Forwarded from the Aliens Listserver
Date: Fri, 09 Sep 2011 09:53:55 +0300
From: "Witt, Arne (CABI-Africa)" <[email protected]>
Subject: Re: [Aliens-L] Opinion Article in TheScientist
Dear All
As an invasion biologist and ecologist I am all
too aware of the impacts that invasive plants
have on biodiversity but I would like to raise
an issue that seems to have been forgotten in
this whole debate and that is the impact that
invasive species have on livelihoods in Africa
it is not just about biodiversity. I have seen
homes and villages abandoned, cultures and
traditions being eroded, conflict being driven
by a lack of resources due to the impacts of
invasive plants, etc. etc. it is a livelihood
issue for many people and as such a matter of
life and death for hundreds of thousands of people on this continent.
In a continent where more than 80% of the
population is reliant on natural resources for
their very survival trivializing the issue of
invasive plants for whatever reason is a real
cause for concern for those amongst us trying to
manage IAS in Africa and elsewhere in the
developing world the same applies to many
parts of SE Asia. I suggest that those critical
of our efforts to control IAS look at the bigger
picture instead of only focussing on IAS issues
in the so-called developed world no doubt
donors also get to read these articles and there
is a fear amongst people like me that it may
lead to donor apathy in the long term IAS are
not a serious issue so why should we fund IAS projects?
I often ask myself what contribution these
anti-IAS management papers make to development
and improving the livelihoods of millions of
people on this planet or are they merely an
attempt to criticize other scientists or to
convince donors to put their money elsewhere
maybe someone has the answer for me!! We are
being overwhelmed by invasive species and they
are impacting on all sectors of our society something needs to be done now.
Below is a short excerpt from a popular article
I wrote on the impacts of some invasive plants
on livelihoods in Africa in an attempt to get
the message across I could write a book about
this to most of you this is probably common
knowledge so my apologies for that but those
critical of IAS management should take heed and
look at the bigger picture as I have said before.
Regards
Arne
It has been estimated that weeds in general
cause a yield loss of about 10% in less
developed countries and 25% in the least
developed countries (Akobundu, 1987). Currently
49 countries worldwide have least developed
country (LDC) status, with 33 of these in Africa
in other words more than half of the countries
in Africa loose 25% of their potential yields as
a result of the presence of weeds. In most
countries it is the responsibility of women and
children to weed - it has been estimated that
100 million women in Africa spend 20 billion
hours weeding per annum which I consider to be a
gross underestimate. These yield losses as a
result of weeds were calculated prior to
parthenium becoming a serious problem we can
now assume that yield losses thanks to weeds are
significantly higher. In fact in Ethiopia
parthenium is currently considered to be the
most important weed both in croplands and
grazing areas by 90% of farmers in the lowlands
(Tamado and Millberg, 2000) with sorghum yields
being reduced by 97% in experimental fields with
high densities of parthenium (Tamado et al.,
2002). The impact of parthenium has also been
well documented in Australia and India (Evans,
1997) where studies have revealed that
parthenium is allelopathic and that infestations
reduce crop yields and that the weed displaces
palatable species in natural and improved
pasture (Channappagoudar et al., 1990). In
terms of animal husbandry it has also been
reported that this noxious weed can reduce
pasture carrying capacities by as much as 90%
(Jayachandra, 1971). Research has also shown
that the weed poses serious health hazards to
livestock and if eaten can taint their milk and
meat (Towers and Subba Rao, 1992). In fact it
has been claimed by staff at the Somali Regional
State Livestock, Crop and Rural development
Bureau in Jijiga, Ethiopia, that the local
farmers had lost dairy markets in Somalia
because the milk of cattle had been tainted by
parthenium, which is known to make milk
distasteful A conversation with a Masai
pastoralist on the outskirts of Nairobi National
Park, Kenya, revealed that the milk of nanny
goats was distasteful after they had eaten the
inflorescences of parthenium this response was
totally unsolicited. 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
(McFadyen, 1995). These may include hayfever,
asthma, and skin conditions. In interviews in
Ethiopia Wiesner et al. (unpubl.) asked a total
of 64 farmers (1944 years old) in different
infested territories about their health problems
when handling parthenium. The following symptoms
could be associated with parthenium: general
illness (80 %, tired, lethargic), allergic
reactions (90%, hay fever), asthmatic problems
(62%, contraction of chest muscles, coughing
fits), irritations of skin and pustules on palms
(30 %), stretching and cracking of skin (21%),
stomach pains (22 %, caused by the inhalation of
pollen). This combination of ill-effects on
people and their livelihoods (either crop
farming, dairy farming or pastoralism) has
resulted in mass abandonment of farms in India
and other places because the areas are overcome
by plants that make the continuation of
livelihood support and cash income impossible as
well as causing extreme discomfort and
disease. We have not heard of farmers
abandoning their land in Africa as a result of
parthenium infestations yet but are aware of
land being abandoned because of severe infestations of prosopis.
Various Prosopis species have been introduced to
Africa over the past 190 years for their
beneficial qualities which include erosion
control, shade, fuelwood, building materials,
and pods for animal and human consumption in
arid and semi-arid regions. Introduced
Prosopis species are now present in much of
Africa including Morocco, Algeria, Mali, Burkina
Faso, Niger, Chad, Sudan, South Africa,
Ethiopia, Kenya, and other countries (Pasiecznik
et al., 2001). In most of these countries the
introduced Prosopis species are considered to be
invasive with approximately 1.8 million, 500 000
and 700 000 hectares invaded in South Africa,
Kenya and Ethiopia, respectively. The invasion
rate at some sites in South Africa has been
estimated to be 18% per annum, which is
equivalent to doubling in area every 5
years. This rate of invasion is considerably
less than that recorded for more tropical
regions in Kenya and Ethiopia (Zimmermann et
al., 2006). A probability map developed by
Maundu et al. (2009) indicates that nearly 50%
of Kenyas surface area has a 30% or more
probability of P. juliflora invasion with arid
lands facing the greatest risk. In fact Maundu
et al. (2009) predicted that large tracts of
Tanzania and Mozambique also have a high probability of being invaded.
Despite some positive attributes, communities in
Ethiopia, Kenya and elsewhere are becoming
increasingly concerned about the negative
impacts of P. juliflora which include the impact
of this invasive tree on beneficial native
species; encroachment onto paths, villages,
homes, water sources, crop- and pastureland; and
injuries due to thorns have had negative impacts
on animal and human health apparently resulting
in some human fatalities (Mwangi and Swallow,
2008; Maundu et al., 2009). Livestock owners
around Lake Baringo, Kenya, claim that they now
have to move 40-50km away, from where they
reside, in search of grazing (Mwangi and
Swallow, 2008). Crop farmers from Chemonke
village, Kenya, have had to seek alternative
settlement elsewhere because they have lost
their land to P. juliflora invasions, often
resulting in conflict with established
communities, (Mwangi and Swallow, 2008). In
fact I have heard of a number of reports of
homes and villages being abandoned in Ethiopia
and Somalia as a result of prosopis
invasions. Surveys of local communities around
Lake Baringo revealed that 85-90% of respondents
to a questionnaire favoured complete eradication
of invasive Prosopis species (Mwangi and
Swallow, 2008). In another study Maundu et al.
(2009) found that 64, 79, and 67% of respondents
interviewed in the Garissa, Loiyangalani, and
Baringo areas of Kenya, respectively, said that
life would be better without prosopis. Over 90%
of livestock owners in eastern Sudan regard
invasive prosopis as a liability (Elsidig et
al., 1998) and pastoralists in Ethiopia refer to
prosopis as the Devil Tree. During a survey
trip in Ethiopia one pastoralist, looking at the
thickets of prosopis around us, said that they
now live in a region where they are forced to eat what cannot be eaten.
The loss of native species has significant
impacts on rural communities who have multiple
uses for many indigenous plants. In Kenya, a
number of riverine and flood plain species have
been displaced by invasive prosopis, including
umbrella thorn (Acacia tortilis), Faidherbia
albida, Hyphaena compressa, Salvadora persica,
and others (Maundu et al., 2009). In Turkana,
Kenya, where Prosopis species are displacing
native plants, 85% of 113 woody species
assessed, had a domestic or pastoral use (Stave
et al., 2007). Uses included palm leaves for
thatching, wood for charcoal, edible fruits,
browse for livestock, medicinal uses, materials
for traditional stools, shade provision, resin
used as a glue substitute, and even flowers for
decoration (Stave et al., 2007). For example,
Acacia tortilis is used for construction,
energy, food, browse, veterinary and human
medicine, utensils, and for religious and/or
cultural purposes. The flowers are a major
source of good quality honey in some regions and
the pods are used to make porridge after
extracting the seeds, while the Masai eat the
immature seeds. The leaves, bark, seeds, and a
red gum have medicinal properties with two
pharmacologically active compounds for treating
asthma having been isolated from the bark (Hagos
et al., 1987). Of the 98 plant species
identified, with one or more uses, in the Tana
River National Primate Reserve (dryland Kenya),
which is being encroached upon by invasive
Prosopis species, 15 were used as food or
beverages; 34 for construction material which
included poles, canoes, and furniture; 43 for
technological purposes including rope, traps,
arrows, baskets, drums, brooms, etc.; 23 for
medicinal uses; two 8for commerce (traded
items), and 20 for other uses including firewood
(Medley, 1993). Mimosa pigra which is also
rapidly invading floodplains and wetlands
throughout Africa will no doubt also have a
significant negative impact on
livelihoods. Wetlands provide resources for
people such as food, water, raw materials for
building and clothing and medicine. For
example, the annual economic values of the
Zambezi basin wetllands have been estimated to
be, amongst others, US$50 million for flood
plain recession agriculture, US$78.6 million for
fish production, US$70.6 million for livestock
grazing, and US$2.6 million for natural products
and medicine (Seyam et al. (2001). The latter
is significant because the loss of native plant
species, especially medicinal plants, can have
serious consequences for rural communities. Up
to 80% of the worlds rural populations depend
on plants for their primary health care, since
western pharmaceuticals are often expensive,
inaccessible or unsuitable (WHO,
1978). Traditional medicine is seen as one of
the surest means to achieve total health care
coverage of the worlds population (WHO,
1978). This is especially relevant in many
African countries where there are very few
university-trained doctors. In Tanzania there
are approximately 30,000-40,000 traditional
practitioners in comparison to 600 medical
doctors (Rukangira, 2001). In the Kwahu
district in Ghana, for example, there are 224
people for every traditional practitioner,
compared to nearly 21,000 people for every
university-trained doctor (Rukangira,
2001). The trade in medicinal plants also
contributes largely to income generation with at
least 133 000 people employed in the trade of
about 771 plant species in South Africa (Mander
et al., n.d.). The trade in traditional
medicines in South Africa is worth about ZAR2.9
billion per annum with approximately 27 million
consumers (Mander et al., n.d.). The value of
native plant species in contributing to the
welfare of rural communities can therefore not
be underestimated. Biodiversity also
contributes to the welfare of communities by
creating job opportunities and other sources of
revenue through tourism. Although poor
countries only command a small share of the
international tourism market, tourism can make a
significant contribution to their economies
provided that they can retain and enhance their
Protected Area networks and the biodiversity within them.
Unfortunately a large number of Protected Areas
in Africa are threatened by invasive species
such parthenium, prosopis, lantana, chromolaena,
Mimosa pigra, and others. Lantana is present in
virtually every Protected Area in East Africa
while invasive Prosopis species have already
invaded or are threatening to invade Tsavo
National Park, and a number of National Reserves
including the Tana River Primate, Arawale, Lake
Bogoria, Shaba, Samburu and Marsabit National
Reserves (Maundu et al. 2009; A.B.R. Witt, pers.
obs.). Tsavo East National Park has also been
invaded by O. stricta which now occupies more
than 25 km2 of the park on the south-eastern
boundary. In Ethiopia, P. juliflora and
parthenium have invaded the Awash National Park
with the latter also being found during a recent
survey of the Queen Elizabeth National Park,
Uganda, together with a number of other
species. Chromolaena odorata is present in most
Protected Areas in Ghana and has recently been
found in Tanzania and Uganda and we suspect that
it is also present in Kenya. This weed poses a
very serious threat to the Serengeti and
Masai-Mara ecosystems and pastoralism in East
Africa as a whole. Mimosa pigra has been
recorded in wetlands/floodplains/rivers in
Murchison Falls N.P. in Uganda, Gorongoza N.P.
in Mozambique, Lochinvar N.P. in Zambia and in a
number of other critically important wetlands
throughout the continent. Mimosa infestations
on the floodplains of the Lochinvar N.P. have
had a negative impact on the endemic Kafue
lechwe and a range of birds. In a survey 46 (19
579 individual birds) compared to 24 (314
individual birds) bird species were recorded in
the uninvaded versus invaded floodplain,
respectively (Shanungu, 2009). In fact the
endangered wattled crane was not present in
invaded areas with 94 individuals recorded in the uninvaded areas.
David Cameron Duffy
Professor of Botany and Unit Leader
Pacific Cooperative Studies Unit (PCSU)
University of Hawai`i
3190 Maile Way St. John 410
Honolulu, HI 96822-2279
(808) 956-8218 phone
(808) 956-4710 fax / (808) 956-3923 (backup fax)
email address: [email protected]
