More is Not Better in Lake Restoration : Non-Linear Restoration Effectivenss on Ecosystem Services Under Climate Change

Healthy freshwater ecosystems can provide vital ecosystem services (ESs), and this capacity may be hampered due water quality deterioration and climate change. In the currently available ES modelling tools, ecosystem processes are either absent or oversimplified, hindering the evaluation of impacts of restoration measures on ES provisioning. In this study, we propose an ES modelling tool that integrates lake physics, ecology and service provisioning into a holistic modelling framework. We applied this model to a Dutch quarry lake, to evaluate how nine ESs respond to technological-based (phosphorus-P reduction) and nature-based measures (wetland restoration). As climate change might be affecting the future effectiveness of restoration efforts, we also studied the climate change impacts on restorations and ESs provisioning, using climate scenarios for the Netherlands in 2050. Our results support that both phosphorus reduction and wetland restoration controlled eutrophication symptoms, with increased oxygen concentrations and water transparency, and decreased phytoplankton biomass. Delivery of most ESs was improved, including swimming, P retention, and macrophyte habitat, whereas the ES provisioning that requires a more productive system was impaired (Sport fishing and bird watching). However, our modelling results suggested hampered effectiveness by restoration measures upon exposure to future climate conditions, which means intensification of restoration efforts may be needed in the future for meeting restoration targets. Importantly, ESs provisioning showed non-linear responses to increasing intensity of restoration measures, indicating that effectiveness of restoration measures does not necessarily increase proportionally. In conclusion, the ecosystem service modelling framework proposed in this study, provides a holistic evaluation of lake restoration measures on ecosystem services provisioning, and can contribute to development of climate-robust management strategies