National Park staff work with researchers, the shire and the island community on a wide range of projects to protect the unique natural environment.
A dedicated team of rangers is rehabilitating the rainforest to ensure the survival of the rare and threatened Abbott’s booby.
Parks staff are fighting yellow crazy ants, the biggest threat to the island’s iconic red crabs and the health of the rainforest.
Like many oceanic islands, Christmas Island has many exotic plants and pests, often accidentally introduced by ship and sometimes deliberately by settlers.
Protecting Abbotts booby
The rare and threatened Abbott’s booby spends most of its life out at sea, but nests on Christmas Island and nowhere else in the world. The tall, emergent rainforest trees high on the plateau provide the only suitable nesting habitat, making this ecosystem critically important for the survival of the species.
In some areas, settlement and phosphate mining removed the original tall evergreen rainforest, with the loss of countless birds. There were indirect impacts too: open expanses of cleared mine lease caused wind turbulence over the forest canopy strong enough to dislodge Abbott’s booby chicks from their nests and limit the ability of parent birds to land and feed the young.
Rehabilitating the rainforest
The Abbott’s Booby Recovery Plan identified ecological restoration and reforestation of minefields as essential for the bird’s long-term survival.
Since the early 1990s, Parks Australia has established and maintained more than 320 hectares of rehabilitation forest. The current program, known as the Christmas Island Minesite to Forest Rehabilitation program, is funded by a conservation levy paid by by Phosphate Resources Ltd. Since 2004, more than 230,000 native trees have been planted under this program.
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Twenty six native species are propagated from seed in the national park’s nursery. Over a two to three year period, park staff planted the seedlings in two stages, first with with pioneer and then forest canopy species. Eight years of maintenance is required before the site is established enough to out compete weeds.
The good news is that native species such as red and robber crabs are returning to these areas. A measure of success has been that two to four years after planting, red crabs start burrowing and living in rehabilitated sites.
EPBC listed forest birds such as the emerald dove and the Christmas Island goshawk are and forest birds are also returning to these areas using these areas - and over time we hope to see an increase in Abbott’s booby populations.
Yellow crazy ants
Crazy ants are one of the world’s most invasive species. They were introduced to Christmas Island somewhere between 1915 and 1934.
In the 1990s, the numbers of crazy ants exploded and they began forming high density ‘super-colonies’. The ants decimated tens of millions of red crabs - the island’s keystone species, responsible for shaping and maintaining the health of the island’s unique rainforest ecosystems.
National park staff and researchers are leading the world in the effort to control these pests. They survey and map the ants spread and periodically undertake aerial baiting of super colonies. Aerial and ground baiting successfully eliminates more than 99 per cent of the ants within super colonies targeted. However Christmas Island’s steep and often inaccessible terrain makes total eradication by baiting impossible – and so the ants return.
The crazy ant control program is informed by the results of a rigorous biennial island-wide survey and expert advice from the Crazy Ant Scientific Advisory Panel.
Latrobe University is working with park staff to develop a way to control the honey-dew producing scale insects which provide the ant’s major food source. If scales insects can be controlled this may reduce crazy ant populations.
Weeds and pests
Like many oceanic islands, Christmas Island has many exotic plants, often accidentally introduced by ship and sometimes deliberately by settlers.
One quarter of the island’s native vegetation has been cleared since settlement, making it easier for introduced plants to spread. Most of these species are not a threat to the island’s native species or intact rainforests. Island residents collect introduced food plants such as chilli, lime, papaya and pumpkin which are sometimes found in the island’s forests.
Most introduced species have not yet invaded undisturbed rainforest vegetation – but managing weeds like Siam weed and false curry bush is a priority for national park staff to protect the habitats of native plants and animals.
Cats and rats
Feral cats and rats are a threat to native species around the world – but especially on oceanic islands like Christmas Island. Here cats are known to prey on native reptiles, ground nesting seabirds - including the golden bosun - flying foxes and forest birds. Rats eat the eggs of native wildlife particularly seabirds and forest birds.
Control of cats and rats is an ongoing challenge.The park works with the local shire to coordinate a multi-stakeholder program that includes several island agencies and the WA Department of Environment and Conservation.