|Free-flying colony of sacred ibis in a zoo in Northern Italy © Photo: Riccardo Scalera|
According to the study over one third of species included within the CMS appendixes are under some level of threat from IAS, with seabird and marine turtle populations in their breeding/nesting grounds on island ecosystems being most under the threat of IAS. In total, 78 IAS have been recorded as having some measure of impact on CMS listed species, e.g. through predation, competition and genetic changes caused by hybridization, as well as through the transmission of diseases, impairment of breeding and by causing loss of habitat and resources crucial for migratory species. The top ten IAS include introduced mammal predators - such as cats, rats, dogs, pigs, and house mouse - and introduced herbivores - such as European rabbits, goats and domestic livestock. The spread of invasive alien plants, such as grasses and macrophytes, are another cause of habitat alteration and loss, as they may alter habitats of bird species through competition and displacement of native plants. An example is the intentional introduction of ornamental and “useful” plants such as the ironwood (planted for erosion control and as wind breaks along coastland), which is also known for its impacts on dune ecosystems, on native dune plants and nesting grounds of turtles. The spread of alien pathogens is also a serious threat to migratory species. For example migratory bird species especially waterfowl, shorebirds and gulls are both victims and vectors of the highly pathogenic avian influenza. Interspecific hybridisation is a concern among sturgeon populations.
|The sacred ibis: a conservation paradox © Photo: Riccardo Scalera|
The risk of migratory species to become invasive themselves if translocated and/or introduced outside their natural range, can help understand the complexities which characterize the interactions between IAS and threatened migratory species. For example, the sacred ibis, a native to Sub-Saharan Africa and the Middle East, is a kind of “conservation paradox” for although it is protected by the CMS, outside its native range is considered a threat to other species, including those protected by the CMS itself. In Europe, where breeding populations of this intra-African migrant are known in Spain (including the Canary Islands), France and Italy, the sacred ibis has been recorded as predating eggs and affecting seabird colonies of sandwich terns, common terns and black terns, all CMS appendix II species. There are other CMS listed species introduced outside their native range, which could represent a threat for the native biodiversity. Examples are the beluga whale and the grey seal, introduced outside their native range in the Black Sea (which are CMS Appendix II species, see previous post here), although no specific impacts have been recorded as yet.
An analysis undertaken to identify gaps and synergies of current policy initiatives in relation to IAS, showed that the inadequate action related to the management of IAS is not a result of gaps in international policy but rather it is caused by inadequate enforcement at national level. A more systematic cooperation between different global conventions and multilateral environmental agreements would definitely provide greater and more effective opportunities to address biodiversity issues, including those measures to prevent the introduction and spread of the most harmful species. In this context, key recommendations of CMS Resolution 11.28 include the improvement of understanding of interactions between IAS and threatened migratory species; the development of priorities for intervention; the improvement in international cooperation and the development of adaptable management strategies (including prevention, control, eradication, etc.) when discussing topics for which IAS might be relevant. Other fundamental provisions focus on the need to avoid policies and initiatives that limit the use of effective measures to eradicate or control IAS (or facilitate their introduction and further spread); the importance to take into account the risk of facilitating the introduction or spread of IAS while implementing any climate change mitigation or adaptation measures; the identification of potential strategic partners and relevant stakeholders for developing information campaigns and other outreach activities; and of course the mobilization of appropriate resources for the implementation of the measures directed at dealing with IAS issues in relation to migratory species.