Ascension : Conservation Weekly
Submitted by The Islander (Conservation Office) 25.11.2010 (Article Archived on 09.12.2010)

The native ecosystems present at the time of human arrival on Ascension were still at a relatively early stage of development and of little use to the human colonists.

Ascension Island Conservation Department
 The spread and control of invasive species on Ascension Island

The native ecosystems present at the time of human arrival on Ascension were still at a relatively early stage of development and of little use to the human colonists. Therefore, native habitats were destroyed and replaced. Botanist Joseph Dalton Hooker visited the island in 1843. He advocated the mass introduction and planting of trees, shrubs and grasses for pasture on Ascension. The aim of this was to increase mist interception and soil development, and reduce soil erosion. This plan was implemented by the Royal Botanic Gardens Kew. Over 220 species were introduced to Ascension Island. This has resulted in the spread of non native vegetation.

Today Green Mountain is largely covered with dense vegetation and man-made cloud forest. Following this, the lowland areas have been invaded by these alien invasive species. Even the lowland areas have been substantially invaded by non-native shrublands, species such as Guava (Psidium guajava) Mexican thorn (Prosopis juliflora) and yellowboy (Tecoma stans).

                                           
                                                         Green Mountain

Mexican thorn (Prosopis juliflora), was introduced to Ascension Island in the mid 1960s during the construction of Two Boats village. The aim was to help consolidate soil and improve its water holding capacity. It did not become a problem as an invasive pest until at least the mid 1980s. Mexican thorn is now well established and has colonised many areas which were previously bare of vegetation. It is a particular threat in conservation areas, particularly on the green turtle nesting beaches, the seabird nesting grounds and endemic plant habitats, such as the Ascension Island spurge (Euphorbia origanoides).

                                  Ascension Island spurge (Euphorbia origanoides)

The South Atlantic Invasive Species (SAIS) Project was EU-funded and managed by RSPB. The project has been working with the UK overseas territories in the South Atlantic since 2007. On Ascension an island wide botanical survey was carried out in 2008 and demonstrated how critically endangered Ascension's few unique endemic plants are. The project funded the purchase of equipment and hiring of personnel in attempt to control the spread of invasive species in the sensitive conservation areas. The aim was to try and safeguard the remaining native species. As a result of the botanical survey a number of potentially severe plant species may have been stopped in time. All known examples of the bullgrass Juncus capillaceus and wild mango Schinus terebinthifolium have now been removed.

Other work on Ascension focuses on the control of Mexican thorn in conservation areas, as eradication of this well established species is impractical.

One of the goals of the SAIS project was to produce a Regional Strategy on Invasive Species. The Strategy is intended to present regional priorities in relation to future invasive species work in the South Atlantic, and to provide a set of objectives against which progress can be measured. The Strategy should assist in guiding future projects and facilitating cross-Territory working which may bring more resources into the region from external funders. The Ascension Island Government has signed up to the strategy, along with all other Governments of the South Atlantic UK Overseas Territories.

Propagating Ascension’s endemic plants

Despite the South Atlantic Invasive Species ending in December 2009, the Conservation staff on Ascension continue to keep a check on the spread of the alien invasive species. All of Ascension’s endemic species are on the IUCN Red List of Threatened Species, mostly due to the spread of alien invasive species, taking over the wild populations and pushing the endemics to the brink of extinction. The Conservation team, led by Stedson Stroud, continue to clear and restore sites where invasive species had taken over. Through careful propagation of the threatened endemic species, stable populations of these plants have now been established and efforts are underway to reintroduce more of them to suitable parts of the island.

Volunteers

We would like to thank Georgina Sheehan for her help over the last year with our Conservation work. Georgina has been a regular volunteer and helped with the propagation of Ascension’s endemic plants, the annual plant survey and the control of invasive species. Both Noel and Georgina have helped with the annual beach clean up before the start of the turtle nesting season.  Their help has been very much appreciated and we wish them both best wishes for the future.

The RAF Movements team who have been regularly helping to keep the Green Mountain National Park paths clear from invasive species. Thank you for all your hard work and contribution to conservation on Ascension.

Thank you to Mary Thompson (pictured left with Natasha) who has been a regular volunteer for many years. She has assisted Stedson with numerous jobs and call outs during weekends and evenings.

Recycling

We are looking for used drink cans (not crushed) to use as plant pots for our endemic plants. If anyone is able to save cans please let us know so we can collect them.

Volunteers welcome.

Please contact Olivia Renshaw

olivia.renshaw@ascension.gov.ac Tel: 6359