Unwanted guests

From the moment Tomás de Berlanga and his crew arrived at the Galápagos in 1535, people introduced new plants and animals to the islands. People did not consider the effects these living things might have on existing ones.

Goats, pigs, dogs, and decorative and agricultural plants were brought to the islands on purpose. They were to make life easier for settlers. They are called introduced species. Other living things— rodents, insects, and weeds—probably arrived 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. Most Galápagos plants and animals evolved in isolation. Outside organisms put them at risk of competition, disease, or even attack. It is estimated there are more than 1,700 introduced species in the Galápagos today. We call some invasive species.

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

Plant Invaders

About 700 of these invasive species are plants. One plant, the wild blackberry, has been a cause for concern. It was introduced to the islands in the 1970s as an agricultural plant. Once here, it quickly spread across the islands.

The blackberries crowded out 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. These forests are homes to a variety of bird species, including the woodpecker finch and vermilion flycatcher.

Wild blackberries easily crowd out Scalesia. Across the islands, it’s estimated that blackberries have taken over the equivalent of more than 21,000 soccer fields. They’re a problem 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 hard work. Destroying it by hand can be back‑breaking. And killing it with herbicides is too risky— the poisons could harm other plants.

Crosscutting Concepts

Cause and effect