The Mwarobaini Scenario: Water Hyacinth on Lake Victoria Defies Popular Response

Published on 22nd January 2019

The Semblance of Plenty in a System of Neglect

Mwarobaini (Kiswahili for Neem tree) is well-known in East Africa not only for its conspicuous lush leaves, but more importantly for its medicinal value. It is believed that its leaves can cure an estimated forty types of diseases, hence its Kiswahili name “Mwarobaini” meaning forty.  While the Mwarobaini’s leaves are celebrated, little or no notice is taken about its roots - the critical life-support system for the whole plant, and stem.

In this analogy, the roots represent the system that should guide governance to achieve the desired operational integrity of human activities, processes, and assets. The stem represents the comparative advantages resident in rich resources which, if managed properly, can provide channels and linkages for meaningful development. The promise of a demographic dividend and labour abundance qualify as key examples. The leaves are the desired high-quality outcomes the public and politicians easily talk loud and highly about all the time.

The Swapped Priorities

The “Mwarobaini Scenario” was invented out of a series of thought leaders’ fora spearheaded by the Inter Region Economic Network (IREN). The scenario is a figurative expression of the rich resource diversity in East Africa, whose potential to benefit the region disgracefully gets riddled in the mystery of false starts, disuse of knowledge, and swapped political priorities. We neglect the application of knowledge to decision-making and react using short-term, impatient and desperate measures. 

The stubborn water hyacinth infestation in Lake Victoria and the interventions being fronted warn us to learn the culture of integrated and preventive, or better still, predictive management based on long-term and strategically well-thought-out plans. Decision makers must facilitate effective and sustainable ways of unlearning, relearning, upskilling, and reskilling when facing such odds. There is no shortage in the region of cases demanding inclusive decision-making with meaningful multi-stakeholder involvement and active engagement of the rising youth population.

The Water Hyacinth Menace

The Sound Premise

The water hyacinth thrives well in tropical climates. It has since the late 19th century been an invasive nuisance in many countries away from its native Brazilian Amazon, where it is kept under control by its natural host-specific enemies in the ecosystem. In East Africa, the temperature range it enjoys of 120C – 350C and the absence of natural enemies enhance its survival.

The fact that scientists have discovered two weevil species which keep the weed in check, given well-coordinated mass rearing and release is a pointer that we must learn from nature - the ultimate engineering masterpiece - to understand the root causes of problems in the environment and how to deal with them effectively. Biological problems require biological and ecosystem-wide insights for effective redress. This applies to the stubborn menace of water hyacinth on Lake Victoria.

The Starting Party

On January the 18th 2019, the lakeside city of Kisumu saw the official launch of a dredging vessel and removal of water hyacinth (Eichhornia crassipes) from Lake Victoria. The African Union High Representative for Infrastructure graced the launch. While the dredging vessel from Uganda that is 70 metres long and weighs 4,000 tonnes scores high on might and majesty and inspires public hope that the final solution for eradicating the water hyacinth has arrived, the measured remarks made during the launch and ground evidence show that mechanical control measures against the fast-spreading weed cannot confidently claim any meaningful success story.

Kenya owes her experience in substantially reducing the weed over the 1998 – 2001 period to biological control. Reports from Tanzania delve into the effectiveness of integrated approaches focused on basin-wide management including controlling nutrient loading and hyacinth inflows into the lake from rivers, but still with biological control as the main strategy.

The Scientific Perspective

A Kenyan research based on the soundness of systems thinking and integrative synthesis and conducted over a decade ago at Karlsruhe Institute of Technology (KIT), Faculty of Civil Engineering, Geo- and Environmental Sciences observes that:

Mechanical control approaches are just an addition to the bag of fragmentary, reactive, and linear processes which cannot on their own eradicate the exponentially propagating weed – a non-linear phenomenon. A systems approach which considers all the competing processes leading to the propagation of the weed on the lake is essential to rethinking a long-term solution. - [2006 study by Adero, N.J. entitled “Integrating GIS with Dynamic Environmental Modelling in the Kenyan Basin of Lake Victoria”]

As a result, glorifying mechanical control is symptomatic of focusing on the tip of the iceberg. The linear mechanical approach is at best only complementary to biological control measures and framework changes for integrated basin-wide management informed by the bigger picture in the whole ecosystem.

The water hyacinth grows exponentially by both sexual and asexual means. It is able to double its biomass in about one week. Its seeds can take up to 15 years waiting for favourable conditions. The weed can get into the lake from rivers and other sources, which also supply nutrients. Being in the tropics, Lake Victoria doesn't enjoy the benefits of seasonal mixing of water layers and this makes nutrient loading more lethal. The need to address the root cause and the biological nature of this challenge summon systemic and long-term interventions.

The Successful Past

As experimented successfully before in Kisumu, Kenya, biological control weevils stress the plant by feeding on it and enabling opportunistic infections, preventing it from flowering and producing seeds. They kill the weed by destroying its leaves, roots, and stem in their larval stages. Biological control has a direct effect on the reproductive capacity of the weed as opposed to mechanical control methods that hardly destroy the seeds, and usually remove 8 – 10 acres per day. Chemical control is not advisable due to ecological and environmental risks.

Using satellite remote sensing for monitoring progress, the Kenyan biological control experience reduced water hyacinth coverage over the period 1998-2001. The following estimates are accessible from various publications: from 6,000 ha in 1998, 3,100 ha in 1999, 900 ha in 2000, to only about 400 ha in 2001.

Why has Kenya not sustained the successful biological control efforts realised earlier? The main point of convergence that published reports and conversations with experts and people on the ground arrive at is a weak governance framework which cannot ensure sustainability. This framework has failed to ensure effective stakeholder participation including community ownership and instituting strategic measures for long-term financial and operational capacity.

The Scenario of Possibilities

In summary, model parameters applied to yield the scenario simulations factored in the period in months, instantaneous coverage extent beginning from an initial area and the predator-prey relationship loop, which is not the case with the externally controlled linear mechanical processes. The inflow of the weed from river inlets (mainly River Kagera) had been observed by LVEMP (2005) to be 0.2 ha per day. The weed is also highly migratory under the influence of winds, a fact which complicates matters and invokes a systemic perspective to rethinking a winning control strategy.

Simulations from the model are instructive to reimagining an effective eradication policy. A clear decay pattern effectively caused by biological control can be seen, simulating the period 1998-2001 based on the derived formula. The hyacinth coverage reduces rapidly from 6,000 ha and levels out towards 200 ha after 48 months.

It is evident that only a low starting coverage of the weed (e.g. 20 ha) can be eradicated by mechanical removal alone. A high coverage (e.g. 12,000 ha in subsequent simulations) must employ a biological means as the main control strategy, with mechanical means only playing a supplementary role. For example, the model shows that mechanical removal at an impressive rate of 100 ha per month needs about 2 months to clear only 20 ha of water hyacinth, with slower reduction at the start due to the weed’s exponential growth. Simulated eradication of 12,000 ha of hyacinth takes 30 months using a combination of mechanical removal at 100 ha per month and biological control, if there is additional hyacinth inflow from rivers at the observed rate of 0.2 ha per day (Adero, 2006).

After showing the weakness of attack by mechanical means, the same model yields outputs in the table on the possibilities for a faster eradication of hyacinth by complementing biological control with mechanical removal. The assumed starting lake coverage is 12,000 ha of hyacinth. Inflow from rivers has a significant effect on completion rates. In any case, meaningful reduction is only realised after two years – but only if biological control is an essential part of the equation.

The Sound Preference

A systems-thinking approach justifies biological control as the effective long-term control strategy, especially under the prevailing high infestation levels. Biological control causes an exponential decay of the weed’s biomass, unlike the linear mechanical processes. Mechanical control should be viewed as a complement to biological control, helping to achieve eradication results faster (if socio-economic reasons justify the higher expenses of mechanical control). Beyond these measures is the crucial basin-wide management approach with ecological sensitivity and a culture of environmental responsibility integrated into processes and people’s behaviour.

With sound transboundary policy and budgetary support, biological control can offer vast opportunities to the rising number of graduates of biological and environmental sciences as well as the local community to ensure the mass rearing of the required host-specific weevils. Innovative ways of effectively removing the hardy seeds from the lake while utilising the plant biomass in various industrial processes require a strategic model of "circular economy" to achieve sustainable solutions.

Performance monitoring is key to progress evaluation. Advances in satellite remote sensing technologies, readily availing high resolutions to the metre level, are another huge opportunity for monitoring the progress of any eradication efforts.

By Nashon Adero

The author   nashon.adero@gmail.com   is a Lecturer at Taita Taveta University.


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