Bidirectional changes in seabird populations drive terrestrial ecosystem function and biodiversity

Seabird populations experience significant fluctuations due to factors such as the current highly pathogenic avian influenza (HPAI) panzootic and fishing practices. These fluctuations lead to the vectoring of marine nutrients into terrestrial and coastal environments, resulting in cascading effects throughout ecosystems. However, understanding the complex interrelationships driving these marine-terrestrial cascades in response to changes in seabird populations poses challenges.

To address this, researchers have simulated decreases and increases in seabird density, using turf transplant experiments and stratified surveys, to quantify marine nutrient cascades and assess their impact on terrestrial ecosystem processes and biodiversity.

By employing structural equation modelling, scientists were able to quantify the relative strengths of various hypothesized mechanistic pathways within the ecological network. The analysis revealed that seabirds primarily influence terrestrial plant and invertebrate biodiversity indirectly, through their role in modifying soil nutrient availability.

The findings shed light on the potential ecosystem changes and the pathways through which they occur due to acute declines and chronic increases in seabird populations caused by HPAI, fishing practices, or other factors.