A Return to Española Island to Understand its Ecosystem Dynamics

July 21, 2016

By Wacho Tapia, Director of the Giant Tortoise Restoration Initiative

Haga clic aquí para ver una versión en Español.

It’s been a year and 24 days since I fell on my final trek from the interior of Española Island to the shore after a week of monitoring the interactions among cactus, tortoises, albatross, and woody plants. Heavy rain had converted the rough lava trail to a slippery trap; my subsequent fall resulted in two broken ribs, one shattered tooth, and another four teeth nearly knocked out of my mouth.

I return this year with a bit of dread and taking extra precautions (uncommon for me) while walking with my nearly 100-pound backpack, climbing that same lava trail up to camp. We are here to continue our research to help answer a series of questions about the island and its inhabitants, such as:

  • What is the ecological role of giant tortoises in the island ecosystem?
  • Why there are so few Opuntia cactus on Española?
  • Does the woody vegetation play a role in the lack of regeneration of Opuntia?

A tortoise on Española

This trip the trail is dry. Due to the extreme drought that the Archipelago has experienced over the last months, it seems like we are in another place altogether. Nearly the entire island appears grayish brown, with a complete absence of herbaceous plants. Along with ensuring a dry, non-slippery trail, this eases our work. Inside our permanent sampling plots we find only the one Opuntia tree, which occupies the center, and a few woody species.

Mockingbird eating cactusMany of you may think this makes the work boring and the data uninteresting, but the dry conditions provide a precious opportunity to observe and understand things we’d never seen before or even read about in the scientific literature. We had always thought giant tortoises were responsible for the lack of recruitment of young Opuntia plants. However, when drought conditions persist making both food and water scarce for all, many other endemic species, primarily birds, feed on cactus fruits and pads. With the cactus population already low, a probable result of the once-present introduced goats, its long-term survival may be compromised, with extinction a real possibility.

This finding, which must be confirmed with additional research in both wet and dry years, suggests that the Opuntia population needs urgent attention. With a healthy and growing population of giant tortoises, it is all the more important to have a healthy and growing cactus population. This will be a long-term project and might include methodologies not unlike those we use for tortoises, with ex situ germination and rearing of young seedlings, which are then repatriated to the island; or perhaps careful in situ production of cactus, protecting the young from destruction by the native animals. Restoration of the natural vegetation community of this island is a long-term challenge.

Field work on Española

As we move forward, collecting and analyzing more data and discussing potential methodologies to fully restore the Española ecosystem, I will continue to return each year, enjoying the wonderful opportunity to work on this island, which like all Galapagos Islands will always be beautiful.

All photos © Wacho Tapia.

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