EDUCATIONAL AWARENESS ON UTILIZATION OF ALIEN PLANTS INVADERS IN NIGERIA
Background to the Study
Various species of alien plants have been brought into Nigeria, either deliberately as commercial plants or accidentally through seed pollution (Holmes et al., 2008; Vosse et al., 2008; DEA, 2009; Strydom and King, 2009). The DEA (2009) further states that without adequate control and through seed distribution by wind and birds, plant growth had spread to areas where they are causing serious and negative effects. With no natural enemies present in their new environment many become invading and spread aggressively. Seventy percent of invading alien plants in Nigeria came from Australia and South America (Poona, 2008). The black wattle (Acacia mearnsii), Silver water (A. dialbata), Blackwood (A melanoxylon), bluegum (Eucalyptus sp), the notorious alien plant invader (Eihhornia crassipes), the water milfoil or parrot’s feather (Myriophyllum aquaticum) and pines (mostly Pinus Pinaster) had, according to van Wilgen et al. (1997) the largest negative impact on water usability and availability.
Global research on the effects of plant invasions by Richardson and van Wilgen (2004) suggest that most damaging species transform ecosystems by using excessive amounts of resources (notably nitrogen, light, oxygen and water) by adding resources (notably nitrogen), by stabilising sand movement and/or promoting erosion, by accumulating or redistributing salt. Invasive plants have also invaded river banks, affecting the indigenous riparian trees, and thereby reducing the flow of water. The leaves of riparian trees, which are the natural food for the aquatic organisms, are also replaced by the less suitable leaves of the alien trees. The accumulation of leaves of invasive alien plants on river beds reduces water levels causing fish deaths and give rise to algal blooms and other poor water quality impacts. These also have impact on the recreational value of the rivers and lakes (van Wilgen et al., 1997).
Further to that, it is now well recognised that invasive alien species particularly tree species often have much increased water usage compared with native vegetation. Perhaps less well understood are the reasons for this increased water use and whether it should be expected from all species of invading alien plants under all conditions. Answers to these questions are important so that financial resources directed towards the eradication of alien invaders can be used to maximum (Preenthlall et al., 2007).
Many of these aquatic alien plants such as, the alien plant invader, the water milfoil and the Kariba weed blanket many of African dams, lakes and rivers.
An example of the most dangerous, notorious and troublesome of an invasive plant is the alien plant invader (Eichhornia crassipes) of South American origin (Groote et al., 2003; UNEP, 2012). It gained attention as an ornamental plant because of its attractive purple flower, and was first distributed by gardens and horticulturists more than a century ago. Malik (2007) argues that the alien plant invader is a tropical species belonging to the pickerelweed family (Pontederiaceae). A native of Brazil and possibly other central South American countries, now it occurs in lakes, slowly moving rivers and swamps in most countries of the world lying between 400 N and 400S, including India, Nigeria and the USA. As such alien plant invader is found across the tropical and subtropical regions. Originally from the Amazon Basin, its entry into Africa, Asia, Australia and North America was facilitated by human activities (Dagno et al., 2012).
The alien plant invader is a free floating aquatic plant well known for its production abilities and the removal of pollutants from water. Keller and Lodge (2009) add that it multiplies faster than any other known freshwater plant. However, the alien plant invader has also been labelled as the world’s worst water weed and has garnered increasing international attention as an invasive species (Zhang et al., 2010). Efficient in utilising aquatic nutrients and solar energy for profuse biomass production, the alien plant invader can cause extensive environmental, social and economic problems. It is found in lakes, estuaries, wetlands, marshes, ponds, dambos, slow flowing rivers, streams and waterways where growth is stimulated by the inflow of nutrient rich water from urban and agricultural runoff, deforestation, products and industrial waste and insufficient wastewater treatment. According to recent climate change models, its distribution may expand into higher latitudes as temperatures rise, posing problems to formerly hyacinth free areas (Rachel and Olden, 2008; Zhang, 2012).
However, the alien plant invader can tolerate considerable variation in nutrients, temperature and pH levels. The Optimum pH for growth is 6–8. It can grow in a wide range of temperature from 1 to 40 0C (optimum growth at 25-27, 5 0C) but it is thought to be cold-sensitive (Wilson et al., 2007). It can quickly grow to very high density (over 60kg m-2), thereby completely clogging water bodies, which in turn may have negative effects on the environment, human health and economic development. Salinity is a major constraint on alien plant invader growth in coastal regions as salinity levels at 6.0% and 8.0% are lethal (Malik, 2007).
Although the alien plant invader removes both nutrients and pollutants from aquatic environments very effectively, it is a pollutant itself for several reasons: Firstly, a dense canopy of hyacinth plants will prevent oxygen transfer to the water from the atmosphere. It will also block out sunlight and prevent production of dissolved oxygen by algal photosynthesis. Secondly when the plants die, they quickly sink to the floor where they decompose. Conditions in the deep water near the lake floor become anaerobic very quickly because of the rotting plant on dissolved oxygen can no longer inhabit these areas of the lake. Thirdly an adequate level of oxygen is also an important factor in the treatment of lake/dam water. Very low dissolved oxygen concentrations require greatly increased doses of alum (aluminium sulphate) to clarify the water by flocculation and sedimentation of suspended solids (Groote et al., 2003; Stanley et al., 2007; Forpah, 2009; Keller and Lodge, 2009).
Today, it is a native invasive plant species devastating the watersheds of the Chad Basin and Hadejia-Nguru wetlands, causing flooding, loss of farmlands and conflict among farmers, herdsmen and fishermen. NCF/WOW (2011) reported that Typha weed has colonized areas of the wetland, blocking channels and open water, and preventing water reaching some seasonal pools, so that farming has ceased in these areas, while flooding has displaced many communities.
In an effort to reduce the extent of typha in the area, NCF/WOW and other supporting organizations, assisted the communities of DabarMagini, Kasaga and Matafari/MataraUku, to physically clear typha that blocked and hindered free movement of water in the Marma channel, a key freshwater channel that serves as the lifeblood to the people living in these locations.
Statement of the Problem
Invasive alien species introduced in Nigeria from different parts of the world (both intentionally and unintentionally) are affecting indigenous plants and animal communities. The intentional spread has been as a result of ongoing and increasing human redistribution of species to support agriculture, forestry, mariculture, horticulture and recreation. This supplies a continuous pool of species from which invasive aliens are recruited (WfW, 2004). The invasive alien species were also introduced as commercial plants or ornamental garden plants for example the Australian acacias in KwaZulu Natal and in the south-western state was introduced for timber, bark products and to stabilise sand dunes. Invasions also occurred countrywide as a result of seed introductions, of tree and shrub clearing for pasture and grazing infestations (Richardson and van Wilgen, 2004). The unintentional introductions of IAPs include disease organisms, agricultural weeds and insect pests. However, they were brought here in this country without their natural enemies, which results in plants reproducing copiously.
Furthermore, as the global climate patterns shift, the distribution of invasive species will change, and so will the susceptibility of particular habitats to the impacts of new species introductions. The abundance of the water hyacinth in an environment fluctuates over time, as it is often flushed out of water systems by floods, only to cover them again when conditions improve. Water hyacinth hinders irrigation by impending water flow, by clogging irrigation pumps, and by interfering with weirs. Multi-million dollar flood control and water supply projects, which require decades to construct, can be rendered useless by water hyacinth infestations. Infestations also block access to recreational areas and make them unattractive, decreasing the value of waterfront properties. Invasive alien species often impact the livelihoods of the communities that depend on fishing and water sports for revenue. Challenges posed by IAPs in dams are also seen in the Hartbeespoort Dam which has increasingly become eutrophic due to severe algae growth. Secondly to algae blooms has been the prolonged growth of water hyacinths in the dam due to rapid urbanisation, associated with increased run off, erosion, sedimentation and solid waste entering the dam annually (DWAF, 2007). This pose a high risk to human health and detrimental impacts on recreational in the North West Province and entire aquatic ecosystems. Therefore, invasive species are of concern, not only nationally but globally.
Purpose of the Study
The primary purpose of this study is to examine educational awareness on utilization of alien plants invaders in Nigeria. The specific objectives of the study are to:
- Investigate the educational awareness on the impact of utilization of plant invaders.
- Assess the utilization of alien plants invasions.
- Demonstrate how climate change and variability aid the invasion of alien species.
- Demonstrate how plant invaders affects the economic, recreational and environmental uses of the lakes.
The overall aim of this research is reflected in the following research questions:
- How does educational awareness have impact on the utilization of plant invaders?
- What was the utilization of alien plants invasions?
- How does climate change and variability aid the invasion of alien species?
- How does alien plant invaders affects the economic, recreational and environmental uses?
Significance of the Study
Previous studies have shown that invasive alien plants use significant amount of water. The projections were made by combining the results of hydrological experiments conducted to assess the effects of afforestation with alien trees on water resources with an ecological understanding of the spread and establishment of invasive trees. The projections were then scaled up to arrive at national estimates of corresponding water consumption (Gorgens and van Wilgen, 2004; Richardson and van Wilgen, 2004; Mgidi et al., 2006; Holmes et al., 2008). While there are some studies that have assessed the effects of invasive plants on native biodiversity and the underlying community dynamics, there is still a gap on measuring the effect of invasive plants (both terrestrial and aquatic) on water usability and availability.
The ecological rationale for this research is that water hyacinth reduce water yield, threaten biodiversity and reduce land productivity. The research draws on published and unpublished sources, and highlights some important research challenges in invasion ecology filling the critical research gap in the understanding of the impact of invasive alien species on water availability and its usability. Although Nigeria has problems with invasive alien organisms from most major taxonomic groups (van Wilgen et al., 1997; Gorgens et al., 2004; Henderson, 2001; Holmes et al., 2008), this study focuses only on water hyacinth plants in semi-natural freshwater ecosystems.
Furthermore information on the spatial distribution of these aquatic plants is required for understanding the evolution of the invasion and propagation rates. According to Shekede et al. (2008), such information is vital in identifying affected areas and relating weed abundance to probable changes in environmental conditions and human actions including management practices within the study area. Information on aquatic weed distribution also assists in evaluating the effectiveness of control measures and management actions.
Due to overexploitation, the remaining natural ecosystems and primary forests in Nigeria are restricted to the protected areas which include one biosphere reserve, seven national parks, one World Heritage site, 12 Strict Nature Reserves (SNRs), 32 game reserves/wildlife sanctuaries, and hundreds of forest reserves. These are in addition to several ex-situ conservation sites such as arboreta, botanical gardens, zoological gardens, and gene banks managed by several tertiary and research institutions. Therefore, in order to make a reliable assessment of invasive species in Nigeria, such studies should be limited to the protected areas. This pilot survey was conducted to assess the level of invasiveness and the impacts of IAS on the field gene bank of the National Centre for Genetic Resources and Biotechnology (NACGRAB), Ibadan, southwestern Nigeria.
Description of the Study Area
Nigeria is situated in the West African region and lies between longitudes 30E and 150E and latitudes 40N and 140N. It has a land mass of 923,768 sq.km. It is bordered to the north by the Republics of Niger and Chad. It shares borders to the west with the Republic of Benin, while the Republic of Cameroun shares the eastern borders right down to the shores of the Atlantic Ocean which forms the southern limits of Nigerian Territory. The about 853km of coastline confers on the country the potentials of a maritime power.
Temperature across the country is relatively high with a very narrow variation in seasonal and diurnal ranges (22 – 360C). There are two basic seasons: wet season which lasts from April to October; and the dry season which lasts from November till March. The dry season commences with Harmattan, a dry chilly spell that lasts till February and is associated with lower temperatures, a dusty and hazy atmosphere brought about by the North-Easterly winds blowing from the Arabian Peninsula across the Sahara; the second half of the dry season, February – March, is the hottest period of the year when temperatures range from 33-400C. The extremes of the wet season are felt on the south-eastern coast where annual rainfall might reach a height of 330cm; while the extremes of the dry season, in aridity and high temperatures, are felt in the north third of the country.
The population of Nigeria is estimated at 183, 523, 434 people with an annual growth rate of 2.8% as at July 2015, which is equivalent to 2.51% of the total world population and makes Nigeria number 7 in the list of the total world population (Source: Worldometers).
Nigeria, Africa’s most populous country, is composed of more than 250 ethnic groups. The following are the most populous and politically influential: Hausa and Fulani 29%, Yoruba 21%, Igbo (Ibo) 18%, Ijaw 10%, Kanuri 4%, Ibibio 3.5%, and Tiv 2.5%.
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