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We have been warned about climate change. Now it's over to us, Colin Campbell Hunt writes.
When our great-grandchildren look back on our stewardship of the planet, they may well struggle to understand why we left it so late, and did so little, to avert the dislocations they will have to live with.
But there is one group of people that will escape their judgement: the climate scientists who have done such a magnificent job over the past few decades of warning us of the risks we are running.
This month has seen the publication of a report from the Royal Society on Implications of Climate Change for New Zealand.
I imagine young minds reading this in a century's time and staring in wonder that "they saw it coming and still they didn't stop it''.
The report highlights six key risks. For each it asks a few key questions: What is already happening? What might the future hold? What would be the implications for us if we manage to achieve a low-carbon future? Or a high-carbon future? And what are the knowledge gaps that we need to fill?
Risk one is our exposure to coastal change: rising sea levels, increased frequency and severity of storm surges, flooding, and salination of water tables.
All of these will affect east coast communities such as Dunedin more sharply.
In a high-carbon world, sea levels would rise by up to a metre by the end of the century, and keep rising after that; and today's one-in-100-year high tides will occur "almost daily''.
Considerable infrastructure, both public and private, will be affected and "landward migration'' will be the unwelcome result.
Risk two is flooding.
A warmer world is a wetter world and the volume of rainwater during storms will be beyond the capacity of current stormwater systems.
Saturated land will see runoff swell rivers and increase the frequency and magnitude of floods with "widespread impacts to property and assets''.
Risk three is to fresh water.
In the east of both islands, major droughts will be more frequent and more severe.
The risk of fires will rise.
Competition for water will increase for agriculture, town supply and hydro power.
Regimes of water management will have to change to allocate supply across competing needs.
For some regions, this may result in "transformational changes in farm and land management''.
Water may increasingly be priced, and recycled.
New Zealand has an exclusive economic zone of 4million square kilometres, the fourth largest in the world.
In a high carbon world, the oceans will become warmer and more acidic.
Fish species may migrate south from lower latitudes (and with them, I would add, the fishing fleets that feed off them).
Paua, mussels and other marine organisms that form shells will struggle, including some types of plankton upon which extensive food chains rely.
Risk five is to our ecosystems.
Some 50,000 species that call New Zealand home are found nowhere else on Earth.
The most severe immediate impacts of climate change on biodiversity are likely to come from human responses to the challenge: new diseases; more weeds, pests, fires; less water; changes to land use and coastal land; renewable energy systems (hydro, biomass, wind and marine).
Risk six is international. Climate change, particularly in a high-carbon scenario, will have widespread and dramatic impacts on the world's productive, economic, political and social systems.
Feeding a 2050 population of nine billion people will require a 70% increase in food production from a world in which the productive potential of many regions will be severely disrupted.
Migrations will increase in scale and frequency.
The economic viability of some nation states will be undermined.
The risks of violent conflicts will increase.
New Zealand will be less likely than most to experience these effects directly, but as a trading nation that has so much of what the rest of the world will increasingly need (water, food, space for people) the pressures building up in the world outside will surely find their way to our shores also.
All of this sounds quite apocalyptic, and it is natural for us to be sceptical of doomsayers.
Few people alive today in New Zealand have experienced the collapse of a world they knew and kept them safe.
Radical change on the scale being described is perhaps just not something we can imagine.
But if we were to ask Dunedin's newest residents just arrived from Syria, they would tell us how quickly human institutions can crumble under pressure.
Believe it or not, I am an optimist. I think humanity will avoid the worst that climate change can do. But only if we are brave enough to recognise the risks we run.
Just maybe, our great-grandchildren will be grateful. What do you reckon?
- Colin Campbell-Hunt is an emeritus professor at the CSAFE Centre for Sustainability, University of Otago. Each week in this column, one of a panel of writers addresses issues of sustainability.
Some of the Royal Society's recommended actions:
• Plant more forestry
• More efficient vehicles including the introduction of fuel efficiency standards, carpooling, taking the bus, cycling or walking
• Move freight by rail or seaUse solar, bioenergy and geothermal to replace coal for heating
• Encourage compact urban areas to incentivise non-motorised transport and provide low-carbon intercity transport options
• Increase share of renewables in electricity generation to 90% by 2025Promote energy-efficient appliances and remove least efficient from the marketUse best practice approaches to reduce agriculture emissions
• Incorporate more wood in building (lower carbon than steel and concrete), improve insulationIncrease the focus on energy efficiency in industrial processes
• Reform emissions trading and pricing
- From "Transition to a low-carbon economy for New Zealand''. For more go to royalsociety.org.nz.