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http://edit.niwa.co.nz/our-science/pacific-rim/publications/all/pacific-update/test-publication-issue-2010-1/test-publication-article-2010-1

 

Asia-Pacific Update 02, July 2010 

Invasive aquatic weeds in Micronesia 

 

Searching for potential weeds in a taro patch on Palau. (Photo: Paul Champion) 

Invasive aquatic weeds are a problem in other countries as well as New Zealand. NIWA 
scientists were recently in Micronesia, assessing the risks posed by invasive aquatic 
weeds to some of the main islands there. 

Our job was to help identify aquatic weeds in Guam, Northern Mariana Islands, 
Federated States of Micronesia and the Republic of Palau.  We were also asked to carry 
out assessment of weed potential, and predict how severe the impact of these plants could 
become. 

“We visited aquatic habitats such as forest streams, reservoirs, natural lakes, ponds and 
wetlands, including taro cultivations. While out in the field we found new naturalized 
populations of serious aquatic weeds, along with a number of species in cultivation, not 
previously found on the islands,” reports NIWA weed specialist Dr Paul Champion. 

 

 

Roadside population of water hyacinth on Pohnpei, the first naturalised record of this species for that 
island. (Photo: Paul Champion) 

“There is a range of species that potentially could be imported into Micronesia from 
Hawaii, Southeast Asia or from other risky sources such as the USA and Australia, so we 
also reviewed possible import pathways and likelihood of introduction.”   

 

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The weed risk assessment used a version of NIWA’s Aquatic Weed Risk Assessment 
Model (Champion & Clayton 2000). The highest-ranked weeds included species already 
present on one or more island, such as water hyacinth, water lettuce and two salvinia 
species. The distribution of these weeds is still limited enough to investigate ways of 
eradicating them. Tropical weeds such as giant sensitive plant, alligator weed, and yellow 
burrhead are examples of highly ranked species not yet present on, but of high risk to, 
Micronesia.  

We recommended a total of 29 species or genera for a ‘banned’ list for imports. Some 
species which are currently imported for the aquarium trade in Guam were ranked as a 
low risk to Micronesia's economy and environment, so we supported their continued use. 

NIWA was contracted by Portland State University in this project.  

 

Contact: Paul Champion