2017 Guest blog: South Georgia

During Invasive Species Week 2017 we heard lots about how invasive non-native species (INNS) are having an impact in Great Britain, but further afield they are also an important issue.

The UK has 14 Overseas Territories (OTs), all of which are islands except for the British Antarctic and Gibraltar. Biodiversity in the OTs is globally significant, supporting unique species and ecosystems and a large number of rare and threatened species.

The impacts of invasive non-native species on small islands is often much worse than elsewhere because the native flora and fauna have evolved in isolation from predators, competitors and diseases. As a result native species are less able to compete and defend themselves in the face of new threats.

Read on for a guest blog from one of the UK OTs.

South Georgia: Invasive species and their management

South Georgia is a haven for wildlife. The waters around the remote South Atlantic Island are one of the worlds largest Marine Protected Areas it is home to about five million seals of four different species, and 65 million breeding birds of 30 different species.

However, past human activities have had profound impacts on the flora and fauna. Sealing began in the late 1700’s and by the early 1800’s fur seal populations were severely depleted. Then, between 1904 and the 1960s, a shore based whaling industry hunted tens of thousands of whales bringing some species close to the brink of extinction. These industries also brought with them a host of invasive species which had a huge impact on the islands native biodiversity.

One of the most destructive was rats that were inadvertently introduced by sealing parties along the entire north coast line. The rats preyed on the chicks and eggs of the native birds which nested in shallow burrows making them particularly vulnerable to predation. They also preyed on the South Georgia pipit, an endemic species and the Antarctic’s only song bird.

Then on the early 1900’s reindeer were introduced by a Norwegian whaling station manager, Carl Larson as a source of recreational hunting and a reminder of home. In the absence of disease or natural predators were able to thrive and multiply rapidly. Reindeer are voracious grazers and quickly denuded the local tussock vegetation. Without the cover of vegetation, the underlying peat dried out and caused the collapse of the bird burrows below.

As well as introduced mammals, over the years, a wide range of non-native plants have been introduced to the island. There are now more than twice as many introduced plant species as there are native plant species. In the right conditions, these quickly growing species which thrive on disturbed ground can outcompete the much slower growing native plants.

Action to protect South Georgia from invasive species was urgently needed and so over the last 5-years several eradication programmes have been initiated. The Government of South Georgia & the South Sandwich Islands undertook a reindeer eradication programme which was conducted in collaboration with the Norwegian Nature Inspectorate (SNO) and involved the removal of almost 7,000 reindeer using a combination of herding and corralling and ground shooting methods. Once the reindeer were removed, the way was open for the South Georgia Heritage Trust to undertake the worlds largest attempted rodent eradication project. This involved using helicopters to spread poison bait so it was important that the reindeer were removed first so they did not eat the bait and jeopardise the success of the project. Tackling introduced plants began in earnest in the years following. In the absence of grazing pressure it was possible to accurately map distributions and identify high priority species and areas. A strategic management plan has been developed and it is hoped by 2020 33 out of the islands 41 non-native plants will be eradicated or managed to zero population density.

Article written by Jennifer Lee, Environment Officer for Government of South Georgia & South Sandwich Islands

More information on the UK OTs can be found here

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