Standard Presentation (15 mins) Australian Marine Sciences Association 2022

The impact of cumulative stressor effects on uncertainty and ecological risk (#57)

Vera Rullens 1 , Fabrice Stephenson 1 2 , Judi E. Hewitt 2 3 , Dana E. Clark 4 , Conrad A. Pilditch 1 , Simon F. Trush 5 , Joanne I. Ellis 6
  1. School of Science, University of Waikato, Hamilton, New Zealand
  2. National Institute of Water and Atmospheric research, Hamilton, New Zealand
  3. Department of Statistics, University of Auckland, Auckland, New Zealand
  4. Cawthron Institute, Nelson, New Zealand
  5. Institute of Marine Science, University of Auckland, Auckland, New Zealand
  6. School of Science, University of Waikato, Tauranga, New Zealand

Estuarine and coastal environments are experiencing unprecedented anthropogenic pressures. Ecological risk and uncertainty are generally high when multiple stressors occur, and in the face of high uncertainty, transparent communication is essential to inform decision-making. Environmental management must therefore consider the complex interactions between multiple stressors and account for uncertainty in risk assessments. Our study addressed the ecological risk and uncertainty associated with cumulative effects of multiple stressors in a New Zealand case study. We examined the impact of six anthropogenic stressors, including local pressures from land and stress originating from climate change on estuarine macro-invertebrate species as indicators of environmental health. Species response to multiple stressors were modelled additively and multiplicatively to enable a comparison between model performance and highlighted that non-additive effects dominated. 3D-plots were important to visualise complex stressor effects, the steep gradients of change along increasing stress for synergistic interactions, and directionality shifts where the nature of the interaction changes along increasing stressor gradients. We argue that visualising stressor interactions and the model uncertainties provide a way to improve transparency and communication about complex stressor effects, reduce the risk associated with mis-identification of interaction types, and invoke precautionary management when uncertainty about stressor interactions is high.