MANGAWHAI'S NO.1 NEWSPAPER
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Climate change: Mangawhai under sea?STEVE GREEN Mangawhai’s single biggest climate concern: Are we going to be underwater as sea levels continue to rise? Yes! Well, maybe not just yet. Of all the issues associated with the climate crisis, rising sea levels are perhaps the hardest to predict and 65 per cent of all Kiwi’s live within 5km of the coast. So what’s the minimum rise we can anticipate over the coming years, and what’s the true doomsday rise? Over recent years, according to our Ministry for the Environment, the sea level has risen by 2.44mm annually. This is one centimetre every four years. Not massive. The Ministry is predicting an acceleration of the rise based on levels of global emissions remaining high, potentially rising by a further 21cm by 2040 and 67cm by 2090. That’s rising by two feet over the next 70 years. The Wood St shops are 26m above sea level, Lincoln St 13m, our school – considered ‘medium risk of flooding’ – only 8m. A quick look at the science. The dominant reasons for the rises are that land-based ice is melting and as oceans get warmer, the mass of water increases. Melting glaciers are causing a multitude of problems including impacting tourism, reducing downstream supplies of water, and negatively impacting water for irrigation of crops. However glacial water entering the oceans does not really have any noticeable impact on sea levels. The two largest land masses of ice are firstly Antarctica, the white chunk on the map below Invercargill, and Greenland, not named after me, where the depth of ice exceeds 3km in places. If these ice masses melt, the overall rise in sea levels will be approximately 66m! Greenland’s recent melting has contributed about 25 per cent of our sea rise. Local factors can also influence the rise. Tides, currents, storms, and tectonic plates can all have an impact, and New Zealand’s land is slightly lowering, therefore making the sea rise appear higher. The only way to delay the sea rising is to reduce the rate at which the temperatures are rising, and the only way to achieve this is by reducing the emissions that contribute to global warming. The UN 2015 Paris Agreement targets us to limit temperature increases by 2degC by 2050, and with a dream of limiting them to 1.5degC. At present we are nowhere even close to achieving these targets. If emissions remain high globally, predictions are that sea levels may rise by 66cm by 2050 and 1.2m by 2100. Currently 10 per cent of the world’s population live in coastal areas and over two-thirds of all cities with over 5 million residents are located here. When we drastically reduce GHG emissions in the next decade the problem will be tough but manageable. If the rise in emissions continues the problem will become unmanageable. What does this mean for Mangawhai Under Sea? Much depends on winning the global climate change war. Certainly there is scope to protect coastal areas by erecting sea walls and planting mangroves, but this is incredibly expensive and possibly an option only available to affluent communities such as Miami and Venice. I am not a politician, but inevitably regulations will be enacted to ‘zone’ low lying areas and prohibit the development of homes that have the potential to flood. Maybe properties, say less that 5m above current sea levels, will be deemed necessary to be moved to higher ground. The insurance industry will apply higher premiums for properties with the potential of flooding, and may elect simply not to offer insurance. In the short term, say the next 70 years, if sea levels increase by two feet, the Ministry’s prediction, it may simply be a case of ‘buyer beware’ as very few properties in Mangawhai are located lower than this. Rising sea levels will inevitably impact much more than just the mass of water. Fishing stocks will be impacted, coral reefs die, local water from artesian wells impacted by acidification, and coastal bird colonies will be endangered to suggest just a few outcomes. If Greenland and Antarctica become ice free and sea levels rise by 66m, all bets are off as the world as we know it will simply not exist anymore! n Steve Green, Mangawhai’s ‘computer chap’, has been retired here for 12 years having previously lived and worked in London, New York and Auckland. He welcomes your feedback at theclimatechap@gmail.com if you have any climate questions, recommendations or concerns to raise. If the rise in emissions continues the problem will become unmanageable. |