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Tanzania, Uganda and Kenya Suffer as
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 growing season.  


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 disastrous ramifications.

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
Salvinia auriculata.

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 survival." 

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 can survive.

It's truly amazing, distressing and alarming just how devastating a delicate-looking and exceptionally beautiful pond and aquarium favourite can be.

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