New research by NIWA scientists suggests environmental targets for managing fine sediment in rivers may need to be revised to better account for the impacts of climate change.
Currently, attribute states indicating freshwater ecosystem health are often set based on historic conditions, with limited consideration of future climate-driven effects. However, given that climate plays a crucial role in shaping these attributes, the NIWA study shows a need for a more adaptive approach.
The recent study has introduced a method to predict how target attribute states for suspended and deposited fine sediment might shift in response to climate change. The research focuses on existing environmental policy in Aotearoa-New Zealand, where a river environment classification system - based on climate, topography, and geology - determines spatially-distributed sediment targets.
Using regional climate projections, researchers have calculated and mapped future class membership for river segments under different climate scenarios. The study found significant spatial shifts toward warmer and drier climate classes under the highest future emissions scenario by the end of the century. These changes led to corresponding shifts in target attribute states, with sediment targets either increasing or decreasing depending on location. Additionally, the study identified emerging conditions that do not fit within existing classification systems, highlighting a potential gap in current environmental policies.
“The findings underscore the importance of accounting for climate change within environmental management frameworks,” said NIWA Quantitative Freshwater Ecologist, Rachel Smith.
“We suggest policymakers should consider both climate-driven and local anthropogenic influences when setting attribute states to ensure effective sediment management in the face of climate change,” she said.
The study’s methodology provides a practical approach for anticipating climate-induced shifts in environmental classifications and target attributes, which could be applied to other ecosystems and management systems Dr Smith says as climate change continues to reshape environmental conditions, proactive adaptation strategies will be key to maintaining freshwater ecosystem health.
