“Invasive alien species” (IAS) is the term used to describe animal and plant (and even bacteria, viruses) species that have been deliberately or accidentally introduced to new parts of the world, generally through human a
gency, and having been introduced they have the capacity to thrive in their new environments. In so doing they can play significant roles in their new environments. Sometimes these roles have negative impacts on native species, their environments and even on man’s interests.
On small islands it is often easy to see some of the deleterious impacts of introduced species, especially rodents, which have devastated some populations of native species even to the extent of global extinction. Huge resources are now being devoted to removing some IAS from islands throughout the world in order to “rescue” native species that are threatened with extinction. In Seychelles both Green Islands Foundation and Seychelles Islands Foundation are active in such projects and I have been fortunate in being able to initiate some of these, notably the removal of Common Mynas from Denis and North Islands and the removal of Red-whiskered Bulbuls and Madagascar Fodies from Assumption Island, where their presence posed a threat
to endemic and indigenous birds on neighbouring Aldabra atoll. Our successful removal of mynas from Denis Island has already demonstrated benefits in that the populations of endemic birds have already shown marked increases (and we think some seabirds are benefiting too).
IAS can also have serious consequences on larger land masses, however, and native Australian mammals have suffered widely as a result of the introduction of European mammals, both predators and grazers. The Common Starling, now a bird of conservation concern in Britain, remains an IAS of major concern to agriculture, and also to some aspects of conservation, following its deliberate introduction to the United States in the late 19th century.
The threats to global ecosystems are such that Dr Piero Genovesi, Chair of the IUCN Species Survival Group Invasive Species Specialist Group (ISSG), led debates that highlighted the negative roles of IAS, especially in relation to biodiversity loss, at the recent World Conservation Congress in Hawaii.
Closer to home, the European Union has now published a list of 37 plants and animals whose breeding, deliberate release, keeping, sale and transportation is now illegal. The list includes (only) three species of bird: Indian House Crow, Sacred Ibis and Ruddy Duck, all species that are already present in Europe. The last species is already well down the path of eradication in the UK, while the House Crow has established a small population in the Netherlands and Sacred Ibises have a large population at various locations in western France.
Surprisingly, other invasive birds are omitted, such as Ring-necked and Monk Parakeets (both already present in the wild in UK and elsewhere in Europe) and Common Myna (some small populations have been eradicated in western Europe but larger incursions are knocking at the doors of south-eastern Europe).
Where invasive birds are established in Europe there are mixed feelings about their eradication. Undoubtedly the best time to eradicate, in terms of ease and cost, is when a population is very small. However, the people most likely to encounter invasive birds on their first arrival in a country are birdwatchers. Those of the rarity-hunting type may be reluctant to report a new country record if they know the bird is likely to be shot or trapped and this secrecy risks losing the best opportunity to prevent the establishment invasive birds, both those on the new EU list and others that arguably should be on it.