Sustainable ecosystem restoration requires a flexible yet scientifically-robust approach informed by ecological theory and local context. When managing complex socio-ecological systems, often the biophysical science needed to inform management decisions is incomplete. Such is the case where intensive dairy farming is the primary land use in lowland Canterbury, New Zealand. Unsurprisingly, critical freshwater ecosystem services of drainage, clean water and biodiversity have become heavily compromised by decades of intensive farming practices that have caused aquatic weed proliferation, deposited fine sediment legacies, nitrate levels well above acceptable human health limits, and, loss of endemic and culturally-significant species across the regions waterways. Several restoration tools are available but evidence of their effectiveness and best practices associated with their use are lacking, particularly in combination with one another. Improving ecological conditions across these waterways is further complicated by a range of stakeholders, each with different priorities.
We sought to develop a framework for applying restoration tools that reflected current management scenarios, engaged stakeholders and were informed by ecological theory at multiple spatial and temporal scales. We predicted relationships between the effort required to recover a specific ecosystem function and the appropriate scale for fourteen available management tools in Canterbury. We applied the framework across nine one-kilometre long waterways in actively-farmed, privately-owned farms with riparian management practices in place.
Results/Conclusions
Here we present the framework, locally referred to as the Canterbury Waterway Rehabilitation Experiment (CAREX), and show evidence of ecosystem responses at the predicted spatial and temporal scale. We found that a systematic approach to diagnosing waterways and their surrounding land use identified “hot spots” or “leaky plumbing” that were responsible for a disproportionate amount of sediment, nutrient and habitat degradation. Larger-scale tools such as bank re-shaping and riparian planting were found to be more effective when “leaky plumbing” issues were addressed and started at the top of the catchment. Habitat- and reach-scale tools such as riparian shading (natural and experimental), sediment removal interventions (i.e., sediment traps) and organic matter manipulations (e.g., denitrification bioreactors) further enhance the recovery of functions at small and larger scales. Ongoing monitoring of larger-scale, longer-term trials will further build on these relationships to include realistic expectations for nitrate remediation and biodiversity recovery. We show that the CAREX approach has been effective at influencing local management practices (i.e., at the farm scale) while also achieving national-scale aspirations of freshwater health and ecosystem service recovery.