US: Strawberry guava's hold has proven devastating

A photo taken near Glenwood on the Big Island in 1917 shows an impressive native forest of enormous 'ohi'a trees draped in 'ie'ie vines. Here lived a plant found nowhere else: the giant haha (Cyanea giffardii). Today Glenwood is the site of one of the worst infestations of strawberry guava in Hawaii, and the giant haha is extinct.

Strawberry guava (originally from Brazil) has been in Hawaii for nearly 200 years, and in the absence of natural enemies it has steadily expanded its range, silently filling in the places where native species used to be. The haha is only one of more than 100 extinct plant species that will never again grace our wao akua. Another 100 plant species survive with fewer than 100 individuals in the wild. One in three native plants is an endangered species, and strawberry guava is specifically listed as a primary threat to many. Endangered birds like 'akepa and 'akiapola'au are also pushed out; they do not feed on strawberry guava, but instead depend on the 'ohi'a and koa trees that it has displaced year by year. It now infests hundreds of thousands of acres of native forest and continues to spread. Despite extreme efforts, conservationists can only control it in areas far smaller than what is needed. Removing it from larger areas is utterly impossible using standard removal methods.

Researchers have controversially proposed introducing a scale insect they hope might slow the spread of strawberry guava. While Sydney Ross Singer's op-ed piece ("Killing strawberry guava might prove devastating," Star-Bulletin, June 9) raises worthwhile questions about biocontrol, he minimizes the problems of strawberry guava and makes little distinction between native and alien species (his Web site, www.hawaiiancoqui.org, promotes his "nature preserve" for invasive coqui frogs). Singer's perspective notwithstanding, there are two general concerns about this insect.

First is the prospect that it will damage our native ecosystems. Unlike the days when the infamous mongoose was introduced, state and federal laws now mandate that extensive research be done before any introduction can take place. After 15 years of detailed studies, this insect has been tested on numerous native plants, crop plants and even the closely related common guava and has been shown to feed on none of them, even when there is no strawberry guava present. Given this information, it is very difficult to see how this insect could possibly do more damage to native ecosystems than strawberry guava does.

Second is the concern that strawberry guava will disappear and deprive people of a source of free food. Consider that the scale insect co-occurs with strawberry guava in its native habitat in Brazil. There, strawberry guava is not so rare that people cannot enjoy its fruit, but it is slowed down just enough so that it cannot form extensive thickets like it does in Hawaii. A reduction of strawberry guava to the level seen in Brazil would still leave plenty for people who use it here, while creating "breathing room" for native species.

I could dwell on scientific studies, but all I need is that picture from 1917 to know what is at stake. I strongly urge people to read the draft environmental assessment, which will soon be made available to the public. Is biocontrol the answer? It might be part of the answer. Are there risks? Yes, but in this very heavily studied case they are smaller than Singer asserts. An equally important question is: What are the risks of letting strawberry guava continue to expand its dominance? I hope that our unique native species will not have to answer with the silence of their extinction.

Source: starbulletin.com

Publication date: 6/16/2008

respond to this article  email this article    print

Receive the daily newsletter in your email for free | Click here

 

<< back | www.freshplaza.com