* Scientists and sharpshooters work hand in glove to blast wild goat herds that eat rare plants and erode slopes, giving invasive species a foothold. On the Big Island, scientists capture a single wild goat, affix a homing beacon and turn the animal loose. When the "Judas goat" rejoins the herd, helicopters ferry sharpshooters to canyons and shoot animals whose location has been betrayed.
* Schoolchildren are recruited as anti-ant agents on the Big Island. Dan "the ant man" Gruner, a University of Hawaii graduate student, assigns 500 schoolchildren to find ants. No social insects are native to Hawaii. The children leave peanut butter-coated chopsticks outside and report ant colonies to authorities, who poison the pests.
If Hawaii ever adopted Amber alerts, they might be used to locate snakes. Reptiles are not native to the islands, and are particularly loathed by Hawaiians, in part because they pose a mortal threat to birds.
It is a crime to own a snake here, although 13 sightings were reported last year and three snakes were confiscated, including a python stuffed into an airport collection box. Inspectors use beagles to sniff the landing gear of some arriving planes, so wary are they of snakes.
Brown tree snakes are a chief concern and have been known to travel in landing gear. On Guam, they virtually wiped out the island's birds; they also inflict venomous bites and cause one of every four power outages when they slither across power lines.
When the alien invaders can't be kept out, Hawaiians attempt to throw up defenses to protect the native species that remain.
On a ridge overlooking a military base in Oahu's Makua Valley, ecologists have erected a veritable Maginot Line for a mollusk. Inside a fortified perimeter lives one of the last substantial remaining colonies of banded tree snails. Once so prolific they dripped from trees in dense clusters and were used by natives to make leis, the tiny creatures are now endangered and surrounded by a 4-foot-high plywood barricade.
The barrier is rimmed with a trough of salt to stop nonnative predatory snails. An electric current and barbed wire keep out rats and other predators. About 150 snails are in the enclosure, which is half the size of a basketball court.
When physical barriers don't suffice, the last remaining refuge in Hawaii for some plants becomes several prominent gardens maintained by human hosts.
Limahuli Garden on Kauai has become a sort of emergency room and museum. New plants are grown there from seeds, cuttings or cloned tissue. Visitors can see an oha tree, of which three remain in the wild, or a lovely white hibiscus thought to be extinct until one was found near a remote waterfall in 1976.
For many plants, survival in the wild is threatened because dozens of birds and insects that pollinated them are gone or disappearing.
Into the void has stepped a lanky, bearded scientist with deep-set eyes. Ken Wood spends three-quarters of the year in the back country searching for the rarest of the rare -- then brings these plants the precious pollen they no longer can count on nature to deliver.
In an example of extreme botany, Wood rappels down 3,000-foot cliffs above roaring seas at Molokai, rope in one hand and a Q-tip or makeup brush in the other, to dab pollen on rare alula trees, which look like cabbages stuck on baseball bats.
The Indiana Jones image makes Wood squirm, but strangers have seen him so much in the media that they ask questions about the environment when they run into him at the Kalaheo Coffee Co. and cafe on Kauai.
As the rain subsides, Wood heads for Kokee State Park and an endangered alani tree, a distant cousin of the orange. Just 12 alanis remain in the wild, and the trail to this one is treacherous.
Red soil is slick atop spiny ridges of the Na Pali mountains. Goats at the edge of the precipice watch Wood's every step. It is a place few people visit, but where this one-time gold miner and philosophy student can be on the front lines of the fight for biological diversity.
Wood came weeks earlier and dabbed pollen onto flowers of the tree. Now he crawls gingerly up into the spindly alani. Wood examines tiny seed clusters tucked in the leaves and grins like a proud parent.
Down from the tree, Wood quips: "I was ready to smoke a cigarette.... I think I'm about to become a father. Soon I'll be passing out cigars."
In a few more weeks, Wood will collect mature seeds to propagate new plants at the National Tropical Botanical Garden.
Man's interventions here have not always been so thoughtful, or promising.
For example, mongoose were brought to Hawaii in 1883 to control rats ravaging Hawaii's birds and sugar cane. But the nocturnal rats and the day-traveling mongoose seldom crossed paths. Instead, the mongoose became another voracious bird predator.
Like many other island environments, Hawaii's delicate balance is particularly vulnerable to alien species. Before man came, ecosystems were simple, without a full complement of predators and competitors.