When Invasive Species Become Local Cuisine

When strong winds blew through Maui in February, Jan Yokoyama was out in the orchard behind her house collecting 1,500 pounds of green mangoes that dropped from the trees. The sudden windfall meant days of peeling and slicing to turn the fruit into mango chutney, one of the dozens of spreads Yokoyama sells at Maui Upcountry Jams and Jellies, a small business she runs from home. Most of the fruits she steams, juices, mashes, and pulps for her jams grown there.

The jars for Yokoyama’s products bear colorful labels proclaiming “Farm Fresh Maui Grown Fruits.” The irony is that none of her fruits—not the pineapples, the mangoes, the guavas, the passion fruit—are actually native to Hawaii. They’re all invaders, carried by immigrants from South America and Asia and other Polynesian islands. And in the case of one particular fruit, the invasion has been deadly: The strawberry guava tree, which produces a fragrant, flavorful red fruit, has been decimating native Hawaiian forests since it was first transported to the islands in 1825.

After decades of research, scientists introduced their own invader to the island in 2011 to curtail the spread of the strawberry guava tree: The Brazilian scale, a small insect whose young settle on strawberry guava leaves and weaken the plant by forcing it to form lumps that sap its energy stores. The State of Hawaii and other partners have been working to establish the insect in forests for several years now. If the insect is effective, it could avert the destruction of a quarter of the state’s endangered plant species and the degradation of hundreds of thousands of acres of native forest land—which protects the watershed and is home to many endangered birds.

But for those whose livelihoods depend on the health of fruiting plants, “biocontrol”—the technique of fending off unwanted species with other living organisms—is practically a dirty word. To them, the bug isn’t a savior; it’s just another pest. “I got to really take care of my trees,” Yokoyama says of her 15 strawberry guava plants. She’s heard that the insect has been released and worries that rescuing the island may mean damaging her business.

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The state of Hawaii contributes less than 1 percent to the U.S. landmass, but the islands contain 44 percent of its endangered and threatened plant species. Harmful invasive plants and animals cause much of this destruction. The Nature Conservancy estimates a new pest species arrives in the islands every 18 days, and the cost of controlling these invaders and repairing damage to property and natural resources costs about $137 billion annually.

Strawberry guava (Psidium cattleianum) is one of the most widespread invasive plants. It lives in a range of habitats and quickly converts forests into monocultures and sucks up water that would otherwise be available for native trees. It’s almost impossible to kill: The tree is a prolific fruit-producer, which helps spread seeds, and it can grow multiple trunks from the same plant. Chuck Chimera, an invasive weed specialist, compares Strawberry guava to the mythical Hydra: “Cut off its head and five or 10 will spring up in its place.”

Given the plant’s resilience, botanists have had to consider every option for getting rid of it, and believe that if the Brazilian scale (which grows on no plant except the strawberry guava) can slow the plant’s spread even a little, it will be a major victory. But then there are farmers like Chuck Boerner, owner of ONO Organic Farms, a 50-acre family farm on Maui that grows everything from papayas to the infamously smelly durian fruit. They also sell strawberry guava jam. Boerner remembers hunting around the island for strawberry guava trees with his family as a kid, and fears that the biocontrol might put an end to the delicious spread. Normally conservation organizations like the National Park Service can only control the plants growing within their property, but now that the Brazilian scale has been released, it’s anyone’s guess how far it might spread. Fences won’t stop the bug, and since Boerner’s farm is organic, they don’t use any pesticides.

“I know they’re trying,” Boerner said of the scientists’ efforts. “It’s just we need more communication. More of these botanists and researchers need to listen to the public who lives here, listen to the farmers, listen to the Tropical Fruit Growers association.” What concerns him most is the unknown: Has the Brazilian scale been properly tested? Which plant will scientists want to weed out next?

The case of the strawberry guava is hardly the first time conservationists have run into trouble with members of Hawaii’s eating public. There’s also been some pushback against efforts to control the ivy gourd, a plant that’s used in Asian cuisine and is listed as a state noxious weed. Then there’s the rose apple, which spread throughout forests unchecked for decades, feeding hikers and feral pigs, until it was destroyed by an invasive rust fungus. Though some botanists were secretly happy the plant was removed, hunters who valued the fruit because it fed the pigs speculated that conservationists introduced the fungus on purpose. (Chimera says that conservationists wouldn’t have been allowed to take such drastic measures because the use of biocontrols is so thoroughly tested and regulated.)

The first thing most Hawaii residents think of when they hear the word “biocontrol” actually is a much older attempt at conservation on the islands: European plantation owners’ botched 1883 effort to control the rat population by importing mongooses. The owners didn’t realize that mongooses are diurnal, while rats are nocturnal, so instead of the one hunting the other, both ended up preying on endangered birds.

Today, farmers worry that the strawberry guava interventions will be similarly rash. There have been public hearings to discuss the use of the Brazilian scale, and conservationists have worked to include outreach in most of their projects. But the farmers still want to be consulted before any biocontrol measures move forward. The scientists are committed to conducting studies according to their own research, not what the farmers say.

Beyond invasive plants, scientists and citizens on the islands have been debating the control of feral animals like sheep, deer, wild cattle, and pigs for decades. The pigs, for instance, were introduced by Polynesian travelers who canoed to Hawaii from other islands in the Pacific. They were domesticated and pork was highly valued in celebrations like luaus. But now the pigs are feral, and their rooting causes native plant damage, increases the spread of invasive plants, and results in harmful erosion. Most protected forests are fenced off to keep the animals from trampling through the land, but agencies have also used snares to trap and kill the animals, which is often an unpopular measure.  

“You’re always going to get somebody that says, ‘No, my value is just as important as your value, my freedom to grow whatever I want trumps anything else,’” Chimera said. “It’s very challenging.”

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Conservation can be seen as a stubborn, too, of course. To attempt to preserve something in the face of extinction similarly privileges that thing and the effort to conserve it over any opposing interests. What landscape are scientists trying to preserve in Hawaii—the environment as it was before Europeans arrived? Before the first humans arrived? Who ultimately benefits? Conflicts like this are playing out around the country. Consider the 41-day armed occupation of Malheur Wildlife Refuge earlier this year by ranchers who disliked the government’s management of federal land; the ranchers wanted to run their businesses and graze their cattle how they please, but the federal government, which owns 47 percent of all land in the West, parcels it out. Then there’s the furor over oil exploration in the Arctic National Wildlife Refuge. Oil companies wanted to drill for the billions of barrel of oil estimated to lie beneath the region, but the Federal Bureau of Ocean Energy Management decided the risk of spills was too great. Ultimately, President Obama effectively banned oil exploration on 22 million acres of federal lands and waters in Alaska.

Hawaii is just a piece of a much larger puzzle, one we haven’t managed to solve yet. Yet for Yokoyama, the farmer who owns the orchard, the philosophical principles underlying this debate are far less of a concern than preserving the quality of her jams. She wants to keep cultivating tasty fruits, not fight a losing battle with bugs. “It’s like going to the market and not finding the mustard cabbage that is the real mustard cabbage,” she said of the potential downfall of her prized strawberry guava plants. “We don’t want to lose our flavors that we’re known for.”