Conservation Measures

Measuring the Impact of Island Conservation

To assess if island restoration efforts are protecting imperiled species, Island Conservation monitors, measures and maps targeted species and their habitats before and after our intervention. Scientifically documenting the response of island species and ecosystems also enables us to adjust and improve island restoration strategies and tools.

Complete island recovery after the removal of invasive species can take decades. To monitor recovery in the interim, Island Conservation also uses short-term measures (1-5 years post removal) that are indicative of longer-term change. Examples of these measures include quantifying the calling activity of seabirds returning to breed on Hawadax (formerly Rat) Island, Alaska, and counting the number of native plant seedlings on Palmyra Atoll, both of which we expect to respond quickly following restoration of these islands.

How we measure impact

We use standardized methods ranging from using satellite imagery to map vegetation change, using artificial habitat to count threatened reptiles, and trained experts to identify bird nests and measure breeding success. We evaluate islands before and after the removal of invasive species and where possible, we compare restoration efforts to control islands where no invasive vertebrates are being removed, or where they have never been present, to provide a yardstick for recovery expectations.

Who we work with

We aim to work with scientific experts to undertake monitoring on project islands. In many cases we are fortunate that robust data sets already exist, and valuable scientific resources are already being directed at places we work. Examples of partners we work with include University of California at Santa Cruz Coastal Conservation Action Lab on Rat Island in Alaska and Palmyra Atoll in the Line Islands, Oikonos in the Juan Fernandez Archipelago, Dr Christine Parent in the Galapagos, and Pacific Rim Conservation and Kauai Endangered Seabird Recovery Project on Lehua in Hawaii.

Conservation Measures in action

DESECHEO ISLAND, PUERTO RICO Before we began removing invasive species from Desecheo Island in 2008, we started counting Higo Chumbo (Harrisia portoricensis) plants, a rare and threatened cactus. To date, since the removal of majority of invasive species, 72 new cactus plants have been discovered in island-wide field surveys, compared to only nine reported in 2003.

HAWADAX (formerly RAT) ISLAND, ALASKA Rats, an invasive, non-native species on this Aleutian Island, had invaded what came to be known as Rat Island several decades ago. The rat found easy prey in the island’s abundance of birds, including the Song Sparrow, a small songbird. Not surprisingly no records of this species were collected during surveys in the presence of rats. Following the removal of rats from the island in 2008, this charming bird was identified first time during 2010 bird counts, potentially indicating a return of this species to Rat Island. Additionally, In June-August 2011, biologists recorded Leach’s Storm-petrels calling on the island. The presence of these birds and their behavior is strong evidence that the island is quickly recovering. The island was renamed in May 2012.

DIISE Database