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MEA Bulletin - Guest Article No. 112a - Friday, 25 March 2011
Migratory Species and Ecological Networks
By Borja Heredia, CMS Scientific and Technical Officer
Migratory species move across long distances from breeding to wintering areas or from areas with limited food supplies to others where food is abundant.  Migration has evolved as a means to adapt and exploit seasonal changes and to make an optimal use of available resources. We can find migration patterns across a wide range of taxonomic groups of animals including birds, terrestrial mammals, marine mammals, fish, insects, marine turtles and others.  Bird migration is probably the biological phenomenon that fascinates most.  It is very diverse ranging from the spectacular mass migration of large soaring species such as storks to the nearly indiscernible movements of aquatic warblers and other small songbirds that travel huge distances individually at night.

Migratory species have different ecological requirements during their annual cycle: In particular they depend on habitats that are well conserved to provide food and shelter. Habitat destruction and alteration is recognized as the first cause of biodiversity loss worldwide. This also applies to migratory species. Landscapes have undergone serious degradation as a result of urban development and expanding infrastructure that disrupt natural ecosystems. 

Human pressure on the environment can result in the overall loss of habitat, but also in reduced areas of available habitat made more isolated.  As a result, populations of migratory species cannot cross the areas of degraded land. They become increasingly isolated both geographically and genetically, a process that considerably increases the risk of species extinction. Habitat fragmentation generates species loss as decreased areas of habitat can support fewer individuals than larger areas of the same vegetation. Isolation impedes migration opportunities for many populations across vital habitats.

Ecological connectivity thus emerges as a key issue for the conservation of migratory species.  It can be achieved by establishing well managed ecological networks comprising biodiversity hotspots, corridors or stepping stones. The ecological network approach promotes connectivity among areas of high biodiversity value and between habitats used by species for different purposes. These corridors or linking areas are essential for migratory species. Corridors can be linear as in the case of a river and associated vegetation, contrary to habitats comprising a variety of vegetation types, or stepping stones for species.

The Convention on the Conservation of Migratory Species of Wild Animals (CMS) is an international policy instrument that provides a unique opportunity to promote ecological networks for migratory species worldwide. By doing so, it facilitates the process of migration and thus a better implementation of its conservation instruments on all continents. Its definition of migratory species is broad enough to cover those undertaking journeys of thousands of kilometers each year such as storks, but  also many other species that make small scale movements across national boundaries in a cyclical way such as gorillas. Species listed under Appendix I require habitat protection; those included in Appendix II need regional cooperation to ensure their migrations across borders.

Efforts to conserve the Siberian Crane, a flagship species, demonstrate how a network of critical sites can be established along the flyway to ensure that the key habitats are maintained. The UNEP-GEF Siberian Crane Project was a collaborative initiative of China, the Islamic Republic of Iran, Kazakhstan and the Russian Federation to develop a coordinated approach towards the conservation of a chain of internationally important wetlands along the two flyways used by this critically endangered species. Its main achievement has been the sustained ecological integrity of a network of globally important wetlands in Asia and the migratory waterbirds that depend on them.

In the case of terrestrial mammals, uncontrolled development and other obstacles such as fences or road construction are barriers that block traditional pathways and impede migratory movements. Increased poaching is usually another consequence.

CMS is deeply involved in the conservation of Sahelo-Saharan antelopes, which undertake extensive movements in search of water and pasture. Corridors are essential to make these movements happen. CMS is currently collaborating with the Sahara Conservation Fund and other partners to ensure that the last strongholds of species such as the Addax are protected and that habitat fragmentation does not affect the last remaining populations in the wild. Efforts now concentrate on designating a protected area in Termit-Tin Toumma in Niger, which is supported by the Fonds Français pour l’Environnement Mondial (FFEM) and the EU.       

The theme of the next session of the CMS Conference of the Parties (COP), “Networking for Migratory Species,” highlights ecological networks as a priority. A specific resolution is expected to provide guidance for the future of CMS. CMS COP 10 will take place in Bergen (Norway) from 20-25 November 2011.
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