ABSTRACT
The human race has 850 million members when it entered the industrial age, sharing earth with life forms nearly as diverse as the planet has ever possessed. In the 20th Century, it became obvious that biological resources have limits and that we are exceeding those limits and thereby reducing biodiversity. Biodiversity is the term used to describe the total variety of living organisms (plants, animals, fungi and microbes) that exist on our planet. The biodiversity of Nigerian aquatic ecosystems is increasingly being destroyed or depleted by persistent threat of sediment pollution, organic pollution, eutrophication, acidification, heavy metals and organochlorines, thermal pollution, nuclear pollution, human introductions (voluntary or accidental) and oil pollution. This is the aftermath of intense human activities such as indiscriminate use of fertilizers and pesticides in agriculture, industrialization, urbanization, pressure due to rapid population growth; malutilization and mismanagement of natural aquatic resource; dam, road and bridge construction; irrigation; draining and filling of wetlands; petroleum exploration, exploitation and refining as well as the transportation, storage, marketing and use of petroleum products. The rapid decline in biodiversity of aquatic ecosystems in Nigeria could be reversed if there is sound engineering solutions based on ecological awareness. This should be determined on the basis of sound scientific evaluations of the existing resources and the carrying capacity of the ecosystem.
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INTRODUCTION
The human race had 850 million members when it entered the industrial age, sharing earth with life forms nearly as diverse as the planet had ever possessed. In the 20th century, it became obvious that biological resources have limits and that we are exceeding those limits and thereby reducing biodiversity. This is therefore the time of extraordinary change in the relationship between people and the biological resources upon which their welfare depends. Each year, more people are added to the human population than ever before, species are becoming extinct at the fastest rate known in geological history and climate appears to be changing more rapidly than every day1. Human and industrial activities result in the discharge or various pollutants in to the aquatic environment, threatening the health of the population and damaging the quality of the environment by rendering water bodies unsuitable2-3.
Biodiversity is the term used to describe the total variety of living organisms (plants, animals, fungi and microbes) that exist on our planet4. It is the totality of genes, species and ecosystems in a region5. The term is also used to describe the number, variety and variability of living organisms. A massive review of our current knowledge on the broad field of biological diversity commissioned by UNEP considers humans as an integral and critical important part of biodiversity. In the past, there was the tendency to treat human species as separate from the rest of nature6. In recent times, biodiversity had become easy targets for human over-exploitation due to burgeoning human populations and the quest for a "better life" through improvements in science and technology. Biodiversity, therefore, is being exploited at much faster rates than ever before with negative implications for sustainable human livelihood7-8. Biodiversity is facing a doctrine of crisis proportions which could ultimately lead to mass extinctions in the very near future9.
The biodiversity of the Nigerian aquatic ecosystems is increasingly being destroyed or depleted by persistent threat of aquatic pollution resulting from intense human activities such as indiscriminate use of fertilizers and pesticides in agriculture; industrialization; urbanization; pressure due to rapid population growth; malutilization and mismanagement of natural aquatic resources; dam, road and bridge construction; irrigation; draining and filling of wetlands. The negative environmental and social impacts of these projects are becoming evident and cannot be ignored if we are to avoid the sorts of problems which they have brought in other parts of the World10. This study therefore, presents information on different types of human activities in Nigeria, their impacts on biodiversity in the Nigerian aquatic ecosystems, control and management of human activities to minimize damage on biodiversity.
DIVERSITY OF AQUATIC ECOSYSTEMS IN NIGERIA
The landmass of Nigeria is enclosed between latitudes 4°16-13°52 N and longitudes 2°49-14°32 E and being 1100 km on a North/West axis. The finite natural resource base shared by 158 million humans11 and unknown number of plants and other animals is estimated as 923,700 km2 of land12-14. Approximately 125,471 km2 of Nigeria land mass is covered by the waters of the nations major rivers, lakes, ponds and pools15. This excludes the coastal region. Nigeria is a West African maritime State with a coastline that is about 853 km, long, stretching from the Western border with the Benin Republic to the Eastern border with the Cameroon Republic. The Nigerian coastal zone can be defined as the area which extends from the shelf break, inland to the limit of tidal influence16. This coastline is interrupted by a series of estuaries, which open into an extensive lagoon system in Lagos and Ondo States. In Lagos State, the creeks, floodplains, lagoons and rivers account for approximately 22% of the 790 km2 land mass17. There are at least twenty-two estuaries from Benin River in Delta State coastal region to Cross River in Akwa Ibom State. Figure 1 and 2 show the aquatic ecosystems of Nigeria. The Nigerian coastal zone is generally low lying, resulting in extensive wetlands and mangrove swamps. Nigerian had the largest area of mangrove forest in Africa18.
SPECIES DIVERSITY IN NIGERIAN AQUATIC ECOSYSTEMS
Nigerian aquatic ecosystems are characterized with diverse species of plants and animals. Unlike the terrestrial habitats, animals in the oceans are found at all depths, so that the total habitable space of a 4 km (average) deep ocean is 1,263,804 km3. It is therefore reasonable to assume that Nigerias aquatic flora and faunal biodiversity is higher than that of the terrestrial habitats14.
The total fauna of the World is comprised of 25 phyla of which 24 phyla are invertebrates. The phylum chordata consists of the non-vertebrate and vertebrate chordates.
Invertebrate species diversity is much higher in the aquatic ecosystem than in the terrestrial ecosystem. The significance of greater protection to the aquatic ecosystems cannot be over-emphasized, since its diverse fauna is of great economic and social importance.
A summary of the faunal biodiversity of Nigeria aquatic ecosystems is shown in Table 1. There are at least 2570 faunal species
A vegetation map of the Nigerian coastal zone is presented in Fig. 3. Species compositions of vegetation in the mangrove forest are; climbers, grasses, sedges, herbs, shrubs and trees.
The species compositions of freshwater swamps in Nigeria are floating aquatics, submerged aquatic plants and fringe vegetation.
HUMAN ACTIVITIES RESULTING IN CONTAMINATION OF AQUATIC ECOSYSTEMS
Almost everything produced by man or resulting from his activities can bring about contamination and eventual pollution of our diverse ecosystems. Pollution is defined as the production and or introduction by man, directly or indirectly of substances or energy into the environment, resulting in deleterious effects or harm living resources, including human beings or interfere with amenities and other uses of the environment20.
Human activities such as deforestation, channelization, filling and construction of canals, levees, dams, roads and bridges, agricultural, industrial and domestic activities, introduction of exotic species, over-exploitation of plant and animal species upset the hydrological regime, sediment characteristics and several biotic components. Upstream activities bring pollutants into mangrove swamps and estuaries.
Table 2 shows the types, sources and routes of entry into the aquatic environment of pollutants from human activities.
IMPACT OF DISCHARGES FROM HUMAN ACTIVITIES ON AQUATIC BIODIVERSITY
The most important aquatic pollution forms resulting from pollutants due to human activities and which impact the biodiversity of aquatic ecosystems are; sediment pollution, organic pollution, eutrophication, acidification, heavy metals and organochlorines, thermal pollution, unclear pollution, human introductions (voluntary or accidental) and oil pollution.
The studies of impacts of human activities on biodiversity of aquatic ecosystems in the industrial sector (particularly oil companies in Nigeria) are not available in the scientific sector. Some available studies in the scientific sector are presented in Table 3.
ORGANIC POLLUTION
Organic pollutants such as domestic sewage, urban run-off, farm wastes and effluents from food processing industries, brewing industries, dairies, abattoirs, tanneries, textile and paper making factories have diverse adverse effects. These pollutants are biodegradable and are easily oxidized by making use of the dissolved oxygen in water. As dissolved oxygen drops, fish and other aquatic life are threatened or killed in the extreme case. Number of algae and bacteria is increased. Macrophytes are also adversely affected due to light reduction and solids rendering the bed of the river unstable for plants.
The faecal contamination of water can introduce a variety of pathogens into waterways.
The surest confirmation of serious and widespread water pollution in Nigeria is, in fact, the level of incidence of water related diseases. The most serious of these are dysentery, cholera, typhoid, guinea worm infestation and bilharziasis.
Table 4 shows some news reports on water related diseases in Nigerian dailies, while Table 5 shows cases of water related diseases in Nigeria from 2002-2008.
EUTROPHICATION
Eutrophication will be defined as an increase in the rate of income of nutrients28. The income of nutrients may be considered as artificial or cultural eutrophication if the increase is due to human activities, or natural eutrophication if the rate of increase is caused by a non-human process, such as forest fire. Only artificial eutrophication is considered under pollution.
The menace of water hyacinth in the Lagoons of Ogun, Lagos and Ondo state is to some extent, attributed to the unintended fertilization of aquatic ecosystems by run-off from fertilized farmlands. The process of eutrophication of aquatic ecosystems can be observed around the edges of water reservoirs throughout the country.
PESTICIDES
Pesticides such as insecticides and herbicides get washed into aquatic ecosystems where they may kill aquatic life or be absorbed by them and passed up the food chain until they become toxic to man. DDT for example is an insecticide, which was once widely used but the use of which had now been banned or severely restricted in many countries with Nigeria being a notable and unfortunate exception.
Agrochemicals such as Gammalin 20 (for spray of cocoa tree), Aldrin dust (for seed preservation) and DDT (for tsetse fly and simulium fly control), have been used from ignorance by some of our people, in fishing and hunting. This is a very dangerous habit, which could adversely affect biota of any kind of ecosystem, either directly or indirectly.
OIL POLLUTION
The discovery of oil in 1956 in Oloibiri, Bayelsa State, Nigeria and its exploitation two years later, marked the beginning of an important era in Nigeria. About a decade later, the significance of oil to the economic, social and political well being of Nigeria had become obvious. Presently, the nation depends solely on oil and efforts to shift the dependence from petroleum industry to other sectors of the economy have not been entirely successful29.
The inextricable adverse effects of petroleum exploration, prospecting and marketing on plants, animals, man and his environment, has until very recently received no attention. These adverse effects are alarming in the Niger Delta where there is predominance of oil wells. Petroleum exploration, exploitation and refining as well as the transportation, storage, marketing and use of petroleum products have all created problems in various parts of the country.
The formation of a film of oil on water bodies effectively prevents natural aeration, leading to the death of organisms trapped below. Fish may also ingest spilled oil directly or indirectly, becoming unpalatable or even poisonous.
The oil spilled into the Nigerian environ between 1976-80 above is over 56 million gallon. "The number of registered oil spillages is increasing. Depending on the area, oil pollution could cause adverse impact on people (water quality), vegetation (smothering mangrove trees, crops, shore vegetation and fauna (fish, shellfish, soil fauna). This is demonstrated in several post impact studies on the recent or old spill sites. The 25 years old mystery spill of trunkline in the Ejama-Ebubu caused during the civil war is a well-known-but not sufficiently studies yet-example"6.
Table 6 shows the physical presence of the oil industry in Nigeria, while Table 7 shows the number of spills in the Niger Delta between 1979 and 2005.
Research findings based on information on fish and fisheries for freshwater oil spillage in the Niger Delta viz. the 1986 GENECO barge spillage (tidal New Calabar River) and several pipeline spillages: 1983 Utorogu and Ikata (both black water rivers/streams), 1985 Okoma (tidal Sombreiro black water river, stream and swamp) and 1983 Oshika (seasonal swamp) have shown that:
• | No major species loss, but a 50% reduction in abundance of fish and an increase in diversity indices and abundance of prawns (Sombreiro and New Calabar Rivers) |
• | Loss of all species lacking accessory air breathing organs (Oshika and Okoma Swamps) |
• | Major loss of species without any obvious physiological patterns, Okoma Streams |
Environmental impact research on effect of Oshika oil spill on aquatic biology showed that:
• | After a year, oil-in-water values dropped to non-detectable limits (0.2 ppm), but oil-and-grease in sediments remained high. Many of the fluctuations observed in water quality parameters appeared to be due more to seasonal changes than to pollution |
• | Plankton and invertebrate studies generally showed high biomass and low-diversity communities during the dry season following the spill. Pollution related differences were clearly evident in March (7 months post-spill). In June/July, they showed evidence of recovery and normal aquatic vegetation was re-established |
• | The shrimp, Desmocaris in downstream areas free of visible oil, suffered heavy embryonic mortality for 2-3 months after the spill. In oiled areas, embryonic mortality was detected for up to 8 months after the spill. The mortality led to marked changes in population structure and reduced population sizes, at least to July (11 months post-spill). Fecundity was depressed after the spill, but after several months, it increased to levels above that of control site32 |
GAS FLARING
Global estimate indicates that the flaring of petroleum dissociated gas in the coastal area of Nigeria alone account for 28% of total gas flared in the world. Nigeria, like every coastal country has a coastal based economy through the onshore and offshore oil exploration and hence majority of industries and commerce are located along the area in proximity with ports and borders for effective transit of goods and services. These factors put so much pressure on the coastal biodiversity and reduce their suitability11.
CONTROL AND MANAGEMENT OF HUMAN ACTIVITIES TO MINIMIZE DAMAGE ON BIODIVERSITY
Measures to curb the damage on biodiversity by human activities, which impact aquatic ecosystems in Nigeria, are the most intricate and expensive and have attracted insignificant attention from both the public and government. Biodiversity of aquatic ecosystems in Nigeria is threatened by various human activities, which culminate in diverse forms of pollution. There is the urgent need for proper control and management of the various negative effects resulting from diverse cultural and social-economically important human activities in order to attain sustainable development.
There is an obvious need for an integrated approach to the control and management of human activities that impact biodiversity. This integrated approach should be an activity that will provide the framework for decision-making on how biodiversity can be conserved. The success of management depends on the level of awareness and co-operation of the public, decision-makers in government and managers. Control and management can further be enhanced by having national and regional coordination mechanisms. This is because marine waters and some of the marine living resources do not recognize national boundaries and therefore planning and management of marine resources and pollution prevention require a regional approach33. The regional approach has an additional approach in terms of the rational utilization of financial resources and manpower.
The key problems associated with human activities, with respect to biodiversity of aquatic ecosystem are related to inadequate planning for sustainable environmentally-sound, socio-economic development and the rational utilization of natural resources. These problems can only be overcome by adopting the following control and management options: Proper management of hydrological cycle, Environmental Impact Assessment (EIA), Environmental Auditing (EA), monitoring and research related to the sources, levels and effects of pollutants, legislation, technical methods of waste manage which include non waste (zero waste) option, waste minimization and waste treatment; multiagency projects; population control and environmental education.
CONCLUSION
The decline in biodiversity of aquatic ecosystems is largely caused by human activities and poses a serious threat to sustainable development. There is the need for urgent and decisive action to conserve and maintain genes, species and ecosystems.
Technological developments, coupled with the growing resource needs of rapid population growth, has increased the environmental hazards to biodiversity of all natural ecosystems.
The rapid decline in biodiversity of aquatic ecosystems in Nigeria could be reversed if there is sound engineering solutions based on ecological awareness. This should be determined on the basis of sound scientific evaluations of the existing resources and the carrying capacity of the ecosystem. In areas with rapid population growth, it may be necessary to invest in major carbon and nutrient-absorbing systems to avoid further degradation and to preserve the biological productivity of existing systems.
REFERENCES
- Ekubo, A.J. and J.F.N. Abowei, 2011. Aspects of aquatic pollution in Nigeria. Res. J. Environ. Earth Sci., 3: 673-693.
Direct Link - Stuart, S.N., R.J. Adams and M.D. Jenkins, 1990. Biodiversity in sub-saharan Africa and its islands: Conservation, management and sustainable use. Proceedings of the International Union for Conservation of Nature and Natural Resources (Spring Commission No. 6, 1990), December 2-5, 1990, Switzerland.
- Zabbey, N., 2004. Impacts of extractive industries on the biodiversity of the Niger Delta Region, Nigeria. Proceedings of the National Workshop on Coastal and Marine Biodiversity Management, September 7-9, 2004, Calabar, Cross River State, Nigeria.
Direct Link - Wuver, A.M. and D.K. Attuquayefio, 2006. The impact of human activities on biodiversity conservation in a coastal wetland in Ghana. West Afr. J. Applied Ecol., 9: 115-129.
Direct Link - Amosu, A.O., O.W. Bashorun, O.O. Babalola, R.A. Olowu and K.A. Togunde, 2012. Impact of climate change and anthropogenic activities on renewable coastal resources and biodiversity in Nigeria. J. Ecol. Nat. Environ., 4: 201-211.
Direct Link - Oyewo, E.O., T.O. Ajayi, C.O. Dublin-Green, E. Ajao and L.F. Awosika, 1999. Anthropogenic activities and their impact on aquatic resources in the Nigerian coastal zone: Impact of pollution on aquatic living resources in Africa. Proceedings on the 5th Session of the Organization of African Unity's Scientific, Technical and Research Commission (OAU/STRC) Inter-African Committee and Symposium on Oceanography, Sea and Inland Fisheries, May 4-8, 1998, Mombasa, Kenya, pp: 79-102.
- Ogbeibu, A.E. and R. Victor, 1989. The effects of road and bridge construction on the bank-root macrobenthic invertebrates of a Southern Nigerian stream. Environ. Pollut., 56: 85-100.
CrossRefDirect Link - Ogbeibu, A.E. and B.J. Oribhabor, 2002. Ecological impact of river impoundment using benthic macro-invertebrates as indicators. Water Res., 36: 2427-2436.
CrossRefDirect Link - Mustapha, M.K., 2006. Effect of human activities on the Biodiversity of a tropical man-made lake. Niger. J. Pure Applied Sci., 21: 1960-1968.
Direct Link - Oribhabor, B.J. and A.E. Ogbeibu, 2009. The ecological impact of anthropogenic activities on the macrobenthic invertebrates of a mangrove creek in the Niger Delta, Nigeria. Asian J. Microbiol. Biotechnol. Environ. Sci. Pap., 11: 513-524.
Direct Link - Oribhabor, B.J. and A.E. Ogbeibu, 2010. The ecological impact of anthropogenic activities on the predatory fish assemblage of a tidal creek in the Niger Delta, Nigeria. Res. J. Environ. Sci., 4: 271-279.
CrossRefDirect Link - Udoidiong, O.M., B.J. Oribhabor, E.E. Munam and J.J. Bernard, 2013. Assessment of the impact of human settlement on the heavy metal concentrations of lower cross river, Nigeria. Scient. J. Pure Applied Sci., 2: 270-278.
Direct Link - Yusuff, A.S., W. John and A.C. Oloruntoba, 2014. Review on prevalence of waterborne diseases in Nigeria. J. Adv. Med. Life Sci., 1: 1-3.
Direct Link - Ajide, O.M. and O.O. Isaac, 2013. An assessment of the physical impact of oil spillage using GIS and remote sensing technologies: Empirical evidence from Jesse Town, Delta State, Nigeria. Br. J. Arts Social Sci., 12: 235-252.
Direct Link - Powel, C.B., S.A. Whiyte, B.B. Dutkiewicz, D.D. Ibiebele, M. Isoun and F.U. Ofoegbu, 1985. Oshika oil spill environmental impact: Effect on aquatic environment. Proceedings of the International Seminar on the Petroleum Industry and the Nigerian Environment, November 11-14, 1985, Federal Ministry of Works and Housing and the Nigerian National Petroleum Co-Operation, Nigeria, pp: 181-201.