A Chronic Epidemic
Water Hyacinth is gaining ground in Lake Victoria, and gaining it quickly. It forms thick mats on the surfaces of water. In doing so, it prevents light from entering the water, causing the death of indigenous plants and marine animals. Over the past few decades, scientists and researchers have set out to discover the characteristics of this invasive specie in order to address possible solutions to this growing problem. In doing so, water hyacinth has gained public awareness and press.
In Wilson et al. (2007) and Williams et al. (2007), a thorough debate took place in which supporting arguments were used to provide insight to the problem and potential solutions. In Wilson et al. (2007), biological control in the form of Neochetina eichhorniae is argued to be the best attempt to control the growing specie. Wilson argues that while the water hyacinth population grew after the El Niño season ended, this could actually be a result of the El Niño weather. It explains that waves and wind could carry the plant across bodies of water, and thereby actually help spread this invasive specie. It concludes that the only substantial evidence of maintaining and controlling the water hyacinth is through the continued presence of the weevil.
Williams et al. (2007) counters these claims in the belief that exclusively using biological control is not sufficient to manage this epidemic. Although the author agrees that “the introduction of weevils into Lake Victoria has had an impact on water hyacinth population” (Williams), he further attributes the sharp decline of this invasive species due to the prolonged wet and cloudy weather of 1997. During this time, the El Niño weather produced harsh conditions for plants to live in. The NASA Earth Observatory (2007) confirms this statement by stating that extremely heavy rainfalls would affect the use of biological control. During 1998, floods would cause plants to sink, taking with them weevil eggs, larvae and pupae. (Williams et al. 2007). As a result of the low light level from cloud coverage, which slowly reduces growth and reproduction rates, and the disruptive waves, water quality, humidity, and temperature brought on by this storm, water hyacinth had an accelerated decline in Lake Victoria at this time.
As discussed in Wilson and Williams, a heavy debate exists regarding the power and effectiveness of biological control in Lake Victoria. While Wilson argues that the decrease in water hyacinth can be attributed to biological control alone, Williams counters with other convincing evidence. After finding a solid correlation between rainfall, cloud coverage, and the presence of water hyacinth, Williams concludes that the steady decrease in this plant mass is caused by both the conditions produced by El Niño and the introduction of weevils. According to the evidence in these two literary journals, I am inclined to believe that the loss of water hyacinth can be credited to both the El Niño season and the presence of the Neochetina weevil. With compelling graphs and credible evidence, as well as strong counterarguments, Williams et al.’s solidifies the viewpoint that multiple measurements are needed to manage and control this chronic epidemic.
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 20 Jan 2010.
Williams, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline across Lake Victoria – Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87: 94-96.
Wilson, J. R. U., O. Ajuonu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenschwander, S. W. Njoka, J. Ogwang, R. H. Reeder, and T. Van. 2007. The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp. Aquatic Botany 87: 90-93.