The utilization of alien plant invaders in Nigeria

Bachelor Thesis, 2019

57 Pages, Grade: A



Title Page





Table of Content:

Background to the Study:
Statement of the Problem:
Purpose of the Study:
Significance of the Study:
Description of the Study Area:

Literature Review:
Range and Scale of Impacts:
Pathways for Introduction and Spread:
Removal or Eradication of Invasive Plants:
Factors Conferring Invasiveness:
Geographical Range and Impact of the Problem in Nigeria:
Reproduction of the Alien Plant Invader:
Environmental Problem caused by Alien Plant Invader:
Control Measures:
Potential Utilization of Alien Plant Invader:
The educational Awareness:
Impact of biodiversity on Plant Invaders:
Summary of Related Literature reviewed:

Control Methods:
Eradication by Utilization:

Utilization potentials of selected Invasive Species in Nigeria:






This project work is dedicated to the most high God for his love, mercy, protection, provision for sparing life and for making the successful completion of my B.Sc Biology in Education programme in Adeyemi College of Education a reality.

Also to my wonderful family Ogundare’s family as a whole and my sweet mother in person of Mrs. Susan Ogundare for her support.


All praise glory, honour, Adoration and thanks to the Lord of Omniscience, Omnipotent who gave me wisdom, knowledge and understanding to enable me finish my project successfully, may his peace and blessings continue to radiate the earth in which he had created for us human being to live (Amen).

I will like to express and acknowledge the effort of my wonderful supervisor for her criticism; corrections and supervision in person of Dr. (Mrs.) Ayomiposi Akinkuolie, for making this project work a successful one. May almighty God shower his mercy on you and bless you abundantly (AMEN).

I am also appreciating God on behalf of my wonderful mother Mrs. Susan Ogundare that God used to pilot me into this world and have been there for me in many areas, financially, spiritually and in terms of constant words of advice, may you eat the fruits of your labour in Jesus name (Amen).

I will be a greatest fool if I fail to acknowledge my siblings Ogundare Mosunmola, Ogundare Dayo, Ogundare Ibukun and Ogundare Oluwafiropo and my brothers-in-law Mr. Lamidi Ishola and Mr. Lanre Ajibade for their words of advice and support, May the Lord not stop his blessings upon you.

My appreciation goes to my wonderful friend in person of Oluwole Kelly for his support, and advice and for been there for me; I say a very big thank you. May the Lord continue to bless you beyond your imagination.


This study reviewed the utilization of alien plant invaders in Nigeria, with a view to recommending this plants to Nigerians considering their utilization potentials.

Many of them are useful in curing of many aliments, production of biogas, paper work, brooms, insulation board and in the treatment of sewage and industrial effluents and also some are useful in improving soil fertility and among others.

Also control measures of these alien plant invaders that can be adopted as reviewed include mechanical, biological and chemical control measures among several other methods.



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 mearns ii), 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 Hartbees poort 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:

(i) Investigate the educational awareness on the impact of utilization of plant invaders.
(ii) Assess the utilization of alien plants invasions.
(iii) Demonstrate how climate change and variability aid the invasion of alien species.
(iv) Demonstrate how plant invaders affects the economic, recreational and environmental uses of the lakes.

Research Questions

The overall aim of this research is reflected in the following research questions:

(i) How does educational awareness have impact on the utilization of plant invaders?
(ii) What was the utilization of alien plants invasions?
(iii) How does climate change and variability aid the invasion of alien species?
(iv) 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 3[0]E and 15[0]E and latitudes 4[0]N and 14[0]N. It has a land mass of 923,768 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 - 36[0]C). 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 33-40[0]C. 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%.



This chapter is concerned with the review of relevant literature on the topic “educational awareness on utilization of alien plants invaders in Nigeria”. The review was carried out under the following sub-headings:

Invasive Species: The Concept and Invasion Process

Invasion is considered as the second most important threat to biodiversity after habitat destruction (Holmes et al., 2008). Alien species, which become dominant in the local environment and invade natural communities, are referred to as invasive species. The term invasive alien species (IAS) is defined by the National Invasive Species Council (NISC, 2006) as a species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Versfeld et al. (1998) also defines IAS as species that becomes established in natural or semi-natural ecosystem or habitat, is an agent of change and threatens biological diversity. Invasive species are such a threat to the environment so much that the Biodiversity Convention advocates for measures to prevent the introduction, control or even eradication of these alien species (Versfeld et al., 1998). These invaders could be a plant, animal or microbial species. Invasive species are either accidentally introduced or they are introduced by man to fill his needs. After their introduction they can propagate their population and create non-specific thickets.

After consultation with stakeholders the Benoni Municipality opted to use the Watermaster Classic III to remove the invasive alien species from the water-bodies within its vicinity. The Watermaster Classic III shown in Figure 2.1 was recommended for the removal of alien species as it does not pollute the water itself. However, by 2011 the alien plant invader team had completely removed the plant from Kleinfontein and Civic lakes (Meela, 2011). But the invasive plants somehow and notoriously reappear after a short while.

The municipality and other stakeholders persistently urge local communities to refrain from dumping waste in the wetlands and water-bodies as these create conducive environments for invasive alien species. The local environmental groups like the Hyacinth Aquatic Committee have repeatedly warned residents against dumping waste anywhere as these are responsible for the growth of the alien plant invader (Meela, 2010).

Historically the lakes in Benoni have always been playing an important role of filtering water, facilitation of groundwater recharge, maintenance of biodiversity, retention of agricultural pollutants, income generation by harvesting of reeds, fishing and eco-tourism, recreational activities and aesthetics. However, these lakes have been affected by a number of stresses caused by sewage spills, mining and industrial activities, improper waste disposal and erosion gullies (Naledzi, 2007). Urban development particularly the construction of the Lakeside Mall in Benoni and the road construction (the Gauteng N12 Freeway Development Project) are equally contributing to the current deterioration of the lakes. In many instances the outlets of the lakes are poorly maintained creating opportunities for erosion gullies and bursting. Gauteng is one area that is heavily infested with alien invasive plant species and Ekurhuleni Metropolitan Municipality is no exception (Palmer, 2002). The invasive plant species are associated with excessive water consumption, allelopathetic inhibition, and they also outcompete the native species for other resources. As a result they impact upon indigenous plant species which are essential for maintaining ecosystem processes.

The alien plant invaders can double its biomass in less than 2 weeks during the peak of its growing season. This means that it can reproduce quicker than it can be removed mechanically. The absence of natural enemies and highly enriched/polluted water allows for prolific growth. Kleinfontein Lake and neighbouring lakes require an integrated strategy, combining biological control with herbicides and/or mechanical control and water purification (Henderson, 2010).

Why are invasive alien species an international environmental issue?

Introductions of species beyond their natural range are rising sharply because of increased trade, transport, travel and tourism associated with globalization. These provide vectors and pathways for live plants, animals and biological material to cross biogeographical barriers that would usually block their way.

Range and Scale of Impacts

Most alien (non-indigenous) species do not become invasive or cause problems in their new locations: many have great benefits to society, for example in agriculture, horticulture, forestry and aquaculture. However, the subset of alien species that do become invasive have major environmental, economic, public health or political implications for the country or countries concerned. For example:

- Environmental impacts. Invasive alien species are now considered to be the second cause of global biodiversity loss after direct habitat destruction and among the top drivers of global environmental change (Sala et al., 2000).
- Economic impacts. One estimate puts general IAS-related costs to the United States as at least $100 billion/year (Pimentel et al., 2000). Costs associated with individual species include:

- the golden apple snail (introduced to the Philippines from Latin America as a high protein food source: estimated losses to rice crops during the 1980s of $1 billion)
- European gypsy moth (introduced into North Carolina in 1993: four-year eradication programme cost $19 million)
- sea lamprey (the United States Department of State spends over $10 million on control measures per year in the Great Lakes of the United States/Canada)
- brown tree snake (control efforts in Guam and other Pacific islands have cost the United States military $2 million annually since 1993).

- Health-related impacts. The invasive giant African snail (Achatina fulica) provides an intermediate host for rat lungworm (Angiostrongylus cantonensis) which can infect the human brain, causing paralysis, coma and even death. The red imported fire ant affects public health as well as agriculture and livestock production, electrical systems and biodiversity in much of the United States and the Caribbean. West Nile virus was introduced to New York via an imported non-native bird and then transmitted to local mosquitoes: hundreds of people have now died.
- Political impacts. Invasive alien species can hamper sustainable development opportunities by affecting food security, water supply, regional stability, poverty and migration. They can also affect international trade and economic growth if they prevent governments and industries from selling some types of food products or living commodities and/or using certain kinds of containers. Invasive alien plants have a range of impacts on native biodiversity including competition with native taxa of flora, hybridization with genetically close species, alteration of the physical and chemical characteristics of soil, modification of natural and semi-natural habitats and propagation of pests and diseases. Plants that are invasive in certain parts of the world and have caused severe impacts include water hyacinth (Eichhornia crassipes), melaleuca or paper bark tree (Melaleuca quinquenervia) and Miconia calvescens. The latter is considered the most damaging alien plant species in wet forests of Pacific islands. Over 60 percent of the island of Tahiti is heavily invaded, replacing the forest and its wildlife. This plant was introduced to Hawaii as an ornamental in the 1960s and sold by several nurseries before being listed as a noxious weed in 1992 (Loope, 1997).

Nigeria’s Working for Water programme (refer and chapter 29 in this publication) was set up to control invasive alien plants established in over 10 million hectares of land, following an assessment of their multiple impacts. These included consumption of 7 percent of national water resources, reduced ability to farm, intensified flooding and fires, erosion, siltation of dams and estuaries and reduction in water quality. These plants were determined to pose the single biggest threat to the country’s native plant and animal biodiversity. The cost of these impacts was estimated at R600 million a year over 20 years (around US$ 100 million annually), likely to double within 15 years unless control measures were taken.

From a biodiversity perspective, the ecosystems most vulnerable to invasion are geographically and evolutionarily isolated ecosystems (islands, mountain ranges, lakes etc.) whose unique flora and fauna and biological communities have evolved over millions of years. Hawaii, for example, has 90 percent endemism for flowering plants and 99 percent for insects (Gagné, 1988).

Pathways for Introduction and Spread

Although impacts of biological invasions may be local, at least at first, the causes of introduction are mostly international. Through trade and transport pathways (see box overleaf), countries both send and receive non-native species. Species are also translocated within countries to areas or islands where they are not currently present and may become invasive in these new locations.

Unilateral action by some states is not enough to manage pathways for transmission of invasive alien species. Cooperation at the international, regional, transboundary and local level is needed to develop efficient and consistent approaches to shared pathways to minimize unwanted introductions.

Examples of pathways for introduction of species beyond their natural range

Pathways include:

- movement of goods (species translocated in containers, planting media, untreated wood packaging, some food products)
- movement of people (by air, road, rail and sea transport)
- shipping and boating (ballast water, sediment, hull fouling, anchors)
- aviation (in cargo and on and in the aircraft itself)
- postal and courier services (including biological material purchased via the Internet)
- agriculture and forestry (direct introductions of crops and livestock, unintentional introduction of pests and diseases)
- horticulture (dispersal of ornamentals from gardens, ponds etc.)
- habitat restoration and landscaping (use of non-native genotypes of native plants, escapes)
- infrastructure development, interbasin transfers of water (e.g. between canals)
- mariculture and aquaculture (fish, molluscs and crustaceans introduced for production)
- aquaria (deliberate discards, discharge of organisms with waste water)
- hunting and fishing (game species and live fish and bait introduced for sport and restocking)
- release of pets or other domestic animals.


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The utilization of alien plant invaders in Nigeria
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Udufo Gbadamashi (Author), 2019, The utilization of alien plant invaders in Nigeria, Munich, GRIN Verlag,


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