By Daniel Sikazwe –
The day was clear. The weather was good for fishing. The Kafue River was calm – like the speech of silence; so when a hippo struck, killing a fisherman whose day had started with a great promise, the death was unacceptable.
It was unacceptable because there was no sign. The large flowery plants whose leaves lay sprawled over the Kafue River did not show any sign of anxiety. There, in their serenity and beauty lurked the pangs of death.
‘A cousin of mine was caught by a crocodile that had been hiding under the water Hyacinth. His body has never been seen or retrieved’, narrated John Chilapa, a fisherman in Kafue.
What happened on that day on the Kafue River was the result of an old problem that community members had either tolerated or had not been aware of for many years.
‘We first saw the Water Hyacinth around 1990. They looked so beautiful and so we would even come to the river to pick some of the weeds to plant around our homes. We would throw some around the Kafue. We did not know that they would cause us problems,” said Chilapa.
The water hyacinth, more commonly known as the Kafue weed or Amajaveni by people in Kafue, is one of the thousands of living plants and other organisms called invasive alien species.
‘The water hyacinth covers and clogs our river so that we cannot see the water ahead and where we are going. The problem with this water Hyacinth is that underneath its roots there are a lot of dangerous things that hide there. Crocodiles and Hippos find cover beneath the weeds. We have had very dangerous attacks on fishermen by hippos and crocodiles’,  Chilapa added.
Invasive alien species are a variety of once upon a time foreign plants or animals, pathogens (organisms that cause disease), or other organisms that have been introduced either intentionally or accidentally through trade, transport, tourism and travel.
The Centre for Agro Biosciences International, (CABI), notes that invasive alien species are estimated to cause destruction worth 1.4 trillion dollars per annum, worldwide
In the extreme of cases, invasive alien species have led to conflicts that have not been seen since the centuries of great migrations in Africa.
CABI International Representative for Southern Africa, Dr Noah Phiri has noted that in Kenya, invasive alien species have already spurred some conflicts.
‘Invasive alien species are indeed becoming an issue of national security. As natural resources like water and land are eroded, there will be conflicts as a result of shortages of grazing land but the highest threat to political stability is food insecurity.
When people go hungry we see a dramatic increase in political conflict. The recent land invasions in Kenya were driven by pastoralists in search of grazing land and water, Dr Phiri said.
In the developing world estimates indicate that invasive alien species have led to a drop in crop yields by more than 25 per cent while in some adversely affected areas like Ethiopia where the invasive alien weed Parthenium has taken over thousands of hectares, crop yield losses of above 75 per cent have been reported.
In Kafue, gardeners who grow their crops in the fertile soils near the banks of the Kafue River are already feeling the impact of the water hyacinth.
Atanalasi Mwiinga, a  gardener in the riparian Kafue District has had his income from the gardening business reduced because of the water hyacinth.
‘We have got a problem because they (weeds) have covered all the areas where we draw water to supply our vegetables. These weeds are very strong. We have tried to remove them with Pangas, but we cannot remove them’, he said.
A study in South Africa revealed that invasive alien plants alone gobble more than 3 thousand million cubic litres – about 10 per cent of available underground water.
Invasive alien species have the power to hit the lifeline of a community or country.
In one of Zambia’s most beautiful national parks, Lochnivar, which is located just over 2 hundred kilometres south of Lusaka, an invasive species called Mimosa Pigra has taken over more than 3 thousand hectares of pasture rangelands.
‘We are losing out a lot on the value of our national parks because of invasive alien species. For example, Mimosa Pigra is taking up the most important habitat of the Kafue Lechwe, thereby chasing away this semi-aquatic animal which is native to our country that tourists want to come and see,’ bemoaned Sakabilo Kalembwe, the spokesperson of the Department of Wildlife and National Parks.
The Zambezi River, an invaluable source of water for development is also threatened by invasive weeds as attested by Florence Nawa of the Zambezi River Authority.
‘We are worried about the weed proliferation in terms of it clogging the water intakes for Zesco (the Zambian Power Company) and ZESA (the Zimbabwean power company).We try to make sure that we give them clean water and that water should not be polluted and should not even have the proliferation of the water hyacinth because it will clog their intakes so we try by all means to make sure that we remove the water hyacinth before it reaches the intakes,” she said.
How invasive alien species arrive in a community or environment is a scientifically well-studied issue but often times community members are either unaware or too tolerant of their presence. Such is the story of the water hyacinth as told by Atanasi Mwiinga, a local gardener in Kafue.
‘The problem in Kafue River started in 1996. The rain was very heavy. There were (some) white people who had dams where they had been growing the Kafue weed (as ornamental plants). Because the rains were very heavy that year, all the dams broke down. All the weeds were swept into the Kafue River,” Mwiinga recalled.
When invasive alien species are introduced into environments to which they do not naturally belong, they are able to become so well established as to transform and dominate the environment and species’ relationships and conditions of their adoptive homes.
The new species, do not necessarily hit the ground running when introduced into a new environment. They have what is called a lag period – a time in which they settle into the new place. This time may be a few years or even decades.
Chilapa, a Kafue fisherman remembers how long it had taken before the people of Kafue began to notice the weed spreading on the river.
‘It took about 5 years before we saw the weeds start growing and springing up wildly on the river. When this happened, the growth was unprecedented. The river got terribly infested and disturbed. They were so wild that at one time they even covered and closed up a bridge on the river. At that time we thought we could get rid of them by simply cutting them off. We were wrong!’
Invasive alien species remain in our water bodies and other habitats at great cost to agriculture, forestry, fisheries, and transport industry.
Samuel Kapesa, a boat driver with one of Kafue’s tourism companies recounts his experience of the destruction caused by the water hyacinth.
‘There was a boat recently that was raked by the weeds around an island near the Kafue River Cliff. The weeds had blocked a large part of the waterway. They wrapped around the propeller. The boat driver struggled to remove the weeds from the propeller. In the process of doing so, the seals of the boat got affected. Water started getting into the engine,’ Kapesa said.
Kapesa recounts an experience of the destruction caused by the water hyacinth to boats.
Managing invasive alien species
One way to control the introduction and spread of invasive alien species is through stringent monitoring of water bodies and other natural habitats using modern technology of land monitoring, Drones can be used.
This is according to Dr Faustin Banda, head of the department of Geomatic engineering, school of engineering, University of Zambia.
‘Geomatic engineering would be useful in the removal of weeds like the water hyacinth using what we call supervised classification, we can identify and classify the weeds we see, Dr Banda stated.
the Zambezi River Authority has been managing the Kariba weed through constant monitoring of biological activities around problematic areas like Saliate, Gacegace and Nyaoze.
‘In the monitoring proper we go there to see the spread and we take pictures. We also undertake biological monitoring of invasives activity. Some time back, Zambezi River Authority introduced some weevils that would help to remove the Water Hyacinth by eating it’, Nawa said.
Internationally there are a number of conventions designed to fight invasive alien species across borders. Rodwell Chandipo, an inspector at the Zambia Environmental Management Authority in a radio interview with this writer particularly noted the Convention on Biological Diversity.
‘It states clearly that every country is called upon to manage invasive alien species that are within their territories’, Chandipo said. He said this in the wake of a response to invasive alien species in the mid-2000S to manage Lantana Camara around the Victoria Falls and Mos-oa-tunya National Park in Livingstone and Mimosa Pigra in Lochnivar National Park in Monze.