When the Killing's Done, by T.C. Boyle

T.C. Boyle, in his storytelling prime, weaves the inevitable and improbable into a tapestry, giving individual faces to social movements and global issues.  His 2011 novel When the Killing's Done sets up a clash between fanatical nature-lovers, raising questions that should make any thoughtful person uncomfortable:

Why should some species be allowed to flourish while others, considered invasive, merit eradication?
What makes any species "native" to an isolated place?
To what extent is it even possible for us to undo the mistakes of earlier generations?
Why do we still think, "We know what we're doing"?

The setting is a California archipelago opposite Santa Barbara, twenty to thirty miles offshore but a world apart: three small rocky Anacapa Islands, and the larger Santa Cruz Island.
The main characters, tenacious and intolerant in pursuit of causes on collision course, are:
Alma Takesue, Ph.D biologist working for the National Park Service, in charge of restoration of the islands - which means extermination of the rats on the Anacapas and the pigs on Santa Cruz; and
David LaJoy, successful businessman and leader of FPA, For the Protection of Animals, a local animal rights group resisting the slaughter of rats and pigs.

Takesue's circle is rounded out with biologists, Park rangers, her lover Tim who's both, the exterminators, the local representative of The Nature Conservancy - which owns a large portion of Santa Cruz Island; her grandmother whose husband and his brother died in a storm off the Anacapas while she, pregnant, survived; and her own father, a sea urchin diver until an accident off those islands ended his life.

LaJoy's compatriots are his musician girlfriend Anise, who spent her youth and adolescence on Santa Cruz Island where her mother Rita was cook and general factotum for a sheeping operation; his right-hand-man Wilson, skilled handling a boat, delighting in the mischief LaJoy dreams up to interfere with the Park Service's plans; journalist Tina who applies her muckraking skills on behalf of LaJoy's cause; a young woman who works in Takesue's office, sharing inside information with FPA; and a group of impassioned youth following their fearless leader.

The other significant characters are sea and land and sky:
Glassy still one moment, raging the next, the unpredictable Pacific.
The craggy inhospitable islands - rocky coastlines, the only fresh water what falls from the sky.
The sky, by turns blistering, torrential and fog-bound, as different from Santa Barbara as if the islands were a thousand miles away.

Along the way, we learn enough about the ecology of the islands and what they demand of those who would survive on them, to confront the big questions and come up empty-handed.  A rat is a living creature.  Rats have lived on the Anacapas for centuries, survivors of a shipwreck.  The island birds, having no experience with them, have made easy prey for nest-robbers.  The sheep, imported to the islands as a money-making concern in the 19th century, wreak environmental havoc as they overgraze, denuding the landscape which is then at the mercy of erosion and runoff from fierce storms.  But to the sheepherders, the worst enemy is the ravens that gather at lambing time, bewildering the ewes then picking off their newborns with appalling efficiency.

Boyle is unsparing about the devastation of invasives: brown snakes, stowaways on planes or ships during World War II, have eradicated nearly all bird life from Guam.  That ecosystem is changed - the Guam before the snakes showed up is irretrievable.  Foxes and skunks live on Santa Cruz Island - how and when did they arrive?  They've been there long enough to evolve into smaller versions of their mainland counterparts, but does that make them "native"?  More "native" than the rats?  By what measure?

We can't un-break the egg.  Here in the Anthropocene era, we rely on the twin indices of appeal and efficiency, in deciding which species are good and which must go.  Water managers across the American West have declared war on Russian olive and tamarisk, which crowd riverbanks, sucking up water and blocking access for native creatures - but the primary creatures that want that water, and that riverbank access, are humans.  Fish and elk have no voice, neither do Russian olive trees.  Rats and snakes are "pest" species, raiding the nests of other creatures - but they're just doing what nature has equipped them to, and perhaps it's their survival skill that makes us hate them.  A weed is a successful plant; a pest is a successful animal. Human interference is the beating heart of the problem.