Selecting Suitable Nitrogen Offset Strategies In Tropical And Subtropical Regions Globally With Implications To The Great Barrier Reef, Australia

Water pollution from agricultural, industrial, and urban activities threatens aquatic ecosystems and the essential services they provide. Excess nitrogen has been identified as a key driver of water quality degradation, impacting biodiversity, food security, and human health. One approach to mitigating nitrogen pollution is water quality offsetting, compensating for pollution impacts by implementing nitrogen reduction measures elsewhere to achieve no net decline in water quality. Selecting and implementing suitable nitrogen offset types remains challenging. This study presents a framework for identifying, selecting, and implementing effective nitrogen offset strategies in tropical and subtropical regions globally, using the Great Barrier Reef Catchment Area (GBRCA) as an example. This framework is based on the premise that effective nitrogen offset design requires integrating evidence on nitrogen mitigation performance, appropriate criteria for selecting offset types, and adaptive management to address uncertainty in environmental outcomes. Accordingly, the framework comprises three interrelated components: (1) assessment of water quality improvement methods for nitrogen reduction in the GBRCA and other tropical and subtropical regions based on performance (i.e., efficacy, effectiveness, and efficiency); (2) selection of suitable offset types based on their performance, co-benefits, and spatial and technical feasibility; and (3) integration of adaptive management strategies, Geographic Information Systems (GIS) tools, and monitoring systems to strengthen the effectiveness of nitrogen offsetting. This is the first global assessment of nitrogen offset performance in tropical and subtropical regions, offering insights to improve water quality management through offsetting. This framework is adaptable to other regions and pollutants, guiding effective offset implementation to enhance watershed resilience.