NZ scientists and media acknowledge cliamte change and ocean acidification

Should we rejoice at our scientists and media playing catch-up. The will always be many steps behind reality.

This has been on RNZ news broadcast but nothing on their website so far.

"Breaking news on RNZ at mid day, warmer temperatures beginning to affect sea life. Better late than never eh Nat Rad?"

How will climate change hurt our ocean species? Scientists investigate

NZ Herald,

8 October, 2017

A decade of science has revealed how climate change is slowly shifting the chemistry of New Zealand's oceans, threatening the multitude of life found in our waters.

But, in a sweeping new stocktake, Kiwi scientists say there's still much uncertainty about how our marine species will fare in a warmer world.

Measured by a reduction in sea water pH, ocean acidification is mostly driven by oceans absorbing and storing the increasing load of carbon dioxide that humans are pumping into the atmosphere.

Between 1909 and 2009, New Zealand's sea-surface temperatures had warmed by a statistically significant 0.71C, while pH levels of subantarctic waters had dropped by 0.0015 units per year since 1998.

Globally, the oceans' average pH is currently 8.1, which is 0.1 lower than it was 250 years ago.

While that might not sound much, a decrease of one pH unit represented a 10-fold increase in the acidity.

The decline in pH was projected to continue in line with the increase in atmospheric CO2, leading to the most rapid decrease in ocean pH in the past 50 million years.

The effect is associated with decreases in nutrients such as nitrate and phosphate in the surface ocean, where most marine organisms live.

Even small shifts had big consequences: mussels and paua might struggle to build their carbonate shells, while some fish species could experience changes in behaviour, physiology and even habitat distribution.

Niwa scientists estimate that perhaps 25 per cent or less of the existing cold water coral locations around New Zealand will be able to sustain their growth by 2100 due to ocean acidification.

Photo / Niwa

Early research on juvenile paua had shown the species grew more slowly under acidic conditions and their shells showed clear signs of being dissolved, with similar effects observed in flat oysters.

Another study suggested suitable habitat regions would shrink for many coral species in our part of the planet, although the Chatham Rise would likely remain a suitable coral habitat in a high-carbon world.

'It's got more and more complicated'

Green-lipped mussels are among the long list of New Zealand species which could be affected by ocean acidification. Photo / File

Ten years after Kiwi scientists first started exploring ocean acidification, the same experts have spelt out a pressing need for new research.

"It's important that after a decade of research, we identify where the research is going and pinpoint the knowledge gaps," explained Professor Cliff Law, a Niwa marine biogeochemist and lead author of the review, published in the New Zealand Journal of Marine and Freshwater Research.

"Ten years ago we were doing basic experiments, now we're looking at everything together - how changing temperatures, pH levels, nutrient run-off and turbidity for example, are affecting our coastal waters.

"It's got more and more complicated as it's gone on but what we know is that New Zealand waters are already exposed to ocean acidification and will be subject to further pH stress in the future."

Niwa scientists have been aided by the Munida transect time series, a 20-year record of pH measurements taken along a 65km line in the open ocean off Otago.

This, the only time series of its kind in the Southern Hemisphere, had shown the water acidifying at the same rate as CO2 levels have risen in the atmosphere.

While the paper showed species were meeting ocean acidification with a variety of responses, there had been only limited research into the resilience of marine organisms.

Niwa marine geochemist Dr Cliff Law. Photo / Dave Allen

Current research included a large four-year, Niwa-led collaboration monitoring spots like the Firth of Thames, Karitane and Nelson bays, with experiments focused on species such as green-lipped mussels, paua and snapper.

"We want to understand whether different life stages of these key species are affected by lower pH and how other factors in the environment might influence this impact," Law said.

"Coastal waters are the most variable in their natural pH levels; they are where we get the most benefits in terms of food, recreation and other amenities, yet also where we affect the ocean most."

There was a need to better understand whether our coastal areas would grow more resilient or vulnerable, and whether measures like selective breeding of shellfish might help.

"We are looking for tools and solutions as well as conducting research to determine if there is something we can do at the local level," Law said.

"The outcome will be better models, allowing more accurate predictions of the impacts of acidification in coastal waters, as well as management options for stakeholders."

Can some of our species stand change?

A new study will boost our understanding of how climate change might affect rocky reefs - and whether kelp forest habitats could protect resident organisms. Photo / File

Meanwhile, a Victoria University marine botanist is investigating why some New Zealand species may be able to cope more easily with ocean acidification.

Because of their highly soluble calcium carbonate skeletons, reef-building algae are widely considered to be among the species most at risk.

But Dr Christopher Cornwall challenged this idea, suggesting certain species of calcifying algae might pack the physiological machinery needed to tolerate change.

He aimed to find out whether the resilience seen in some populations of local coralline algae was due to them having evolved in more variable pH environments.

Coralline algae are ecologically important calcifying algae that create and bind together rocky reefs and act as nurseries for species important to fisheries in New Zealand and worldwide.

Our underwater kelp forests are a common habitat for coralline algae, which are exposed to large daily shifts in pH as a result of fluctuating CO2 concentrations in the surrounding seawater.

This fluctuation was created by the kelp taking up CO2 during daytime photosynthesis and releasing it at night during respiration.

The variability in sea water pH in these forests could be extreme, with pH dropping at night to levels often lower than those estimated to occur by the end of this century.

In his five-year study, supported with an $800,000 Rutherford Discovery Fellowship, Cornwall will draw on cutting-edge geochemical techniques and other measures to find the factors at play.

Cornwall also wanted to reveal whether any tolerance is maintained after successive generations in constant pH conditions.

The findings would boost our understanding of how climate change might affect rocky reefs and whether kelp forest habitats could protect resident organisms, helping us plan for shallow reef systems in years to come.

Climate change professor issues warning to Kiwis

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50°C days by end of century

Sydney and Melbourne have been warned to prepare for scorcher days reaching 50°C by the end of the century - even if global warming is contained to the Paris Agreement target of a 2° increase.

Photo: Max Pixel (free image)

A new study led by Australian National University (ANU) climate scientist Dr Sophie Lewis has projected daily temperatures 3.8° above existing records for the two cities and even hotter extremes.

"We have to be thinking now about how we can be prepared for large population groups commuting to and from the CBD on these extremely hot days, how we send young children to school on 50° days, how our hospitals are prepared for a larger number of admissions of young or old people, and how our infrastructure can cope with it," Dr Lewis said.

Photo: SUPPLIED

The study found containing global warming to 1.5° - the more ambitious target set by the Paris Agreement - would limit extreme heat, but Dr Lewis said angrier summers were inevitable.

"We've already seen an increase in excess heat deaths in heatwaves in 2009, due to those extreme heatwaves, and that's likely to occur even more under these 50° days."

Pockets of Australia have tasted temperatures close to 50°, mostly remote country towns.

But Dr Lewis said heat like that would look very different in Sydney or Melbourne.

The ANU study only analysed Bureau of Meteorology data from Sydney and Melbourne, but Dr Lewis said all of Australia could expect to see hotter extremes in the future.

"It's not great news, obviously," Deputy Lord Mayor of Sydney Jess Miller said.

Ms Miller said one of the issues facing Sydney and Melbourne was the emergence of "heat continents", where entire suburbs baked for a significant period of time without relief.

"When you've got grey infrastructure and roads and buildings absorbing all that heat, not only does it get much hotter, but it takes twice to three times as long to cool down," she said.

And Ms Miller said 50° days also posed a threat to city transport.

All Sydneysiders know the sense of dread as they pack into Central Station on a sweaty day, but Ms Miller said it was not only the commuters who would suffer if the temperature reached 50°.

"When you have a bunch of days one by one, it stops the whole system."

Ms Miller said city planners needed to begin designing cities that took advantage of wind, green spaces and shade whilst still being cost-effective.

"We need to think of ourselves as part of the ecology of a city, and that a city is not just a bunch of buildings and roads," she said.