Scholars debate the main factor of the significant decrease of water hyacinth on Lake Victoria around 1999-2000 in Wilson et al. (2007) and Williams et al. (2007). First, Wilson et al. (2007) replies to a previously published article by Williams et al. (2005) which claims that although weevils played a role in the eventual decrease of water hyacinth on Lake Victoria, the invasive species’ population was ultimately and predominately the result of the 1997/1998 El Nino. Williams et al. (2005) cites the condition of “low light availability” from El Nino and its subsequent effect on water hyacinth’s growth as the main contributor to the weed’s destruction.
Wilson et al. (2007) counters the referenced article by stating first, Neochetina bruchi and Neochetina eichhorniae (collectively Neochetina spp.) were the primary destructive agents to water hyacinth; second, El Nino caused waves and strong currents on Lake Victoria which dispersed its water hyacinth and made the weed easier to destroy by weevils; and third, water hyacinth will not reemerge in Lake Victoria unless its Neochetina spp. populations are disturbed. The authors reevaluated the light conditions around the time of El Nino, but found that by mid-1998, water hyacinth was already rebounding on Lake Victoria. Wilson et al. (2007) acknowledged that weevils took nearly four years to take effect against the invasive species in 1999 (weevils were released into the lake in 1994), but this timetable was expected and is congruent with weevil versus water hyacinth time frames from other countries with similar climates.
Lastly, in Williams et al. (2007)’s rebuttal to Wilson et al. (2007), the authors restate their aforementioned claim that weevils contributed to the reduction of water hyacinth around 1999-2000, but the invasive species would certainly still be growing strong in the absence of the 1997/1998 El Nino. Williams et al. (2007) believe Wilson et al (2007)’s arguments are oversimplified and thus erroneous because Lake Victoria is simply too vast to be considered on an individual graph of experimental results. Williams et al. (2007) maintains the diminution of water hyacinth was a result of El Nino’s flooding because it transpired “synchronously…during the second quarter of 1998”. The authors claim the hyacinth’s first reduction occurred because the floodwaters dislodged the mats that held the weed to the lake floor, and the hyacinth simply washed away into the lake. While Wilson et al. (2007) stated that Williams et al. (2005) believed low light levels caused the reduction, Williams et al. (2007) stressed that the plant mortality was due to prolonged low light, not intermittent glares, which then caused minimal growth in the plants and weak mats.
Ultimately, I believe Wilson et al. (2007) had the soundest argument, which claimed that weevils played the most significant role in reducing the population of water hyacinth on Lake Victoria. While both articles acknowledged the “lesser” cause (whether it was weevils or the effects of El Nino), I felt that Williams et al. (2007) was especially narrow-minded and barely accredited weevils as a destructive force to weevils, when they were clearly a great contributor to the hyacinth’s periodical demise. However, the fact that the water hyacinth continues to make reappearances on Lake Victoria suggests tha solely biocontrol as a method of eradication is insufficient and ultimately non-cost effective. There needs to be a more radical and long-lasting approach to ridding Lake Victoria from the ruthless water hyacinth.
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 10 Sept 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.
Water Hyacinth
The water hyacinth has been the subject of both much concern and debate over the past years. It’s dramatic takeover of Lake Victoria in Uganda has sparked a heated discussion on why the invader suddenly receded, though it later came back. The opposing views were in expressed in Wilson et al, arguing that weevils should be given the most credit for the reduction of the water hyacinth, whereas Williams et. al presented the argument that El Niño should be given the credit.
The Wilson et al. paper presents a strong argument, saying that the weevils introduction to Lake Victoria was the main reason for the water hyacinth’s decline. Though they acknowledge that El Niño may have had a slight effect on the water hyacinth population, the light levels that got through the cloudy weather as a result of the altered climate pattern would’ve been enough to keep the water hyacinth population alive and growing, so the answer to the question of why the water hyacinth declined muse lie in the biocontrol, or the weevils. Williams et al. presents essentially the opposite argument, saying that El Niño’s cloud pattern would’ve blocked out light for the water hyacinth, therefore making it hard from them to photosynthesize and expand throughout the lake. To back their argument, they cited that this wet and cloudy weather had a detrimental effect upon vegetation throughout other parts of Africa as well, and that the weevils may had a helping hand in the decline, but were in the end, of nominal effect in the larger scheme of things.
I think that Wilson et al.’s argument in favor of the biocontrol makes the most sense, given the dramatic reduction of water hyacinth population after the introduction of the weevils, and the sustained decline even after the passing of El Niño. Though the light levels made have adversely effected the population of the water hyacinth, the light levels despite the cloudy weather wouldn’t have stopped their growth and caused the population reduction. Though, as MODIS images revealed, the water hyacinth has returned, it just reminds us that when using biocontrol, that constant monitoring is required, and problems with invasive species will be something that our society will have to learn to cope with for many years to come.
References:
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 13 Sept 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.
Photo from here.
Ever since first being recorded in 1989, the water hyacinth plant has plagued Lake Victoria in Africa. The plant is causing substantial problems for the local ecosystems, such as reducing fishing levels, threatening biodiversity and tampering with the many transport routes across the lake. Because of these issues, measures to try to reduce the hyacinth’s population have been taken, but much controversy exists questioning whether man or nature removed the vast majority of the plant from the lake. Much of the debate spawned from two conflicting research articles, which attempted to clarify whether the seasonal El Niño storm had destroyed the hyacinth or if the introduction of hyacinth-eating weevils caused the plant’s demise.
Wilson et al. first proposed that through biological control the hyacinth populations started decreasing. In their article, they express that the introduction of Neochetina (weevils) was the primary factor in the limitation of the hyacinth. The article does acknowledge the presence of the 1998 El Niño weather pattern however, and does recognize that the increase in waves and water levels played a role (albeit small) in controlling the hyacinth. And although they also do say high cloud levels could also have decreased hyacinth levels, Wilson stands firm that El Niño only propagated the effects of the weevils.
On the other hand, Williams et al. claimed the weevils assisted El Niño. This article believes that if El Niño had not occurred, the weevils never would have controlled hyacinth levels. Williams affirms that while biocontrol through weevils “is an integral part of the future management of Lake Victoria”, lake wide reduction in hyacinth populations resulted from El Niño. Williams also supports this claim with more in-depth studies of the factors mentioned above (cloud level, wave, and water lever) to prove that El Niño nearly wiped out the hyacinth.
While in hindsight we do know that Williams et al. hypothesized correctly (once El Niño subsided hyacinth populations increased once again), I do have to say that Williams did provide a more convincing argument from the start. Williams provided and researched numerous points that Wilson seemed to look at from the wrong angle, such as water levels and waves. Although both researchers do claim that one would not have been as effective without the other, Williams is successful in convincing me that El Niño played a larger, more important role the reduction of hyacinth levels in the late 90s.
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.
Biocontrol, defined as the introduction of predatory species in areas where invasive species have proliferated, is a burgeoning method for managing invasive species. The predator introduced is expected to control the invasive population and to decline in numbers relative to the invasive. Lake Victoria in Uganda has become home to the water hyacinth, a pervasive species that covers the shoreline and prevents fishermen’s ease of movement. Biocontrol in the form of the weevil was implemented in 1995, and water hyacinth decline was apparent in 1999.
However, the occurrence of an El Nino in 1997-1998 clouded the explanation for water hyacinth decline. An El Nino event consists of weather pattern fluctuations usually resulting in an increase in natural phenomena like storms, and enacting global water-level changes.
Several scientific articles strove to explain water hyacinth population decline, namely Wilson et al. (2007) and Williams et al. (2007). Wilson contrives to explain the decline based on biocontrol, stating that weevils brought to Lake Victoria were effective. Wilson asserts that water hyacinth populations did decrease in early 1998 during El Nino, but then rose again in late 1998, not nosediving again until 1999. Based off this time inconsistency, Wilson hypotheses that observed patterns of weevil control in other countries match this four-year gap between introduction and results (i.e.: water hyacinth declining).
Contrarily, Williams et al. (2007) states that biocontrol alone is not responsible for the water hyacinth reduction. Rather, the El Nino event in 1997-8 caused such flooding of tributaries into Lake Victoria as to upset the hyacinth and carry mats of it free from lakeside resting places. Williams states that while weevils impacted the decline, El Nino accelerated it—however future regulation should maintain weevil populations against the return of water hyacinth. Interestingly, both articles referenced the same data to support their different points, revealing the diversity in scientific evaluations that exists.
In lei of recent increases by water hyacinth in Lake Victoria (NASA Earth Observatory 2007) following the publication of the above referenced articles, biocontrol doesn’t seem like a viable long-term restraint for water hyacinth. Personally, I think that the revitalization of water hyacinth by 2006 (NASA Earth Observatory 2007) is proof that El Nino was likely a larger component to the 1999 reduction than weevils were, as Williams hypothesizes. Broadly though, biocontrol necessitates a case-by-case determination and cannot be used to obtain the same results in each instance.
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.
In 1989, the invasive species known as water hyacinth was first reported on Lake Victoria. In 1998, an outbreak of the plant covered as much as 17,231 hectares (NASA Earth Observatory, 2007) of the lake. Weevils, insects that eat the plant, were introduced into the lake in 1995 (Williams et al., 2007) and by 2000, an almost complete eradication of water hyacinth was observed in Lake Victoria (NASA Earth Observatory, 2007). Scientists are debating over the cause of the decreasing population of the water hyacinth. The question is: Was the decrease in water hyacinth on Lake Victoria caused by the introduction of weevils or a weather phenomenon El Niño?
Wilson et al. (2007) argues that the decline in water hyacinth on Lake Victoria was due to biological control by Neochetina weevils. They cite how the reduction of water hyacinth occurred four years after the introduction of the weevils, and how this time frame has also been observed in other parts of the world where weevils have been introduced to reduce water hyacinth populations. Wilson et al. (2007) shows that only a few years after the initial introduction of the Neochetina weevils the water hyacinth populations crashed.
Contrastingly, Williams et al. (2007) contributes the majority of the water hyacinth decrease to the natural weather phenomenon El Niño. Williams et al. (2007) claim that the low light conditions caused by El Niño “will reduce growth and reproduction rates and relatively increase the effect of other debilitating influences such as other weather related factors, e.g. water level, wave action, water quality, temperature and humidity as well as weevil herbivory and phytopathogenic attack”.
The low populations of water hyacinth Lake Victoria did not last. By December of 2007 the water hyacinth was back in the lake (NASA Earth Observatory, 2007). NASA determined this using a satellite Moderate Resolution Imaging Spectroradiometer (MODIS). NASA contributes the rise in water hyacinth populations to “unusually heavy rains that flooded the rivers … and swept agricultural run-off and nutrient rich sediment into the water”. This new data may mean that the biocontrol in Lake Victoria was ineffective.
I believe that the Neochetina weevils undoubtedly contributed to the initial drop in the water hyacinth (Wilson et al., 2007), however, Wilson et al. (2007) presented a more convincing argument that the majority of the decline in water hyacinth was caused by El Niño. This is apparent when looking at the graphs presented in Wilson et al. (2007), they clearly show that there is a more direct connection to the decline in water hyacinth with El Niño than there is with the introduction of weevils. The problem of water hyacinth needs to be solved and hopefully scientists can find affective methods to keep the growth of the plant controled.
References:
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 12 Sept 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.
Revised SW3:
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.
Reference:
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.
Conflicting Opinions on Water Hyacinth Invasion Control in Lake Victoria
In 1879 Water Hyacinth was introduced to Lake Victoria NASA Earth Observatory (2007). This invasive species took root over the next one hundred years and wreaked havoc by blocking oxygen to native species, impeding fishing boats and spreading disease. To control the Water Hyacinth, biocontrol in the form of the Neochitina weevil was implemented. An El Nino that occurred between 1997 and 1998 also played a role in Water Hyacinth reduction Wilson et. al. (2007). In 2007 two scholarly papers were published that offer differing opinions on the Water Hyacinth control issue.
The first paper, entitled “The Decline of Water Hyacinth on Lake Victoria Was Due to Biological Control” argues that Neochitina weevils were the primary reason for reduced Water Hyacinth levels between 1998 and 2007. Wilson et. al. (2007) report that weevils were reducing Water Hyacinth at a steady rate and they believe that the El Nino confused data on the Water Hyacinth issue. During the storm matts of Water Hyacinth broke loose and drifted to other areas of the lake, and El Nino kicked up sediment with Water Hyacinth seeds in it that started new Water Hyacinth growth, which lead to unusual data. Despite the uneven Water Hyacinth growth following the storm, Wilson et. al. (2007) believe that the Water Hyacinth will continue to be controlled by the weevils.
The second paper, “Water Hyacinth Decline Across Lake Victoria- Was it Caused by Climatic Perturbation or Biological Control? A Reply” is a response to the findings of Wilson et. al. (2007). Williams et. al. (2007) are concerned that a resurgence of Water Hyacinth may occur. They believe that lack of light and harsh weather conditions during El Nino reduced the growth rate and health of the Water Hyacinth. Williams et. al. (2007) therefore believe that El Nino, and not just the weevils, is responsible for the recent reductions in Water Hyacinth growth. Williams et. al. (2007) also believe that when Water Hyacinth levels are reduced they will have a negative impact on weevil health thus leading to a long term resurgence in Water Hyacinth growth.
Recently data from NASA Earth Observatory (2007) has shown that Water Hyacinth growth has increased. NASA Earth Observatory (2007) believe that stormy weather in December of 2006 caused increased water levels and released nutrient rich sediment into Lake Victoria. I believe that Water Hyacinth is going to be an ongoing problem in Lake Victoria and while both storms and biocontrol have reduced its growth, the most important thing is to keep monitoring Water Hyacinth growth and researching other methods that can reduce it’s growth. The recent resurgence shows that El Nino did have a role in reducing the Water Hyacinth growth, so it will be difficult to control the Water Hyacinth in the future with weevils alone.
References:
NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria. http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 12 Sept 2010.
William, A. E., R. E. Hecky, and H. C. Duthie. 2007. Water hyacinth decline accross Lake Victoria- Was it caused by climatic perturbation or biological control? A reply. Aquatic Botany 87:94096.
Wilson, J. R. U., O. Ajounu, T. D. Center, M. P. Hill, M. H. Julien, F. F. Katagira, P. Neuenshwander, S. E. 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.
In Lake Victoria, an invasive species is covering the water’s surface with green mats and blocking plants underneath it from direct sunlight, causing their death and many other related problems such as decrease in water quality and spread of waterborne disease. This species, the water hyacinth, has been a great puzzle for scientists. The original method of biological control, weevils (or Neochetina spp.), were introduced to reduce the water hyacinth population in 1995. A sharp decline of water hyacinth in 1998 and 1999 and again in 2000 is attributed to the weevils’ destruction by Wilson et al. (2007). However, according to a rebuttal article from Williams et al. (2007), the weather patterns brought by El Niño in 1997 and 1998 were mostly responsible for the water hyacinth’s decline.
According to Wilson et al. (2007), it is apparent that weevils caused the decline of the water hyacinth population because after their introduction, they normally take about three to four years to act, consistent with their introduction in 1995 and the decline in 1998 and 1999. They also claim that the resurgence shown on their graph of Lake Victoria hyacinth levels in 2000 occurred simultaneously with a low weevil population.
In contrast, Williams et al. (2007) argue against the claims made in Wilson et al. (2007). An interesting fact cited by Williams et al. states that El Niño caused a 1.70 meter rise in Lake Victoria’s water levels, which led to stable shoreline stands of water hyacinth washing into the lake. This compelling evidence, as well as individualized graphs for each region of the lake and explanations of how low light levels from El Niño’s stormy effects combined with other factors, including biological control using weevils, reduced water hyacinth populations, solidify Williams et al.’s conclusions.
Considering MODIS satellite images from 2005 and 2006, the re-invasion of water hyacinth adds another piece to the puzzle. The NASA Earth Observatory (2007) states that the reappearance of the invasive species coincided with extremely heavy rains. Reexamining Wilson and Williams’ claims, it is clear that Williams et al.’s (2007) worries about stormy El Niño and cloud cover are relevant in this situation as well. In my opinion, this correlation of information between two sources in two different time frames shines in favor of Williams’ argument. Also, Williams et al. (2007) use more area-specific graphs which seem to more accurately depict the water hyacinth problem. I agree with Wilson et al. (2007) that biological control is essential in controlling the water hyacinth invasion, but Williams et al. (2007) present more convincing data. Hopefully, we will be able to find the ideal balance and solution to maintain control in Lake Victoria.
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.
In the 1980s a new invasive species, known as the water hyacinth, was introduced to Lake Victoria. This exotic plant was able to successfully plant its roots in its new home and thus the population of water hyacinth sky rocketed. In order to combat this alien vegetation, the weevil, which feeds on the hyacinth, was introduced into the area.
By 1998 a significant decrease in the hyacinth population was observed. Based on this information one could easily conclude that the weevils seemed to be responsible for the eradication of the water hyacinth. That is the opinion of John R.U Wilson et al. (2007), who in his scientific article, published in the journal Aquatic Botany, expressed his firm belief that the weevil was the main factor contributing to the decline of the hyacinth. However, for Adrian E. Williams, this conclusion was not as cut in stone as it appeared to be. In Williams’ et al. (2007) article published in the journal, Aquatic Botany, he attributes the rapid decline of the hyacinth population in 1998 to the presence of an El Niño (a climate pattern exhibiting high pressure, warmer temperatures, and extreme weather.) Both Williams and Wilson illustrate their opinions through their analysis of a variety of experiments and collections of data however, Williams et al (2007) thoroughly considers Wilson’s data and draws significant attention to the population spikes that happened in the exact years of the El Niño event. In doing so, Williams et al(2007) presents a strong case for the impact of the El Niño that Wilson can do little to disparage.
In more recent years, an article titled “Water Hyacinth Reinvades Lake Victoria” was released by NASA which illustrated the reemergence of this invasive plant into the area despite the efforts of the weevil. This article seems to give more support to the argument made by Williams as well as indicating the possible need to find alternative methods of eradicating the water hyacinth from Lake Victoria.
While no answer currently exists to this debate, I believe that Williams does a better job of analyzing the spikes in both the growth and decline of the hyacinth population and illustrating their significance in correlation with the El Niño event that occurred in 1998. He explains that while the weevil has been successful at halting the exponential growth of the hyacinth, the extremely wet and cloudy conditions brought by the El Niño definitely had a colossal impact.
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.
Revision Strategy
In order to revise my SW3 post, I decided to utilize each of the three suggestions that I was given in the comment section of my blog. I agree with Cole who stated that I should switch around the order of my third and fourth paragraphs. Doing so seems to make the arguments presented in my paper connect in a more logical manner. I also tried to add in a few more details supporting why I believe Williams et al(2007) presented the stronger argument while also trying to stay within my word limit.