The latitudes, attitudes, and platitudes of watershed phosphorus management in North America

Authors: Smith, Douglas; MACRAE, M - University Of Waterloo; Kleinman, Peter; JARVIE, H - Centre For Ecology And Hydrology; King, Kevin; Bryant, Ray

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2019
Publication Date: 8/15/2019
Publication URL: https://handle.nal.usda.gov/10113/6746506
Citation: Smith, D.R., Macrae, M., Kleinman, P.J., Jarvie, H.P., King, K.W., Bryant, R.B. 2019. The latitudes, attitudes, and platitudes of watershed phosphorus management in North America. Journal of Environmental Quality. 48(5):1176-1190. https://doi.org/10.2134/jeq2019.03.0136.
DOI: https://doi.org/10.2134/jeq2019.03.0136

Interpretive Summary: Phosphorus was discovered 350 years ago by the alchemist, Hennig Brandt. This discovery is in large part responsible for the green revolution and our ability to feed a growing population. However, too much phosphorus in some regions lead to massive algal blooms in water. This is the case in Lake Okeechobee in Florida, the Chesapeake Bay on the east coast, Lake Erie on the border of the U.S. and Canada and Lake Winnipeg in Manitoba, Canada. This paper examines the role of various factors that change with latitude play in these algae blooms. We also examine how attitudes have changed over the last 50 years regarding some of these aspects, including manure, supplemental drainage and regulation. One common theme in these watersheds are that some interested parties throw around platitudes to identify phosphorus sources or provide solutions to the problems; however, this often serves only to distill the real issues too much which in turns may ‘muddy the water.’ To truly solve the phosphorus conundrum of balancing crop requirements and water quality protection, we as a society must address the issue with action and continually assess our progress to ensure we are not trading one problem for another.

Technical Abstract: Phosphorus (P) plays a crucial role in agriculture through its use as a fertilizer and its content in manure. Excess P loads in runoff to surface water bodies are causing the eutrophication of surface waters throughout North America, and globally. Despite decades of efforts to keep P on agricultural fields and reduce losses to waterways, frequent algal blooms persist, leading to ecological, economic, social and political consequences. Four key watersheds across latitudes in North America are discussed: Lake Winnipeg, Lake Erie, the Chesapeake Bay and Lake Okeechobee/Everglades. Although these watersheds have some unique features, there are also some striking similarities across them. These water bodies span across 26 degrees of latitude, from cold regions through warm regions, and consequently, there are differences in climate drivers leading to phosphorus mobilization in the landscape. There are also differences in the dominant agricultural activity in these regions. Potential reasons for the lack of impact of conservation efforts in reducing algal blooms are discussed. The role of latitude, attitudes, and platitudes in the P conundrum are evaluated, and the importance of thresholds is discussed. While there are differences in some mechanisms across latitudes (i.e., snowmelt driven processes in the north versus convective storms in the south), there are also commonalities (e.g., short-circuited hydrologic pathways and P sources). In order to solve the vexing issues associated with balancing agronomic production to support a growing population while protecting water quality, we will have to move away from platitudes, such as finding a single solution that will solve the P conundrum.