Tanzania, Uganda and Kenya Suffer
Water Hyacinth Claims Another Victim
by John Dawes, United Kingdom
Click images to enlarge
The water hyacinth (Eichhornia crassipes) continues to
be a popular aquarium and pond plant within the trade and hobby.
It is, undoubtedly, a very interesting looking plant at all times,
and a particularly
beautiful one when in full bloom. I have cultivated it many
times over the years and, like so many before me, feel that a
pond full of water hyacinths in flower is a truly spectacular
and unforgettable sight.
But, like so many other beautiful plants, the hyacinth has
a dark side to it, one that I have reported in the past (China
Tackles the Water Hyacinth in WGI
Online 2.4). It is extremely vigorous and reproduces at an
alarming rate when conditions are favourable. In fact, a single
plant can end up producing so many offsets that it will cover
the whole surface of a modest-sized pond in a single favourable
Multiply this several billion times over, and it is easy to
see how even a large watercourse can end up being totally choked
by water hyacinths. In its natural South American waters, this
does not usually happen, since the plant is kept in check by
its natural enemies, such as the giant rodent, the capybara.
However, away from its home and its natural "controllers",
the situation is quite different, as Africa's massive Lake Victoria
is finding to its cost.
This particular story shows how action taken in one country
can have devastating effects in another. It also shows how an
apparently innocuous decision, taken quite innocently but in
ignorance of its potential consequences, can end up having monumentally
Reportedly, the water hyacinth was introduced into Rwanda,
probably some 100 years ago, by Belgian colonists who wanted
to beautify their holdings (presumably, their ponds). It is believed
that the plant then spread to Lake Victoria via the River Kagera,
which originates in Rwanda and passes through Tanzania and Uganda.
It was first spotted in the lake in 1988 and, by 1989, it
was already colonising parts of the shoreline. It has been estimated
that enough water hyacinths are carried into the lake each day
to cover an area of 3 hectares (7.4 acres). And this is without
taking account of the prolific nature of these plants once they
reach the lake.
By 1995, no less than 90% of Uganda's Lake Victoria coastline
was covered in water hyacinths. In 1998, it was estimated that
about 2,000 hectares (4,942 acres) of lake surface around the
major port of Kisumu were smothered by the plant. In the Winam
Gulf on the northeastern Kenyan corner of the lake, about 17,230
hectares (42,576 acres) were affected.
Water hyacinths clog the shoreline
of Lake Victoria, Kusa Beach, Kenya
Image from http://www.iec.ac.uk/
Then, dramatically, the hyacinths began to disappear. It is
not clear if this was as a result of the introduction of the
weevils, Neochetinia eichhorniae and N. bruchi,
which feed on the hyacinth, or if the severe El Niño of
1997/98 was a major factor
or if it was a combination
of both. The fact is that parts of the lake were virtually cleared
within a short period of time. As recently as 2005 and 2006,
there was even optimism that the hyacinth plague would not return.
This optimism has, however, been short-lived, because the
last few years have seen a resurgence of massive proportions.
This trigger could have been unusually heavy rains towards the
end of 2006, which resulted in flooding of the rivers that feed
the Winam Gulf. This, in turn, produced nutrient-rich agricultural
run-off into the lake.
Such water provides excellent growing and spreading conditions
for the hyacinths, as well as the two metre (6.6 foot) high hippo
grass, Echinochloa stagnina, (also often listed as E.
scabra), which is reported as being able to grow to 10 metres
(33 feet) in deep water and which is occasionally grown as an
ornamental garden plant.
The explosion in both species has been such that, according
to a report published by East African Business Week at
the end of March 2008, "marine business (sic) between
the East African states that share Lake Victoria is likely to
close following the inability of the said states to combat the
dreadly (sic) Hippo grass and water hyacinth despite the
multibillion funded research on the weeds."
Dense growth of Eichhornia crassipes
chokes a Malaysian pool. The plant in the
top right corner is another potentially
invasive species, the aquatic fern
Tanzania, Uganda and Kenya have, together, spent US$77.8 million
and, yet, they have been unable to eradicate the problem. Indeed,
their lack of success is such, and the current situation is so
bad, that it could soon paralyse free movement of vessels in
the lake, "putting at stake the integration of the East
African Community." This could also "put at stake lives
of the over 30 million people depending on the lake for daily
Kenya is also feeling the effects of the violence that followed
the recent elections and which forced operators to take their
vessels elsewhere in fear for their own safety and that of their
ships and cargo. Kisumu Port has, reportedly, lost about 75%
of its trade owing to this, to which must now be added losses
owing to the hippo grass and water hyacinth plague.
The weed problem is so bad that large commercial vessels are
being affected. They also consume more fuel (about double) to
reach their destinations "as they seek for safer routes"
and journeys now take almost twice as long as they used to a
short while back.
Devastating though all these consequences are for the countries
with Lake Victoria shorelines, they are not the only negative
knock-on-effects of the proliferation of the plants. There are
also other, less obvious, but equally serious, effects on the
ecology of the lake and its inhabitants, as well as the fishing
communities that depend on the lake for their livelihoods. Fishermen,
for instance, cannot cast their nets in hyacinth-infested waters;
often, they cannot even launch their boats or bring any worthwhile
catches to market.
Not everything about the water hyacinth
is negative. Here, newly-hatched
snakehead (Channa sp) larvae can be
seen sheltering in a small area of clear
water among Eichhornia plants.
The thick plant mats also exclude light from reaching the
water below. Native aquatic plants therefore die and this affects
fish and aquatic invertebrate populations. Further, the plants
clog up intake pipes which draw water for the shoreline urbanisations;
they also clog up irrigation canals and create standing water
bodies which serve as breeding grounds for disease-carrying mosquitos.
Finally, they also create zones in which there is no dissolved
oxygen in the water and in which neither other plants nor fish
It's truly amazing, distressing and alarming just how devastating
a delicate-looking and exceptionally beautiful pond and aquarium
favourite can be.