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Climate Change Effects and Impacts Assessment: A Guidance Manual for Local Government in New Zealand

• Executive Summary
• Roadmaps: Using the Guidance Manual
• 1 Introduction
• 2 Projections of Future New Zealand Climate Change
• 3 Relationship to Current Climate Variability and Change
• 4 Effects on Local Government Functions and Services
• 5 Developing the Scenarios
• 6 Risk Assessment
• 7 Integrating Climate Change Risk Assessment into Council Decisions
• Glossary
• References
• Appendix 1: IPCC Emissions Scenarios
• Appendix 2: Scaling to Full IPCC Range of Emissions
• Appendix 3: Further Details of Projected New Zealand Climate Change
• Appendix 4: An Example of the Preliminary Scenario Method for Extreme Rainfall
• Appendix 5: Climate Change in Plans – Checklist for Contents

4 Effects on Local Government Functions and Services

4.1 Introduction

This chapter provides guidance on identifying which local government functions and activities could be affected by the climate changes and fluctuations identified in chapters 2 and 3. It lists key climate influences and possible effects of climate change, for each of these functions and activities. It provides guidance on data, sources of information, models and specialist expertise in New Zealand that councils can use, along with the climate change scenarios covered by chapter 5, to quantify the likely magnitude of particular effects. Examples are given of some expected climate change effects, from studies that have been carried out in various parts of New Zealand.

The interactions between climate change and local government functions and services are likely to be quite complex. Identifying which effects are important in terms of responding now might seem quite a daunting task. However, assessing the effects of climate change can be broken down into manageable steps, as explained in chapter 1, and risk assessment can be used to guide judgements on where to focus adaptation effort (chapter 6). Practical hints are as follows:

• Staff responsible for a particular council function or service should integrate consideration of climate change into their assessment and planning activities.

• Prioritise and then focus on only those functions and services of importance to your council and for which climate change may have a material effect.

• For a particular function or service, start out with a straightforward initial screening analysis using simple initial estimates of how climate factors relevant to this function may change (chapter 5). It is necessary to embark on a more detailed effects study only if this initial analysis indicates material climate change impacts or opportunities are likely.

4.1.1 Making use of this chapter

This chapter provides resource material to help users follow through the assessment steps outlined in the ‘Roadmaps’ at the beginning of this Guidance Manual. We recommend that you refer to Figures R1 and R2, and to the Risk Assessment chapter (particularly section 6.4) for background. There are two particular ways in which information from the current chapter can be applied:

(a) When assessing effects of climate change on a particular council function or responsibility (Roadmap Figure R1). In this case, examine the entry for this particular function in Table 4.1 and the related entries in Table 4.2 to identify key climate variables and possible climate change effects. Then, use Table 4.3 for guidance on sources of information, models and expertise for use in quantifying these effects, in combination with the climate scenario guidance from chapter 5.

(b) When identifying and prioritising climate change risks and opportunities across all council functions and opportunities (Roadmap Figure R2). In this case, most of the entries in Tables 4.1 and 4.2 should be examined; they will aid identifying the council functions possibly affected by climate change and the key climate influences on them. Once these functions have been identified, an initial screening analysis can be performed (the fifth box on the left of Figure R2), using scenarios from chapter 5 and information from Table 4.3.

4.1.2 Making use of Tables 4.1, 4.2 and 4.3

Central to these tables is the link:

Key climate influence - Possible effects

Table 4.1 looks at this relationship from the perspective of:

Who is affected That is, which function(s)/asset(s)/activity(ies) – primarily of interest to city and district councils

Table 4.2 looks at this relationship from the perspective of:

What is affected That is, which resource(s) – (primarily of interest to regional councils

Table 4.3 provides useful information for all councils.

Tables 4.2 and 4.3 both help the reader through an assessment:

• by looking at the present and future (Table 4.2)

• by identifying who has expertise and what tools could be used (Table 4.3).

In using these tables, keep in mind that climate change and its effects should be considered relative to other changes. Climate change will not occur independently of other future changes, including changes due to natural climate variability, and future social and economic changes.

4.2 Links between climate influences and possible impacts

Table 4.1: Local government functions and possible climate change outcomes.

View local government functions and possible climate change outcomes (large table).

Table 4.2: Sensitivity of natural resources to present climate and climate change.

View sensitivity of natural resources to present climate and climate change (large table).

4.3 Assessing effects – methods, data, sources of information

There are three main approaches to assessing the effects of climate change at regional and local levels in New Zealand:

1. Modelling. These incorporate computer-generated scenarios of climate change. An example is modelling that links historical weather data and information generated from General Circulation Models (translated to New Zealand’s situation, see chapter 2) to a model of river flow. This approach can be readily applied to existing models and data used by hydrologists and engineers. A variation of this approach is to draw on historical data to determine possible effects in the future (for example, using information on past flood events to assess what the effects would be if floods comparable to those experienced in the past, such as those connected with El Niño-Southern Oscillation (ENSO) or different Interdecadal Pacific Oscillation (IPO) phases, become more prevalent).
2. Expert opinion. Seeking expert opinion can involve the presentation of plausible scenarios of climate change for your region (chapters 2 and 3) to knowledgeable people in your region, or national experts, to seek their views. In a flooding example, analysis as in (1) above could be undertaken using the input of experts. Often (see Table 4.3), there may be insufficient data and capability to follow the modelling approach, and it may be necessary to rely strongly on expert opinion. For example, local pest management people will have a good knowledge of current pest problems, and will have the capability to provide ‘expert opinion’ on the likely effects of climate change.
3. Monitoring. The real effects of climate change will be detected only through ongoing monitoring. In some cases, monitoring may be the only way that effects can be quantified over time. See section 7.9 for further discussion on monitoring.

When selecting the assessment method, some judgement will be required on which is most applicable to the problem or issue of concern. Considerable capability already exists for assessing physical impacts – in terms of expertise, data and quantitative models. For example, there is a strong capability in New Zealand for predicting river flows in many parts of the country. In general, there is a much lower capability for quantitative assessment of biological and social/human impacts. In areas such as asset management (where investment in infrastructure is required), quantitative modelling is the principal approach. For issues such as biodiversity, a combination of approaches may be necessary, with monitoring playing a very important role. A broad summary of the capabilities that exist for identifying the effects of climate change on key local government services and functions is provided in Table 4.3.

4.3.1 Uncertainties and assumptions

Whichever method or approach is chosen, there will be assumptions that are made and/or inherent uncertainties. These need to be taken account of, along with the uncertainties that presently exist in projections of future climate.

In a study by Lincoln Environmental (see Table 4.4) on the impacts of climate change on water resources,⁷⁵ there were key assumptions made with the models that were used. For example, key assumptions made with the river flow model were:

• There will be no hydrologically significant changesin vegetation (eg, no major conversions between pasture and forest).

• There will be no new diversion or abstraction of river water (nor any new extraction of groundwater that sustains river flow).

Table 4.3: Data, sources of information and assessment capabilities relating to the effects of climate change.

View data, sources of information and assessment capabilities relating to the effects of climate change (large table).

4.4 Examples of what is known about effects

The following examples demonstrate how the information presented in the preceding tables might be drawn together. The summary information on effects comes from a variety of sources. In the first example relating to water allocation, results from a published study are briefly presented. In the other examples, information on effects is mostly based on the expert opinion of regional council staff. Finally, a brief example of the interrelationships between climate change and climate variability (in this case the IPO) is presented, drawing from an Environment Bay of Plenty study.

4.4.1 River flows and irrigation

Local government function: water allocation for irrigation

Natural resource: rivers

Key climate variables: 30-year time series of daily precipitation, maximum temperature, minimum temperature, dew point temperature, solar radiation and wind run

Climate change effects: reduced river flows possible in eastern New Zealand

Key risk: less surface water available for irrigation

Uncertainty: changes in river flows in catchments that reach into the Main Divide or central North Island are dependent on precipitation changes in these areas, which are uncertain

A study for the Tukituki catchment in Hawke’s Bay predicted that river flow would generally decrease by 2050 with climate change. Based on the climate change scenarios used, river flows would decrease by 20–30% in summer and autumn, and by 0–10% in winter. It was concluded that peak irrigation demand could increase by 10% by 2050, but that there would not be any change in irrigation days lost (principally because there is already a 100% frequency of occurrence of irrigation seasons with some irrigation time lost). This study was based on mean changes in climate and did not take account of the possible effects of changes in frequency or intensity of climatic extremes. (Source: Lincoln Environmental 2001.)

4.4.2 Erosion and landslides

Local government function: erosion control

Natural resource: land

Key climate variables: intense rainfall events

Climate change effects: increasing frequency of intense rainfall events

Key risk: increased erosion risk

Uncertainty: lack of regional detail

On the West Coast of the South Island an increase in rainfall would also increase the potential for landslides, and potentially landslide dam-break flood events, as occurred in the Poerua River catchment in 1998. (Source: West Coast Regional Council 2002.)

Erosion risk is high over significant tracts of land in Manawatu. For example, 500,000 hectares of hill country is at risk of accelerated erosion in Manawatu. This risk could be exacerbated with any increase in rainfall frequency and intensity. (Source: Horizons.mw 2002.)

4.4.3 Water supply and demand

Local government function: water supply

Natural resource: surface and groundwater

Key climate variables: average rainfall (monthly, seasonal, annual)

Climate change effects: decreased rainfall in the north and east of New Zealand

Key risk: decreased security of water supply

Uncertainty: average decreases in rainfall appear more likely in the east of New Zealand than in the north

Peak daily water demand in Wellington is usually at the end of an extended dry, hot spell of 10 days or more. If such events increase with climate change, then the number of peak days can be expected to increase. (Source: Wellington Regional Council 2002.)

4.4.4 Biosecurity

Local government function: pest management

Natural resource: land

Key climate variables: temperature and rainfall

Climate change effects: increasing temperatures and rainfall changes

Key risk: increased biosecurity threats

Uncertainty: the rate and magnitude of climate change, which remain uncertain, will determine the extent of the problem

Warmer conditions in recent years have highlighted the sort of pest problems that are likely to arise more often in coming decades. For example, the tropical grass webworm, a wind-blown invader from Australia, has decimated all pasture species, in fact anything green, on the Aupouri Peninsula in the far north of Northland in recent years. There are several pest plants currently found in small or not very vigorous infestations in Northland that would become a serious pest, not only in Northland but also through other parts of northern New Zealand, if there were even a slight increase in temperature. (Source: Northland Regional Council 2002.)

4.5 Published studies on effects and adaptation

Various studies and reports published since 2000 that have focused on climate change effects and adaptation in New Zealand are listed in Table 4. Some of these contain results from quantitative assessments (such as the CLIMPACTS report (Warrick et al 2001) and the Lincoln Environmental study (Lincoln Environmental 2001), and some are reviews of what is known, drawing from published studies and the knowledge of experts. Many of these reports, plus some further background material, are available through the Ministry for the Environment’s web page of local government guidance materials on climate change http://www.mfe.govt.nz/issues/climate/resources/local-govt/index.html (3 April 2008). There are still many gaps in knowledge about regional and local detail, along with the uncertainties that exist about future changes in climate.

Table 4.4: Reports on the effects of, and adaptation to, climate change in New Zealand.

Note: Full citations for these reports, including web locations for many of them, are provided in the References section located immediately before the appendices in this Guidance Manual.

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