| Natural resource |
Key climate influence |
Impacts of climate change |
Present sensitivity to climate |
| Rivers |
Rainfall |
- River flows likely to increase, on average, in the west and decrease in the east of New Zealand
- More intense precipitation events would increase flooding (by 2070 there could be no change up to a fourfold increase in the frequency of heavy rainfall events)
- Less water for irrigation in northern and eastern areas
- Increased problems with water quality
|
Strong seasonal, interannual, and interdecadal fluctuations (see the example in Box 4.1 at the end of Section 4.4, on peak flows in Bay of Plenty) |
| Lakes |
Temperature and rainfall |
- Lake levels likely to increase, on average, in western and central parts of New Zealand, and possibly to decrease in some eastern areas
- Higher temperatures and changes in rainfall, particularly in areas such as the Rotorua Lakes, could result in a range of effects, including:
- an increased degree of eutrophication and greater frequency of algal blooms
- altering of lake margin habitats, including wetlands, with either increased or decreased rainfall
- declining lake levels could have negative impacts on aquatic macrophytes, particularly native species
- the range of trout may decrease with increased water temperatures
- the range of pest species (e.g. carp) may increase, placing even more pressure on aquatic ecosystems
|
Seasonal and interannual fluctuations |
| Wetlands |
Temperature, rainfall, sea-level rise |
- Coastal and inland wetlands would be adversely affected by temperature increases, rainfall increases or decreases and sea-level rise
|
Many already under threat |
| Groundwater |
Rainfall |
- Little change to groundwater recharge is expected in eastern New Zealand, but increased demand for water is likely
- Some localised aquifers in northern and eastern regions could experience reduced recharge. For example, small coastal aquifers in Northland would be under threat from reduced rainfall
|
Seasonal fluctuations; but at present generally stable over the longer-term |
| Water quality |
Temperature and rainfall |
- Reduced rainfall and increased temperatures could have significant impacts on the quality of surface water resources in northern and eastern New Zealand
- Lower stream flows or lake levels would increase nutrient loading and lead to increased eutrophication
|
Most sensitive during summer months and in drier years |
| Drainage |
Rainfall |
- Increased frequency of intense rainfall events could occur throughout New Zealand, which would lead to increased surface flooding and stormwater flows, and increased frequency of groundwater level changes
|
Natural year to year variation in heavy rainfall event location and magnitude |
| Water availability |
Rainfall |
- Decreases in rainfall, which are most likely in the north and east of New Zealand, coupled with increased demand, would lead to decreased security of water supply
|
Dry summers, or extended droughts |
| Erosion |
Rainfall and wind |
- Increased rainfall in the west, and more intense rainfall events throughout New Zealand, could lead to increased soil erosion, including landslides
|
Intense rainfall events can arise with sub-tropical lows, and localised low pressure cells |
| Biodiversity |
Temperature, rainfall, wind |
- Increased temperature, reduced rainfall, and more frequent drying westerly winds (possible in the east) would lead to changes in distribution and composition of native forest ecosystems throughout New Zealand
- Most vulnerable will be fragmented native forests in the north and east of New Zealand
- An increased biosecurity risk, with invasive temperate and sub-tropical species, would also have negative impacts on native flora and fauna
|
Drought can have a severe impact, e.g. some native vegetation adversely affected in Hawke's Bay with the 1997/98 El Niño drought |
| Biosecurity |
Temperature and rainfall |
- Even small increases in temperature will significantly increase the incidence of pest outbreaks in New Zealand, particularly in North Island and the north of South Island
- Both existing and potential new plant and animal pests could become established more widely, even with a slight increase in temperature
|
Pest outbreaks can be triggered by specific weather events, or from steadily changing conditions, e.g. spread of Tasmanian grass grub in Hawke's Bay triggered by warmer, drier conditions in the late 1980s early 1990s |
| Coastal areas |
Sea-level rise, storm frequency and intensity, wave climate, sediment supply |
- Effects of sea-level rise and other changes will vary regionally and locally
- Coastal erosion is likely to be accelerated where it is already occurring and erosion may become a problem over time in coastal areas that are presently either stable or are advancing
|
Short and medium term sea levels (i.e. up to about 30 years) are dominated by ENSO and IPO variations |
| Air |
Temperature, rainfall, wind |
- Increased temperatures in Auckland might increase photochemical smog
- Fewer cold nights may reduce winter time particulate smog problems in affected towns and cities
|
|
| Natural hazards |
Temperature, rainfall, wind |
- The general indications are that New Zealand could experience more climatic extremes in the future. This could include:
- more intense rainfall events, and associated flooding, in most parts of the country
- more frequent and/or intense droughts in the east
- more damaging windstorms
- more heat waves
- increased fire risk in drier eastern areas
|
There have been more frequent and intense El Niño events in recent decades, possibly associated with the IPO. The worldwide cost of extreme weather damage has increased due to a mixture of climatic, economic and social factors |
