Evidence, causes, and consequences of declining nitrogen availability in terrestrial ecosystems

Area of Science:

• Ecology
• Environmental Science
• Biogeochemistry

Background:

• Ecosystem productivity relies on reactive nitrogen (N).
• Human activities have doubled global reactive N supply over the last century.
• Long-term data indicate declining N availability in many global regions.

Purpose of the Study:

• To review the current understanding of declining reactive nitrogen availability.
• To highlight the impact of global changes on the N supply-demand balance.
• To propose strategies for addressing this environmental challenge.

Main Methods:

• Analysis of long-term ecological records.
• Assessment of global changes (CO2, temperature) effects on N dynamics.
• Synthesis of current knowledge on N availability.

Main Results:

• Reactive nitrogen (N) availability is declining in many ecosystems globally.
• Global changes, including elevated CO2 and temperatures, alter N supply relative to demand.
• Declining N availability constrains primary productivity and reduces diet quality for herbivores.

Conclusions:

• Declining N availability poses a significant threat to ecosystem function and services.
• Further research and proactive management are needed to address this emerging issue.
• Understanding and responding to declining N availability is crucial for ecosystem resilience.