Harmful Hitchhiker: Water Hyacinth

Not all invasive species are ugly, but not all beauty is harmless. This is never more evident in the Amazonian beauty water hyacinth now pestering the southern United States. The aquatic ecosystems of the southeastern United States have been colonized by vast, floating, dense carpets of water hyacinth that were introduced to New Orleans for a horticultural exposition in 1884. It since has devastated numerous aquatic ecosystems by completely cutting off sunlight to benthic species living below the surface of the water, causing them to die, decompose & use up all of the oxygen supply. Despite it's obvious beauty, it's not hard to hate it's very existence, even if its durable, wicker like stem can be used to make furniture.

The explosive growth of this plant is due, largely to the influx of nutrients coming into the waterways from fertilizers or other agricultural runoff that creates a boom in plant growth, as well as water hyacinth being free from natural predators. Today, water hyacinth is controlled in Florida's waterways, but it is still a major nuisance in Louisiana.

One way to control invasive species is by biological control, such as introducing plant species that feed on the plant, such as hyacinth weevils. Here is a website I found that lists & discusses the different weevil species that are used as control mechanisms.

Several risk factors are involved when a new species is introduced. I am not a very big advocate of biological control because of all the variables involved. Even though there are many, thorough studies that are designed to make sure the new species will not disrupt the environment, there's no way to predict the response a species of insects might have ten years down the line when other factors in the ecosystem change. The ideal situation would be for the new species to eradicated the pest species & simply die when there were no more resources, but in most cases, that simply isn't the case. New species will adapt to the environment they are in in order to survive. While the introduction of the initial pest is definitely not natural, introducing a new species certainly isn't a natural response. I would only advocate biological control as a last resort, when hand pulling & pesticides are no longer a viable option. Spartina alterniflora is successfully managed in the Pacific Northwest by a dedicated group of individuals who use weed whackers & poison to prevent spread.

I guess there really are no easy answers once a plant has been introduced, but I am wary of a solution where one species that doesn't belong is swapped out for another.

Not surprisingly, water hyacinth isn't the only species to be causing such issues, check out this website dedicated to PBS' Nova for a few facts about common invasive species.

How can you protect your waterways & fishing holes from water hyacinth spread? Clean your boats & make sure you aren't carrying any hijackers with you when you transfer your boats from waterway to waterway. Keep our waters clear & healthy!