Research Aim 3

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Identifying Feedbacks, Understanding Cumulative Impacts, and Recognising Limits

While various national analyses have been undertaken to address different climate-related and resource management issues (e.g., biodiversity, infrastructure, soils, water resources, primary production, forestry, land-use change, ecosystem services, population), New Zealand lacks a comprehensive  systems analysis that considers their interactions and feedbacks. This raises challenges to understanding impacts across a range of scales, especially cumulative impacts. As a result, we often only learn of environmental limits after they have been crossed. This research will  undertake a first-ever comprehensive national multi-scale systems analysis across New Zealand to understand the interplay among climate, land, water, soils, ecosystems, ecosystem services,  economics, land-use/land-cover change, and population. It will improve knowledge of feedbacks  and trade-offs among different resources and facilitate study of cumulative impacts and  identification of environmental limits and how they vary under different climate change pathways.

Leadership of Research Aim 3:

Primary Support:


  • Research Aim 3 (RA3) undertook a national integrated assessment that explored the impacts and implications of climate change to 2100 to better understand feedbacks, cumulative impacts, and limits among economic, social, and environmental outcomes.
  • The assessment evaluated six globally linked, New Zealand-focused scenarios using a loosely coupled national human-natural systems model developed for RA3. The systems model integrated a suite of climate, economic, land use, hydrology, and primary productivity models.
  • The six scenarios were a subset of 20 global scenarios formulated under a new global scenario architecture developed for the IPCC’s 5th assessment.
  • Global scenarios combine 1) socioeconomic pathways exploring different levels of challenges to mitigation and adaptation, 2) greenhouse gas concentration pathways, and 3) shared policy assumptions about global efforts to mitigate greenhouse gas emissions.
  • By design, socioeconomic pathways evolve independently of greenhouse gas concentration pathways. Any pair of pathways can be combined to form a scenario. As a result, climate change does not directly impact socioeconomic development. Instead, evaluation of climate change impacts and implications occurs indirectly by comparing and contrasting different scenarios.
  • A global integrated assessment study found that any global scenario is plausible but not all are equally feasible. Feasibility decreased when pairing socioeconomic pathways with high challenges to mitigation and the lowest greenhouse gas concentration pathway.
  • Any global scenario with a mitigation target assumes a functional global carbon market, although that assumption is not equally plausible across all mitigation scenarios.
  • RA3 modelling followed global integrated assessment study protocols. Scenario evaluation specified that country-level population and GDP followed fixed projections unique to the selected global socioeconomic pathway and that all climate-related modelling use climate projections based on the selected concentration pathway.
  • CCII scenarios also implemented relevant global shared policy assumptions as required, e.g. non-mitigation scenarios assumed no carbon market or carbon price while mitigation scenarios modelled a functional carbon market following global study protocols.
  • Improved climate projections for New Zealand reinforce earlier findings that higher greenhouse gas concentrations leading to increasing radiative forcing will likely cause larger degrees of change for New Zealand’s climate and its various facets, including means, extremes, frequencies, and shifts in patterns.
  • Uncertainty, risks, and vulnerabilities resulting from climate change will also likely scale with increasing concentration pathways. Different locations will experience different impacts depending upon combined changes to daily, seasonal and annual weather patterns.
  • Hydrological systems will change both positively and negatively with climate change. Total variability tends to increase with increasing concentration pathways such that low flows become smaller and occur earlier and high flows (i.e. flooding) become larger. Mean flows show more complex spatial patterns but tend to increase in a west-to-east direction.
  • Across scenarios, summer soil moisture deficits intensify such that soils become drier except in a few areas of the South Island.
  • Climate impacts on primary production varied. Pastoral and forestry (Pinus radiata) yields to 2100 increased positively with increasing concentration pathway because positive effects from CO2 fertilisation outweighed negative effects of higher temperatures.
  • Sheep & beef and dairy mean annual pasture productivity increased 1–10% across scenarios in most locations, although changes in seasonal trends might cause larger summer feed gaps.
  • Irrigated maize silage modelling demonstrated potential for adaptation for minimising impacts on national maize yields. Nationally, cropping could shift from northern regions showing decreasing yields to southern regions showing increasing yields. Locally, farming could adopt new agronomic practices such as earlier sowing dates and long-cycle genotypes.
  • The lack of links between hydrological and primary productivity modelling is a key limitation of the current national systems model and corresponding analysis.
  • A novel modelling experiment demonstrated the use of new climate projection ensembles to better characterise and quantify uncertainty. The model developed statistical methods that quantified potential changes and associated uncertainties to habitat suitability for whitebait (banded kōkopu juveniles).
  • New Zealand’s fixed population projections started at 4.4 million in 2010 and ranged by 2100 from 3.8 (low) to 9.8 (high) million people. The large range in population projections has implications related to and independent of climate change including, for example, landuse change, food security, energy security, water resources, conservation,and biosecurity.
  • Demographic modelling found that climate change will cause regional populations to shift north slightly and the magnitude of the shift increases with increasing concentration pathways. For example, under the same socioeconomic pathway, Auckland’s population at 2100 was ~30,000 higher under a high concentration pathway than a low concentration pathway.
  • New Zealand’s fixed GDP projections started at $66,813 billion US2005 in 2010 and ranged by 2100 from $277,733 (low) to $1,014,793 (high) billion. New Zealand’s GDP per capita begins and always remains higher than the global average for all global socioeconomic pathways. That result suggests that New Zealand remains relatively better off on a global basis although the magnitude of the difference depends on socioeconomic pathway assumptions.
  • Agricultural economic and land-use change modelling showed that changes to productivity via climate change will interact with market forces (e.g. price mechanisms) to drive landuse change in complex ways. For example, in one scenario projected global sheep & beef commodity prices went well beyond historic observed ranges and counterbalanced dairy farming expansion that would occur assuming only climate change effects.
  • Given global scenario architecture design and assumptions, broad social and economic outcomes for New Zealand, as indicated by population and GDP, depend primarily on the global socioeconomic pathway selected, whereas environmental outcomes reflect a more balanced combination of socioeconomic pathways and concentration pathways.
  • Climate change does substantially impact the specific nature of social and economic outcomes. Comparing two scenarios with the same global socioeconomic pathway but a higher and lower concentration pathway, the structure of New Zealand’s economy changed substantially. In the high concentration scenario, the economy became more inwardly focused and dominated by domestic household consumption. In the lower concentration scenario, the economy became more outwardly focused and dominated by exports.

Click here to download a full copy of the RA3 Synthesis Report.

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