Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Preparing New Zealand for rising seas: certainty and uncertainty Technical Report

Parliamentary Commissioner for the Environment
Publisher / Organisation
Parliamentary Commissioner for the Environment
Over many millennia, the Earth’s climate has cycled between ice ages and warm ‘interglacial’ periods. Over the last seven thousand years the climate has been relatively stable, but this is now changing. Increasing concentrations of carbon dioxide and other greenhouse gases in the atmosphere are trapping heat and the climate has begun to respond. One of the major and certain consequences is rising sea level. Nowhere in our island nation is far from the sea, and most of us live within a few kilometres of the coast. Houses, roads, wastewater systems, and other infrastructure have been built in coastal areas with an understanding of the reach of the tides and the recognition that storms will occasionally combine with high tides to cause flooding. However, with rising seas, tides, waves and storm surges will reach further inland than before, resulting in more frequent and extensive flooding. Along some coasts, erosion will increase and shorelines will recede. In some areas, the water table will rise. The vulnerability of different coastal areas to the rising sea depends on many factors. Elevation – height above the sea – is the first factor that comes to mind when considering the potential impacts of sea level rise, but it is far from the only one. The shape of the coastline, the topography of the land and the seabed, the proximity to the sea, the presence of barriers such as sand dunes, and other local characteristics will affect what happens in different coastal areas. Other consequences of climate change, such as changing wind and rainfall patterns, will also come into play, increasing or reducing the impacts of rising seas. For instance, more intense rainfall coinciding with storm surges will exacerbate coastal flooding. 10 Like other countries, New Zealand needs to prepare for rising seas. Under New Zealand law, the enormously challenging task of planning for sea level rise is the responsibility of local government. It is challenging on many levels. For a start, it is technically complex, and the size and timing of impacts are uncertain. Perhaps the most difficult aspect is the impact on people’s homes, which for many are not just their homes, but also their financial security.