Inputs of total phosphorus (TP) to a small lake (0.4 km2) located in western suburban Boston were compared during a drought (fall 1995) and a normal rainfall period (fall 1994) to explore potential effects of Canada geese (Branta canadensis maxima) and climate change on phosphorus loading to suburban lakes of the Northeastern U.S.A. In fall 1994, the watershed supplied 18 times more TP than Canada geese, but during the fall drought of 1995, TP from Canada geese exceeded that from the watershed by more than 7 times. Differences in the relative importance of TP loading from Canada geese and the watershed were caused by variation in streamflow between years. Under conditions of climatic warming, annual streamflow in the Northeast (U.S.A.) is projected to decline by ~30% with greatest reductions (~60%) occurring in the fall. At this time of year, Canada geese are most abundant and are likely to become the major contributor of TP to urban lakes. Furthermore, annual absolute inputs of TP from geese to suburban and urban lakes of the Northeast are likely to increase with warmer conditions associated with climate change, because ice cover in winter is unlikely to form on lakes in this region. Consequently, geese are likely to remain on such lakes during the winter rather than moving to open coastal waters as they do presently when lakes freeze. Thus, both the warmer and drier conditions predicted to accompany climate change may exacerbate effects of Canada geese on the water quality of suburban-urban lakes in this region of North America.