Introduction of invasive alien species and diseases
The beginning of the islands natural environment and ecosystems affection started long time ago, back in the 1700s when sailors and pirates introduced alien species such as goats, rats and insects that had never had the chance to arrive without human help. This caused pressure especially in the reptile and bird populations.
After the first colonization, domestic animals were brought and started feral populations. Animals such as: dogs, cats, pigs, goats, rats and the little fire ant, among others were introduced to the Islands. These animals are not deadly themselves, but started to feed and destroy by competition the endemic fauna that never before had experienced this kind of predation and interspecific competition, after reaching the actual development point in such an isolated location.
Goats have a special ability to feed on nearly any plant and reproduce rapidly. Four individuals were introduced in Santiago Island in the early 1800s and reached a population of about 100,000. This lead for the extinction of five species of vegetation and endangered the tortoise population, competing for food and destroying marine iguana nesting sites.
Rats slowly took over the place of the native rats, as these introduced ones were more an aggressive specie. This caused big problems to endemic species specially feeding on tortoise, iguana, turtle eggs, flamingo and many other birds, and roots of several endemic species of plants.
Wasps are responsible for the decline of one specific specie of caterpillar; an important food source for finches.
Introduced plants spread mostly in the highlands creating competition with native and endemic vegetation. Most of these introduced species, such as blackberry, guava plants, and the cinchona (quinine), are highly developed in matters of survival strategies. They evolved in many very wild places where the use of features such as fast growing skills, defense spines, thousands of seeds per fruit, etc., made them worldwide successful species, and a real treat to the very slow growing flora of the islands.