Long before the era of post-Sept. 11 security precautions in the U.S., an unknown person or group of people may have begun carrying out a series of bioterrorism attacks in California.
The target? Menthol-scented eucalyptus trees.
Before you wonder why you hadn't heard of this, it's because the story isn't necessarily true. It's a hypothesis, a theory promoted by a noted California entomologist and eucalyptus expert named Timothy Paine.
If his theory is correct, then somebody out there wants those trees dead.
Digging For Clues
Paine first noticed a problem around 1985.
"We started seeing eucalyptus trees dying," he says.
At the time, Paine's first suspect was the longhorned borer, a beetle that looks like a cockroach. But as soon as he found a natural enemy to combat the beetle, he got word of another pest.
"We were seeing insect after insect coming in," Paine says. "We started working on the longhorned borer, and then another would come in, and another one would come in."
Over the last 25 years, Paine has come across a total of 16 new insects — all of them after the eucalyptus tree.
After a while, Paine became suspicious and started digging for clues. He found that the pests didn't come to California in a steady stream, they came a few at a time, in batches from different regions.
"They would be from Queensland, or they would be from New South Wales, or South Australia," he says.
Plus, for these kinds of insects, which plaster themselves to leaves, it's not so easy to hop a flight to Los Angeles. That's when Paine thought these pests might be getting a helping hand.
"If you see something one time, you accept it. If you see another pattern, you wonder if it's a coincidence," Paine says. "If you start seeing five or six different patterns that all point in the same direction, then you start to raise questions."
Over the years, Paine has become increasingly convinced that someone or some group has brought these pests from Australia to California for the strict purpose of getting rid of California's eucalyptus trees.
"We can't imagine that it was done for any other reason," Paine says.
In other words, he believes it's a case of biological terrorism.
An Invasive Plant Itself
If you're wondering why anyone would do such a thing, here's some context.
Eucalyptus trees are not native to California. The seeds arrived from Australia in the 1850s, during California's Gold Rush days. The trees are sturdy, they grow fast, and now the state is covered with eucalyptus groves.
The red gum and blue gum eucalyptus are even categorized by some environmental groups as "invasive plants." For that reason, some Californians aren't thrilled about the eucalyptus.
"California's got a lot of fantastic and lovely native plants, and the native plant advocates argue that the trees sort of prohibit those from flourishing," says Zoe Corbyn, a freelance science journalist who recently wrote about Paine's theory of biological terrorism for Failure Magazine.
She says that if Paine is right, this might be the first documented case of an intentional introduction of a plant pest into the U.S.
No Smoking Gun
There's just one problem.
"The evidence is only circumstantial," Corbyn says. "Nobody's come forward and put their hand up and said, 'I did this.'"
In 2010, Paine published his findings in a peer-reviewed academic journal. Corbyn spoke to several of Paine's colleagues, and his theory was met with skepticism.
"There's so many more flights from Australia to L.A. than there was in the past," Corbyn says. "It's very possible that something could've come in that way. You know, crawled on board and crawled out the other side."
When confronted with other theories, Paine doesn't disagree.
"You can find alternative explanations for all of this, no question about it," he says. "This is something we think is likely to have happened, but we don't have a smoking gun."
Without that smoking gun, he's out of luck. But, Paine says, for him, it's not just about the eucalyptus. It's the possibility of biological terrorism that really scares him.
"Eucalyptus are important for this state, but they're not life or death," he says. "But if you're talking about a major food crop, or a disease organism, the prospects are very, very disturbing."
For now, Paine is moving on with his work. He's found natural enemies to fight four of the insects. The other 12 are still doing their best to annihilate the eucalyptus trees of California.