Due to its  location and distance from the mainland, the Galapagos Islands have been a home for many unique species throughout the centuries. However, ever since the first European settlers began to bring domestic animals onto the islands, the native species have been going into decline. The rapid rate at which new species were introduced gave no time for the indigenous species to adapt. As a result, feral animals (those who escaped, or were let loose, from farms and homes) roam freely over the islands, destroying habitat and competing with native species. More recently, with an increase in tourism and worldwide travel, new plants are often brought onto the island for agricultural and ornamental purposes. Another worry is new insects, which come with the shipments of imported food needed to feed the growing population (Perry 1984). In 2003, according to the Charles Darwin Foundation (CDF) Annual Report, 440 newly introduced insect species were recorded in the islands.
    In general, good solutions are hard to find. Hunting is difficult due to the rough island terrain and the abundant vegetation. Poisons and traps will harm native species as well unless great care is taken. Fences are expensive and only a short-term solution, and biological controls require intensive research before they can be used effectively and safely (Thornton 1971).
    Floreana has a hotel and a small native population. As a result, there are many invasive species there. Espanola has no human settlements (due to its lack of freshwater resources) and contains very few invasive species.

Unless otherwise noted, the information in the table above is from (Jackson 1993; Perry 1984; Still et al. 2000; Thornton 1971).