Effect of alternative regional urban growth scenarios on a major urban lake

Abstract Costadone L, Sytsma MD. 2022. Effect of alternative regional urban growth scenarios on a major urban lake. Lake Reserv Manage. 38:228–239. Land use management decisions developed at the regional scale that are intended to optimize environmental quality could have negative results at a local scale. We downscaled 3 regional urban growth scenarios (low, medium, and high land conversion) to a watershed scale and assessed how different regional land-use scenarios can impact important ecosystem services provided by a major urban lake. The scenario that depicted a low land conversion and concentrated future urban growth within an urban growth boundary at the regional scale resulted in a high-density development in the area surrounding the lake at the watershed scale. This type of development resulted in an increase of more than 30% in external phosphorus input to the lake compared to current conditions. Higher external phosphorus input will likely lead to water quality deterioration, with detrimental consequences for the ecosystem services provided by the lake. Our model forecasted a reduction of 3 to 4 m in lake water transparency, which will diminish recreational benefits provided by the lake and degrade wildlife habitat. In the next decades, population growth and land conversion will likely cause the resurgence of serious eutrophication symptoms. The reinforcement of nutrient management practices in the lake watershed will be necessary to offset the negative impact of urbanization from regional scale planning. Land-use policies developed at regional scales should consider trade-offs that impact highly valued local sources of ecosystem services.