New Zealand’s biodiversity in for changes as the heat goes on
Scientists have been reviewing evidence of changes to New Zealand's climate. They've also been projecting future changes to New Zealand's climate, and the impact on biodiversity and marine habitats.
NIWA scientist Carolyn Lundquist will be speaking on this topic at the International Congress for Conservation Biology. The congress is being held on 8 December, at SkyCity in Auckland, with over 1500 delegates registered for the meeting. It is the first time this meeting has been held in New Zealand.
New Zealand's extensive seascape is a global hotspot for marine diversity, supporting 17,135 known species (with over 50 per cent of them unique to New Zealand), and at least 17,000 undescribed species.
Models suggest that sea-level rise and temperature increase will have impacts on biodiversity, and that the anticipated changes will impact on marine ecosystems, as well as on terrestrial and freshwater ecosystems. The average air temperature in New Zealand is projected to warm by about 2.0°C by 2090 for a mid-range greenhouse gas emission scenario. Increasing temperature is predicted to result in migration southward for marine species, and migration upwards for terrestrial species, with increased mortality during extreme weather events.
Field observations and reports from fishermen in New Zealand coastal areas show "tropical species popping up where they normally wouldn't in warmer than usual years," says Lundquist.
New Zealand's marine territory is over 3.5 million square kilometres, which is about 15 times its land area. It has complex circulation patterns, resulting from the interaction of sub-tropical and sub-Antarctic fronts and New Zealand's proximity to the strong Antarctic Circumpolar Current. Changes in sea surface temperature, location and intensity of winds, and sea-level rise, will all interact with the potential to change circulation patterns.
"No-one knows exactly what will happen to these currents following substantial changes in temperature," says Lundquist.
Oceans are expected to become more acidic globally and New Zealand waters are no exception.
Increasing atmospheric CO2 increases CO2 concentrations in the oceans. As more CO2 is absorbed by seawater, it makes the seawater more acidic. Marine animals and plants that have carbon-based skeletons will find it increasingly difficult to form hard structures as the waters become more acidic.
Ocean acidification is expected to cause declines in carbonate communities such as coral reefs, with cold-water communities predicted to decline first. "In New Zealand, key species that are likely to be affected as the ocean gets more acidic include our coastal shellfish and diverse deep-sea coral reefs, so this is not just an issue for tropical coral reefs," says Lundquist.
The IPCC sea-level rise projections range between 0.18 – 0.59 metres by the 2090s but rises of more than a metre can't be ruled out. Sea-level rise is likely to impact on coastal and estuary plant and animal life, reducing coastal habitats, changing inundation patterns, and increasing vulnerability to storm surges and tides.
"In some areas of New Zealand, our coastlines are so built up and developed that, as the sea-level goes up, there is nowhere inland for mangroves and other shallow habitats to move," says Lundquist. Climate change models have predicted significant changes in the extent of mangrove habitats in Auckland east coast estuaries for the 2050s –2090s.
Model projections suggest that there will be more extreme rainfalls, with increased average precipitation in the west of New Zealand, and reduced precipitation in the east, especially in winter and spring.
Climate change is expected to change storm conditions, altering the frequency and magnitude of storm tides and wave and swell conditions.
"This will impact the marine environment. Large storm events often result in flooding and erosion of sediments from hillsides, and these sediments are transported into estuaries and coasts, where it can smother marine communities," says Lundquist.
New Zealand's 2010 coastal policy statement emphasises the need to adapt to potential climate change effects, with emphasis on protecting coastal habitats from potentially damaging impacts.
Further research is needed to develop general principles for prediction of changes to New Zealand's terrestrial and aquatic biodiversity, which can guide decision-making.
This review of climate change impacts was driven by an initiative of the Society for Conservation Biology to review potential impacts of climate change in the Oceania region.