Nitrogen critical loads using biodiversity-related critical limits.

Area of Science:

• Ecology
• Environmental Science
• Biogeochemistry

Background:

• Critical loads are standard for assessing emission reduction policies, particularly concerning nitrogen deposition effects on terrestrial ecosystems.
• While acidification impacts have lessened, nitrogen deposition poses a growing threat to ecosystem health.
• Current methods often focus on empirical critical loads or complex models, with limited adaptation of simple mass balance approaches.

Purpose of the Study:

• To adapt the mass balance approach for assessing nitrogen and acidity impacts on terrestrial ecosystems.
• To move beyond single-factor critical loads towards a more holistic assessment of deposition effects.
• To define an 'optimal' deposition envelope considering both nitrogen and acidity for plant occurrence.

Main Methods:

• Utilized a simple mass balance approach, adapted for regional applicability.
• Incorporated linked chemical criteria for nitrogen and acidity to protect specified ecosystem receptors.
• Focused on plant occurrence and biodiversity as key indicators of ecosystem status.

Main Results:

• Demonstrated that a single chemical criterion (like critical load) is insufficient for assessing ecosystem health.
• Showcased the development of an 'optimal' deposition envelope by linking nitrogen and acidity criteria.
• Highlighted the benefits of the adapted mass balance approach for regional assessments.

Conclusions:

• The adapted mass balance approach provides a more comprehensive method for evaluating nitrogen and sulfur deposition impacts.
• Linked nitrogen and acidity criteria are essential for protecting plant biodiversity and ecosystem function.
• This approach offers a practical tool for informing emission reduction policies for terrestrial ecosystems.