This alien plant is lethal for the environment. Now it’s being turned into a plastic to regrow forests

Lake Naivasha, northwest of Nairobi, Kenya is becoming increasingly unnavigable. Water hyacinth, the world's most widespread invasive species, is blanketing the lake, choking its fish and leaving people stranded.

Lake Naivasha, northwest of Nairobi, Kenya is becoming increasingly unnavigable. Water hyacinth, the world’s most widespread invasive species, is blanketing the lake, choking its fish and leaving people stranded.

“Sometimes it becomes very serious,” says Simon Macharia, a local fisherman, about the weed problem. “There was this incident where fishermen were trapped by hyacinth inside the lake for three days. We had to seek help from the government (who) used a helicopter to rescue them.”

Macharia says that some days he’s simply unable to fish on the lake because of the plant. When he does, he can lose his nets underneath the floating weed, incurring costs while preventing him from earning that day. Water hyacinths also cover the surface, cutting off sunlight, outcompeting other plant species and starving water of oxygen. That means there are fewer fish for Macharia to catch in the first place.

The problem is so vast it can be seen from space. It also threatens the cut off the flower industry in the wetlands surrounding the 150 square kilometre (58 square mile) lake.

What’s happening in Lake Naivasha is a story repeated all over the world. Water hyacinths are native to South America, but were introduced as an exotic ornamental to many other countries. They’ve since taken over freshwater environments and are labeled an alien invasive species on every other continent aside from Antarctica.

As well as their impact on biodiversity and livelihoods, the floating plant can clog hydroelectric and irrigation systems, meaning that one does not need to live in their proximity to be affected. It’s the highest-profile example of an invasive aquatic plant crisis that has cost the global economy tens of billions of dollars historically, and now more than US$700 million annually.

The problem with water hyacinths is particularly acute in Africa. A 2024 report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), a body founded by the UN Environment Programme, described the plant’s “exponential expansion,” with land use changes and climate change adding potential fuel to the fire.