Mangroves of the Niger Delta

Abstract

The Niger Delta is located in the southern part of Nigeria; three core states, Rivers, Bayelsa, and Delta house the largest concentration of Mangroves. The Niger Delta has the most extensive mangroves in Africa; six true mangrove species are found in the Niger Delta, Rhizophora spp. (R. mangle, R. harrisonii, R. racemosa) Known as red mangrove; Avicenna germinans, known as black mangrove; Langucularia racemosa, known as white mangrove; and Conocarpus erectus, known as buttonwood. Rhizophora spp. is the dominant mangrove in the Niger Delta and constitutes over 90% of the entire mangrove species in the region. Niger Delta mangroves are essential in providing ecosystem goods and services to the people. Unfortunately, the Niger Mangrove ecosystem faces severe threats from crude oil spills resulting from equipment failure, bunkering, vandalisation, and illegal refining. The invasion of mangroves by Nipa palm in the Niger Delta has become a threat to the mangrove ecosystem; deforestation and urbanisation are also significant threats affecting mangroves in the region. Providing sustainable alternatives to mangrove forest wood, conservation of mangrove forests, and enforcement of strict regulations in the oil and gas industry are some measures to ensure the sustainability of the Niger Delta mangrove forest.

1. Introduction

The Niger Delta region of Nigeria is home to Africa’s largest mangrove forest and one of the world’s most extensive mangrove forests. The area of mangrove forest habitat coverage in Nigeria is estimated at 8442.43 km² [1]. The Niger Delta region is located in the southern part of Nigeria; this region contains the majority of the mangrove forest in the country. Mangroves are trees and shrubs that grow on intertidal coastlines of tropical and subtropical regions. Mangroves are salt-tolerant plants that survive mostly in brackish water. In the Niger Delta, four mangrove genera exist; Rhizophora, Aviecina, Langucularia, and Conocarpus. Rhizophora spp. include R. racemosa, R. mangle and R. harrisonni. Other mangrove species in the Niger Delta are Langucularia racemosa, Avicennia germinans, and Conocarpus erectus. Rhizophora sp. Langucularia racemosa and Aviecina germinans are also known as red, white, and black mangroves, respectively, while C. erectus is known as buttonwood in the Niger Delta [2, 3]. Red mangroves are easily identified in the Niger Delta by their prop roots, leaves, and propagules; white mangroves are easily identified by their oval leaves, fruits, and seeds; and black mangroves can easily be distinguished from other mangroves by their elongated leaves, fruits, and seeds, including the presence of pneumatophores.

Mangroves in the region have been severely depleted; just like mangroves worldwide, mangroves in the Niger Delta are being lost at an alarming rate. However, data are readily not available for the hectares of mangrove forests lost over the last two decades in the Niger Delta. Several researchers have reported significant losses. Today’s leading cause of mangrove loss in the Niger Delta is crude oil spills and artisanal refining [4]. Other factors have also been reported to cause the loss of mangrove forests in the region: urbanisation, conversion of mangrove forests for agriculture and aquaculture, construction, deforestation, overpopulation, and the invasion of nipa palm in the mangrove ecosystem. The importance of the mangrove ecosystem has been widely researched and documented, so the need to protect and preserve these ecosystems becomes very dire owing to their uniqueness and myriads of ecosystem goods and services [5].

While the degradation and destruction of mangrove forests in Africa’s most extensive mangrove continues, efforts have been made to restore hectares of mangrove forest destroyed by a crude oil spill. One such effort is a litigation case between a small community in River’s state and an international oil and gas company operating in the region, where an agreement was reached between the community and the international oil and gas company to clean up and revegetate approximately 1000 ha of degraded mangrove forest in the community. Furthermore, the United Nations Environmental Program (UNEP) report [6] led a government agency to clean up the oil spill in Ogoniland and revegetate damaged mangrove forests, among other functions. While clean-up and revegetation efforts have commenced in the earlier case study, clean-up is currently ongoing in the government-managed cleanup process in Ogoniland [7, 8].

2. The Niger Delta

The Niger Delta of Nigeria is among the largest delta in the world. A delta is a landform that originates due to depositions of sediments carried by a river as the flow leaves the mouth of the river and enters slower-standing or moving water. Deltas occur when a river joins a sea or an ocean and cannot transport away the supplied sediments. The Niger Delta region has the largest wetland in Africa and the third-largest wetland in the world. Projections of the estimate of the current population in the region at a growth rate of 2.9% place the population of the Niger Delta as of 2022 to be well over 45 million people. The core Delta areas in the region lie in three central states: Delta, Rivers, and Bayelsa; these three states hold the most significant amount of mangrove forest in the country. Politically the Niger Delta region in Nigeria comprises nine states: Abia, Akwa Ibom, Cross River, Edo, Imo, and Ondo states, including the core states of the Niger Delta [9]. Figure 1 shows the map of Nigeria and the extent of coverage and distribution of mangrove forests in the Niger Delta and Nigeria.

Figure 1.

Map of Nigeria showing areas of mangrove coverage in the Niger Delta and Nigeria.

Other states with mangroves in Nigeria include Akwa Ibom, Cross River, Ondo, Ogun, and Lagos. The mangroves of the Niger Delta are located in the lower tidal floodplain, which also comprises various creeks and estuaries. The delta has a very high rainfall of more than 2500 mm per year, with a temperature range from 18 to 30°C. The tide in the mangrove forest is diurnal and can reach an amplitude of 2.8 m during spring tide and 0.2 m at the shallow tide. The poverty rate in the Niger Delta is at an average of 30%, and the region is densely populated with a literacy rate of 70%. Most rural dwellers are into fishing and farming and mostly depend on forests and surrounding water bodies for their primary source of income and survival [9].

The Niger Delta is also an extremely prolific hydrocarbon province where oil and gas have been explored and exploited over decades. A significant percentage of Nigeria’s oil and gas facilities run through the mangrove forest in the region; this has led to the rapidly under-reported degradation of mangroves in the region either by direct or indirect consequences of oil and gas exploration. Crude oil spills resulting from equipment failure, sabotage, bunkering, and artisanal (illegal) refining in the region have destroyed vast hectares of mangrove forest in the entire Niger Delta. Although the extent of the destruction is not known throughout the entire region, significant damage to the mangrove forest has been reported in the past by researchers [4, 10, 11].

3. Mangrove autecology in the Niger Delta

3.1 Red mangrove

Rhizophora spp. is the dominant mangrove species in the Niger Delta; it is distributed on all intertidal mangrove platforms and is found in almost all forest zones in the region. Mangrove platforms are areas where mangroves thrive; platforms are mostly intertidal areas in a mangrove forest. Rhizophora spp. Consist of over 90% of the total mangrove plant in the Niger Delta forest. Three species of Rhizophora exist in the Niger Delta: Rhizophora racemosa, Rhizophora mangle, and Rhizophora harrisonii. The differences between Rhizophora species in the Niger Delta can mainly be observed when the plants are fruiting. These distinctions are only observable once the plants mature enough to bear fruits. For this reason, it is not easy to differentiate the various Rhizophora species. Rhizophora racemosa is dominant among the three species, according to [2, 3]; in some instances, a different Rhizophora species is dominant in a different mangrove forest in the Niger Delta. Rhizophora mangroves have been known to grow as tall as 25-30 m in a pristine mangrove forest. They can be clearly distinguished by their prop root, which drops down from tree trunks and branches as high as 10 m in some plants, and the prop root mostly touches the soil or can be suspended in the air. Their prop roots have tiny pores all over them, which are used for gaseous exchange; these pores are known as lenticels. All year round, red mangroves in the Niger Delta flower exhibit a form of reproduction known as vivipary, where flowers develop into seedlings while still attached to the parent plant. Rhizophora seedlings are often referred to as propagules. Rhizophora propagules are distinct from other species in the Niger Delta. Thus, due to their dominance, most people confuse them for being the only mangrove species in the Niger Delta. Rhizophora propagules fall off the parent plant upon maturity and are carried by tidal currents until it finds suitable soil where it roots itself and begins to grow. Red mangroves are the most cultivated mangrove in nurseries all over the region (Figure 2). Shows various life stages of a typical red mangrove plant in the Niger Delta, its prop root, and propagules.

Figure 2.

Shows a typical red mangrove plant in the Niger Delta, and its various life stages.

3.2 Black and white mangrove

White and black mangroves make up less than 10% of the total mangrove species population in the region. White mangroves clearly distinguish from black mangroves in the Niger Delta as seen from their leaves. The leaves of white mangroves are oval in shape with a thick, dark green colouration in most cases, while the leaves of black mangroves are elongated and attenuated with a light green colouration. Also, one common feature of black mangroves that distinguishes them from white mangroves is the presence of pneumatophores. Pneumatophores are the lateral root that grows out of the soil, also used for gaseous exchange by black mangrove plants. Pneumatophores are found on all black mangrove plants, extending as far as 10 m from the parent plants in matured black mangrove plants. White mangroves can grow into trees but are mainly shrubs in the Niger Delta; some white mangrove plants have pneumathodes similar to black mangrove pneumatophores but are not the same and are not found on all white mangrove plants in the region. In the Niger Delta, white and black mangroves are always found in the intertidal zones of the mangrove forest.

In contrast, black mangroves are majorly found along shorelines where the sediments contain lots of sand; black mangroves are also found on intertidal platforms where the sediments are dominated by mud. White mangroves also grow on muddy and sandy sediments like black mangroves, but they also thrive on the fringes of platforms close to the channel edges [3]. Figure 3 shows black and white mangrove plants and their different life stages.

Figure 3.

Is black and white mangrove plants showing their various life stages.

3.3 Buttonwood

Buttonwood is the least common mangrove species in the Niger Delta, and they are less than 1% of the total mangrove population in the region. Buttonwood grows majorly high up the platform in the mangrove forest of the Niger Delta; they are found in areas close to the high tide swash line on the platform; buttonwood does not grow on intertidal zones in the Niger Delta and grows best on sandy sediments. Their leaves are elongated and attenuated with dark green colouration, and their seeds are round and green but turn brownish red upon maturity. Figure 4 shows a buttonwood mangrove plant in the Niger Delta and its seeds (propagule).

Figure 4.

Shows a buttonwood mangrove plant in the Niger Delta and its seeds.

3.4 Mangrove associate species in the Niger Delta

Nipa palm, although an exotic species in the region, is also referred to as a mangrove associate plant despite the plant invasion of the mangrove forest in the region. Other commonly found associate mangrove species found in the region’s mangrove forest are mangrove fern (Achrostichum aureum), mangrove grass (Paspalum vaginatum), and wild palm (Phoenix reclinata). All later species mentioned are not invasive but can be found in a different zone and intertidal areas in a mangrove forest. Mangrove fern is evenly distributed on almost all mangrove platforms; mangrove grass is mainly found on shorelines, sandy sediments, and areas close to the high tide swash line along the mangrove platform. The wild palm grows along the buttonwood corridor but is sometimes found on the intertidal platform. Wild palm and mangrove ferns grow mainly as shrubs in the region. Figure 5 shows mangrove fern and wild palm in a mangrove forest in River’s state.

Figure 5.

Shows mangrove fern and wild palm common mangrove associate plant in the Niger Delta.

3.5 Mangrove zonation in the Niger Delta

Figure 6 below is a drone picture of a remediated mangrove forest platform with little vegetation. The arrows indicate areas where each mangrove species will likely grow in the Niger Delta. The yellow arrow indicates the intertidal zone of the platform, and the yellow arrowhead to the right is the high tide swash line. In a pristine mangrove forest, due to the dominance of red mangroves, they mostly occupy the intertidal zones, as noted by the red arrow in the picture below. White mangrove also thrives in areas where red mangrove thrives but are outcompeted by red mangrove, as seen from the white arrow in the picture. Black mangroves thrive best at the upper platforms and shorelines, as indicated by the black arrow in the picture. Buttonwood typically grows in areas outside the intertidal zone or close to the mangrove high tide swash line, or it can grow in higher platforms with minor inundation. In a degraded mangrove forest, black, white, and red mangroves can thrive in any intertidal area in a mangrove platform in the Niger Delta.

Figure 6.

Below is a drone picture of a remediated mangrove forest platform with little vegetation. The arrows indicate areas where each mangrove species will likely grow in the Niger Delta.

3.6 Sediment types in a typical Niger Delta mangrove forest

The sediment in a typical Niger Delta mangrove forest varies from platform fringes, which are usually composed of pure mud, down to the intertidal platform, where a mix of mud and Chikoko roots start to build up, down to the inner fringe of the platform and shoreline, which consist of mud, Chikoko root and sand. Chikoko roots are the thick fibrous peaty composition of mangrove roots, leaves, and other organic components of mangrove plants that have decayed over a long period and are often found in the sediments of mangrove soils. In some mangrove platforms, these fibrous peaty materials are found as deep as 1 m when you dig the soil of the mangrove platform. In certain areas, Chikoko roots make up over 95% of the entire soil sediment in the Niger Delta. Sandy soil is a significant sediment found in mangrove platforms and often along the shoreline and areas close to the high tide swash line on the platform. Soil sediments also vary from one location to the other in the Niger Delta; specific platforms in some mangrove areas are composed of two or more sediment types in different proportions. Typically, muddy sediment is the dominant sediment type in Niger Delta; it is common to see a mixture of two or more sediment types mixed or in layers. A mixture of mud and Chikoko root is a common sight when you dig up to 30 cm beneath the surface [12]. Figure 7 below shows various sediment types commonly found in the Niger Delta mangrove forest 0.3 m below the surface sediment.

Figure 7.

Below shows various sediment types commonly found in the Niger Delta mangrove forest at a depth of 30cm.

4. Threats to Niger Delta mangrove forest

Over the years, mangroves in the Niger Delta have faced challenges common to mangroves forest worldwide: the conversion of mangrove habitats for agriculture and aquaculture. It is a common site in most mangrove areas in the Niger Delta for locals to construct fish ponds, where they rear fish and use such areas sometimes to trap fish at high tide. Areas converted to fish ponds are mainly mangrove forests cleared and used as fish ponds; in some instances, these fish ponds can be as large as 900sqm. Fishing in the Niger Delta is one of the biggest employers of labour for both men, women, and children living near mangrove habitats. Mangrove forests are cleared so nets can be used to set traps for fish; However, fish pond construction completely clears mangrove trees on the land where it is constructed; the surrounding mangrove environment is usually left undisturbed; the impact of the fish pond on the degradation of the Niger Delta mangroves forest can be said to be minor when you assess the risk of fish pond construction in a mangrove forest in the Niger Delta.

Deforestation of mangrove forests is also a significant threat to mangroves in the Niger Delta. In the Niger Delta today, due to the high poverty and illiteracy level, most communities still use wood as their primary energy source. This has led to the constant deforestation of mangrove forests in the region. Mangrove trees make good wood for local consumption; logging trees in mangrove forests for commercial and subsistence purposes is a common site in the region. The need for cheaper energy sources and lack of alternative cheaper energy for cooking in the Niger Delta have been the reason for the constant deforestation of the Niger Delta mangrove forest. It is also common to see fishermen use deforested trees as sails for their boats. Deforestation has increased due to harsh economic realities and rising poverty levels, which have increased in the Niger Delta in the last decade. Steps must be taken to enlighten the locals on the dangers of deforesting mangrove forests. Still, most importantly, an alternative and a cheap source of cooking must be provided to the low-income earners in the community to reduce the incidence of deforestation and reduce the dependence on the local community for the use of mangrove wood as a primary source of energy. Figure 8 shows wood harvesters in Goi, a small Ogoni community, in boats returning to their base after harvesting mangroves.

Figure 8.

Shows wood harvesters in Goi Gokana LGA, a small Ogoni community, in boats returning to their base after harvesting mangroves.

Population growth, urbanisation, and construction are significant threats to the mangrove ecosystem in the Niger Delta. As the population of the people of the Niger Delta increases, the demand for forest products such as wood also increases. Population growth would automatically mean people require more land for farming, building, and other social needs and, by extension, additional pressure on the surrounding forest. Construction of roads and oil and gas facilities, such as pipeline networks, have extensively degraded mangrove forests in the Niger Delta. Proper enlightenment of the local community on the need to protect the forest must be a task that the government and civil societies would have to embark on so mangrove forest goods and services can be used sustainably in the Niger Delta. Despite the threat discussed so far, the effect of petroleum hydrocarbon spillage and the invasion of Nipa palm in mangrove habitat in the Niger Delta remain two of the biggest threats currently facing the Niger Delta mangrove forest at the moment and will be discussed broadly.

4.1 Nipa palm invasion of mangrove forest in the Niger Delta

Nypa fruticans, also known as Nypa or Nipa palm, are commonly found in Asia. They are large green palms forming loose clumps from a subterranean stem. Nipa palm has clumps of individual erect and large leaves that can grow as long as 6 m. In Asia, Nipa palm seeds and saps are edible and used for thatching. Nipa palms are not natural flora in the Niger Delta mangrove forest; their presence in the Niger Delta was due to their introduction in Calabar, Nigeria, in 1906 from a Singapore botanical garden. In 1964, thousands of seeds originating from Malaya were planted throughout the brackish swamps of the Niger Delta. These were the major points where Nipa was introduced to the Niger Delta. Introducing these plants in the Niger Delta provided an alternative palm for the people to the native palm (Elaeis guineensis), mainly used for thatching, food, and alcoholic wine [13]. It is safe to say that at the time these decisions were made, the value of mangroves had not been fully understood by those who made the decision, and the unintended consequences of Nipa palm invading the mangrove forest were not anticipated.

In the Niger Delta, Nipa palm has become an invasive species and is taking over mangrove habitat. Nipa palm can be found along the coastline of the Niger Delta mangrove forest down to Lagos and Ogun. Unfortunately, the local community does not use Nipa palm in the Niger Delta for any purpose, as they are not the palm of choice for thatching; their sap and seeds are edible in other parts of the world but are currently not eaten in Nigeria. Nipa palm grows on the fringes of the Niger Delta mangrove platform, competing with mangroves for space, food, and habitat, and expanding its reach when the opportunity provides itself. In a healthy, matured mangrove forest, the only available areas Nipa can grow are the fringes and sometimes channel edges of the mangrove platform and along the coastline.

The current degradation of mangrove forests in the Niger Delta has provided Nipa palms with the opportunity to thrive in areas where mangroves would naturally outcompete them in the Niger Delta. This has allowed Nipa palm to find its way into the heart of mangrove platforms and establish itself, thereby colonising areas where mangrove plants should grow. Nipa palm and mangroves have similar modes of seed dispersal; unfortunately, Nipa tends to outgrow and outcompete mangroves when the two plants are simultaneously established on the same soil in a mangrove habitat [14]. Nipa palm invasion of mangroves has been described as one of the significant threats to the mangrove ecosystem in the Niger Delta, the growth and spread of Nipa palm, if not checked, would spiral out of control. The current effort to stop the spread of the plant in the region has been to mechanically remove the plant from the mangrove habitat by cutting down the plant and taking their seeds away, as it is currently done in Bodo, a small Ogoni Community where restoration efforts are being made in the Niger Delta [7].

The sustainability of mechanical removal of Nipa palm would require a concerted effort of the entire Niger Delta and Nigeria, including its west African Neighbours whose coastlines have also been overrun by Nipa palm. Today Nipa palm has become not just an invasive species in the Niger Delta; it has also formed part of the associated mangrove species in the Niger Delta since their number cannot be overlooked and can no longer be considered an exotic species if nothing is done about their rapid growth and spread. Figure 9 shows the Nipa palm growing on the fringes of a mangrove platform in the Niger Delta and the mechanical removal of the Nipa palm from a remediated mangrove forest in the Niger Delta.

Figure 9.

Shows the Nipa palm growing on the fringes of a mangrove platform in the Niger Delta and the mechanical removal of the Nipa palm from a remediated mangrove forest in the Niger Delta.

4.2 Crude oil spills on mangroves in the Niger Delta

Petroleum hydrocarbon is one of the vast natural resources in the Niger Delta and the primary income of Nigeria today. Unfortunately, the Niger Delta of Nigeria has been on the receiving end of many environmental disasters resulting from petroleum hydrocarbon pollution. In the Niger Delta, some oil and gas exploration well heads are located on mangrove forests, and vast networks of oil and gas pipelines in the Niger Delta run through mangroves forest or creeks and estuaries adjourning mangrove forests; this has made it possible for mangroves to be readily degraded by petroleum hydrocarbon whenever there is an accident, sabotage or equipment failure on any of these facilities. The oil spill history in the Niger Delta dates back to when commercial exploration of oil began in Oloibiri, current Bayelsa state, in February 1958. Since the commercial exploration of oil and gas in Nigeria, thousands of oil spill incidents have been reported in the Niger Delta. Some of these have been noted to affect mangrove habitat; one such incident where large-scale mangrove destruction occurred in the Niger Delta is in Ogoni and Bonny in River state, Nembe in Bayelsa state, and many other regions in the Niger Delta.

A case study of a significant oil spill incident in the Niger Delta happened in 2008 and 2009 along the Trans Niger Pipeline (TNP), which carries Bonny light crude oil to an export terminal in Bonny River State. The TNP is critical to Nigeria’s crude oil export and is jointly operated by the Nigerian government and a major international oil and gas company; the TNP carries 180,000 barrels daily to the Bonny export terminal. In October 2008, there was a leak along the TNP, which happened to be along the creeks in a community known as Bodo. After a joint investigation, it was discovered that the leak was caused by equipment failure due to corrosion due to the old pipeline conveying crude, which was laid in the 1960s. Locals reported that the leaks in the pipeline occurred for weeks before it was clamped, and thousands of barrels of crude were spilled into the surrounding creeks, which eventually damaged hectares of mangrove forest along Bodo, Goi, Kpor, and Bomu in Gokana River state. In February 2009, another leak occurred in Bodo along the TNP, a few kilometres away from the previous leak; no data was put out on the exact amount of oil introduced to the environment. The effect of the two spills resulted in the degradation of over 1000 hectares of mangrove forest and the destruction of fauna and flora within and around the affected areas [15, 16].

4.3 The effect of crude oil spill on mangroves

Mangroves are susceptible to oil exposure depending on the degree of oiling, length of exposure, and, to an extent, the type of crude oil. Mangroves exposed to crude oil in sufficient amounts to cause harm will suffer from their leaves turning yellow and falling off (defoliation) and eventually death. The smaller and younger trees or plants whose stems and leaves are entirely coated by oil are usually among the first to die off because the plant’s lenticels and leaves used for transpiration and salt excretion are covered with crude, thereby preventing the natural biological function of the entire plant [17].

Following the two spills in Bodo creek, crude oil floated freely on the surface of the creek; being an intertidal area, crude oil was constantly being carried into intertidal platforms where they are deposited on sediments, leaves, stems, and prop roots of mangroves. A few weeks after the spills, all plants that were coated with oil from their stems to their leaves died; it did not take long after areas that had high crude oil deposits, all plants gradually started dying off, and hectares of mangrove forest was left with stumps of interwoven dead mangrove plant. Years after the spill, the entire dead plant stumps collapsed, leaving an open island of degraded mangrove platform with dead mangrove stumps littered all over the platform.

The effect of crude oil on mangrove habitat has a ripple effect on the faunal community and the livelihood of the people who depends on mangroves for the many goods and services it provides to the locals in the community. Most Niger Delta communities, as noted earlier, are heavily dependent on fishing, and polluted creeks resulting from crude oil spills are often devoid of fish even after cleanup, it takes a significant amount of time for the fish communities in most of these creeks to be back to its pristine conditions. The cascading effect of spill damage on mangroves forest has been experienced in many Niger Delta communities in Ogoni Rivers State; due to the death of mangroves closer to the shorelines where the people reside, wood harvesters have had to go deeper into areas where the spill barely affected to harvest wood, this has put enormous pressure on the forest as trees which are not matured enough are harvested leading to rapid deforestation of the mangrove forest. Furthermore, the spill’s effect on invertebrate and fish communities has put enormous pressure on the creeks due to the trawling of small and immature fish due to the depleted fish stock in the creeks. Juvenile mangrove plants have also been harvested in these areas, reducing the chances of natural recovery. As a result, human-mediated revegetation is required to restore the lost ecosystem.

Although the damage from a large-scale oil spill has acute and chronic implications, pollution from artisanal (Illegal) refining, bunkering, and crude oil theft have also destroyed hectares of mangrove forest in the Niger Delta, and most of these destructions are largely undocumented. Artisanal or illegal refining of crude oil in the Niger Delta, locally known as “Kpo-Fire,” is the small-scale processing of stolen crude by heating it at high temperatures to distill it into its fractional components. The mangrove forests and other parts of the Niger Delta have become spots and make-shift refineries for artisanal refining crude oil. The implication of this is that mangroves are cleared to set up a refinery, and in most cases, mangrove trees are harvested to provide energy for heating the crude at very high temperatures; the effluent, tar, and asphalt, which are usually bi-product of the refined crude are often discharged in pits in or around the mangrove forest. Crude oil used for artisanal refining in the Niger Delta is stolen chiefly from pipelines running through the mangrove forest. The point at which the pipes are compromised, if not well-engineered, is usually a source of spill in the mangrove forest; transportation of the crude and storage of the crude, including refined artisanal products, are usually significant spill sources in the Niger Delta. Artisanal refining camps in the Niger Delta have been on the increase in the Niger Delta despite several government clamps down; the more camps created, the more pressure on mangroves somewhere in the Niger Delta; unfortunately, most of the damage from artisanal refining and crude oil theft on mangrove forest is not documented as such the extent of damage caused by artisanal refining on mangrove forest in the Niger Delta today is difficult to quantify [10].

Despite the damage from the crude oil spill on mangroves in the Niger Delta, efforts are currently ongoing to restore hectares of damaged mangrove forest in the Niger Delta, mainly due to the UNEP report [6] and a few litigation cases between the host community and international oil and gas companies responsible for the spill in partnership with Nigerian government regulatory agencies. Some of these efforts have shown great restorative potential, and remediation, cleanup, and revegetation have begun in earnest.

5. Mangrove restoration in the Niger Delta

In the Niger Delta, mangrove restoration has been done mainly on a small scale. A mediation-driven mangrove restoration program is currently Nigeria’s most extensive [18]. Although the government-backed cleanup of Ogoniland would involve mangrove restoration, the remediation phase of the cleanup of intertidal areas is currently ongoing. Mangrove forest impacted significantly by crude oil spills requires cleanup/remediation of the contaminated mangrove sediments, planting, and monitoring of mangroves. Mangrove ecosystems are intertidal environments that are usually very challenging to clean up or remediate after a spill. For the first time in the Niger Delta, the shoreline cleanup assessment technique (SCAT) has been deployed to clean up/remediate contaminated mangrove sediment in the Niger Delta [7, 16].

5.1 The use of SCAT in the Niger Delta

The Exxon Valdez spill in 1989 birthed the origin of SCAT, and since then, the technique has been used in several spill cleanups globally. SCAT was first used in the Niger Delta in 2019 and is currently used to clean up spill sites in the Niger Delta. SCAT involves a series of surveys before, during, and after the cleanup/remediation operation. SCAT rapid surveys are initial surveys done during the SCAT process to determine the level of contamination and areas affected by the spill. The SCAT rapid survey serves as a baseline where blueprints for remedial/cleanup actions are designed. SCAT assessment surveys are done to delineate work areas and get in-depth information to characterise work areas. SCAT confirmation or verification surveys are done after cleanup/remedial actions have been done in the affected areas [19].

SCAT process requires the participation of all stakeholders in the remediation process; stakeholders in the Niger Delta usually include the host communities, the oil and gas company, government regulatory agencies, a mediation body (if set up), and civil society organisations. Representatives of all stakeholders would be available at all stages of the SCAT process. Cleanup or remediation is given to contractors with expertise in oil spill remediation. The stakeholders often agree upon remediation techniques, and the SCAT team confirms remediation work. The SCAT team is composed of a representative of all stakeholders at every site or work area to be confirmed; SCAT confirmation is done by digging three pits and assessing the level of oiling in the pit. SCAT assessors are usually trained in SCAT techniques to assess the pit; remediated site maps are designed and produced by the management and SCAT team lead, and coordinates of the sites are handed over to the SCAT team for verification and confirmation.

Pit oiling assessment is critical to verifying and confirming remediated sites; in the cleanup process at Bodo, pit oiling assessment for confirmation of a site is a maximum of 25% oiling per pit. A work area can have as many sites as possible, depending on the size of the area. Irrespective of the number of sites in the remediated area, each site must have three pits, usually in a trisection, with the sum of pit oiling in all three pits less than 75%. Although this process is subjective and open to bias, the oiling level for each pit is agreed upon by the entire stakeholders in the SCAT team. A standard pit oiling chart also guides the SCAT team in their assessment when determining oiling levels in the pit.

5.2 Mangrove planting and monitoring

After cleanup/remediation is completed, the next phase of the restoration program is planting mangroves. In the Niger Delta, mangroves are planted as propagules, sprouted propagules, or seedlings. While propagules are seeds from mangrove plants (Figures 1–4) harvested and put directly on restoration sites to grow, sprouted propagules and seedlings are grown or nursed in a nursery before being transplanted to their restoration site after a certain period. Seedlings are preferred as the life stage of choice in the Niger Delta for restoration, as observed in the Bodo revegetation projects. Seedling also increases restoration costs but improves the survivability of the overall plants during restoration. Seedlings will require the setting up nurseries, usually found in some Niger Delta communities close to intertidal areas. Nurseries are sited close to intertidal areas to avoid the constant need to water the plant with brackish water when the nursery is located far away from intertidal areas [20].

Most mangrove nurseries in the Niger Delta have only Rhizophora spp. Seedlings grown in them might be unconnected with the fact that Rhizophora spp. is the dominant mangrove species in the Niger Delta, and most locals in the community do not see other mangrove species as part of the mangrove community in the Niger Delta. Mangrove planting involves transporting mangrove seedlings to areas where they would be transplanted; care must be taken during transportation since some mangrove areas might be inaccessible on foot. Mangrove seedlings should be planted in a single bag, although to save cost, specific mangrove nurseries in the Niger Delta plant multiple propagules in a single bag. Single bags are advised to reduce stress on the plant during transplanting and to ensure that the soil and the plant are placed in the ground together. Figure 10 shows a mangrove nursery in the Niger Delta and how propagules are planted in single and multiple propagules per bag.

Figure 10.

Is a picture of a mangrove nursery in the Niger Delta and how propagules are planted in single and multiple propagules per bag.

Monitoring mangroves is done to ensure their growth and survivability and to identify areas where significant losses occur, the cause(s) of the loss, and the need to replant after identifying why the loss occurred. Mangrove monitoring is critical to the survivability and growth of large-scale mangrove revegetation programs. The monitoring program in Bodo involves collecting specific data from marked plants in different planting areas. Monitoring is done at intervals of one, six, 12, and 18 months; specific data such as the increase in height, number of leaves and branches, oiling conditions number of prop roots or pneumatophores are collected at every monitoring interval. An overall count of the number of dead mangroves is done after the first month of planting, where deaths exceed 5%; in a delineated planting area, the dead plants are replaced, and monitoring is scheduled for another month after replacing the dead plants. The process is repeated till the death rate in a particular planting area is less than 5%. Restoration of mangrove habitat is a long-term project as mangroves take years to fully mature.

5.3 Challenges of mangrove restoration in the Niger Delta

Corruption, weak government regulatory system, and lack of environmental justice have been the bane of mangrove forest restoration in the Niger Delta. Oil spills in mangrove ecosystems remain un-remediated, and where remediation Is done, they need to be done correctly. Also, most Niger Delta communities impede the cleanup process by demanding outrageous amounts from the oil and gas companies even after compensation has been paid out; in some cases, community leaders demand money to be used for the cleanup process be paid to them.

6. Conclusion

Mangroves of the Niger Delta are the largest and one of the most threatened mangrove ecosystems in Africa. The Niger Delta mangrove is a very significant ecosystem in the Niger Delta as they provide a variety of environmental, economic, and social goods and services to the people of the Niger Delta. Unfortunately, the importance of this vital ecosystem is not well known by most people in the Niger Delta; as such, the Niger Delta mangroves are depleted in certain areas at an alarming rate. Significant threats to the Niger Delta mangroves include Nipa palm invasion, oil spill pollution, deforestation, and urbanisation. Mangroves in the Niger Delta must be protected from the threats it is currently facing for the sustainability of this vital ecosystem. It is also essential to educate the communities around mangrove areas on the importance of protecting these forests; the government must, as a matter of national interest, map out areas of the Niger Delta mangrove forest for conservation; this would ensure the sustainability of the mangroves.

Conservation is a long-term strategy for protecting the Niger Delta mangroves; in the interim, both national and state governments must collaborate with all state actors in the oil and gas industry in the region to ensure the complete cessation of spills in mangroves and other parts of the Niger Delta, and as a matter of urgency stop illegal bunkering and artisanal refining of crude in the Niger Delta. A policy framework must also be drawn up on how to control the rapidly spreading Nipa palm currently invading mangrove forest in the region. Despite the significant threats affecting the mangroves in the Niger Delta, the sustainability of the region’s mangroves is still very realistic if current threats are addressed.

Acknowledgments

I want to acknowledge Dr. Erich Gundlach of the Bodo Mediation Initiative, under whose platform I have been able to learn about the mangroves of the Niger Delta. I also appreciate his mentorship skills and willingness to impart knowledge. Special thanks to my colleagues Nicholas Story, Peter Lenu, and Bariton Lezabby for contributing to various aspects of this book chapter.