EDUCATIONAL AWARENESS ON UTILIZATION OF ALIEN PLANTS INVADERS IN NIGERIA

EDUCATIONAL AWARENESS ON UTILIZATION OF ALIEN PLANTS INVADERS IN
NIGERIA

CHAPTER ONE

INTRODUCTION

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.

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.

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:

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

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.

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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