From exposure to risk: Novel experimental approaches to analyse cumulative impacts and determine thresholds in the Great Barrier Reef World Heritage Area (GBRWHA)

Sven Uthicke

Led by: Dr Sven Uthicke, AIMS


Project Summary

Understanding cumulative impacts from multiple stressors will be critical for successful management of the Great Barrier Reef (GBR) under the Reef2050 Plan. We will produce experimental analyses of concentration-response relationships for selected species under broad, controlled envelopes of local stressors at different climate scenarios. Results will inform assessments of ecological risks, and management opportunities for a range of activities in the coastal zone and on the GBR. In a project-extension we will use exposure maps and ecological models, based on our developed and existing databases and experimental results, to advance our understanding of the contribution of individual disturbances in a cumulative framework (including both acute and chronic disturbances) to the current status of the reef. In turn, this new knowledge will inform management on setting future water quality thresholds, identifying catchments and regions as priorities for management action aimed at ameliorating impacts to reef health and building resilience for large-scale cumulative disturbances.

Project Description

The problem

  • Cumulative impacts result from one or more stressors and their interactions can accumulate in time and space, posing a threat to ecosystem resilience. Cumulative impacts represent added ecological risks and potential surprises not accounted for in conventional risk assessments. Inshore environments in the GBR are high-risk candidates for cumulative impacts as they are exposed to land-based and coastal development activities impacting water quality in addition to regional and global pressures from climate change.
  • While reef managers recognize that cumulative impacts are an added risk dimension, large knowledge gaps exist in our understanding of the effect of individual stressors on key reef species, the interplay of local and global stressors and the way individual stressors combine into cumulative impacts.
  • There is wide acceptance that improvement in water quality will ‘buy time’ for reefs to acclimatize to a warming climate and increasing ocean acidification, yet it is still unclear whether current water quality targets, are set at the right level to achieve this outcome of increased reef resilience under climate change.
  • The National Seas Simulator (SeaSim) facility in Townsville now allows us to investigate such complex interactions using sophisticated state-of-the art system controls. In SeaSim we can control cumulative exposures of sensitive marine organisms and processes under highly controlled yet environmentally relevant settings in an unprecedented way. We can therefore address and fill some of these key knowledge gaps on cumulative impacts far more efficiently than was possible in the past.
  • While previous research on cumulative impacts on the GBR has provided relevant data to inform the issue, few have followed an end-to-end pathway resulting in direct implementation and improvements to policy.

How Research Addresses Problem/Achieved outcomes of original project

  • This collaboration started with a 6-month NESP investment (project 1.6) as a gap analysis and to develop the foundational framework for prioritization of end point measurements, and building on the risk priorities defined in the Great Barrier Reef Marine Park Authority’s (GBRMPA) Outlook Report.
  • During the last 2.5 yrs (NESP 2.1.6) conducted multiple experiments on sediments, light and pesticides as local stressors and quantified their cumulative effects with climate scenarios (including climate-adjusted thresholds) for tropical coral reef species. We explored the concept of applying species-sensitivity curves to temperature for the first time in a coral reef context, and created a literature database available for adjusting pesticide guideline to account for thermal stress. Based on monitoring data and other sources (e.g. eReefs, eAtlas) we produced maps for individual stressors and explored techniques to combine those into cumulative exposure maps. Exposure layers, stressors and benthic reef data have been brought together in an ecological model which can be used to test how individual stressors interact in a cumulative fashion.
  • We investigated novel ways to assess combined risks on sensitive marine organisms and ecological processes, and will use concentration-response studies to determine climate adjusted exposure thresholds. One factsheet produced and > 10 scientific publications published.
  • Two stakeholder workshops were conducted, several workshops from other NESP projects attended. Frequent meetings with individual stakeholders at GBRMPA and the Office of the Great Barrier Reef (OGBR).
  • The findings will facilitate the development of more realistic GBR-wide exposure maps to identify acceptable and unacceptable risks for ecosystem integrity. These will be done for present day conditions and for some selected pressures under future climate scenarios, in collaboration with eAtlas. The thresholds and exposure maps will support integrated monitoring and assessments, including the adequacy of current targets for priority river pollutants.
  • An interactive tool to illustrate principals of cumulative impact and effects of land runoff under certain climate scenarios will be developed and made publically available. This tool will be developed so that findings from other NESP projects (e.g. Benthic Light, Bleaching Sensitivity along a water quality gradient) can be incorporated and communicated effectively to stakeholders. This tool will allow environmental managers to learn about key concepts in cumulative impacts, what the experimental results of the project mean and be able to investigate the model results that breakdown historic cumulative pressures on reefs based on coral functional types and water quality scenarios. This tool will be integrated with the eAtlas..


NESP 2017 Research Priority Alignment

This project has a strong alignment with the following Ministers and NESP Research Plan priorities:

The Ministers priorities:

Theme 1: Improved understanding of the impacts, including cumulative impacts, and pressures on priority freshwater, coastal and marine ecosystems and species.

1.4 Improve our knowledge of cumulative pressures on environmental and social values of the Great Barrier Reef to determine more effective management actions.

  • Develop better capacity to predict ecosystem decline due to cumulative pressures to guide planning and management practices.
  • Determine critical ecosystem thresholds for cumulative stress to guide environmental decision-making and policy under coastal development scenarios.
  • Identify environmental stress indicators for key reef species and habitats to support cumulative impact assessments.

Research Plan 2 priorities:

Priority 1G: Methods for assessing cumulative impacts from human activities and measures/approaches for ensuring a net environmental benefit.

As a secondary focus, the project also addresses: Priority 2A: Developing effective and cost-effective catchment and marine water quality indicators, thresholds and sub-lethal health-indicators for key marine organisms and processes in support of the Reef Integrated Monitoring Program.

Project Keywords

Cumulative impacts; Environmental risk; Thresholds.

Project Funding

This project is jointly funded through AIMS and the Australian Government’s National Environmental Science Program.

Project Publications