GIVEN MAN’S PROCLIVITY for greed and destruction, a wink can have a substantial impact.

The list of man’s effects on the Galápagos is long; some are quite obvious, others nearly invisible. A handful of goats introduced to Isabela Island some 30 years ago exploded into a feral population of more than 100,000, and although many have been removed, they still require careful attention. In 2001, an oil tanker, the Jessica, ran aground at the entry to San Cristobal Island’s Wreck Bay, spilling oil that reached nearby islands (fortunately, the damage was minimized by strong winds that blew most of the oil out to sea). Some fishermen, and, rumor has it, certain tour boats, dump trash and toilet discharge directly into the sea. Spores, insects, molds, and viruses arrive on shoe bottoms and in luggage. A ship anchors off an island for the night, and its blazing lights attract insects. When the ship pulls anchor the next morning, those insects travel on to the next island, adding new imbalance. And there are the towns, four of them, crammed into the three percent of land left to development. Coincidence or not, some tour boats eschew the towns entirely, furthering the illusion that the Galápagos are largely untouched.

Some say tourism is all that stands between the Galápagos and rampant degradation; even the most myopic Ecuadorian regime, they say, realizes that a Galápagos despoiled will no longer bring the tourists and their money. Others argue that tourism is responsible for its own substantial share of ills.

We visit Santa Cruz Island and Puerto Ayora on a bright and sunny day. Our schedule calls for a morning visit to the Charles Darwin Research Station and an afternoon in the highlands observing Galápagos tortoises.

I decide to skip the afternoon bus trip to the highlands because there are people I want to see — one in particular. I find Jack Nelson eating lunch alone at the Galápagos Hotel.

A soft-spoken man with the straightforward gaze of the self-sufficient, Jack came to the Galápagos in 1967. Few have his sense of perspective or his understanding of man’s place in the Galápagos.

“The majority of the people who live here in the Galápagos don’t understand or appreciate the value of conservation and sustainable development for their own future," says Jack. “A fisherman worries about today. Even an intelligent fisherman who sees the supply being wiped out thinks, ‘If I don’t get out there and get the last swordfish, someone else will.’ To make matters worse, Ecuador is a politically unstable country. It’s hard to adopt the long view when you’ve had five or six presidents in the last eight years."I walk with Jack to pick up his daughter at the school-bus stop. We stand in the hot equatorial sun. I ask about the future.