Many plants are introduced into a foreign region because they are highly praised for their aesthetic complexion; however their potentially harmful and destructive consequences are often overlooked unknowingly and unintentionally. Similar to this was the water hyacinth plant that was believed to have been accidently introduced to Lake Victoria in 1989, from a local pond. Due to its versatile characteristics and wide range of tolerance levels, the water hyacinth has been able to dominantly flourish and disrupt several large bodies of water everywhere in the world except Europe. After its drastic population decline in 2000, several scientists have disputed on what was the leading force of maintaining the water hyacinth levels at low levels. Both scientist, Adrian E. Williams and John R.U. Wilson, agree that the hyacinth weevils and the El Nino event contributed to the water hyacinth decline , however both heavily disagree as to the relativity and measure of impact that both the weevils and the El Nino event had on the water hyacinth plant. Whereas Williams argues that El Nino was the driving force of the decline of the water hyacinth, Wilson strongly believes that without the weevils the water hyacinth decline would have not been so extreme.
Within a matter of a few years after its introduction to Lake Victoria, the water hyacinth population had exploded into a massive population size, contributing to the loss of native plants and aquatic species, consequently resulting in the loss of biodiversity, a decline in the economy, and the formation of habitats infested with disease carrying insects. With numerous detrimental dilemmas, local biologist took action and introduced weevils in to Lake Victoria in 1996, as a method of biological control. Weevils are successful in which they puncture holes in the leaves of the hyacinth plant and deteriorate the inside of the stems, collectively resulting in the drowning of the plants. Coincidently, 1997/1998 happened to be the year of El Nino, an event where weather patterns are intensified and the surrounding region encounters abnormal weather conditions. During this time Lake Victoria had experience cloudy weather, contributing to harsher waves and prohibiting (what William argues) light penetration for plant growth.
Wilson explicitly argues that the introduction to weevils is the primary result of the decline in water hyacinth population. Although Lake Victoria did not see drastic decline until after the El Nino event, Wilson argues that it typically takes 3 to 5 years for the weevil population to reach stable levels and establish their threshold within the lake. Four years after their introduction the water hyacinth plant declined from 20,000 hectares to under 1000 hectares. Wilson elucidates on the fact that since the water hyacinth had already incurred so much damage internally and externally, the intense wave action and winds caused by the El Nino event merely added additional stress factors to the already dismantled plant. Wilson essentially argues that the weevil’s actions in disintegrating the plants made it more permissible for the plants to be completely ripped from their stationary position by harsh waves and winds.
William argues that while the introduction of weevils might have played some role in the water hyacinth population decline, that it is without a doubt that El Nino’s weather pattern was the main driving force. With lower light penetration, Williams believe that it can prevent plant growth and reproduction. Other factors included intense wave action, humidity, and water quality. Williams argue that Lake Victoria is too big of a lake for the weevils to have a significant effect and that without the weather patterns of El Nino, water hyacinth population levels would not have rapidly decline.
After gaining insight on both scientist arguments, I find myself sharing similar views with Wilson. I do agree that both the El Nino event and the introduction of weevils played major roles in the decline of the water hyacinth, however without the introduction of weevils, the internal and external structures of the hyacinth plant would not have been as weak for wave action to completely dismantle the plant. The weevil began the process and would have finished their job, the El Nino event simply fasten the process.