Water hyacinth is an invasive species in East Africa, causing significant ecological and economic damage to the Lake Victoria region of Kenya. The plant is native to South America, but over the past century, it has invaded many lakes and waterways around the world.
This is the first of a series of blogs that explores Water Hyacinth, its presence in East Africa, and what can be done to manage its population.
How an Ornamental Plant Took Over the World
Many a steamer docked at Rio de Janeiro in the late 19th century to load up special cargo destined for major ports of the world. At the time, from the USA to Egypt, all the way to Borneo and Australia, a certain plant native to the South American interior was all the rage.
The plant grew on waterways in the Amazon basin. Here, it had existed exclusively for millennia, bobbing away on lakes and ponds until its delicate pink and lavender petals convinced property owners worldwide that it would be an excellent ornamental plant.
Big mistake! Perhaps, the biggest ecological mistake in history.
Anatomy of a Garden Plant
Eichhornia crassipes, better known as water hyacinth, is a plant species native to South America. It's a free-floating plant that evolved in the Amazon’s freshwater ecosystems before spreading to other regions.
The spread wasn’t accidental. Water hyacinth has quite the aesthetics going for it. Its rounded leaves, spongy stalks, and flowers that bloom in shades of lavender are the stuff of dreams if you own a garden pond.
Thus, in the late 1800s and early 1900s, water hyacinth seeds/seedlings were taken out of the Amazon basin to be planted on garden ponds and streams across Africa, Asia, Europe, and America.
Anatomy of an Invasive Species
Any organism introduced to an ecosystem in which it does not naturally live and whose introduction disrupts said ecosystem is considered an invasive species.
So it may or may not surprise you to learn that domestic cats fall into this category. They are cute little fur balls at home. Outdoors, however, their hunting instincts and lack of natural predators pose a severe threat to local wildlife populations.
But this isn't really about cats. It's about what happens when you take an organism outside its home and put it in an ecosystem with all the resources it needs, but not nearly enough competition or predators to keep it in check.
Water hyacinth evolved in a warm and wet environment that also happens to be the most ecologically diverse and competitive region on earth. This is an area housing 10% of all known species, plus thousands of undiscovered ones.
So to survive, the plant developed an ability to absorb nutrients, disperse seedlings, and reproduce offspring at an incredible rate, but one that is also balanced out by the host of predators and competitors evolving alongside it in the Amazon.
The balance, unfortunately, is limited to that corner of the world. People growing the plant in other regions learned this the hard way when suddenly, they had to deal with an organism that can double its population in as little as six days.
And as you can imagine, things got out of hand!
A Flower No Longer
Once outside its natural habitat, it doesn't take water hyacinth long to go from flower to weed. A single plant releases 5000 seeds that can be viable for up to 20 years. It can also propagate vegetatively by cloning itself into daughter plants.
In ideal conditions, wet, warm, and with little competition, the plant doubles its population in six days. What is initially a few plants quickly becomes dense floating mats that aggressively compete and win against the native aquatic life that has had little time to evolve a response.
It's no surprise then that the plant overran the dams and ponds it was introduced to, spread into local streams and rivers, and finally ended up in lakes, where it continues to devastate natural ecosystems and human livelihoods to date.
Lake Victoria is one of the hardest hit lakes in East Africa. In our next installment, we’ll look at the history and scale of the problem in the Lake Victoria basin.
