Success in Invasive Plant Species Removal: A story of the Seychelles’ Aldabra Atoll

After 40 years of invasive management, researchers find a more effective approach to removing invasive plants in Seychelles’ Aldabra Atoll.

Belonging to the most distant islands of the Seychelles Atoll, Aldabra is a UNESCO World Heritage Site, protected for its biodiversity. Aladbra is home to a number of endemic species, some of which include the Seychelles Giant Tortoise, Frigatebirds, Tropic Birds, and the Red-footed booby. Originally found in Mexico the invasive sisal, scientifically known as sisalana agave, quickly began to outcompete native plants. This woody herb has a fast growth rate making it quick to take over available habitat, resulting in island biodiversity lost due to a lack of available food sources for native species.

A banded Seychelles Magpie Robin perched on a branch. Credit: James Russell

Manual eradication efforts of sisal began in the 1970s but were only moderately successful, due to the plant roots’ ability to penetrate Aladbra’s limestone surface—meaning complete removal of plant root through manual labor was impossible. The Seychelles Islands Foundation’s (SIF) needed to find a new solution and began an EU-funded invasive species project in 2012 to investigate alternative methods. Over seven months, between 2013 and 2014, experimental trials took place in order to determine the most efficient conservation tool.

The lagoon of Aldabra Atoll in the Seychelles is surrounded by limestone outcrops. Credit: David Stanley

Preserving biodiversity and sustaining health of the natural environment was of upmost importance to the foundations team, so experiments were carefully implemented. Through precise targeting, individual plants were directly applied an herbicide to the growth tip of the plant. The targeted approach prevented reduced risk to native flora. Ultimately, the research found no negative effects to the surrounding wildlife and was successful in removing the targeted invasive plant, allowing for native species to prosper.

After 40 years the Aladbra Atoll is finally free of the invasive harm caused by sisal. This story only adds to the success of invasive species eradication on the atoll in recent years, creating space for native wildlife to thrive and biodiversity to flourish.

Featured photo: An Aldabra Giant Tortoise. Credit: Peter Steward

About Isabelle Everhart

Isabelle Everhart is a current senior at UC Santa Cruz, pursuing a B.A. in Environmental Studies after transferring from Santa Barbara City College with an A.A. in Liberal Arts. She is expected to graduate summer 2019 after completing a field quarter in California Ecology and Conservation with the UC Natural Reserve System. Her background work in sustainability lead to her involvement in piloting a LEED lab on the UCSC campus, which uses the LEED green building certification standard to assess building operations in creating feasibility studies. Her passion for sustainability, conservation, and marine-related species make her excited to join the Island Conservation Communications team.

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