Climate Change Clouds the Water When it Comes to Excess Phosphorus and Agricultural Land

UMD researchers urge long-term research and innovative tools in small agricultural catchments to preserve water quality

Image Credit: Edwin Remsberg

November 6, 2023 Kimbra Cutlip

A team of UMD researchers found that climate change will alter the amount of phosphorus entering waterways from agricultural lands, and more work needs to be done to understand the implications. They concluded that a combination of conservation practices tailored to specific regions and circumstances are needed to prevent water quality impairment. Their review was published in the journal Current Pollution Reports.

Phosphorus from agricultural land is a significant contributor to water pollution and excess nutrients that can lead to an overgrowth of algae, reducing ecosystem health and leading to significant economic losses. But the issues surrounding phosphorus loss are complex, with many interdependent elements, which makes predicting impacts of climate change difficult. For example, some phosphorus mitigation strategies may increase the loss of nitrogen from farm fields, another nutrient that impacts water quality.

“Phosphorus has not been a major part of the climate change conversation, but we hope our review will lead to targeted research to reduce water quality problems in the future, said Emileigh Rosso Lucas, Environmental Science and Technology Ph.D. student and lead author of the study. “Living in Maryland, where many agricultural soils have high phosphorus, and seeing climate change in action led us to explore this important topic.”

In their comprehensive analysis, the team explored the scientific literature about phosphorus sources and how it moves from soil to water in order to predict phosphorus losses under different climate change scenarios. They reviewed factors affecting phosphorus losses such as extreme precipitation, rising temperatures, increased atmospheric carbon dioxide, and sea level rise.

The researchers found that climate change-induced shifts in precipitation are likely to increase phosphorus losses, while the effects of increased temperature and atmospheric CO2 are less clear. Sea level rise will likely also exacerbate phosphorus losses in some coastal areas.

“One of the challenges with climate change research is that individual impacts have mostly been studied in isolation,” said Graduate Research Assistant Bradley Kennedy, who is a co-author of the paper. “There’s good reason for that: it helps us understand the causes behind what we are observing. But in the real world, the impacts of climate change will occur simultaneously, so we also need research that puts them all together to see what the combined effect will be.”

The study highlights the knowledge gaps in the scientific understanding of how multiple climate change factors interact to impact phosphorus loss, and demonstrates that more research is needed to improve the models and develop effective mitigation strategies. The researchers call for research on phosphorus loss from legacy phosphorus soils—soils with years of phosphorus accumulation from manure and fertilizer application.

Lucas and her colleagues suggest that expanded and improved conservation practices are needed to control phosphorus in soils and trap it at different stages during its pathway from the field to the water. These include traditional practices, such as nutrient management, cover cropping, and maintaining optimal soil phosphorus levels through careful fertilization practices, along with innovative edge-of-field control measures.

As climate change increases the potential for phosphorus loss from agriculture, the researchers stress the need for collaboration among experts from various fields to improve predictions and develop effective strategies for combating nutrient losses and protecting water quality.

Co-authors of this study from the University of Maryland Department of Environmental Science and Technology include, Former Graduate Research Assistant and current environmental law student Taylor Roswall, Former Postdoctoral Associate and current Associate Program Manager at the National Academies of Sciences, Engineering, and Medicine Charles Burgis, and Professor and Extension Specialist Gurpal Toor.