New Publication in Environmental Research

When we hear about droughts, we usually think about really hot summers. But especially in the Northern Hemisphere, droughts may actually start in winter: Many plants rely on meltwater that gradually releases moisture into the soil. And when the winters are too dry or too warm, this important water source is lost or shifted outside the plant’s growing period. These snow-droughts impacts the entire ecosystem – and with that Earth’s carbon cycle.

In their new Environmental Research Letters publication “The emergence of snow droughts as drivers of negative extremes in plant productivity over the past decades”, David Gampe and his colleagues Eyal Sharon, Bano Mehdi-Schulz, Mariangela Varela, Michael O'Sullivan, Wolfgang Buermann, Marianela Fader, and Franziska Koch have cast light on this research blind spot – and found that extreme events where ecosystems absorb significantly less carbon than usual can be linked to such snow droughts.

Key Results

• Less Carbon Uptake: The authors attributed a cumulative reduction of 4.48 Petagrams of Carbon (PgC) to extreme events in plant productivity to preceding snow droughts.
• Global Impact: Snow droughts drive nearly 10% of all global negative extreme events in plant productivity.
• Worrying Dynamics: The impact of these events has surged by 46.5% in recent years (2000–2016) compared to the late 20th century (1982-1998?).
• Stacked Droughts: About 30.7% of productivity losses attributed to summer droughts were actually preceded by snow droughts, creating a "stacked" threat for ecosystems.

As rising temperatures shift precipitation from snow to rain, we are losing a critical buffer to support our terrestrial carbon sink. These "stacked droughts" can create feedback loops beyond the current year and negate years of carbon sequestration in the respective regions. Understanding the full pathway of water, from winter snowpack to summer soil moisture, is essential for projecting the future stability of the terrestrial carbon sink.

Read the Open Access study