The embarrassment of riches: agricultural food subsidies, high goose numbers, and loss of Arctic wetlands – a continuing saga

Abstract

Agriculture has provided a nutritional subsidy to the Anatidae (swans, geese, ducks), which has affected their trophic relationships and the Arctic wetlands where they breed. The Mid-Continent Population of lesser snow geese, which breeds in the Canadian Arctic and which traditionally wintered in the coastal marshes of the Gulf States, now feeds in agricultural landscapes. The geometric growth of this population since 1970 is coincident with increased application of nitrogen to farmland and high crop yields. Widespread availability of agricultural foods allows the birds to meet much of their energy demand for migration and reproduction. Their migration conforms to a stepping stone model linked to land use, but feeding also takes place upon arrival on the Arctic breeding grounds. High bird numbers have dramatically affected coastal marshes of the Canadian Arctic. Foraging has produced alternative stable states characterized by sward destruction and near irreversible changes in soil properties of exposed sediments. Locally, this loss of resilience has adversely affected different groups of organisms, resulting in an apparent trophic cascade. A spring hunt was introduced in 1999 in an attempt to check population growth. The current annual cull is now thought to be higher than the replacement rate. Much of the decline of the Mid-Continent Population is probably linked to shooting, but the harassment of birds that fail to acquire sufficient food for reproduction may contribute. The agricultural food subsidy has led to a mismatch between this avian herbivore and its environment — a consequence of migratory connectivity that links wintering and breeding grounds. Key words: agricultural crops, lesser snow geese, migratory connectivity, Arctic coastal marshes, grubbing, hypersalinity, the spring hunt.

Nutrient Uptake and Short-Term Responses of Phytoplankton and Benthic Algal Communities from a Subarctic Pond to Experimental Nutrient Enrichment in Microcosms

“…Fifteen ponds that span the coastal fen ecotype and that currently have only low (if any) disturbance from the LSG population were sampled to provide insight into the range of hydrolimnological variability for ponds unaffected by the LSG population expansion. Results are compared with analyses from pond WAP 20, which receives heavy use by LSG-its catchment is strongly disturbed by their activities during the breeding season (late May to late August; Jefferies et al, 2003). Our intent was to expand on methods employed in previous limnological studies of waterfowl disturbance.…”

Foliar DMSO:DMSP ratio and metal content as indicators of stress in Spartina alterniflora

“…littorinid snails: Silliman & Bertness 2002; sesarmid crabs: Holdredge et al 2009), and from agricultural subsidies that enhance food supply to herbivore populations (e.g. geese: Jefferies et al 2004). More recently, sudden dieback has resulted in the loss of salt marsh vegetation in areas along the entire US Eastern Atlantic Seaboard and Gulf Coasts since 2000 (reviewed by Alber et al 2008).…”

Spatial patterns of goose grubbing suggest elevated grubbing in dry habitats linked to early snowmelt

“…A classical example is the salt marshes along the Hudson Bay coast in the Canadian Arctic. These have been subject to large-scale vegetation loss and habitat degradation caused by grubbing by lesser snow geese (Anser caerulescens caerulescens; Kerbes et al 1990;Jefferies & Rockwell 2002;Jefferies et al 2003;Walker et al 2003;Jefferies et al 2006). In this case, the transition to an alternative habitat state had negative consequences for both the lesser snow geese as well as other species in the ecosystem (Milakovic et al 2001;Milakovic & Jefferies 2003;Rockwell et al 2003).…”