Are the Water Hyacinth Gone For Good?

Jeremy Joven

There has been recent debate on the forces behind the decline of water hyacinth in Lake Victoria starting in 1999.  At it’s peak infestation of Lake Victoria in the late 1990s, according to Albright et al. (2004), the water hyacinth has had several negative impacts on the native ecosystem in which it has invaded.  They have hindered transportation on the lake, have reduced fishing, and have threatened the biodiversity of the lake (Wilson et al. (2007)).  Researchers are debating whether the introduction of the Neochetina (a type of weevil that eats the water hyacinth) into Lake Victoria or disturbances from El Niño weather patterns was responsible for the diminishing water hyacinth population.

The article by Wilson et al. (2007) mainly supports the belief that the spread of the weevil population was the main reason for the reduction of water hyacinth while the article by Williams et al. (2007) focuses on the chaos caused by El Niño as a contributing factor to the declining hyacinth numbers.  There is a reference in Wilson et al. (2007) from Williams et al. (2005) that describes how the weevil population is unstable and therefore could lead to a resurgence in the water hyacinth population.  In defense to this statement, Williams et al. (2007) clarifies that the unstable ecosystem due to El Niño may lead to “unstable controlling herbivore populations.”  In their argument, Williams et al. (2007) makes it known that they don’t believe El Niño to be the single influence behind the water hyacinth decline, but rather a compliment to the introduction of the weevils.  The main point behind the argument in Wilson et al. (2007) is that the opinions generated in an earlier article by Williams had no direct experimentation or data that supported the claim that El Niño contributed to the diminishing water hyacinth population.

After reading both articles, I felt that Williams et al. (2007) had a more convincing argument.  The article didn’t just specify what they believed, but it also acknowledged the opposing side’s (Wilson et al. 2007) opinion.  It merely combines both factors as the possible driving forces behind the dying hyacinth.  However, the data from Wilson et al. gave it’s argument a more solid stance from a scientific view.  In light of the MODIS satellite images, bio-control in general can work at times but also fail as well.  Bio-control is not the only answer to growing invasive species, but may aid to decline it.

References

NASA Earth Observatory. 2007. Water Hyacinth Re-invades Lake Victoria  http://earthobservatory.nasa.gov/IOTD/view.php?id=7426. Viewed 27 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.



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