State and federal agents say the volume of illegal wildlife streaming into the U.S. still dwarfs the amount heading out. But globalization has altered the balance, and more goods than ever now flow out of the country. Consider the case of Puget Sound's geoduck (pronounced "gooey duck"), the world's largest burrowing clam. The bivalve is found almost exclusively in the Pacific Northwest and Alaska, and wasn't even fished commercially before the 1970s. But rising wealth overseas coupled with great strides in international shipping created high demand for this mollusk in Asia. Soon, poachers made millions selling geoducks to foreign markets. This winter, Hong Kong customs officials broke open a seafood-trafficking ring and seized $1.4 million in undocumented shellfish, including 87 crates of geoduck -- merely the latest in a long string of clam crimes.

The ecological implications of this type of thievery vary by species and location. Sixteen years after Washington state banned abalone gathering, the colorful underwater mollusks have declined 80 percent. Biologists believe illicit harvests by greedy scuba divers helped send the shellfish hurtling toward extinction. One diver told police he'd stolen so many -- tens of thousands, which he sold to local restaurateurs, some of whom shipped the shellfish overseas -- that the proceeds paid for his 26-foot fishing boat and his Jeep Cherokee.

Sometimes the damage is harder to calculate, or even observe. Not long ago Todd Swain, a special agent with the National Park Service, caught a poacher swiping owl pellets from Joshua Tree National Park. The thief sold the undigested feathers and fur to distributors who resold them to public-school science classrooms. "Taking a handful of those things might not seem like a big deal," Swain says. "But they play an ecological role just like everything else, and if you take them over and over from the same place, it's going to have an effect."

Nowhere, perhaps, is policing this crime wave more complex than in California, home to some of the world's busiest international ports and an exquisite terrain of rivers, deserts, forests, mountains and ocean beaches. With the state's human population pushing 40 million, it's not surprising that some fraction of them, like Yoshi Kojima, see the money to be made in fish, plants and animals. So while federal agents in San Ysidro battle every day to keep the world's illicit wildlife out, the theft of nature in California is on the rise. Poaching violations nearly tripled between 2003 and 2007, and some portion of that includes poaching for profit.

Each year, state authorities catch divers illegally bagging hundreds of thousands of dollars worth of abalone, some of it endangered. Most gets resold in San Francisco or Los Angeles or trucked over the border and shipped to Asia. And every year, undercover cops snag groups of major poachers who illegally hook and gut dozens of the state's white sturgeon for their eggs, which are used in caviar. The monstrous, bony sturgeon -- North America's largest freshwater fish­ -- can reach 20 feet, weigh half a ton and live a century. They mate infrequently and reproduce slowly. But the decline in the Caspian Sea sturgeon from which high-quality beluga caviar is made has turned the North American variety into valuable contraband.

Five sturgeon poachers were convicted just this January, and two more were arrested Feb. 25. One of those suspects had been caught five years earlier stirring sturgeon eggs into caviar in plastic buckets in a body shop. "We've got a lot of job security," says Kathy Ponting, who overseas the state's covert wildlife operations. "We consider the wildlife black market in California second only to the drug trade."

Yoshi Kojima had been on law enforcement's radar for years. Back in 2000, a tipster told federal agents that someone named Kojima was netting butterflies in the eastern part of Mojave National Preserve, where removing the slightest vegetation or tiniest creature is a crime. Kojima slipped away before anyone proved he broke the law. When wildlife cops learned three years later that Kojima would attend the bug fair, the tip worked its way to Special Agent Ed Newcomer.

"The plan was to go and snoop around and see if we could find him, and then just kind of see what he was selling and what was what," Newcomer told me. The agent was seated in his U.S. Fish and Wildlife Service office in a nondescript strip mall in Torrance, Calif., where files from old cases formed pillars all around him. "I knew nothing about butterflies, and I'd never been to one of these before so I had no idea what to expect."

Newcomer had only recently become an agent. He'd joined in his 30s, later than most. But he'd prepared for this moment for much of his life. He'd wanted to become a lawman since childhood, when he watched Adam-12 and played cops and robbers. In college he spied an advertisement for Fish and Wildlife special agents -- like FBI agents, but for animals, as he surmised. The poster recommended law school, already part of his plans. He got out and worked as an assistant attorney general for the state of Washington, but he knew he still wanted to be a cop. He flirted with the FBI, but considered Fish and Wildlife an elite posting. The FBI fields nearly 13,000 agents. Fish and Wildlife employs only about 200, who investigate crimes all over the country.

Newcomer had dreamed of working undercover and believed he could blend in almost anywhere. One of his supervisors had made her name chasing alligator poachers in the 1970s. She believed in giving her agents rope. Newcomer believed in using it.

To catch Kojima, Newcomer knew he'd need a fake identity, something beyond a new name and a different haircut. In undercover work, "you can't be judgmental, you can't be afraid," Newcomer told me. "You have to open up your soul in a way. You have to buy in to the philosophy and attitude of those you're after." Newcomer knew from his training not to map his character too precisely. Better to merely draw in rough contours, keep things vague and close to the truth. That made deception easier to manage. Newcomer wanted a name close to his own, one he would answer to if someone shouted it without warning. He wanted to be sure he could fudge a signature, even if he accidentally started signing his real name. The character would need to be vaguely well-educated and free to come and go as he pleased. The boating world includes jobs few people understand, so the agent became a middle-class guy who sold boating supplies -- a boring job that left time for new hobbies. Like bug collecting. Newcomer called this fellow Ted Nelson.