the world, it is highly invasive in southern states, Hawaii, and California (Ramey, 2001). As a 
floating weed, water hyacinth grows quickly, faster than any other saltwater, freshwater, or 
terrestrial vascular aquatic plant (Masifwa et al., 2001; Toft et al., 2003). Forming thick mats, 
water hyacinth rapidly over takes water bodies and significantly blocks water ways (Pimentel et 
al., 2000; Charudattan, 2001). 
Control efforts are intensive and expensive. Florida spends $15 million a year to control 
three aquatic invasive plants including water hyacinth (Charudattan, 2001). Florida also 
mandated a coordinated control effort for water hyacinth including biochemical and chemical 
control measures and surveys, which has been very successful at controlling water hyacinth. 
Biocontrol methods involving weevil species also have proven successful in other parts of the 
world including Lake Victoria, Africa. Prevention, early detection, and regional coordination are 
critical for preventing aquatic weed invasions including water hyacinth (Charudattan, 2001). 
Though water hyacinth is relatively cold tolerant and can survive in open waters 
(Charudattan, 2001), it cannot withstand winter temperatures in more northern states (Ramey, 
2001). Climate-change impacts may enable both the spread and establishment of water hyacinth 
within states as well as into more northern states. Increased rainfall and hurricane intensity could 
result in more frequent and intense flooding events, which can facilitate its dispersal (Michener 
et al., 1997). Water hyacinth are able to survive these types of extreme events and can 
reestablish and colonize both in up- and down-stream systems (Center and Spencer, 1981). The 
increased frequency and intensity of disturbance events may create unsuitable conditions for 
native species, making ecosystems even more vulnerable to invasion by water hyacinth and 
enabling its spread. Water hyacinth is already present as an annual colonizer in some northern 
states, and warmer waters may enable and encourage its spread and establishment further north. 
Of particular concern are nurseries in northern states that sell water hyacinth for water gardens; 
plant escapes are a common mechanism of spread (Charudattan, 2001). These nurseries may 
become a viable pathway for water hyacinth as conditions in northern states become more 
suitable for water hyacinth survival. 
2.5.3. Common Reed 
Phragmites australis, the common reed, is prevalent on the Atlantic Coast and is rapidly 
spreading westward and northward. It is native to some regions of the U.S., but the invasive 
strain is believed to have been introduced from Europe in the late 1800s (Blossey et al., 2002). It 
is most abundant on the Atlantic coast and is expanding in the Midwest. Wilcox et al. (2003) 
mapped changes in Phragmites coverage between 1945 and 1999 by selecting nine different 
years to examine using aerial photos from the Great Lakes region. GIS maps show that its 
distribution expanded and contracted over that time period, but that it increased exponentially 
2-20 
