Water Research Laboratory

Climate change in NSW estuaries

Where the river meets the sea

Shoalhaven taken from a drone

Australians are coastal people with more than 85% living within 50 kms of the coastline (and within an estuarine catchment). As such, tidal rivers (or estuaries) are an integral way of our life. However, these systems are facing a rapidly changing climate, matched with major population increases and an uncertain future.

There are 3 major reasons why estuaries and the ecosystems they support are particularly vulnerable to climate change:

  1. Double whammy impacts
    Estuaries are at the interface between coastal rivers and the ocean; this means they are impacted by climate change from upland catchments (rainfall, heat) and oceanic (sea level rise, temperature, pH, etc) shifts.
  2. Vulnerable eco-hydrology
    Due to their unique hydrologic setting, which often includes shallow, protected, dynamic and nutrient rich brackish waters, estuaries are one of the most productive ecosystems on earth.
  3. Increasing pressures
    Many estuaries are already facing increasing development and population stresses as coastal populations grow, resources are depleted, nutrients increase and flow regimes change. When combined with climate change impacts, these pressures can result in ecological tipping points, drainage declines and forced changes to adjoining land-use.

Assessing the impacts and effect of climate change in estuaries is complex. To help estuarine managers and coastal communities navigate this complexity we have developed a multi-report guideline that details climate change, it’s role in estuaries, existing trends/pressures and the potential impacts. Titled “Climate change in estuaries: State of the science & guidelines for assessment” this report and database is freely available online, below. The guide provides a summary of the relevant climate, ocean and ecosystem science along with best-practice frameworks for prioritising risks.

This research was undertaken in collaboration with scientists at the NSW Office of Environment and Heritage (OEH) and Macquarie University. The research was funded via the NSW Government’s Adaptation Research Hub’s Coastal Processes and Response Node led by the Sydney Institute of Marine Science.

Risk assessment guide

Assessing the impacts of climate change in estuaries is a complex task. To help navigate this complexity, a multi-report guide has been designed for estuarine managers, scientists, practitioners and coastal communities. The guide provides a summary of the relevant climate, ocean and ecosystem science along with best-practice frameworks for prioritising climate risks in estuaries. The guide consists of 7 module reports that cover different aspects of the risk assessment process and are designed to be read together or independently.
  • Changes in climate drivers most relevant to estuaries Illustration by Anna Blacka, UNSW Water Research Laboratory

    This module provides an introduction to various aspects of climate change in estuaries. The module addresses the following questions:

    • Why assess climate change risk in estuaries?
    • How do estuaries function?
    • What are the main types of estuaries in NSW?
    • How does climate change affect estuaries?

    Download Module 1: "Climate change in estuaries - State of the science & guideline for assessment"
  • The buffering of an acid plume in the mixing zone of an estuary Illustration by Anna Blacka, UNSW Water Research Laboratory

    Prioritising changes in the climate and ocean systems

    This module provides guidance on estimating the potential changes in climate and ocean boundary conditions that will be faced by estuaries in the near and far future. It presents an introduction to climate change and climate science along with methods for prioritising changes based on climate projection data. This module addresses the following questions:

    • What is climate change and what are the main causes?
    • What are climate models and emission scenarios and how are they used to project the future climate?
    • How can changes in the climate be prioritised based on their relevance for estuaries?
    • What are the key climatic changes faced by estuaries now and in the future?

    Assessing climate change in estuaries requires a robust understanding of how projections of future climate are generated and how the severity of change can be derived from these projections. This guide uses climate projections from the New South Wales and Australian Capital Territory Regional Climate Modelling (NARCliM) project, and illustrates how statistics and extreme indices can be applied to prioritise change in the climate system based on their deviation from historic variability envelopes.

    Download Module 2: "Prioritising climatic changes"
  • Golden Tino Heimhuber, UNSW Water Research Laboratory

    Determining the physical response of estuaries to changes in the climate and ocean boundary conditions

    Module-2 introduced methods for estimating likely changes in the climate and ocean boundary conditions of estuaries (i.e. rainfall and sea level rise). However, estuaries are highly dynamic and complex systems and each estuary will have a unique physical response to these changes, depending on its geomorphologic regime and hydrologic setting.

    Estimating the likely physical and chemical response of estuaries to changes in the climate and ocean system often requires some form of modelling. Module-3 provides an overview of available modelling approaches, their respective data requirements as well as their advantages and disadvantages. It also provides a conceptual model that can be used to generate a first-pass estimate of the physical response of estuaries to different climatic stressors.

    Module-3 addresses the following questions:

    • What are the available modelling approaches?
    • What are the available data sets?
    • What is the likely response of different types of estuaries to different climatic stressors?
    • How can changes in the climate be prioritised based on their relevance for estuaries?
    • What are the key changes in climate faced by estuaries in NSW?

    Download Module 3: "Physical responses to climate change"
  • Key impacts of increased temperatures and atmospheric CO2 on estuarine environments Illustration by Anna Blacka, UNSW Water Research Laboratory

    Assessing the impacts of climate change to estuary ecosystems

    In a climate change risk assessment, an estimate of likely changes in the physical and chemical estuarine environment is typically followed by an assessment of estuarine ecohealth. Module-4 provides an overview of the ecological significance of estuaries and their most abundant ecological communities. The Module summarises likely ecological responses of ecological communities to climate change stressors and provides a qualitative rating of climate change risks for each type of estuary found in NSW.

    Module-4 addresses the following questions:

    • What is the ecological significance of estuarine habitats in NSW?
    • Which ecological estuarine communities are found in NSW estuaries?
    • How might estuarine organisms respond to environmental stressors due to climate change?
    • How does the type of estuary influence the level of exposure to climate change stressors and which communities are most sensitive?
    • What is the likely climate change impact on NSW estuarine species?

    Download Module 4: "Ecological responses to climate change"
  • Merimbula Lake Duncan Rayner, UNSW Water Research Laboratory

    Managing local stressors to enhance the resilience of estuarine ecosystems to climate stressors

    Worldwide estuaries are a location subject to increasing population pressures. However they will also be subject to increasing climate change pressures. Module-5 details how these two forces interact and how the local stressors on an estuarine ecosystem can influence the way it responds to climate change. Understanding how developmental and climate change stressors interact will help identify local management actions and minimise ecosystem impacts.

    Module-5 addresses the following questions:

    • What are the local stressors operating within our estuaries that act synergistically with climate stressors?
    • When and where are negative interactions between local and climate stressors greatest along the coast?
    • How might local stressors be managed to enhance the resilience of estuarine ecosystems to climate stressors?

    Download Module 5: "Managing local stressors to enhance ecological resilience"
  • Oyster channel avifauna Tino Heimhuber, UNSW Water Research Laboratory

    A review of sea level rise in estuaries

    In practice, each estuary requires a site-specific risk assessment that takes into account the locally variable changes in climate, the unique hydrological and geomorphological setting, and the ecosystem that it supports.

    This Module is a detailed review paper on how sea level rise will influence estuarine dynamics. Published in the prestigious journal, Science of the Total Environment, this paper illustrates the range of potential changes within estuaries due to rising sea levels. Unlike other modules, this section is written in the form of a peer-reviewed research paper.

    Additional papers on estuary dynamics under climate change are also available and listed below:

    Download Module 6: "Sea level rise impacts on estuarine dynamics: A review"
  • Saltmarsh sunset Tino Heimhuber, UNSW Water Research Laboratory

    Thresholds and ecological responses of estuarine species: Calculating eco-thresholds for baseline climate change risk assessments

    Understanding how organisms respond to environmental stressors is paramount in evaluating the ecological impacts of climate change on estuarine communities. The sensitivity and resilience of species to stressors depends on their physiological tolerance and their behavioural responses.

    This module presents a comprehensive review of published data on physiological thresholds of key estuarine species to climate change driven stressors. A total of 50 NSW estuarine species and more than 300 publications are reviewed and collated into a unique database of physiological tolerance thresholds.

    Module-5 also provides the conceptual basis for generating the table of estuarine ecological community sensitivities presented in Module-4.

    Download Module 7: "Physiological thresholds and ecological responses of New South Wales estuarine species: A review"

Learn from the experts

Estuaries are at the very interface of where rivers and the ocean meet, making them particularly complex environments. Understanding the impacts and consequences of climate change to these systems is often difficult to understand. Each video below addresses a key aspect of climate change in estuaries and the risk assessment resources provided on this webpage. 

What is an estuary? What are the risks of climate change to estuaries? How does that affect me?

Professor William Glamore
Water engineer and scientist with extensive experience in estuarine science and management.

What is the purpose of the Risk Assessment Guide, why are there 8 modules and who is it for?

Dr Valentin Heimhuber
Water engineer and scientist with expertise in estuarine science, hydrology and climate change.

Why does the Risk Assessment require a multidisciplinary team, and why is it a challenge?

Dr Valentin Heimhuber
Water engineer and scientist with expertise in estuarine science, hydrology and climate change.

What are some of the ecosystem services that estuaries provide to us? Why should we care about estuaries and the risks of climate change?

A/Prof Melanie Bishop
Marine ecologist with extensive experience in estuarine ecology, climate change and adaptation.

What are the most relevant and dangerous climate change impacts to estuaries? What are “double-whammy” impacts?

A/Prof Melanie Bishop
Marine ecologist with extensive experience in estuarine ecology, climate change and adaptation.

How can we quantify the impacts of climate change to specific estuarine species, and what are physiological thresholds?

Dr Gabriel Dominguez
Marine ecologist with expertise in estuarine science, hydrology and climate change.

What is an estuary? What do we know about climate change in estuaries? What is the NSW Government doing to better manage estuaries in a changing climate?

Dr Peter Scanes
Estuarine scientist with extensive knowledge and experience working in and around estuaries in NSW. Expert in estuarine hydrology, ecology and climate change impacts.

For further information, please contact:

Professor William Glamore | w.glamore@wrl.unsw.edu.au

Toby Tucker | Principal Engineer | t.tucker@wrl.unsw.edu.au

Alice Harrison | Principal Engineer | a.harrison@wrl.unsw.edu.au