Water hyacinth (Eichhornia crassipes) is an aggressively invasive plant that has caused billions of dollars worth of economic and environmental damage to aquatic systems world-wide.  Native to the Brazilian Amazon, it has been introduced to Asia, Africa, Australia, and North America.  Hyacinth grows quickly in warm waters with high nutrient concentrations, and can double in biomass in as little as six days.  Hyacinth can form dense, impenetrable floating mats which restrict boat traffic and fishing activities, cause local reductions in aquatic biodiversity, and support populations of disease vectors such as malarial mosquitoes and the Biomphalaria snails that host schistosomiasis.

Both climate change and land use change (e.g., urbanization) create conditions likely to increase the range and invasiveness of water hyacinth in North America.  Hyacinth has historically been restricted to tropical and sub-tropical regions of the world, as individual plants are killed by prolonged periods of cold and freezing temperatures.  However, predicted climate changes in temperate zones, including increased winter temperatures, fewer frost days, and longer growing seasons, may allow it to persist at higher latitudes.  At the same time, the explosive growth and increasing urbanization of human populations may also support hyacinth growth and range expansion, as water bodies near urban areas typically show increases in both temperature and nutrient concentrations.  

Anecdotal evidence suggests that water hyacinth populations are moving northward, possibly in response to the combined perturbations of climate and land use change.  We are using a combination of field surveys, museum records, and coordinating with local, regional and federal agencies to determine whether the range of water hyacinth in eastern North America has been increasing in recent years.  At the same time we are using field surveys, greenhouse and mesocosm experiments to (1) examine the interacting effects of elevated temperatures and nutrient concentrations on hyacinth physiology, and (2) determine the impact of hyacinth on local biodiversity. 

Links to more information on water hyacinth:

In the Global Invasive Species Database 

In the Southeast Exotic Pest Plant Council’s Invasive Plant Manual 

Satellite images of hyacinth onLake Victoria, courtesy of NASA