Climate change risk assessment for Auckland’s marine and freshwater ecosystems

Author:
Melissa M Foley, Megan Carbines
Source:
Auckland Council Research and Evaluation Unit (RIMU) and Chief Sustainability Office
Publication date:
2019

Executive summary

The Climate Change Risk Assessment (CCRA) has been developed in support of the Auckland Climate Action Plan (ACAP). Its aim is to provide information about the risk and vulnerabilities the Auckland region may face under a changing climate regime. This CCRA adopted the Intergovernmental Panel on Climate Change’s (IPCC) representative concentration pathway (RCP) 8.5 (“business as usual”) scenario as its guiding projection. This report details an assessment of risk for Auckland’s aquatic environments informed by published expert surveys and studies both international and from New Zealand.

The NIWA climate change projections for the Auckland region (Pearce et al., 2018) highlight changes that could affect the structure and functioning of aquatic ecosystems, and in turn, affect their ability to provide ecosystem services that we rely on throughout the region. For marine ecosystems, the changes of most concern include increasing air and water temperatures, decreasing ocean pH and nutrient concentrations, alterations to current and wind patterns, and sea level rise. For freshwater ecosystems, increasing air temperature, number of dry days, frequency of extreme rainfall events, as well as decreasing river flows and number of rainy days could all have significant effects. It is important to note that our current understanding of climate change impacts in New Zealand waters is limited by the spatial resolution of available models and there is likely to be regional variations in changes in environmental conditions and ecological impact influenced by local physical and biotic interactions (Law et al., 2017). What is outlined in this report reflects our current state of knowledge applied in a regional context.

In marine ecosystems, intertidal habitats (soft- and hard-bottom), kelp forests, and subtidal rocky reefs are the most sensitive to changing conditions. Marine shellfish are also highly sensitive, mainly due to decreasing pH and increasing extreme rainfall events and water temperature. In freshwater ecosystems, habitats and species are sensitive to increasing extreme rainfall events because they can be scoured or buried due to flooding and additional sediment inputs. Freshwater fish and macroinvertebrates are also particularly sensitive to increasing water temperatures, especially species that are already living close to their maximum thermal threshold.

While climate change impacts alone are enough to drive changes in community structure in aquatic ecosystems, it is important to recognise that these climate-driven changes are occurring within systems that are already heavily affected by other human activities (i.e., altered flow, habitat loss, increased nutrient and sediment discharge). Understanding the ability of species and habitats to adapt to changing conditions is vitally important in the context of recent anthropogenic (human-caused) changes in addition to climate change. In the absence of understanding how multiple stressors cumulatively affect aquatic ecosystems, precautionary and adaptive approaches to decision-making must be used at every step in the process.

Auckland Council technical report TR2019/015

Climate Change Risk Assessment CCRA 2019 series

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Climate Change Risk Assessment 2019

As communities across the world set out to plan for climate change mitigation and adaptation, they first seek to understand how climate change will affect their city, region, or country.

The Climate Change Risk Assessment (CCRA) has been produced by Auckland Council’s Research and Evaluation Unit (RIMU) in support of the Auckland Climate Action Plan (ACAP) at the request of the Chief Sustainability Office. Its aim is to provide information about the risk and vulnerabilities the Auckland region may face under a changing climate regime, which is already underway. In 2018, national climate change projections were scaled-down to produce a more specific picture of their likely effects within the Auckland region. Based on this, CCRA adopted the Intergovernmental Panel on Climate Change’s (IPCC) representative concentration pathway (RCP) 8.5 (“business as usual”) scenario as its guiding projection, given the lack of evidence of any meaningful and sustained decreases in emissions that would shift to other projection pathways.

The eight reports in the CCRA consider various components of key risks – that is, hazard, exposure, and vulnerability – across sectors and systems of interest: people (heat vulnerability, climate change and air quality), society (social vulnerability and flooding), and natural environment (terrestrial and marine ecosystems), as well sea level rise at regional and local scales. A summary report has also been produced.

Titles in the Climate Change Risk Assessment (CCRA) series:

An assessment of vulnerability to climate change in Auckland. Fernandez, M. A. and N. E. Golubiewski

Development of the Auckland Heat Vulnerability Index. Joynt, J. L. R. and N. E. Golubiewski

Air quality and societal impacts from predicted climate change in Auckland. Talbot, N.

Climate change risk assessment for terrestrial species and ecosystems in the Auckland region. Bishop, C. D. and T. J. Landers 

Climate change risk assessment for Auckland’s marine and freshwater ecosystems. Foley, M. M. and M. Carbines

Flooding risk in a changing climate. Golubiewski, N. E., J. L. R. Joynt and K. Balderston

Auckland’s exposure to sea level rise: part 1 – regional inventory. Golubiewski, N. E., K. Balderston, C. Hu and J. Boyle

Auckland’s exposure to sea level rise: part 2 – local inventory (forthcoming). Boyle, J., N. E. Golubiewski, K. Balderston and C. Hu

Summary: Climate change risks in Auckland. Auckland Council. Prepared by Arup for Auckland Council 

Last updated: 2019-03-20

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