Dew is disappearing from much of Germany, what does it mean for seasonal plant growth?

Trends of increasing global air temperatures are shifting the water balance of many ecosystems with drastic subsequent effects for vegetation. Dew is thought to be particularly sensitive to atmospheric changes due to its fundamental reliance on the interaction between water vapor and temperature. While several studies have shown that dew can be an important water source for specific plant species, efforts have consisted of a subset of species over short periods, leaving a knowledge gap concerning the effects of dew on ecosystems across larger spatial and temporal extents. Here we use hourly climate data from 221 stations in Germany and remote sensing of plant greenness during the growing season to understand: What are the long-term trends in dew amount in Germany, and are they influencing seasonal plant growth? Our results indicate that long-term changes in dewfall are common across Germany, with 30% of our sites showing significant declines in dew amount over the last 20 years, whereas 12% show significant increases in dew. We found that total dew accumulation had small but significant effects on vegetation greenness across Germany. On average, we estimate that during the growing season, dew increases peak greenness by four percent and total cumulative greenness by three percent. Dew impacts on greenness metrics indicate it has an important role in plant ecosystem health and productivity. Current atmospheric trends may not only decrease the amount of dew during the growing season in Germany, but also lead to higher water deficit, where dew amount plays a larger role in water and energy balance.