Climate Change Report
NZers can expect to feel the effect of wide-ranging impacts from climate change over the next 100 years, according to a major new report called "Climate Change Impacts on NZ". It is based on reports and scientific studies published internationally and in NZ, and it updates the last government-led assessment produced in 1990. It concentrates on areas where new knowledge has been gained over the last decade.
The Main Findings
The report presents its findings under a number of headings:
Global Impacts
Evidence shows that the world has warmed during the 20th century. Most of the warming over the last 50 years is due to human activities, namely the emission of greenhouse gases.
This report uses two emission models to try and work out future climate change and its impacts. Model 1 assumes no attempts to control greenhouse gas emissions, while model 2 assumes that steps are taken to stabilise the atmospheric concentration of carbon dioxide and to limit emissions of the other major greenhouse gases methane and nitrous oxide.
Climate models predict a global warming by 2100 between 2.1 and 3.8 degrees Celsius for model 1 and between 1.4 and 2.6 degrees Celsius for model 2, compared to an observed warming of about 0.6 degrees Celsius during the 20th century.
Global impacts of climate change, particularly on world markets and developing countries, will affect NZ. However, because very few clear predictions of these indirect effects can be made at this stage, this report focuses on the impacts of local climate change in NZ.
Projected NZ Climate Changes
Some of the broad climate changes expected to occur are:
· temperatures in NZ are likely to increase faster in the North Island than in the South Island, but generally less than the global average;
· rainfall is likely to increase in the west of the country and decrease in many eastern regions;
· dry periods will increase in some regions;
· at the same time, extremely heavy rain-fall events could become more frequent in many areas, increasing the risk of flooding and erosion; and
· on average, there should be fewer frost days during winter and more hot days during summer.
Sea-Level Rise and Coastal Processes
Sea levels are expected to rise under global warming, but by how much is largely open to debate. Global sea levels are estimated to rise between 9 and 88 cm by 2100 under global warming, with ranges from 13 to 70 cm for model 1, and from 9 to 53 cm for model 2 (during the 20th century global sea levels rose on average between 10 and 20 cm). However, it is possible to say that rising seas are expected to increase the erosion of vulnerable beaches and cause more frequent breaches of coastal protection structures in the long term.
Agriculture
The agricultural sector has opportunities for productivity gains and diversification under climate change, but it also faces risks. The most important benefit to agriculture is likely to be from elevated carbon dioxide concentrations, which could lead to substantial improvement in growth rates and water-use efficiency. Also, warmer conditions and lengthened growing seasons could allow the long-term southward shift of climate-limited activities, and new crops and related industries could be introduced. Currently resource-poor areas could benefit from such shifts.
The biggest risks are associated with the potential increase of droughts and floods and water limitations in some areas, particularly in the east of NZ. Warmer temperatures could also make the growing of some current fruit crops in some northern areas uneconomical. Shifting land-use activities to adapt to altered climate conditions will incur costs, resulting in regional winners and losers. Pests and diseases could spread in range and severity, and pasture composition is likely to change with uncertain outcomes to animal productivity and nutrient balances. The full range of effects has not been figured out yet.
Overseas markets will also change under a warming climate, offering indirect market risks and opportunities to NZ farmers.
Native Ecosystems
With few exceptions, climate change alone is unlikely to be the dominant cause of native species extinction, but may act as another pressure on already threatened ecosystems. Fragmented native forests of drier lowland environments in Northland, Waikato, Manawatu, and in the east from East Cape to Southland are probably the most vulnerable to climate change, and some terrestrial and freshwater species which are currently at their climatic limit may be at long-term risk of extinction. However, many complex interactions between elements of natural ecosystems, introduced exotic species and climate are not yet fully incorporated in assessment models.
Urban Environment, Transport and Energy
The main threat to the urban environment comes from possible increases in heavy rainfall which would put pressure on drainage and stormwater systems and increase the risk of flooding in some areas. Erosion could also increase road maintenance costs, but warmer winters would lead to reduced costs for snow and ice clearing. Warmer conditions will substantially reduce home heating costs during winter, but may increase demand for air conditioning during summer. The reduced winter demand would combine with an increased availability of water in hydroelectric storage lakes from projected rainfall increases over the Main Divide, providing the opportunity for a more balanced electricity supply and demand.
Health
Higher temperatures are expected to reduce winter illnesses, but have also been found to be correlated with increased mortality during summer. A warmer climate would also allow the better establishment and spread of mosquitoes capable of transmitting diseases such as Ross River virus and dengue fever.
Climate Impacts on Maori
The reliance of Maori on the environment as both a spiritual and economic resource makes them more vulnerable and less adaptable to climate change. Land presently owned by Maori is often of lower quality, making it more prone to invasion by subtropical grasses and erosion. Because of the high spiritual and cultural value placed on Maori traditional lands and statutory sales restrictions on those lands, relocating one's business in response to climate change may not be an option. Multiple land-ownership and generally lower socio-economic status could hinder the putting in place of costly or non-traditional adaptation measures. This may increase the risk of reduced economic output from Maori land compared to the NZ agricultural sector as a whole. Impacts on the coastal environment are also of great importance to Maori culture and economy, but the impact of climate change on fisheries production is highly uncertain at present.
International Links
Many Pacific Island countries are highly vulnerable to climate change from rising sea-levels, changes in rainfall patterns affecting agricultural productivity, destruction of coral reefs, and human health effects of higher temperatures and vector-borne diseases. Such impacts could have considerable flow-on effects for NZ through increased demand for development aid and, in worst cases, disaster relief. Climate change in competing export countries will contribute to changing commodity prices and market structures in some key export markets. These changes offer both risks and opportunities to NZ exports, but there is still too little information to allow predictions or outline specific countering strategies.
Summary and Outlook
NZ's climate is very likely to change during the 21st century. Estimates of impact are limited by uncertainties of regional climate changes and frequency of extreme events. At this stage, an assessment of the overall impact of climate change on NZ's society and economy is impossible, but it's likely that there will be short-term winners and losers. Negative impacts could be reduced and potential gains increased by developing "proactive" strategies for dealing with changing climate.
The full report is available at www.climatechange.govt.nz |
Contact for Enquiries
The Ministry of Agriculture and Forestry
Pastoral House
25 The Terrace
PO Box 2526, Wellington
Tel: 0800 00 83 33
Fax: +64 4 894 0720
Contact this person
