How Climate Extremes Are Changing Nitrogen Flow

By Blake Jackson

Nitrogen plays a vital role in plant growth, making it a cornerstone of modern agriculture. However, not all applied nitrogen remains in the soil.

Excess reactive nitrogen can run off into rivers and coastal waters, contributing to harmful algal blooms and low oxygen “dead zones,” including those found in the Gulf of Mexico.

A new study published in Environmental Research Letters shows that climate extremes-such as droughts, heat waves and heavy rainfall are significantly altering how nitrogen moves from land into waterways across the United States. These shifts have important implications for ecosystems, farming practices and public health.

The research, led by Nicolas Maxfield, a Ph.D. candidate at the CUNY Graduate Center and part of the CUNY ASRC Environmental Sciences Initiative, analyzed how both long-term climate patterns and short-term extreme events influence nitrogen transport.

By using a widely recognized watershed model and examining data from hundreds of monitoring sites over a 20-year period, the team found that extreme weather can dramatically influence nitrogen movement, sometimes even reversing expected patterns.

“Most models focus on average temperature and rainfall, but our results show that extreme events can fundamentally change how nitrogen behaves,” Maxfield said.

“In some regions, increases in extreme weather actually outweigh the effects of long-term climate trends, leading to more nitrogen entering rivers than we would otherwise predict.”

The study identified that wetter summers and cooler years tend to increase nitrogen flow into rivers, while drier summers generally reduce it.

However, brief periods of hot, dry weather were sometimes linked to increased nitrogen runoff, likely due to disruptions in soil microbes that typically help retain nutrients.

“These findings highlight that the timing and intensity of weather events matter just as much as long-term averages,” said Charles Vörösmarty, the study’s principal investigator.

“If we ignore climate extremes, we risk underestimating future threats to water quality and coastal ecosystems.”

Researchers also noted the importance of adopting soil-friendly farming practices to better manage nitrogen under changing climate conditions.

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