[Excerpts from Adventure Guide to Ecuador & the Galapagos Islands, by Peter D. Krahenbuhl] One of the most amazing and interesting facts about the Galapagos Islands is their role in influencing ou...
Invasive Species & Biosecurity
Since humans first arrived in the Galapagos in 1535, we have introduced a whole host of alien plant and animal species to the islands. Because Galapagos plants and animals evolved in relative isolation, they are extremely vulnerable to competition, predation and diseases from outside organisms. As such, invasive species pose perhaps the most serious threat to the ecological integrity of the Galapagos Islands and to the long-term survival of the many unique and remarkable species that live there.
Many new species were brought to the islands intentionally, before humans knew better or understood the impacts they would have on native life forms and ecosystems. These include goats, pigs, dogs and a variety of ornamental and agricultural plants. But many species were, and continue to be, introduced unintentionally, including rodents, insects, weeds, and harmful microscopic organisms.
The Charles Darwin Foundation estimates that there are over 1,700 introduced species in the Galapagos today. Many of them are relatively benign or even harmless, but others, categorized as invasive, pose an immediate and dire threat to native species.
It is believed that there are around 700 invasive plant species in the Galapagos. While most are not considered overly invasive, some have wreaked utter havoc on the endemic flora of the Galapagos. For example, wild blackberry (also known as Mora) was introduced in the 1970s as an agricultural plant and eventually spread throughout much of the islands, devastating endemic Scalesia forests in the highlands of Santa Cruz, Isabella, Floreana, and San Cristóbal. On Santa Cruz alone, where wild blackberry covers 15,000 hectares, only 1% of the original Scalesia forests remain intact. Scalesia forests are found only in the Galapagos and provide habitat for a variety of bird species, including the woodpecker finch and vermillion flycatcher. Efforts to control wild blackberry have been unsuccessful thus far.
There are nearly 550 species of introduced insects in the Galapagos – more than a quarter of the total insect fauna. Among the most troublesome are two species of fire ant, two species of wasp, and an ectoparasitic fly called Philornis downsi, which lays its eggs in the nests of birds so that its larvae, once hatched, may consume the hatchlings. The mangrove finch, with a total estimated population of just 100 individuals in the wild, has been particularly hard hit and faces the serious threat of extinction.
There are thirteen introduced mammal species in the Galapagos. Some of the more problematic ones include dogs, cats, pigs, rats and goats. Whalers, who were looking for a steady source of meat, introduced goats to the islands in the 1850s. They thrived here and destroyed massive swaths of habitat, turning once intact native ecosystems into vast expanses of desert. This harmfully impacted many native species, including the giant tortoise, whose preferred diet of prickly pear cactus is also favored by goats.
Efforts to Control Invasive Species
The Galapagos National Park, the Charles Darwin Foundation, and other organizations are working diligently to combat and control invasive species and prevent new ones from arriving. In the 1990s, the Galapagos Inspection and Quarantine System (SICGAL) was established to inspect goods arriving on cargo ships and the luggage of newly arrived tourists with the goal of catching any “stowaway” insects or seeds that could prove harmful. And today, a massive overhaul of the cargo supply chain and quarantine system is underway which, when complete, will greatly reduce the risk that new invasive species will be introduced.
Efforts to control invaders already in the islands include the practice of biological control, which involves introducing the natural enemies of the invaders into the Galapagos ecosystem. For example, after years of extensive research, the Australian ladybug was introduced to combat the invasive cottony cushion scale, an insect that threatened more than 60 native plants. Thus far, the ladybugs have managed to control cottony cushion scale numbers with no apparent negative impact on other species.
Project Isabela is perhaps the best know and most successful invasive species control initiative to date. In 2006, tens of thousands of feral goats were eradicated from the island of Isabela, paving the way for the restoration of native habitat on the island.
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