Restore island ecosystems
Overall effectiveness category Awaiting assessment
Number of studies: 3
Background information and definitions
Islands account for approximately 5% of the earth’s landmass. They are home to high levels of biodiversity; however biodiversity is disproportionately threatened on islands compared to continental areas, with 61% of all extinct and 37% of all critically endangered species endemic to islands (Tershy et al., 2015). Restoration efforts often incorporate multiple actions such as: native vegetation planting, removal of invasive species, beach restoration and translocating native or surrogate fauna to re-establish ecosystem function across the whole island. The outcomes of island restoration are often realised over long timescales and study results should be considered with this in mind.
This action includes studies that have carried out a large combination of different interventions to restore the whole island ecosystem, including both plant and animal communities.
Studies discussing the effectiveness of individual actions or actions carried out on only parts of an island are covered elsewhere. For example, replanting vegetation (Plant native species), removing invasive or problematic species (Threat: Invasive or problematic species), or species reintroductions (Species Management).
Tershy B.R., Shen K.W., Newton K.M., Holmes N.D. & Croll D.A. (2015) The importance of islands for the protection of biological and linguistic diversity. Bioscience, 65, 592–597.
Supporting evidence from individual studies
A study in 1992–2006 on a tropical island in Seychelles (Samways et al. 2010) found that a programme of island restoration, including a large range of measures such as eradicating many invasive, non-native species and measures to control poaching, resulted in an increase in the number of hawksbill Eretmochelys imbricata and green turtle Chelonia mydas nests. Between 22 and 25 years after the start of an island restoration programme there were 19–43 sea turtle nests/year and 25–35 years after the programme’s anti-poaching measures were introduced, there were 66–108 sea turtle nests/year. The authors reported that the number of sea turtle nests had increased in each year of the study. In 1970s–2000s, Cousine Island (27 ha) underwent restoration, including invasive plant and animal removal, introduction of poaching controls and anti-poaching initiatives (details not provided), reintroducing native plants and bird species, increased biosecurity measures for incoming goods and the confinement of agricultural plants to a designated area (see original paper for details on all measures undertaken). Sea turtle nests were monitored from the 1990s onwards (no details were provided).Study and other actions tested
A replicated study in 2002–2011 in beaches on Poplar Island, Maryland, USA (Roosenburg et al. 2014) found that during the island rebuilding process, diamondback terrapins Malaclemys terrapin continued to nest on the island. Two years after island rebuilding began, 68 nests were laid on the island compared to 211 nests laid 11 years after rebuilding began. The highest number observed (282 nests) were laid five years after rebuilding began. Nest survival rates ranged from 59–85% over the period of 3–11 years after rebuilding began. Poplar Island was rebuilt from three 4 ha remnants starting in 2000 using the footprint of the island from 1850 (450 ha). A perimeter dyke was constructed in 2002 and the interior began to be filled with stone and dredged sand (expected completion in 2027). Nesting areas were monitored daily, and nests marked with flagging and covered with hardware cloth (1.25 cm2 mesh) to prevent bird predation. After 45–50 days, the hardware cloth was removed, and a metal flashing ring buried 10 cm around nests to capture hatchlings.Study and other actions tested
Referenced paperRoosenburg W.M., Spontak D.M., Sullivan S.P., Matthews E.L., Heckman M.L., Trimbath R.J., Dunn R.P., Dustman E.A., Smith L. & Graham L.J. (2014) Nesting Habitat Creation Enhances Recruitment in a Predator-Free Environment: Malaclemys Nesting at the Paul S. Sarbanes Ecosystem Restoration Project. Restoration Ecology, 22, 815-823.
A study in 2013–2015 on a mixed forest and scrubland island in the US Virgin Islands (Angeli et al. 2018) found that St. Croix ground lizards Ameiva polops translocated to a restored island continued to increase their range annually in the fifth to seventh year after being released. Five years after St. Croix ground lizards were released, lizards occupied 41% of sites surveyed and 69% of sightings were <200 m from the release site. Six years after release, lizards occupied 60–66% of sites surveyed and seven years after release this increased to 74–87% of sites surveyed. Lizards recolonised the island from west to east (see original paper for details). Restoration of native habitat, including forest, woodland, scrubland and sandy beaches, had been underway on Buck Island (71 ha) for 40 years prior to lizards being released in 2008. A total of 57 lizards were introduced to the island in 2007 and population surveys were carried out in 63 sites (1,260 m2 circular sites, at least 80 m apart). Sites were surveyed for three days, five times/season in May 2013, May 2014, October 2015, May 2015 and October 2015. In addition, in May 2013 a total of 192 extra surveys were carried out in 32 sites, which were surveyed twice a day for three consecutive days.Study and other actions tested