Unwanted Guests

From the moment Tomás de Berlanga and his crew were blown off course and arrived at the Galápagos in 1535, people began to introduce new plants and animals to the islands. Many were brought here intentionally, long before people thought about the effects these new living things might have on the existing ones.

Goats, pigs, dogs, and plants were brought to the islands on purpose. They were there to make life easier for travelers and settlers. They are what we call introduced species. Other living things—rodents, insects, and weeds—probably arrived as stowaways on ships.

Cats are not from the Galápagos. A cat can harm native and endemic wildlife.

Wild boars, or wild pigs, now roam the islands.

Is this important? Yes. Because most Galápagos plants and animals evolved in isolation, which means they are vulnerable to competition, predation, and diseases from these invaders. The Charles Darwin Foundation estimates that there are more than 1,700 introduced species in the Galápagos today. Many are harmless, but others pose a threat to native species. We call these invasive species.

Blackberry plants grow and spread quickly. They take up space native plants need to grow.

Plant Invaders

Of these invasive species, probably 700 of them are plants. One plant, in particular, has been a cause for concern: the wild blackberry. It was first introduced to the islands in the 1970s. Once here, it quickly spread across the islands.

Some of the hardest hit places have been the Scalesia forests on the highlands of Santa Cruz, Isabela, Floreana, and San Cristóbal. Scalesia plants are giant members of the daisy family. They can grow up to 15 meters (49 feet) tall and have a trunk that measures 60 centimeters (2 feet) around. These forests are homes to a variety of bird species, including the woodpecker finch and vermilion flycatcher.

Wild blackberries easily crowd out Scalesia. On Santa Cruz alone, only one percent of the original Scalesia forests remain intact, according to the Galápagos Conservation Trust. Across the islands, it’s estimated that blackberries have taken over the equivalent of more than 21,000 soccer fields. Blackberries are problematic to Galápagos farmers, too.

Farmers consider the blackberry a weed. It grows in dense, thorny thickets up to four meters (13 feet) tall. It turns farms into wastelands by choking out other plants. Fighting the blackberry is harder than you might think. Destroying it by hand is back‑breaking work. And killing it with herbicides is too risky—those poisons could harm other plants and wildlife, too.

Life Science

Ecosystems and Introduced Spieces