Spatial Extent of the Risk of Pipeline Explosion and Fire Outbreak on the Vegetation Health and Abundance in Rivers State, Nigeria: A Thought for Adequate Regional Development Planning

Introduction 

For four decades, the petroleum industry has been economically extracting oil from the Niger Delta and at that moment, it has caused significant damage to nature and its inhabitants. Annually, much oil is spilled in the Niger Delta regions, and gas flaring still pollutes the air and environment leading to environmental dangers and associated disputes. The oil and gas industry’s negligence towards the environment threatens the people of the Niger Delta, which is a serious issue. This is particularly urgent since over 60% of the populace relies on the nature and its inhabitants for their livelihoods, necessitating healthy soil for agriculture and uncontaminated rivers for fishing. The Geographic Niger Delta covers about 26,000 square kilometers, accounting for 2.8% of Nigeria’s total land area.

A study by the World Bank in 1995 recognized four unique ecological zones within the Delta as; mangrove ecosystems, freshwater swamp forests, lowland rainforests, and forests on barrier islands. In contrast, vegetation cover is crucial for maintaining the ecosystem’s balance, as it safeguards the soil and aids in controlling erosion. It mitigates the impact of rainfall by lessening the force of falling raindrops, enhances the soil’s ability to absorb water, and slows down surface runoff [13;26].  Additionally, vegetation supports biodiversity and shields catchment areas from natural disasters like landslides and floods [16]. Thus, it is vital to maintain vegetation cover, particularly in rainforest and mangrove environments.

The largest mangrove swamp forest in Africa and the third largest in the world is situated in Nigeria, mostly in the Niger Delta. This ecosystem is delicate and plays a crucial role in the local economy. It represents the most ecologically diverse area, featuring a greater variety of plant life. It is important to acknowledge that to promote a cleaner environment and foster political stability in the oil-producing regions of the Niger Delta, the Nigerian government has implemented various environmental regulations to oversee and regulate the activities of Shell-BP, Chevron Nigeria, and other multinational oil companies. In the early 1960s, the government made this decision with the understanding that oil drilling leads to environmental degradation, impacting natural vegetation and resulting in pollution of waterways and rivers [25]. which ultimately reduces the quality of life. This indicates that the government anticipated the significant risk of pollution linked to oil production that could arise from mechanical malfunctions or deliberate sabotage of pipelines. The design and operation of pipelines allow for the safest and most cost-effective method of transporting and distributing both crude oil and petroleum products, particularly over lengthy distances in both rural and urban areas. Regrettably, the oil and gas pipeline systems running throughout the Niger Delta have recently become significant sources of human, environmental, and ecological health disasters, leading to economic losses. Data on pipeline fires and explosions over a six-year span from 1998 to 2003 reveals a concerning rise in both the frequency of incidents and the extent of damage to the environment, the loss of valuable resources, lives, and effects on the national economy, among other consequences.

Thus, the selection of Niger Delta communities where oil pipeline failures have happened in the past and present is very appropriate for this study in order to guarantee proper regional planning and to ensure moderation in people’s quality of life, particularly in Rivers State, Nigeria.

Materials and Methods

The entire Rivers State in Nigeria, which served as the study area, is located between latitudes 4° 30’N and 5° 40’N and longitudes 6° 25’E and 7° 33’E (Figure 1). The Atlantic Ocean borders Rivers State to the south, Bayelsa and Delta States to the west, Imo, Abia, and Anambra States to the north, and Akwa Ibom State to the east. There are now 23 local government areas in Rivers State. The Coastal Plain sands, which are part of the Pleistocenic Formation, geologically underlie the research region [15]. The sediments are composed of silt, sands, clays, peats, and gravel deposits from the Niger River [9]. However, the remains of plants and animals that are found in shallow holes give rise to peat. The final subsurface rock types are gravels and pebbles, which are found at the bottom of river channels [19]. There are both upland and riverine regions in Rivers State. There are natural gas reserves in the area, and the uplands have topography that varies from 15 to 40 meters above sea level, while the riverine sections have a mean elevation of roughly 15 meters [12].

However, because of the abundance of natural gas and crude oil reserves in the region, Rivers State is well-known for its oil and gas production. Rivers State is home to over 40% of Nigeria’s crude oil reserves, as a result, numerous petrochemical enterprises were established. The sub-equatorial zone is home to Rivers State, with an average annual temperature of 300°C, a relative humidity of 80% to 100%, and an average annual rainfall of roughly 2,300mm, it has a tropical climate. Although it fluctuates with the seasons, the   rainfall is consistently substantial [14]. The Atlantic Ocean moderates the tropical climate, the warmest months are January through May, with more than 20 days with temperatures of 32°C or above.

The region is also known for its abundant rainfall, which ranges from 2000 to 2500 mm from April to October. There are also sporadic rainfall throughout the drier months of December, January, and February. With primarily north-easterly and south-westerly breezes, the state experiences comparatively calm weather. The town is located in a rather quiet place, nonetheless, and data indicate that there are no breezes 47% of the time. Wind speeds between 5 and 17 m/s occur only 2% of the time, and they hardly ever surpass 17 m/s. The Tropical Maritime Air Mass (mT) is the main air mass system in Rivers State. This air mass, known as the SW Monsoon, is damp, humid, and brings rainfall to the area. According to [1], the vegetation is the most diversified, complex, and lush terrestrial ecosystem the world has ever seen. Fruit trees, palms, and moist evergreen plant species that are rich in timber make up the vegetation of tropical rainforests. High rainfall and high temperatures nourish the vegetation, creating favorable conditions for the growth of tall and large tree species like mahogany, Obeche, and Afara, as well as an abundance of oil palm trees and   other economically valuable plant species like raffia palms, Abura, ferns, and grasses [7]. Because there is a lot of surface water and a lot of rainfall between 2000 and 2400 mm, the research region has poor drainage [13]. Rainfall is the primary source of underground water in the region [24]. It is also found that Rivers State contains tidally and seasonally flooded areas, making it difficult and limited to practice agriculture. Additionally, there is a restriction on the amount of nucleated urban development. The Bonny River, its tributaries, and creeks play a major role in regulating Rivers State’s primary drainage pattern. It serves as a significant feeder for a number of creeks and creeklets that collectively drain the many outcrops of comparatively higher ground that are mostly encircled by mangrove swamps [4]. The three main types of soil in Rivers State were mangrove swamp alluvial soils, fluvial marine sediments, and freshwater and sandy loams [17].

The study used near real-time data from the Terra and Aqua Normalized Difference Vegetation Index (NDVI) of 16 Day L3 Global 250m resolution, which was obtained from https://earthexplorer.usgs.gov using the Moderate Resolution Imaging Spectroradiometer (MODIS). For the study, 2020 NDVI images was taken into account. According to [11], the NDVI is one of the most widely used and applied indices that are computed from multispectral data as a normalized ratio between the red and near-infrared bands. The NDVI is directly used to describe canopy vigor or growth. Since it has been demonstrated to be correlated with biomass, percentage green cover, and vegetation vigor, NDVI is the most widely used vegetation index [22;2]. When both Pred and Pnir are zero, the non-linear function, which fluctuates between -1 and +1, is undefined [2]. According to [5], Pred and Pnir are reflectance in the satellite imagery’s red and near-infrared bands, respectively. Dense vegetation is indicated by values larger than 0.5, while places that are built up, rock, sand, water, snow, and barren are indicated by values less than 0.1 [2]. Active vegetation has a positive NDVI, which is normally between 0.1 and 0.6 values at the higher end of the range, signifying stronger photosynthetic activity and a higher canopy density. ArcGIS 10.5 was used for the analysis. The NDVI photos of several years were clipped from the Rivers State boundary shapefile, and data was extracted from the images using zonal statistics to create graduated maps and tables. The mean, standard deviation, minimum, and maximum were displayed using the zonal statistics. For additional analysis, the NDVI mean values were used. To scale the original NDVI value to range from 0 to 1, the mean NDVI values were multiplied by 0.0001 (Land Processes Distributed Active Archive Center (LP DAAC), 2014). Numerous vegetation indices have been developed using numerical combinations of remotely sensed data’s red and near-infrared values. When mapping vegetation and vegetation conditions, the ratio of red bands (TM4/TM3) to near infrared (NIR) bands is helpful.

It is a common technique for analyzing vegetation. After subtracting the respective cell values in the two bands, the NDVI “normalizes” the difference by dividing the total of the two brightness values. The following formula is used to calculate the NDVI:

NDVI = (Near-infrared – Red) / (Near-infrared + Red) ………………….. (Equ. 1)

The data was analyzed using both descriptive and inferential statistics. Inferential analysis was utilized to ascertain the relationship between the impact of fire explosions on the spatial extent of landuse/land cover and the distance from the oil pipeline, whereas descriptive analysis used frequencies and percentages. Additionally, the change in the spatial extent of landuse use with increasing distance from the oil pipeline was ascertained using analysis of variance.

Results and Discussions

Figure 2 presents the vegetation health across the Rivers State in 2020 while Table 1 displays the values of the health of vegetation as the distance increases from the oil pipeline. The mean vegetation health at 50m distance from the oil pipeline was 0.5087, 100m was 0.5113, at 200m was 0.5123, at 300m was 0.5193, at 500m was 0.5500 and at 1000m was 0.5619. This invariably shows that the vegetation health increased with increasing distance from the oil pipeline. This is attributed to the intensity of the fire which burns down vegetal resources and other environmental resources in the study area. 

The variation of the effect of fire explosion on vegetation health at different distances from the oil pipeline shows that there was significant variation in the effect on the vegetation health (F=11.69; p=0.024) (Table 3). The significant variation was totally due to the impact of fire explosion especially as low vegetation health was found at the nearby place close to the oil pipeline. Talking about the post hoc comparison in Table 4, it is shown that there is significant variation in the effect of fire explosion on vegetation health in the study area as the p>0.05 especially between 1000m and other distances which are 50m, 100m, 200m, 300m and 500m..

R = -0.593 and R square = 0.352 are the results of the regression study between the distance from the oil pipeline and the impact of fire explosion on vegetation health in Table 5. The fire explosion and distance have a moderately negative correlation, according to the regression coefficient R = -0.593. It implies that the distance tends to decrease as the impact of the fire explosion on vegetation health rises. The distance in the model accounts for 35.2% of the variance in the fire explosion on vegetation health, according to the R2 = 0.352. The remaining 64.8% might result from random variation or other causes that the model did not consider. Table 6 reveals the analysis of variance of the regression analysis proving of the significance of the regression. The mean vegetation health of the non-affected and affected communities in Table 8 reveals that the mean value in the non-affected communities was 0.4652 while for the affected communities was 0.4585. This shows the impact of fire explosion on vegetation health in the study area. The regression model generated from Table 7 is given in Equation 1.

Y_{Vegetation Health} = 0.538 + 0.140 _{Distance from oil pipeline}                                             Equ. 1

Discussion of Findings

It has been discovered that fire explosions and oil pollution have had a significant impact on the health and abundance of flora in the research area, particularly in the areas nearest to the oil pipeline. This is consistent with [6] mapping of vegetation loss using NDVI and burn indices. As a result, it demonstrates that the NDVI decreases significantly around the explosion site, whereas the vegetation is less impacted farther away. Near fire explosions along crude oil pipelines, the health of the vegetation drastically deteriorates. Research conducted in Nigeria, including in Ilado-Odo, revealed that vegetation within 500 meters of explosion sites has poorer morphological traits, lower stem density, and less species diversity than control sites, which are roughly 2 kilometers distant [21]. Similarly, land cover analyses in Rivers State reveal greater vegetation loss within 300–500 m of explosion sites, with impact severity decreasing as distance increases [8].

Oil pollution decreases vegetation abundance and by damaging plant physiology, reducing photosynthesis and growth, and causing oxidative stress, with responses varying significantly by plant species, oil type, and environmental conditions. Plants may experience reduced seed germination, hindered root development, lower stem density and biomass, and overall mortality, leading to significant biodiversity loss and altered community composition in affected areas. Although (high) heterogeneity is the norm rather than the exception in re-vegetation and phyto-remediation of polluted soils, little is known about how plant performance and root characteristics respond to the diverse distribution of crude oil pollutants and mycorrhizal colonization [10].

It is therefore recognized that the sustainability of mangroves may be impacted by their degradation, for example, as a result of the oil spill. It might eventually cause the mangroves to disappear, which would have detrimental effects on the Niger Delta’s wildlife and inhabitants. Crude oil spills pose a major hazard to the Niger Mangrove ecology [23]. In particular, the loss of natural defenses from mangrove forest degradation will affect biodiversity and threaten the livelihoods of coastal populations that rely on them for supplies and food, making them more susceptible to extreme weather and tidal flooding [3]

Conclusion and Recommendations

It is concluded that fire explosion and fire outbreak from oil pipeline in River State has caused environmental damage to vegetation health  and invariably affected liveability and well-being of the people in the area This has called for optimum  understanding of the environment to reduce or total avoid oil pipeline leakage or vandalism to reduce the frequency of fire explosion which can cause harm to the vegetation composition and abundance both in the city and rural areas. Based on the findings of this study, it is recommended that the oil companies owing the oil facilities that are causing fire explosion in Rivers State should be on alert to safeguard the facilities from being sabotaged by some people that are crime inclined; there should be proper periodic assessment of the areas being ravaged by the intensity of fire explosion form oil pipeline from time to time; ensure to implement  and integrate the development plans and the environmental attributes of vegetation that have been affected by fire explosion should always be restored with appropriate technology for them to sustain the livelihood of people dwelling in the region.  

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