Carrying capacity of wetland habitats used by breeding greater snow geese

Because geese can damage their arctic breeding habitats through overgrazing , there is debate about limiting the rapid growth of the greater snow goose (Chen caerulescens atlantica) population and setting a population goal. To answer these questions, we assessed the nutritional carrying capacity of f reshwater wetland habitats for breeding greater snow geese at the Bylot Isl and colony, Nunavut, Canada. Specifically: we (1) mapped the different type s of wetlands on the island: (2) estimated net aboveground primary producti on of these habitats; (3) compared total food availability with predicted t otal food requirements of the current population; and (4) validated our pre dictions of plant biomass consumed by comparing them to the intensity of go ose grazing measured. Freshwater wetlands represented 173 =/- 6 km(2) or 11 % of the total area of the south plain of Bylot Island. Streams and wet pol ygons were the most important habitats in terms of availability of suitable forage plants for geese. The average net aboveground primary production ra nged from 21.0 +/- 4.6 along lakes to 46.0 +/- 9.8 g/m(2) in polygon channe ls, We estimated the total food supply available for geese in wetlands at 2 ,625 +/- 461 tons in 1997 but only 1,247 +/- 473 tons in 1996, a year of lo w plant production. We predicted a summer food requirement for goslings at 8.1 +/- 0.6 kg/bird, for breeding adults at 7.9 +/- 2.3. and for nonbreedin g adults at 4.7 +/- 1.5, and we predicted the total summer food requirement s of the goose population at 1,201 +/- 160 tons. The predicted amount of bi omass removed (32 +/- 7%) agreed well with the actual amount of biomass rem oved measured in mid-August (39 +/- 11%) in 1997, but not in 1996 (67 +/- 2 7% vs 26 +/- 17%, respectively), possibly because the goose population was lower that yt ar due to poor breeding success. In 1997, the goose populatio n was at 46 +/- 10% of the theoretical short-term earning capacity (341,000 geese) of the wetlands of Bylot Island. We recommend keeping the goose pop ulation below this theoretical carrying capacity.