Quarantine
When I first visited the Galapagos at the beginning of the last decade, there was only a fledgling, relatively ineffective quarantine system. Since then they have become a core government function, built a public service agency (SESA) with purpose-built offices, and expanded from simple hand inspection to the use of x-rays. Although they still have some serious weaknesses (difficulty inspecting military and VIP traffic for example), my conclusion last time I looked at the system was that it had greatly reduced many of the most significant risks for Galapagos fauna at least.
Take the movement of birds, for example. Fighting cocks and other domestic birds were frequently brought in. Legal movements have now stopped, and smuggling is probably infrequent. That has slashed the risk of the introduction of bird diseases such as avian malaria and West Nile Virus. We only need to look at what happened in Hawaii when Avian Malaria arrived – most of the endemic terrestrial birds in the lowlands disappeared – to see what it would do to the Galapagos. And the Galapagos does not have highland refuges to minimise the damage.