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.
In Uganda, the world’s second-largest lake, Lake Victoria, went through a period of takeover at the hands of the invasive water hyacinth. The beautiful lake provides for multitudes of different species, including man. So when a harmful blanket of shrubbery claimed its territory on top of the lake’s surface, results were devastating. This lead to the use of biocontrol to remove the water hyacinth from the water’s surface, which would allow light to reach into the lake’s depths and allow Ugandans to travel in peace. The solution to the hyacinth was the herbivorous weevil, and four years after the introduction of the controlled plant destroyer, the amount of the harmful water hyacinth had significantly declined. The ecosystem had been saved.
Although, one question arose from the invasive plant’s mysterious disappearance: who was the saviour? According to Wilson et al. (2007), the introduction of the weevil to the ecosystem saved Lake Victoria from the water hyacinth. On the other hand, Williams et al. (2007) claimed that the climatic event known as the El Nino led to the death of the water hyacinth. All in all, Williams et al. (2007) was far more convincing. The constantly changing levels of water hyacinth in 1998, along with the dramatic reduction of the invasive hyacinth from 1999 to 2000 (Williams et al. 2007), shows that the sudden decrease in hyacinth was timed around the El Nino event. After 4 years of weevil exposure and inconsistent levels of water hyacinth, the instantaneous disappearance of the plant cannot be accreditted to the so-called “solution.” It was only a matter of time that nature took its course and ended the terror caused by the water hyacinth of Lake Victoria.
Furthermore, sattelite images show that there was a re-emergence of water hyacinth even after the weevil had supposedly killed off the plant (NASA Earth Observatory 2007). This shows that the use of biocontrol is very unpredictable and may not always result in a permanent solution. The population of biocontrolled species may be very unstable according to the conditions of the ecosystem it is placed in. The weevil, more specifically, would have a hard time to survive in the absence of its major food source, the water hyacinth, so re-emergence is only a matter of time. Natural events such as the El Nino can postpone the effects of invasive species such as the water hyacinth. Nature has always been unpredictable, but we can prevent some harmful consequences to the ecosystems of Earth through practicing carefulness and awareness.
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.
Imagine this: it is a typical Thursday night and you find yourself trying to choose a movie to occupy your time. You are in the mood for a film that could both thrill and provoke thought. Sound familiar? Before you settle on the most recent blockbuster, consider a less conventional cinematic experience, one that offers excitement, stimulation, and raw truth. Although a documentary on invasive species was hardly what you had in mind, “Strange Days on Planet Earth” gives an experience well worth the time.
People generally do not become involved in a problem unless they are directly effected by its outcome. The film examines several areas of the world where the havoc invasive species have wreaked on the environment has directly effected humans. In New Orleans, an invasion of a termite has led to the destruction of the historic homes in the French Quarter. In Guam, children are being attacked by the foreign Brown Tree Snakes. Out of all the examples given, most alarming was the situation in Lake Victoria, Uganda, with water hyacinth. A beautiful and harmless looking plant has directly lead to countless crocodile bites and diseases inflicted on locals. The species had completely canopied the lake, clogging fishing lines and creating stagnant pools. Without the flow of water, diseases such as malaria, have begun to spread more quickly. They have also created waters ideal for crocodiles. As the crocodile population sky rockets, the fish population stays the same. With the lack of food, the crocodiles seek human flesh to satisfy their palate. By bringing light to how invasive species directly effect humanity, the movie uncovers a moral underside the issue. Many scientists may argue that the death of native species is in itself a moral issue, and should have been more heavily focused on in the film. In reality, the percent of the population who are emotionally moved into action over a lost species of plant is very minimal. By focusing on how invasive species pose a threat to humans and not just native species, the film-makers inspire viewers into action; a feat that would otherwise be very difficult to accomplish.
Some may criticize the film for over-dramatizing the problem of invasive species in order to draw viewers. In many ways, this can be distracting to viewers seeking the model unimaginative documentary. However, for the rest of America, the exhilarating methods National Graphic employs are exactly what scientists in the field of preventing the spread of invasive species need. The hype caused by the film will cause a domino effect of awareness. People may find themselves checking their shoes for New Zealand mud snails or avoiding planting foreign species to avoid their spread. While the documentary offers enjoyment over merit, perhaps hype is exactly what is necessary for this issue. So next time you find yourself in the position of not knowing which movie to watch, “Strange Days on Planet Earth” should be the obvious choice: for entertainment that will also inspire action.
The film, “Strange Days on Planet Earth” is an informative documentary about invasive species and the havoc they bring to vulnerable ecosystems. One foreign invader described in the movie was the subterranean termite, which was introduced to the U.S. through crates shipped from Japan after World War II. This insect demolished U.S. cities in the South, especially in places where most buildings consist of mostly wood. The video implements a variety of special effects along with witness accounts of the devastation caused by the invasive species. This not only conveys the extent of this issue to the audience, but also create an emotional appeal as the viewer empathizes with the victims of the termites’ rampage. All of these factors come together to effectively present a case against Subterranean Termites that envokes a desire to take action against the rising invasion.
After detailing the consequences of the subterranean termites’ attacks, the film gives an account of a very unsuccessful attempt at using biocontrol to offset the problem of rapidly spreading species in the Pacific. To deal with an overabundance of rats on the island, monitor lizards were introduced. Unfortunately, the nocturnal rats further thrived in the new presence of the diurnal lizards, although other species suffered from the “controlled invasion.” This showed how sensitive ecosystems are to biocontrol, and the results of the process can be very unpredictable and possibly hazardous to the organisms of a given habitat.
On the other hand, “Strange Days on Planet Earth” depicted one example in Uganda’s Lake Victoria where an invasive weevil was introduced to combat another invasive species known as water hyacinth. The plant blocked sunlight from reaching under the surface of the lake, so entire ecosystems suffered as the world’s second largest freshwater lake was under attack. Human populations near Lake Victoria suffered from increased animal attacks, disease, lack of transportation, and other factors derived from the presence of the hyacinth. Due to careful research and a little desperation, an invasive weevil was introduced to the lake. Five years later, the presence of the suffocating water hyacinth was significantly decreased and the ecosystem had returned to its former state of beauty and importance.
Overall, the film effectively captured the attention of the audience through stunning visual effects and incredible accounts while still presenting facts that depict the growing presence of invasive species all over the world. Many documentaries detail precise and accurate info, but often times that info is viewed as boring or uninteresting by, generally, the younger generation. The flexibility and accessability of “Strange Days on Planet Earth” make it an intense, inspiring film about a problem that exists all around us, whether we realize it or not. By giving adequate info and helping viewers realize the importance of invasive species prevention, the film truly presses the true meaning behind the central questions in the film: “ What would it cost us to be more careful with invasive species? What would it cost us not to?”
Sometime before 1989, the water hyacinth, a native to South America, was introduced to Lake Victoria, Uganda. It only took another seven years before the aquatic plant covered eighty percent of the lake. This massive cover created extreme problems for native fishers and inhabitants of the region. The water hyacinth made it nearly impossible for fishermen to navigate the lake, essentially making fishing impossible. The lake, a source of water for the surrounding are, fell victim to rotting vegetation which effectively contaminated the water. As a result of such sub-par water conditions, Lake Victoria became a large breeding ground for variety of diseases such as malaria and schistosomiasis. Schistosomiasis is a disease that is carried by a parasite that lives in the water snails of the lake.
The main reason that the water hyacinth was so successful at Lake Victoria was due to lack of a natural predator. In South America, the aquatic plant was kept in check by the South American weevil. The weevil attacks the water hyacinth in numerous ways. The adults feed on the leaves of the plant by eating holes in them. As a result the plant takes in less sunlight and begins to sink and die off. The larvae of the weevil live near the roots of the water hyacinth and feed on the plant for nourishment. When the larvae become adults, they swim to the top and join the others on the feasting of their natural enemy.
In the video, Strange Days on Planet Earth: Invaders, James A. Ogwang a Ugandan biological control entomologist took the primary responsibility of disrupting the takeover of Lake Victoria by the water hyacinth. Ogwang decided to import the weevil in hopes that it could quell the takeover of Lake Victoria. After testing the weevil on a few plant species native to Lake Victoria, Ogwang put his plan to work. After about five years, the amount of water hyacinth in Lake Victoria had been greatly reduced. Although this example of biocontrol was successful, this situation is one of its kind.
Some concerns about the use of the South American weevil to manage the water hyacinth are whether or not this relationship can be sustained in an environment different from their homeland, will the weevil only feed on the water hyacinth or will it eventually attack native species to Lake Victoria, and can the water hyacinth be contained by the weevils alone. As for the last concern, it is now well known that the water hyacinth made a resurgence around 2005. Currently, there haven’t been any widely reported issues with the weevil, so it is to be assumed that it has stuck to feeding on the water hyacinth alone.
“Strange Days on Planet Earth” is a documentary created by National Geographic and narrated by Edward Norton. It was created to provide a general audience with a glimpse at a problem that is plaguing the global community. The documentary details the problems associated with invasive species and provides examples from Uganda to New Orleans. Each example shows a different facet of the problem that the global community faces. The documentary opens with Jim Carlton’s work in an Oakland Port. He is in the process of making one of twenty rapid assessments in the area to determine new species in the area. His introduction is brief, but he is reintroduced later.
The viewer sees Claudia Riegel’s research of the Formosan subterranean termite. An invasive species introduced to America after the September 1945 Japanese surrender. When the Americans left they made crates from local wood, but the termites were in the wood. Once in America, the termites prospered in New Orleans because its climate is hot and sticky, similarly to the termites’ native land, and Orleans is composed mostly of wood. The termites then out competed native species because they can live above and below ground unlike the natives, which are only, settle below ground. The viewer even sees the efforts being made to eliminate the species.
Next, James Ogwang’s efforts to save Uganda’s Lake Victoria are shown. Here the viewer sees how the water hyacinth brought Uganda to its knees. Although the events in this part are quite riveting, details will be saved for SW3.
Finally, the documentary shows David Duffy’s research in Hawaii. In Hawaii, Duffy and Greg Asner are working to stop the miconia from destroying the island. The plant was brought to the island as a gift from Europe, but it soon got into the wild and began to outgrow surrounding vegetation. The growth began to shade lower growth until only miconia remained in the area. Areas where this occurred now have loose soil and are therefore prone to landslides. Asner is trying to find miconia colonies by determining how they reflect the sun and using this to find them from the air.
“Strange Days” then shows the viewers that scientists are not the only people contributing to these efforts. Civilians all over the world volunteer to help. In Uganda local fisher are helping to fight the water hyacinth. In America, the Weed Warriors are helping to eliminate the ice plant in their state.
The documentary is put together quite well and provides excellent insight for those who do not know very much about this issue. National Geographic’s usage of the word invaders became a motif present throughout the documentary. Edward Norton primarily uses when he describes the invasive species like they are an invasive alien army. He uses words and phrases such as “alien powers”, “invader assault”, and “encounter with aliens.” These puns provide brief levity to a serious matter. Also, I found one statistic to be quite powerful; 99% of the species in San Francisco, by weight, are foreign. An impressive and powerful statistic that ends an informative documentary.