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Introduction
Ethiopia has great geographic diversity, and macro and micro
-climatic variability. However, there are threats its biodiversity by
habitat conversion, invasive species, unsustainable utilization of
biodiversity resources, replacement of local varieties and breeds,
climate change and pollution, demographic change, poverty, and
lack of awareness and coordination.1 Invasive species are either
indigenous or non indigenous species that can heavily colonize a
particular habitat.2 Alien species are non-native or exotic organisms
that occur outside their adaptive ranges and dispersal ranges.3,4 IAS
are all categories of living organisms (plants, mammals and insects)
which comprise the most common types in terrestrial environments.4
They are also widely distributed in all kinds of ecosystems throughout
the world. IAS have the ability to establish themselves, invade, out-
compete natives and take over the new environment.3,5 They are now
affecting every ecosystem types on the planet and they are the second
greatest global threat to biodiversity after habitat destruction.4,6 They
are pausing threats to ecosystems of the earth, and the services that
they provide to humanity are under risk.5 IAS have induce impacts
on native species directly competing for resource such as: food and
breeding sites indirectly by altering habitat and modify hydrology,
nutrient cycling and other ecosystem processes. Their impacts are
on native biodiversity in ecosystems like agricultural and range
lands, national parks, water ways, lakes, rivers, power dams, road
sides and urban green spaces with huge economical as well as
social consequences. These dramatically change the ecosystem both
positively and negatively. Across impact types, the positive impacts
reported by most authors were found to be largely outweighed by
negative impacts.7–9
IAS are creating complex and far-reaching challenges that a threat
to not only biodiversity, but also food security, health and economic
development. The problems of IAS in developing countries are higher
than in developed nations.3,10 According to Lowe et al.,6 in 2004, IUCN
identied 81 IAS in South Africa, 49 in Mauritius, 44 in Swaziland,
37 in Algeria and Madagascar, 37 in Kenya, 28 in Egypt, 26 in Ghana
and Zimbabwe and 22 in Ethiopia.11 Recently, there are more than 35
IAPS identied in Ethiopia. Some of these IAPS include: Mesquites
(Prosopis juliora), Parthenium weed (Parthenium hysterophorus),
Water hyacinth (Eichhornia crassipes), Lantana weed (Lantana
camara), Acacia species, and Orobanche and Cuscuta species that
are identied as major plant invaders. Recent surveys found also
emerging plant invaders such as Cryptostegia grand ora, Parkinsonia
aculeate, Mimosa diplorotricha, Mimosa pigra, Agrimonies Mexicana
and Nicotine glauca.1 Therefore this review paper aims to discuss
the reasons why IAPS in Ethiopia constitute a threat to biodiversity
locally and globally, examine the ecological impacts of some IAPS
on biodiversity and take up lessons learned elsewhere or in Ethiopia
and discuss on the use and management of IAPS. Thus, the paper
addresses relevant scientic information’s based on evaluation of data
collected from different journals, manuals and various report works.
Invasive alien plant species
A species is considered an “invasive alien species” when it spreads
beyond its natural area of distribution. According to Richardson et
al.,12 Kueffer et al.,13 and Shine et al.4
Alien plants: plant taxa occurrence in a given area results from
their introduction (intentionally or accidentally) by human activity.
(Synonyms: “exotic plants”).
Weeds: Plants (not necessarily alien) that is undesirable from a human
point of view (synonyms: “pests”).
Invasive plants: Alien plants that recruit reproductive offspring, often
in very large numbers, spread rapidly.
Int J Mol Biol Open Access. 2018;3(4):171‒178. 171
©2018 Shiferaw et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which
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Invasive alien plant species in Ethiopia: ecological
impacts on biodiversity a review paper
Volume 3 Issue 4 - 2018
Wakshum Shiferaw,1 Sebsebe Demissew,2
Tamrat Bekele2
1Arba Minch University, Ethiopia
2Addis Ababa University, Ethiopia
Correspondence: Wakshum Shiferaw, Arba Minch
University, College of Agricultural Sciences, Natural Resources
Management, Ethiopia, Email waaqsh@yahoo.com
Received: June 22, 2018 | Published: July 12, 2018
Abstract
Ethiopia has great geographic diversity and climatic variability. This has created diverse
and suitable ecosystems, which are home to large number of ora, fauna and microbial
species. However, there are threats to biodiversity by invasive alien plant species (IAPS).
They cause threats to biodiversity, economic and health problems in Ethiopia. This paper
addresses the ecological impacts of IAPS on biodiversity in the major types of ecosystems,
and discusses the reasons why IAPS in Ethiopia constitute a threat to biodiversity locally
and globally, examine the ecological impacts on biodiversity, discuss its use and suggest
mitigation measures of the IAPS in Ethiopia. Recently, there are about 35 IAPS in Ethiopia.
Some of these species include Prosopis juliora, Parthenium hysterophorus, Eichhornia
crassipes, Lantana camara, and Acacia species, which are the major threats to biodiversity
losses. Water bodies, wetlands, disturbed vegetation types (e.g. Acacia-Commiphora
vegetation type), agro-ecosystems, road sides, urban green areas, range lands are under
threat of IAPS nowadays in the country. To minimize and control such invasions, different
strategies are being applied such as eradication by utilization of P. juliora in Afar Region
for example, and mechanical control of P. hysterophorus in different parts of the country.
For use of sustainable ecosystem services, strategies such as integrated management
strategies, participation of all stockholders and multidisciplinary research approaches
within and across countries should be designed to reverse the situations.
Keywords: biodiversity, ecosystem, Ethiopia, impact, invasive, plants
International Journal of Molecular Biology: Open Access
Review Article Open Access
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 172
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
Invasive alien species: an alien species which threatens ecosystems,
habitats or species. (1) Alien species that escape from human control
go beyond the intended physical boundaries and cause environmental
damage (2) Covers alien species that remain under human control but
damage native ecosystems. Such damage is linked to species being
alien, but not to invasiveness.
Native invasive (or) local invasive: species that get into modied
habitats by their own means and then go through population
explosions, loss to biodiversity and economics.
Historical perspectives of invasive alien plants
Plant invasion is a strong threat to the species diversity around the
world during the 21st century after habitat loss. Large number species
of IAP are introduced to native country in the world and few of these
become problematic; they are introduced in to a country either through
human or natural (e.g. winds, birds, animals, water).5,14 Thousands
of plant species have been transported by humans to areas far from
their natural habitats; accidentally or intentionally (e.g. agro-forestry,
horticulture, forestry, and animal husbandry purposes). However,
invasions by IAPS are one of the largest threats to the ecosystems
of the earth, and the services.15 Few aggressive IAPS which are
threatening biodiversity in Ethiopia and elsewhere in the world are
discussed in the following sections.
Prosopis juliora (Sw.) DC. Fabaceae
It is a perennial evergreen multipurpose dry land tree or shrub native
to the Caribbean, North and South America. It Introduced to Africa in
1822 in Senegal; South Africa (1880), Egypt (1900) and Kenya was
in 1973.16 It introduced to Eritrea from the Sudan, probably during
the early 1980s. It introduced in Ethiopia in the late 1970s at Goro
nursery- Dire-Dawa. Prosopis was planted over large areas until 1982,
continued by the Food for Work Programme from 1986 to 1988. This
species is now commonly found in Afar, Oromia, Amhara, Somali,
Dire-Dawa regions and Sothern Nations and Nationalities. Nowadays,
it is repeatedly reported to be one of the invasive and problematic
trees in the Afar Region and progress to Rift Valley of Ethiopia.17
Parthenium hysterophorus, in the family heliantheae:
asteraceae
It is a perennial herb. Parthenium genus has 16 species native
to northern South America, Central America, Mexico, Texas, and
Florida, Mexico. It introduced to Ethiopia accidentally in the 1970s
when drought induced famine triggered a massive multinational
relief effort. It was rst reported from Ethiopia in 1988 at Dire- Dawa
and Harerge, Eastern Ethiopia and subsequently found near Desse,
Northeastern Ethiopia as well.18,19
Eichhornia crassipes, (Mart.) Solms in A. DC.
(Pontederiaceae)
Water hyacinth is native to South America and it is originally from
the Amazon Basin its entry into Africa, Asia, Australia, and North
America was facilitated by human activities and lack of naturally
occurring enemies. It introduced in to Kenya (1957), Lake Victoria
in East Africa, and began to cause problems in 1990.3,4 Zimbabwe
(1937), Mozambique (1946), Ethiopia (1956), Rwanda and Burundi
colonized in the late 1950s, Tanzania were infested in 1955 and 1959,
Zambia (1960s), Uganda (1988-89), Malawi (1996).20 Water hyacinth
has also spread to West Africa and Cameroon (1997-2000), Nigeria
(almost all water bodies).20 Water hyacinth in Ethiopia has also been
marked on a large scale in many water bodies of the Gambella area, in
Blue Nile Watershed, and Lake Tana.21,22
Lantana camara L. (Verbenaceae)
A shrub IAPS introduced to Ethiopia from native Tropical
America and the West Indies. But, no clear year of introduction from
native range has been indicated in literatures regarding this species
in Ethiopia. Lantana has been introduced throughout the tropics
and subtropics as an ornamental, often used as a hedge plant. It is
a cosmopolitan weed and in many countries it has been declared a
noxious weed.
Geographical distribution and sensitive ecosystems
for invasive alien plant species
Geographical distribution: IAS have invaded and affected
native biota in virtually every ecosystem type on Earth. They
have contributed too many hundreds of extinctions, under island
conditions, freshwater ecosystems. All ecosystems can be invaded
potentially; some appear more vulnerable than others. Evolutionarily
and geographically isolated ecosystems, notably oceanic islands are
particularly vulnerable. Because the natural bio-geographical barriers
of oceans, mountains, rivers, and deserts, which provided the isolation
essential for unique species and ecosystems to evolve and have lost
their effectiveness. Habitats such as urban-industrial areas, habitats
suffering from periodic disturbance, harbors, lagoons, estuaries and
the fringes of water bodies are under threats of IAPs.3 Systems with
low diversity, for example some arid ecosystems, are more susceptible
to invasion than species-rich systems with well established species
interactions. However, species rich landscapes can also be susceptible
to a greater range of invaders because of the greater diversity of
habitats typical of such landscapes.3,23 The most obvious and severe
invasion regions of alien plants in Africa are in sensitive wetland and
aquatic ecosystems.21 In Ethiopia; disturbed ecosystems, along road
sides, agricultural lands, and grass lands, in Vegetation ecosystems:
Desert and semi-desert, Acacia-Commiphora woodland and bush
land, freshwater lakes, lake shores, marshes, swamps and ood plain
vegetation, dry Evergreen Afro-montane forest and grassland complex,
and Acacia wooded grassland of the central rift are under threat of
IAPS in Ethiopia.1,24,25 Many evidences prove that disturbances in
the natural ecosystems provide the great opportunities to the alien
invaders to establish themselves (Table 1). The frequency of the alien
herbal plants increased in the areas of human interference such as
forest fragmentation. Moreover, population pressure, over-stocking,
overgrazing and deforestation have facilitated the disturbance of the
Ethiopian ecosystem and enhanced the effect of weed invasion by
threatening biodiversity of the country.19 According to21 and Beilfuss26
the distribution of IAPS in Ethiopia is indicated in different regions
across the country (Table 2).
Causes for invasion of alien plants
As indicated above the causes of introduction are two types: For
example, human (intentional) introduction of P. juliora in Ethiopia
and natural (unintentionally) introduction of P. hysterophorus in
India, Kenya, Ethiopia and other elsewhere. After natural invasion
by some alien plant species, there is a “lag phase” that may range
from decades to centuries before “an exponential phase” of its
fast spread. The species are in a given time may appear to be non-
invasive for a while then may suddenly begin to spread rapidly (E.g.
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 173
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
P. hysterophorus). Introduction cause is closely linked to the history
of civilization. Colonization in particular led to massive transoceanic
movements and exposed ecological systems, as well as indigenous
communities; to quite new stresses and threats in the world. In the
modern era of globalization, the ‘four Ts’: Trade, Transport, Travel
and Tourism have cause and sharply accelerated the rate of species
movements. Global markets support the increased ow not only of
investment money but also of goods.4 According to Mc Neely et al.,3
there are three steps for invasion of IAS: (1) introduction – intentional
or unintentional, (2) establishment–survives but doesn’t spread,
(3) spread: (3a) Naturalization – becomes part of the ora/fauna
of its new habitat (3b) invasion–expands and impacts on species,
ecosystems, people and development. Species invasions have three
main elements: (1) source population is where the species nds its
natural habitat, where it forms part of the native ecosystem (though
other invaded ecosystems often are a secondary source) and (2)
pathways are the routes by which species move from one political
unit to another, either within a country or between countries. (3)
destinations are where the new species arrives. Climate change also
aggravates IAS to colonize easily and vice versa.27 Climate change
can facilitate IAS as new species, that may become invasive, will
be entering regions due to climate change, species hierarchies in
ecosystems will change leading to new dominants that may have
invasive tendencies, and climate induced stress in an ecosystem will
facilitate invasive pathways. Alternatively, IAS can facilitate climatic
stress by increasing ecosystem susceptibility to climatic perturbation,
through reducing the number of species and their functional types
within the ecosystem.28
Table 1 Identied and prioritised Invasive Alien Species in Ethiopia (Source: GEF, 2002)
Scientic names Common names Scientic names Common names
E. crassipes Water hyacinth P. juliora Mesquite, Prosopis,WoyaneZaf (Amh)
L. camara Lantana, Wefkolo (Amh) P. hysterophorous Parthenium, Congress weed, White top,
Feremsisa (Orm)
P. hysterophorous Parthenium, Congress weed, White top,
Feremsisa (Orm) Striga species Striga
P. juliora Mesquite, Prosopis, Woyanezaf (Amh) E. crassipes Water hyacinth
Striga species Striga L. camara Lantana, Wefkolo (Amh)
Acacia species* Fullsa (Orm) Acacia species* Fullsa (Orm)
Orobanche species Orobanche , Atequrit (Amh) - -
Cuscuta campestris Cuscusta - -
A. mexicana Argemone, Nech Lebash (Amh) - -
Verbesina encelioides Verbesina - -
Opuntia species Opuntia, Qulqual (Amh) - -
* Probably a native species= like A. drepanolobium, Orm=Afaan Oromo, Amh=Amhari
Table 2 Distribution of IAPS across regions in Ethiopia
Oromia Somali Afar Tigray Amhara South Gambela
P.hysterophorus P.hysterophorus P. juliora Striga species Striga species E.crassipes E.crassipes
P. juliora L. camara P.hysterophorus Orobanche species Orobanche species P. juliora -
Striga species P. juliora Acacia species P.hysterophorus P.hysterophorus A. mexicana -
L. camara - - Opuntia species Opuntia species P.hysterophorus -
E. crassipes - - P. juliora P. juliora - -
Orobanche species - - - E. crassipes - -
Acacia species - - - - - -
Argemone mexicana - - - - - -
Mimosa pigra - - - - - -
M. diplotricha - - - - - -
Opuntia species - - - - - -
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 174
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
Properties of invasive alien plants
IAS is one of the most signicant drivers of environmental change
worldwide. Four key features are associated with invasive plants; (1)
show prolic seeding and early age of rst reproduction, (2) have
unpalatable foliage, (3) can easily establish in degraded environments,
and (4)have an ability to regenerate profusely from direct seeds, stems
or roots. These features make them good competitors amongst other
plant species and allow their survival and abundant establishment.29
Parthenium hysterophorus: A deep tap root and an erect stem that
becomes woody with age. Large plants can produce up to 15,000
seeds on average and 100,000 seeds which can be distributed
by oating on still or ood waters or in mud adhering to animals,
vehicles and machinery. In India, 200,000 seeds per m2 in the soil. In
some areas, more than 340 million Parthenium seeds can be present
per hectare in the surface soil, compared to 120,000 native grass
seeds. Dormant in the soil for several years if conditions favorable.
Allelopatic chemicals have been observed to exhibit an inhibitory
effect both on the germination and growth of a wide variety of crops
including pasture grasses, cereals, vegetables, other weeds and even
tree species.
Prosopis juliora: Have characteristics of rapid biomass accumulation,
nitrogen xing root ability, tolerance of arid conditions and saline
soils, coppicing abilities, ability to stay dormant for longer time in a
media (e.g. soil) and germinate during favorable conditions, number
of seeds/pod is high.30 Allelopatic chemicals are other characteristics
of Prosopis species which are used to adapt to compute with other
neighbor species in harsh conditions.
Lantana camara: Forms extensive, dense and impenetrable thickets
in forestry plantations, orchards, pasture land, waste land and in
natural areas. However, lantana showed less vegetative growth, less
reproductive success and more browsed in the forest. So, L. camara
is less successful in the forest gaps than at the edges of the forests and
hedges. The rapid spread of lantana is associated with human induced
disturbance. Fruits are widely dispersed by many birds including
introduced species. In areas where natural res occur they stimulate
thicker re-growth. It tolerates a wide range of climates. It grows well
on poor soils.31 It produces also allelopatic chemicals from its plant
parts.
Impacts of invasive alien plants on biodiversity
Among the invaders that will have the largest impacts are those that
directly modify ecosystems. They have cascading effects for resident
biota (plants, animals and micro-organisms). Exotics can affect
ecosystems by altering system-level ows, availability or quality
of nutrients, food, and physical resources (e.g. living space, water,
heat or light). Many literatures suggest that introduced ecosystem
engineers either: increase habitat complexity or heterogeneity which
tends to cause abundances and /or species richness to raise or decrease
complexity tends to have the reverse effect on ecosystem services.
Ecosystem services can be categorized into four main services in
general; (1) Provisioning service (e.g. food, freshwater, ber, fuel,
genetic resources, (2) Regulating services (e.g. air quality regulation,
climate regulation, water regulation) (3) Cultural services are non-
material benets, (e.g. aesthetic values, recreation/tourism, spiritual/
religious values, (4) Supporting services. Overarching, indirect,
and occur on large temporal scales (e.g. photosynthesis, primary
production, nutrient cycling.32 IAPS threats to these ecosystem
services; IAPS pose a global threat to the conservation of biodiversity
through: their proliferation and spread, displacing or killing native
ora and fauna and affecting ecosystem services. They are particularly
damaging in geographical or ecological islands, which are rich in
endemic species, Invasive plants smother, outcompete and displace
indigenous species, changing the composition and function of entire
ecosystems.21 IAS and other native invasive plants can affect entire
systems in Ethiopia and elsewhere in the world (Table 3).
Table 3 Invasiveness and ecosystem effect status of top 20 Invasive Plants
Species in Ethiopia (Source: Rezene and Taye, 2014)
Species Ecosystems highly
affected*
Distribution
status
P. hysterophorus 1,2,3,4,5,6,7,8 High
P. juliora 1,2,3,4,5,6,7,8 Moderate
Opuntia cus-indica 3,4,5,6, Moderate
O. stricta 3,4,5,6, Moderate
M. diplotricha 1,2,3,4,5,6,8 Moderate
M. pigra 3,4,7 Low
Cryptostegia grandiora 2,3,4,7,8 Low
L .camara 1,2,3,4,5,6,8 High
A. drepanolobium 1,3,4, Moderate
A. saligna 2,3,4,5, Low
Parkinsonia aculeata 2,4,5,6 Low
Nicotiana glauca 1,2,3,4,5,6, Moderate
Argemone ochroleuca 1,2,3,4,5,6, High
Xanthium strumarium 1,2,3,4,5,6, High
X. spinosum 1,2,3,4,5,6, Moderate
Psidium guajava 8 Low
Senna didymobotrya 1.2.3.4.5.6.8 High
S. occidentalis 2,4,5, Moderate
Calotropis procera 1,2,3,4,5,6,7,8 Moderate
Ricinus communis 2,4,5,6, Moderate
1, Cultivated land; 2, Roadside; 3, Grazing areas; 4, Non-cultivated land; 5, Rural
villages; 6, urban areas; 7, Riverside; 8, Forest areas.
Parthenium hysterophorus: It aggressively colonizes: natural and
manmade ecosystems, disturbed sites and causes major negative
impacts on grassland habitats, open woodlands, riverbanks, ood
plains, wildlife parks, and open eld of settlement areas, bare areas
along road sides, crop elds, and gardens heavily stocked areas around
yards and watering points etc. The allelochemicals released from the
weed or from seed leaching inhibit germination of other plants and
the growth of pasture grasses, legumes, cereals, and vegetables, other
weeds and even trees. Parthenium affects nodulation in legumes due
to inhabitation of activity of nitrogen xing and nitrifying bacteria
Viz., Rhizobium, Actynomycetes, Azotobacter and Azosprillium.
It was reported to cause yield losses of up to 40% in several crops
and is reported to reduce forage production by up to 90% in India.33
Parthenium produces enormous quantity of pollen (on average 624
million/plant), It is carried away at least to short distance in clusters of
600-800 grains and settle on the vegetative and oral parts, including
stigmatic surface inhibiting fruit setting in crops like tomato, beans
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 175
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
and maize when its pollen grains are deposited on the stigmatic
surfaces.33 In Ethiopia, the yield in Sorghum bicolor grain was reduced
by 40-97% when P. hysterophorus was left uncontrolled throughout
the season.34 The weed poses serious health hazards to livestock and
if eaten can spoil their milk and meat. Some farmers in Ethiopia also
claim that they have lost livestock during dry periods when there was
little available grazing and the animals had eaten Parthenium out of
desperation. Parthenium can also cause severe allergenic reactions in
people who come into contact with the weed on a regular basis.34 It
induces to alter in the physical and chemical properties of soil such as
soil texture, soil pH, soil organic matter, soil nitrogen, soil potassium,
and soil phosphorus.33
Adane18 reported that P. hysterophorus was found to be the most
frequent and dominant species on road sides, grazing land and crop
elds with important value indices of 102%, 77.5% and 74.5%
respectively out of sampled cases in Adami Tulu-Jido Kombolcha
Woreda of Ethiopia. Under crop elds, the responses of wheat and
teff (63.1% for both crops); maize (6.9%) to Parthenium weed were
less than grass weeds, like Cynodon dactylon L. (72.5%) in the study
area. The result showed that some species have greater sociability or
resistance than other species. In Southern Ethiopia at Gedeo Zone, the
impact of P. hysterophorus weed on biodiversity was also assessed.
It showed that in highly infested areas the impact was more visible
than the moderate and low infested areas.19 These samples indicated
lower diversity index (H’) (highly infested area) as compared to other
sites where the calculated Shannon Diversity Index was high (where
invasion was low).
Prosopis juliora: Although there are few quantitative ndings in
the study area. P. juliora are threatening endemic plant species in
Afar Region of Ethiopia, such as A. prasinata, Boswellia ogadensis,
Euphorbia doeloensis, E. ogadensis and Indigofera kelleri.17 These
habitats which harbor threatened plant species also harbor many
globally threatened and vulnerable mammal and bird species. Because
of disruption of ecosystem integrity in the area, these threatened wild
animals are further endangered.
Abyot & Getachew30 reported also that Prosopis replaced the local
biodiversity in several spots in Afar region, mainly rangelands and dry
riversides. In such areas, the grasslands are no more used for grazing
by the livestock. The species also reduced the total biodiversity of the
arid and semiarid regions by reducing their abundance, distribution,
and more importantly by changing the ecosystem function from
rangeland to Prosopis thicket. Consequently, the local Afar pastoralists
who solely depend on natural pasture for their cattle in Ethiopia
moved further from their home and pasture elds aggravating food
and feed shortage in the region.
Prosopis has severely invaded dense Acacia woodlands, riverine
forest and agricultural lands of Amibara Woreda, Afar. It has highly
distributed in Acacia woodland (9.91 km2) and least around the
settlements (0.35 km2) over the 16 years period land use/land cover
changes from 1986 to 2001 in the area.11 The number of coppices was
relatively few around the settlements and higher in Acacia woodlands.
Moreover, the density of the plant was found least in riverine forest
lands (344stems/ha) and highest in Acacia woodlands (1774 stems/
ha). This result depicts that Acacia and other species are under threat
in the area. Prosopis has been blamed for injuring livestock with its
poisonous thorns and causing goat teeth to rot and fall out because
the small seeds get stuck between the teeth. Thousands of goats have
been rendered toothless and died from starvation following teeth loss
which has been decreasing their number and threaten goat breed in the
region.29 The decrease in the number of sheep and goats in the same
period is estimated to be higher than one third.17 Over the ve years
between 2003 and 2008 alone camel ownership in invaded areas of the
Afar Region has dropped by almost one third as a result of prosopis
invasion. The effect of the species on the number of calves and heifer
is even more pronounced where the reduction rate is ve fold.
Eichhornia crassipes: Few studies showed quantitative impacts of
water hyacinth on biodiversity in Ethiopia, In general, according to
UNEP20 threats posed by water hyacinth are: (i) loss of biodiversity,
(ii) oxygen depletion and reduced water quality, (iii) breeding ground
for pests and vectors and (IV) blockage of waterways hampering
agriculture, sheries, recreation and hydropower. Studies to establish
the negative impact of the weed at the Wonji Sugar Estate in Ethiopia
indicated that the weed inicted multifaceted problems such as excess
water loss that is estimated to be 393,660 to 2,945,160 m3, restricting
water ow.35
Lantana camara: It readily invades pastureland outcompeting
palatable species, resulting in a reduction in carrying capacities and
restricted access and movement of animals, humans and vehicles.
It is also unpalatable, and in large doses (approximately 1% of total
body weight) is poisonous, cause skin lesion in sheep particularly to
cattle. Lantana is one of the known allelopathic weed plants in many
parts of the world. For example, experiment conducted in Northern
Ethiopia.36 Consequently, Lantana leaf powder signicantly inhibits
seed germination, speed of germination, shoot and root length, stem
thickness and biomass of wheat and maize.
Uses of invasive alien plants
Introducing species to new locations has had tremendous
contributions to societal development. Human welfare has been
improved due to the introduction of many crops out of their native
range.17 Accidental and deliberate introduction of some species,
however, resulted into unexpected negative outcomes. Some species
turned into invasive species presenting complex and dynamic
problems to society.3
Parthenium hysterophorus: extracts of the species have been
well documented for their insecticidal, nematicidal and herbicidal
properties by many researchers. However, there are few reports of
these characteristic properties being used and any utilization taking
place. The most practical use of Parthenium weed in India so far has
been through the production of compost and in vermin-composting
along with other weeds.33 Composting signicantly reduces
allelopathic inhibitory effects of Parthenium on plant seed emergence
in Ethiopia.37 For example, report by showed lettuce emergence
percentage was greatly reduced by fresh Parthenium (93%). Fresh
and composted of the species reduced lettuce emergence rate by 95
and 33%, respectively. It Radicle length also reduced by 97 and 35%,
respectively and plumule length (93 and 43%, respectively in Jimma
Zone of Ethiopia. Their result clearly showed that composting greatly
reduced allelopathic effects of Parthenium.
Prosopis juliora: Initially, though the benets of Prosopis are not
well realized in Ethiopia, Prosopis provide valuable products such
as timber and charcoal in USA; honey in Mexico; animal feed in
Brazil; gums, fodder and rewood in north-eastern India; charcoal
and human foods in South America, and rewood in Africa.33 It is
used for high quailty furniture, ooring, ber boards, railway cross-
beams etc. In Ethiopia, Prosopis wood can only be used for fuel wood,
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 176
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
charcoal, and fencing and its crushed pod for animal feed especially
during dry season.17 Flowers of Prosopis are excellent sources of
pollen and nectar and are used to produce high quality honey. The
exudates gums harvested from Prosopis trees are important inputs
in food, pharmaceutical, chemical and manufacturing industries.16,33
Due to its unique tolerance to the harsh environment of dry lands,
Prosopis has become an important source of livelihood for the poor,
hence sometimes referred as ‘the poor man’s tree’.17
Lantana camara: It is used traditionally to treat various ailments
like tetanus, rheumatism, malaria, cough, fevers, cold, rheumatisms,
asthma to mention a few of animal and human diseases. Many
phytochemical investigations have been done on this plant.38,39 The
plant can be also uses as hedges which protects wind erosion in dry
lands. It also used for camel calves as feed because calves cannot
reach to browse like Acacia brevispica during shortage of milk from
their mother in dry season in Eastern Ethiopia.
Management of invasive alien plants
The potential irreversibility of the damage of invasion and the
indecision of the costs they may imply impose countries a preventive
approach to their management.3 Prevention–not allowing a potentially
invasive species to become established in the rst place–is the rst
line of defense. The main management responses after a species
has invaded are mitigation and adaptation. Mitigation can reduce
or eliminate the likelihood that a species will become established
or spread, and decrease or eliminate the presence of an invader.
Adaptation, on the other hand, involves changes in behavior in order
to reduce the impact of an invasive species.
Barriers for management of invasive alien plants
According to,22 in Africa and specically in Ethiopia there are a
number of barriers to effective adoption of this strategy for managing
IAS, (1) the policy environment within which most countries in Africa
are operating is fragmented and weak, (2) the critical information
required by the different stakeholders is not available, (3) the
implementation of prevention and control programmes is slow or
inadequate and capacity is lacking.
Efforts in the Management of invasive alien plants
There are different management strategies of IAPS after invasion:
Strategies are Mechanical, chemical, biological and Fire. The
relatively common control method applied in Ethiopia is the uprooting
of the tree manually.
Parthenium hysterophorus: Like other weeds, control of P.
hysterophorus weed in Ethiopia is entirely based on cultural and
labour intensive practices such as tillage, hand weeding, mowing,
hoeing and slashing. Unlike large-scale farms in developed and
developing countries, small-scale farmers prepare their land using
repeated oxen ploughing and/or hoeing. Some farmers in Ethiopia are
also using chemical eradication methods.18 Zygogramma bicolorata
was found to be safe biological P. hysterophorus.40,41 Another trial was
conducted by Sintu42 there was an evaluation of bio-control agent of
stem-boring weevil (Listronotus setosipennis) on P. hysterophorus in
Ethiopia. L. setosipennis was selective to control P. hysterophorus in
relation to other plant species without affecting the native ones.
Prosopis juliora: The mechanical control of prosopis is, however,
very labor intensive and expensive, and is economically feasible only
for high value lands. Using mechanical control method, Prosopis
plant was recommended to cut at 10 cm for young trees; and 40 cm
for matured trees or shrubs of Prosopis to control coppicing. It can
also serve simply for control of the spread of the species and is not
effective to eradicate it by mobilizing communities. Management of
Prosopis by utilization (e.g. fuel wood, construction, and charcoal
production, feed livestock by crushing pods) is the best management
options.43
Eichhornia crassipes: Mechanical, chemical and biological, re after
water drainage are few strategies to control E. crassipes. Mechanical
eradication of water hyacinth at Lake Tana of Amhara Region and
Awash River irrigation channels are encouraging.1 Mechanical
eradication is labour intensive and costly. Chemical eradication is not
friend environmentally. Release of bio-control agents is also being
considered where these technologies are not feasible.
Lantana camara: Attempts to control L. camara using mechanical,
chemical and biological means have met with limited success.
Lantana is difcult to control, as it will coppice and form denser
thickets if it is simply slashed and left. Management by utilization can
also eradicate L. camara. Lantana inaction can be controlled by using
its biomass before the plant set seeds. The best management option is
an integrated approach is required for management.
Conclusion and recommendation
Ethiopia has diverse ecosystems which are home to large number
of ora, fauna and microbial species. However, there are threats to
ecosystem services and biodiversity loss due to habitat conversion,
invasive species, unsustainable utilization of biodiversity resources,
replacement of local varieties and breeds, and climate change and
pollution. Invasive alien species such as plants are exotic which are
introduced deliberately or unintentionally outside their natural habitat
naturally or through human activities. In new areas, invasive alien
species are colonizing the native ecosystems; have either positive
or negative consequences on the ecosystem services. Invasive alien
species are found in all taxon or organisms and exist all over the world
in all ecosystems. Recently, 35 invasive weed species are identied in
Ethiopia, and they are posing negative impacts on native biodiversity,
agricultural and range lands, national parks, water ways, lakes, rivers,
power dams, road sides and urban green spaces with huge economical
as well as social consequences. Some of these species include:
mesquites (P. juliora), parthenium weed (P. hysterophorus), water
hyacinth (E. crassipes), lantana weed (L. camara), Acacia species,
and other weeds such as Orobanche and Cuscuta species that are
identied as major plant invaders. These IAPS are more aggressive
in disturbed, arid and semiarid vegetation ecosystems like Acacia-
Commiphora woodlands, aquatic, wetlands, agro-ecosystems and
rangelands in Ethiopia.
IAPS have peculiar characteristics of invasiveness and distribution
that overtake the native species such as number seeds they produce,
reproductive outputs and some allelochemicals inhibit other native
species loss. As the result, they have impacts on biodiversity, social
services and health problems both on human and animals in all
ecosystems in the new areas. In order to combat such threats countries
in the world and Ethiopia have their own strategies to control IAPS
in the native ecosystems. But, there are management barriers to
implement such strategies. Mechanical, chemical, re regime for some
invasive species like water hyacinth and biological control methods
Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper 177
Copyright:
©2018 Shiferaw et al.
Citation: Shiferaw W, Demissew S, Bekele T. Invasive alien plant species in Ethiopia: ecological impacts on biodiversity a review paper. Int J Mol Biol Open Access.
2018;3(4):171‒178. DOI: 10.15406/ijmboa.2018.03.00072
are some methods after invasion of the species. These aforementioned
methods have their own cons and prons to control IAPS. Prevention,
integrated management strategies and management of the species by
utilization as measure used to control P. juliora, P. hysterophorus and
L. camara in Ethiopia, are among the best management of the control
measures.
The following recommendations are suggested to prevent, control
the already invaded ecosystems in Ethiopia and elsewhere in the
world:
a. Sustainable and multidisciplinary approach studies regarding
history, properties of the invasiveness of the species and their
impacts in relation to ecological impacts on ecosystems and
socioeconomic consequences have to be conducted.
b. Create awareness for stakeholders about the history, cause and
impacts IAPS is very important.
c. Institutions should join the efforts to better understand IAS and
devise mechanisms for better prevention and control.
d. Close monitoring and management of all natural and agro-
ecosystems from disturbances to reduce the arrival and
colonization of IAPS. Secure quarantine measures needs to be
introduced in boarder areas where tourism, trade, travels agents
are owing. Countries with IAPS countries share information and
working relationships in order to control the transfer of IAPS from
one to another.
Acknowledgements
None.
Conict of interest
The author declares there is no conict of interest.
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