Cummings School graduate Paula Castaño restores ecosystems to protect species on the famous archipelago
Paula Castaño, VG12, is making a difference on the Galapagos Islands. One example? “Three or four years after we removed the invasive rodents from Pinzón, the Pinzón giant tortoise was able to breed in the wild for the first time in more than 150 years,” she says.
As traders and pirates visited the Galapagos over the centuries, they brought some cargo—cattle, goats, feral cats, and rats—that wreaked havoc on the islands' native species. Paula Castaño, VG12, is working to repair the damage so native animals can once again thrive.
“Some of these islands, they never had a predator like rodents before, so they never developed a mechanism to survive,” Castaño said. Without natural checks in the system, introduced species, such as Norwegian and black rats, ran wild.
Enter Island Conservation, where Castaño is a native species manager. The international nonprofit protects threatened wildlife from extinction by removing invasive species and restoring island ecosystems.
While her colleagues target interloping fauna, Castaño’s job is to care for animals native to the Galapagos, minimizing threats to a mind-boggling array of species—many found nowhere else on Earth—that call the Ecuadorian archipelago home. That involves banding, tracking, and monitoring wildlife; temporarily taking at-risk species into captivity; and carefully reintroducing populations back into their natural environments.
On Floreana, one of the archipelago’s 18 main islands, “we’ve already lost around 12 species," Paula Castaño said. "When you lose one species, you potentially lose a resource that’s sustaining the ecosystem as a whole.”
Islands in the Stream
Islands are unparalleled living laboratories for wildlife observation. That’s particularly true of the Galapagos, famously studied by Charles Darwin on an 1835 visit that helped him develop his theory of evolution. While islands collectively represent only 5% of Earth’s landmass, 41% of all endangered vertebrates live on islands, and 75% of animal extinctions since 1500 have occurred on islands.
“And 86% of those cases are due to invasive species,” said Castaño, who worked as a wildlife veterinarian in Colombia and the United States before receiving her master’s degree in conservation medicine from Cummings School of Veterinary Medicine.
Why does that matter? “We’re losing species,” Castaño said. On Floreana, one of the archipelago’s 18 main islands, “we’ve already lost around 12 species. When you lose one species, you potentially lose a resource that’s sustaining the ecosystem as a whole.”
Castaño offers seabirds as an example: “We’ve seen that, on islands where you have rodents, you have fewer seabirds. When you have fewer seabirds, there’s less guano, less input of organic material into the ocean.” Less organic material can mean smaller fish populations, slower-growing coral reefs, and impeded coral recovery from climate-change-induced shocks. Without healthy reefs, shorelines lose a buffer against storm-related erosion.
A Delicate Chain
When removing invasive rats, Island Conservation first identifies every possible impact on every animal in the ecosystem. “It’s very thorough, what we do,” Castaño said. “You have to go through the whole list of species present on the island and identify potential pathways of exposure to the targeting method used.”
The process can take years of planning. In cooperation with Galapagos National Park, Island Conservation started small before working up to larger islands that are home to more elaborate ecosystems.
Now, a decade after the removal of invasive rodents from Pinzón and Rábida Islands, Castaño is witnessing big wins. “Three or four years after we removed the invasive rodents from Pinzón, the Pinzón giant tortoise was able to breed in the wild for the first time in more than 150 years,” she said. And on a trip last fall, the team recorded healthy populations of a species not previously observed on Pinzón (the Galapagos rail), as well as a species locally extinct for the last 40 years (the cactus finch). On Rábida, “We also discovered a thriving gecko species known only from subfossil records dated over 5,000 years old,” Castaño said.
Surviving and Thriving
Soon Castaño will apply lessons learned from earlier restoration projects to what may be her most ambitious assignment yet. While colleagues target invasive rats on Floreana—an island home to a host of native and endemic wildlife, including 54 globally threatened species—Castaño and her team will temporarily capture and care for short-eared owls and five species of Darwin’s finches. “That’s about 830 finches, plus around 60 owls,” she said, excitement and gravity mingling in her voice.
Unlike much of the Galapagos, Floreana is also inhabited by pets, livestock, and people, making the project all the more complex. But locals have been an integral part of the restoration efforts from the very beginning, when they sought Island Conservation’s help more than a decade ago, Castaño said.
“It was not us coming in and saying, ‘We have to remove invasive species, because we say so,’” recalled Castaño, who grew up in Cali, Colombia, and now calls Puerto Varas, Chile, home when she’s not in the field. “They said, ‘Our vision for Floreana is a sustainable island, where we don't have invasive rodents and feral cats, and we are able to protect nature, but we also have sustainable agriculture that allows us the resources and the livelihoods we deserve.’”
She said all parties agree on the end goal: the restoration of an ecosystem unlike anywhere else on the planet, where marine iguanas, Darwin’s finches, and giant tortoises live alongside people who value them.
“We are not looking to rewild an ecosystem and not have humans there anymore,” Castaño said. “The idea is communities continue to thrive together with nature in the long term.”
