Water Hyacinth
Water hyacinth is a marine plant native to South America. Over the last few decades, however, it has infested Lake Victoria and made it hard for local fishermen to maintain their lifestyle. Large mats of water hyacinth have clogged waterways, reduced small local marine life, and blocked sunlight from reaching the lake bottom. Recently, there have been efforts to reduce the water hyacinth population, but whether they have been effective or not is another matter.
Williams et al. (2007) states that the waves caused by El Nino ungrounded water hyacinth plants and allowed for their destruction. Another proposed reason for the hyacinth’s disappearance is the fact that thick cloud cover due to the weather conditions blocked out sunlight, and led to decreased photosynthesis and fertility in established water hyacinth plants (Williams et al. 2007). In early 1998, the latter part of a particularly violent El Nino pattern, water hyacinth populations declined sharply.
Wilson et al. (2007), on the other hand, believes that the ultimate reason for the plant’s disappearance was the introduction of weevils as biocontrol – introducing one species to control another. Although the water hyacinth population did decline sharply in early 1998, plant populations steadied and rose again later that year. They didn’t begin to steadily decline until 1999, 4 years after the introduction of the weevils (Wilson et al. 2007), a typical time period as gathered from other weevil biocontrol situations. Wilson et. al (2007) suggests that El Nino harmed the weevil populations, and that the “new growth was able to proliferate in the absence of weevils”. Weevils were also introduced to other areas – West Africa and Papua New Guinea – and successfully reduced hyacinth populations where they were the only method of control being implemented (Wilson et al. 2007).
To me, it is clear that Wilson et al. (2007) presents a stronger argument. Although Williams et al. (2007) introduces many valid points, Wilson et al. (2007) presents its own evidence and nullifies several parts of Williams’ argument. Despite the fact that I believe Wilson’s argument holds more validity, both documents agree that both El Nino patterns and weevil influence helped decrease water hyacinth populations. As data shows, water hyacinth populations are rising again (NASA 2007). Instead of arguing over who’s more correct, I think the real issue here is to focus on the factors we can control (the weevils) while continuing to search for a more secure solution.
References:
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.