Features


In a (strawberry guava) jam

A debate over how to handle the spread of invasive species leaves the future of one well-known plant hanging in the balance

It hardly looks threatening. The strawberry guava plant’s bright green leaves, hard wooden stalks and heavy ruby-colored fruit appear right at home in Hawai’i. It’s been here for nearly 200 years, and has expanded throughout forests across the islands in dense thickets, displacing native plant species and the birds that rely on them to such an extent that scientists fear widespread species extinction.

It was during the 1820s that strawberry guava came to the islands from Brazil, more than half a century before Hawai’i’s most famous biocontrol blunder saw the introduction of mongooses to attack the rats that were gnawing through sugar crops–the result of which, as any local well knows, was not the intended eradication of rats, but instead a compounded rat and mongoose problem.

Now, strawberry guava is caught up in its own biocontrol controversy. For the past 15 years, a group of federal and state agencies have come to the decision that the best way to beat back strawberry guava overgrowth is to release the Brazilian aphid-like insect Tectococcus ovatus, or T. ovatus, to eat away at the plant and reduce its fruits.

“Once strawberry guava starts spreading, it basically crowds out everything else,” said David Duffy, a University of Hawai’i botany professor. “It makes these impenetrable clumps that remove the food source for endangered Hawaiian birds. Another major concern is that, because pigs use strawberry guava as a food source, it helps spread pigs to places they otherwise wouldn’t go, and the presence of the pigs creates wallows because they like to get down in the mud and roll around, then pools of water collect and mosquitoes that spread avian malaria thrive.”

But many are reluctant to see strawberry guava threatened.

“There’s been no consideration about the environmental and cultural impact of removing a food source at a time when food is so expensive,” said Sidney Singer, a medical anthropologist and environmentalist on the Big Island, where T. ovatus would first be released. “It’s really an attack on our access to wild, free food.”

At least 90 other plant species, including mango, ‘ohi’a, java plum, eucalyptus and koa are related to strawberry guava, inciting worry about the possibility of T. ovatus jumping between species and hurting more than just its intended target. The federal and state agencies and others who have studied T. ovatus and its relationship with strawberry guava, and endorse the insect’s release into Hawaiian forests, say studies have proved that it will only eat strawberry guava.

“In nature, there are these very specific interdependent relationships,” said Christy Martin, spokeswoman for the Coordinating Group on Alien Pest Species. “This insect cannot survive without the strawberry guava. In situations where the strawberry guava is removed but other plants are available, it will die every single time because it does not exist on any other plant, even in Brazil.”

But local environmentalists say the testing to support this claim isn’t substantial enough, and the possible consequences are too potentially devastating to risk.

“We’re talking about an irreversible decision,” said Singer. “The tests are inadequate. They’ve only performed tests on very few species. You can’t just release T. ovatus and see how it goes. Once we got ‘em, you just have to sit back and watch. That’s it.”

Others argue that introducing a potentially harmful insect doesn’t make sense when strawberry guava is harvestable–not only for its fruit but also for its wood.

“The wood can be used for tool making, for firewood, it burns for a long time and it burns very hot,” said O’ahu environmentalist Stuart Scott. “I won’t minimize that it’s an aggressive species. It grows thickly and it crowds out other species but it’s not the only introduced species that does that. Why pick on strawberry guava?”

Scott also said that if strawberry guava is removed, other more aggressive species like fiddlewood will still crowd out the plants that scientists aim to preserve. While harvesting strawberry guava may seem like a win-win solution, Duffy pointed out that it’s not cost-effective and maybe not feasible at all.

“It’s a nice idea and I’d love to see a model that works,” he said. “But assume we’re going to harvest: You’d have to put roads in to get to the forest, so that’s one cost and an enormous amount of destruction. Then you have to chop down the strawberry guava, who’s going to do this? And what are you gonna do with it? What kind of factory needs to be built? It’s nice to have these ideas but you can only take it so far before it costs more, even just to transport it, than what it’s going to be worth.”

But the public outcry on the issue, especially on the Big Island, suggests that strawberry guava may be worth the trouble, at least to those who use it and believe they should have a say in what lives or dies in their own backyards.

“Biocontrol is the current vogue,” said Singer. “Right now, we look back 50 years ago when they were still bringing things over here just because they grew well, not thinking about native species. Now the pendulum has swung, and they aren’t thinking we need food and we need to use the environment for growing food. Just thinking about preservation of native species is extreme.”

As it stands, the state Department of Land and Natural Resources still has to release an environmental assessment of the T. ovatus proposal, then allow 30 days for public comment before moving forward. According to Martin, that likely won’t happen until early 2009.

Duffy said he understands why people are concerned, but that inaction can be just as dangerous as making a rash decisions.

“I am a scientist, and scientists will almost always tell you that you need more research,” Duffy said. “The T. ovatus species is not the most effective possibility for controlling strawberry guava but it is the safest, and given what we know, I do not think we need more research. The one thing we need to think about is, do we want to have native ecosystems in the future? Do we have a responsibility to our grandchildren and our great grandchildren to let them choose whether they want to have native forests, or are our short-term interests more important than theirs? I’m just worried that in a century or two, people are going to look back and say, ‘what in the world were they thinking? Why didn’t they save the things they could have?’”