Coastal fertilizers in a nutrient-poor environment: Arctic seabirds
The Arctic Ocean is one of the most important seabird areas in the world, with an estimated population in excess of 25 million individuals in the European Arctic alone (Walday 2002). Among the most numerous species are guillemots (Uria aalge, Uria lomvia, Cephus grylle), puffins (Fratercula arctica), little auks (Alle alle), and kittiwakes (Rissa tridactyla). Without exception these birds find their food in the sea and breed on land, mostly on steep coastal cliffs. While a few species, such as the fulmar (Fulmarus glacialis) are able to fl y hundreds of kilometres between nesting and feeding sites, the breeding success of most arctic seabirds depends on suitable undisturbed nesting sites and feeding areas being available within a close distance.
Seabirds transfer large amounts of nutrients from the marine to the terrestrial environment. Bird colonies and the lush vegetation that develops below bird cliffs constitute a unique nutrient-rich habitat in the otherwise nutrientpoor arctic environment (e.g. Odasz 1994). This habitat has several spin-off effects on the rest of the terrestrial environment: First, bird cliffs are important foraging areas for arctic terrestrial herbivores such as geese, ptarmigan and small mammals. Furthermore, seabird colonies represent an important and traditional resource for indigenous peoples throughout the Arctic (NRC, 2003). Finally, seabirds constitute the bulk of the diet of coastal predatory birds (especially gulls and skuas) and arctic foxes.
The Arctic: a breeding ground for birds
Figure 6. Major global bird migration routes to the Arctic. Bird species that migrate to the Arctic coasts and wetlands arrive from nearly every corner of the planet.
During the summer, the sun never or nearly never sets, resulting in a short but intensive breeding season when millions of migratory birds arrive in the Arctic to breed. The majority of these birds seek the wetlands and coastal shores of the tundra plains. No other place on Earth receives so many migratory species from nearly all corners of the planet. The Arctic coastal regions therefore hold a very special global conservation value.
The Arctic coastal food web
Figure 7. The coastal Arctic food web is closely related to drift ice conditions and seasonal use of shorelines by both terrestrial and sea mammals. Numerous species depend upon each other and the transport of food to and from the marine areas to the coast and inland. Indigenous peoples use most of the food chain and traditionally use both environments for hunting, fishing and gathering.
An important feature of Arctic ecosystems is the strong dependency of people and wildlife on the interactions between land, coastal and marine resources. Reindeer/caribou, sea mammals and eggs all provide a major contribution to the diet of Arctic peoples (NRC, 2003). The diversity and productivity of ecosystems across the Arctic is to a large extent based upon a continuous fl ow of resources and nutrients between the terrestrial and the marine environment. Furthermore, many Arctic species including birds, reindeer/caribou and sea mammals are migratory or travel long distances, seasonally crossing both land and ice. Hence, they depend upon free access to large amounts of continuous habitat.
The vastness of the Arctic wilderness does not mean it is uninhabited. For thousands of years, people have lived and relied on arctic land and sea for subsistence, as well as for cultural and religious identity.
Living with the coasts: Seals and walrus
Arctic waters are for the most part shallow with a large proportion of continental shelf. High local productivity of fish and benthic invertebrates provide ideal conditions for benthic feeders such as walrus (Odobenus rosmarus) and bearded seal (Erignathus barbatus) and for pelagic species such as ringed seal (Phoca hispida), harbour seal (Phoca vitulina), hooded seal (Cystophora cristata) and harp seal (Phoca groenlandica). Seals and walrus are exclusive marine feeders with poor adaptations to life out of the water. Nevertheless they all depend on land or ice for activities such as moulting, resting/haul out and breeding (e.g. Wiig et al. 1999; Gjertz et al. 2001; Born et al. 2002; Moulton et al. 2002; Frost et al. 2004). Walrus and harbour seals use undisturbed beaches and rocky shores for haul out and socializing and often show great site fidelity (Harkonen and Harding 2001). The walrus in particular has been driven close to extinction by commercial harvesting for meat and ivory. Today the species is protected, apart from subsistence hunting, in most of its range. The coastal habitat it depends on however, remains for the most part unprotected.