 78% dans la zone d’Igoumié. Les moteurs de déforestation sont multiples : expansions résidentielles, installation de quartiers de pêcheurs, implantations hôtelières ou touristiques, création et extension des décharges d’ordures, industrialisation, développement portuaire et installations énergétiques. D’autres activités économiques ont provoqué aquaculture. Toutefois, le taux annuel de déforestation des mangroves urbaines dans la province gabonaise de l’Estuaire est plus élevé que la moyenne mondiale de déforestation des mangroves (0,11%).
Mangroves are productive and biodiverse ecosystems found in the intertidal zones of the tropics and sub-tropics which provide multiple goods and ecosystem services for humanity that are of ecological, economical, social and cultural importance. However, mangrove ecosystems are vulnerable because of several threats. The threats vary globally, regionally and locally. Mangroves can be affected by several different threats simultaneously, or over time as land use patterns change. There are some natural threats such as shoreline erosion and typhoons but predominantly they are human induced such as overexploitation, conversion and encroachment of mangrove habitats for agricultural and settlement purposes, aquaculture, a decline in freshwater and silt deposition and heavy metal pollution. Together with predicted climate change including global warming, sea level rise and extreme weather events, there will be further threats to mangrove ecosystems in the future. Mangrove conservation, restoration and rehabilitation are now being addressed through international agreements, protected areas, integrated policies and planning, reformed government structures, capacity development and environmental education but mangrove biodiversity conservation policies cannot succeed unless there is also consideration given to livelihoods and local communities are involved in all aspects of mangrove planning and management to promote sustainable conservation of mangrove biodiversity for the future.
The migration of oil spills in marine environment is still not clear, especially the key processes of submerging and floating, which is an important concern for effective disposal of oil spills. In mesoscale wave tank (32 m × 0.8 m × 2 m), this study has evaluated the characteristics of oil submergence based on oil concentration and oil droplet size. The concept of effective submergence is put forward for the first time, utilized to analyze the effects of dispersant on submerging stability and associated mechanisms. The results indicate dispersants increase submerged oil concentration and promote homogeneous distribution and vertical penetration. Of concern is that dispersants increase the proportion of small oil droplets (2.5~70 µm), prolonging the residence time of oil droplets in water by delaying the floating process. Dispersants sharply reduce oil droplets size (VMD<44 µm) thus decreasing the coalescence probability. These contribute to better submerging stability. By contrast, the submerged oil, formed as oil patches, oil streamers, and large oil droplets (VMD>170 µm) when without dispersant, will float and reattach to oil slicks more quickly due to their large volume. These findings help to clarify spilled oil behaviors and provide a new idea for the research on oil submergence.
Mangroves are one of the most potential tidal wetlands characterized by their hydrological, ecological, and geological features. They form the diversified and biologically productive ecosystem, populated with heterogeneous groups of plant taxonomy. The transboundary Sundarban mangrove wetland (89°02′ to 89°55′E and 21°30′ to 22°30′N) is situated on the Ganges–Brahmaputra–Meghna river network. This represents the largest continuous tract of mangrove forest in the world, spanning across Bangladesh (62%) and India (38%). The chapter gives an illustrative account of the diversity and distribution patterns of mangroves in India and other coastal regions across the world, along with their anomalous biogeographical patterns, mangrove landform classification and their morphological structure and adaptation strategies. In addition, the mangrove ecosystem goods and services, carbon storage efficiency and application of remote sensing for mangrove mapping have been discussed. A haven for rich biodiversity, Sundarban harbors several rare and globally threatened plants and animals. The overall common key threats for mangrove ecosystems are land-use changes, overexploitation of natural resources, chemical pollution from point and diffusive sources, reduced freshwater supply and silt deposition. Both India and Bangladesh should implement bilateral monitoring programs to resolve those emerging problems and formulate necessary management strategies to restore this diversified and iconic mangrove ecosystem.
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A crude oil polluted soil remediation was investigated using a mixture of avocado pear seed cake and poultry droppings. The seed cake was obtained through the Soxhlet method by extracting the oil from the pear seed. The experiment was carried out within a span of two months. Contamination was done by applying crude oil on 10 experimental reactors containing agricultural soil. The therapeutic treatment was then applied to the reactors, and the soil physicochemical properties were analyzed after set periods. The result shows that pH (6.89%), moisture content (18.1%), electrical conductivity (5430 μs/cm), total organic carbon (0.996%), total petroleum hydrocarbon (32.0 mg/kg) and total nitrogen (2.00%) which is an indication of distinct variation with time with the bacterial count of 9.20 cfu in all the reactors with an increased time. The control reactor does not show significant remediation throughout the study period. However, there was significant degradation of total petroleum hydrocarbon (TPH) in all the experimental reactors as follows: 76, 67, 55, 86, 78, 69, 81, 73 and 62% for T 1 , T 2 , T 3 , U 1 , U 2 , U 3 , V 1 , V 2 and V 3 after 2months. The study revealed that good remediation was achieved by the application of poultry dropping only 0.0324 days-1 compared to the mixture of poultry dropping and avocado pear seed cake (0.0275 days-1). Again, treatment with poultry droppings (PD) only removed 89.65% of TPH while combination of PD+ avocado pear seed cake (APSC) removed 85.41% of TPH after 70 days remediation period as predicted. The 200 g PD only (U 1) also increased the amount of nitrogen in the soil which is favorable for plant growth.
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Reduction in social benefits in form of fishery stock depletion has some fishing techniques seriously fingered as low economic performance among fisher folks is leading to low revenue and unemployment in Mangrove Swamp Zone (MSZ) of Nigeria. Data were obtained from a two-stage sampling technique from 206 artisanal fishermen in two states within MSZ. Data on fisher folks’ socioeconomic features, adoption level of environmental sustainable fishing techniques (ESFT), quantity and unit selling prices of species of catch as well as inputs were elicited using a well-structured questionnaire and analyzed using both descriptive and budgetary tools. Majority (68.9% and 64.2%) of fishing activities are done with dugout canoes with only a few (16.0% and 16.7%) motorized vessels that goes further off-shore in Bayelsa and Rivers State respectively. Adption level of ESFT of 26.1% and 24.1% for Bayelsa and River State respectively is low. Nematopalaemon hastatis recorded the highest (46.6%) returns of USD 345.77/fisherman, as fleet dominated sea-shore for it. Though artisanal fishing in MSZ seems economically sustainable with benefit-cost across different adopters greater than unity and rate of returns to investment ratio of 1.37, ranging from 1.33 in Rivers to 1.44 in Bayelsa State, but poses a high marginal social cost to the breeding areas as catch is very concentrated at the sea shore of less than 5nm. There is a low catch of some pelagic species (Etamopterus penyl). The study recommends a persuasive extension demonstartion, litigation and the use water poilce to enforce strict adherence to principles ESFT for sustainable artisanal fishing activities in the mangrove region of Niger Delta.
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Mangrove forests provide critical services around the globe to both human populations and the ecosystems they occupy. However, losses of mangrove habitat of more than 50% have been recorded in some parts of the world, and these losses are largely attributable to human activities. The importance of mangroves and the threats to their persistence have long been recognized, leading to actions taken locally, by national governments, and through international agreements for their protection. In this review, we explore the status of mangrove forests as well as efforts to protect them. We examine threats to the persistence of mangroves, consequences, and potential solutions for effective conservation. We present case studies from disparate regions of the world, showing that the integration of human livelihood needs in a manner that balances conservation goals can present solutions that could lead to long-term sustainability of mangrove forests throughout the world.
The first life on Earth evolved in the ocean about 3.5 billion years ago. Photosynthetic organisms, which first appeared in the ocean, eventually changed the oxygen and carbon dioxide concentrations in the atmosphere to the current concentrations. This gaseous exchange was the first and can be considered as the most important ecosystem service provided by marine ecosystems. That service has been on-going from the first primitive photosynthetic organism to the present and reflects the ability of the oceans to absorb carbon dioxide. Nevertheless, recent discussions of sequestration of CO2 have mainly promoted the concept of land-based green carbon sequestered by terrestrial ecosystems.
The Niger Delta region of Nigeria is one of the most crude oil impacted deltas globally. The region has experienced over five decades of oil related contamination of the total environment (air, soil, water and biota). In 2011, UNEP released a seminal report on oil impact on Ogoniland environments, which up scaled demands for urgent clean up and restoration of degraded bio-resource rich environments of the Niger Delta, starting from Ogoniland. The Nigerian Government demonstrated renewed political will to remediate contaminated sites in Ogoniland with a launch of the clean-up exercise in June 2016. Stakeholders’ expectations from the clean-up include not only environmental remediation but also restoration and creation of sustainable livelihood opportunities to reduce poverty in the region. Most studies have focused on the environmental restoration aspect and identified bioremediation as the likely appropriate remediation approach for Ogoniland, given its low environmental footprints, and low-cost burden on the weak and overstretched economy of Nigeria. This study mapped opportunities for sustainable livelihood creation during the Ogoniland remediation and restoration exercise. Given the value chain of bioremediation and its ancillary activities, the study analysed opportunities and mechanisms for skilled and unskilled job creation and prospects for sustainable livelihoods and knock-on effects. It is anticipated that the clean-up process would lead to economic prosperity and mitigate resource-driven conflicts in the Niger Delta. The study provides an exemplar for waste-to-wealth transformation in regions where natural resource mining has impacted communities, and has dislocated local economies and age-old livelihood structures.
Commercial exploitation of Nigerian oil and gas reserves began in 1956, shortly after the discovery of oil at Oloibiri in Bayelsa State. The export of the crude oil accounts for 90% of the country's foreign exchange earnings and more than 70% of its total budget expenditure. Over the years, what seems to be a blessing has constituted a nuisance, leading to environmental degradation, loss of farmlands, loss of fishing grounds, communal clashes, militancy, cultism, and the total breakdown of moral values in the Niger Delta region. These calamities were totally avoidable had successive governments utilized the wealth of the region in developing it. The total neglect of the region as a result of poor governance and corruption provided the platform for the twin problems of oil theft for export and illegal refining. It is estimated that the government is losing approximately $1.7 billion a month, although others speculate much more than this figure. Artisanal refining has exacerbated the already degraded environment by oil spills and industrial discharges. The art of this oil theft is an organized crime with local and international participants, including International Oil Company (IOC) staff, government officials, security personnel, local leaders, and sundry. Of course, stolen oil is sold to countries such as the United States, China, Brazil, Singapore, and other West African countries, among others. This scourge has led to environmental degradation, huge economic losses, and social vices, and it must be stopped now. The government needs to team up with well-meaning international governments to employ the recommendations preferred in this report.