Arctic geese, migratory connectivity and agricultural change:Calling the sorcerer's apprentice to order

The current favourable numerical status of most arctic-breeding goose populations conceals an increasing dependence on man-modified habitats for much of the year. Almost all populations are now heavily dependent on agricultural crops when the birds are away from the arctic breeding grounds. We examine the current understanding of the ecology of migration, highlighting the role of hot spots that provide fuelling stations which bridge the gap between the wintering and breeding grounds. Isotopic signatures of eggs indicate nutrients are being flown into the breeding grounds from afar. The susceptibility of geese to disturbance at these stopover sites, many of which are agricultural lands, may lead to reproductive failures. The near-complete loss of natural habitat, even in northern sites, makes the birds captive of agricultural policy. Barnacle Geese Branta leucopsis staging on managed grassland on their spring stopover accumulate more fat but less protein compared to traditional sites, and there is evidence of lower breeding success for individuals feeding on cultivated grass. This population, breeding on Spitsbergen, has been closely followed during a phase of population increase over the past thirty years. We show that although locally on the breeding grounds density-dependent effects have been confirmed (lower reproductive output, enhanced emigration) new colonies are still arising, and there has been no slowing of overall growth of the population. Worldwide, the most spectacular response to agricultural change is that of the Lesser Snow Goose Anser caerulescens cuerulescens. The populations have become so numerous that their spring grubbing activities are having a deleterious impact on arctic wetlands where they breed. It would be erroneous to generalise this example to conclude all long-distance migrating geese should be reduced. Current management polices are insufficiently grounded in basic research on the interaction of geese and their food resources which must include experiments in view of impending climate change. We advocate a vigorous intensification of individual-based research programmes.