Posts Tagged ‘NIWA’

Report explains the science of NZ’s freshwater estate

Sir Peter Gluckman, the Prime Minister’s Chief Science Advisor, has released a report designed to assist in understanding the complexity of issues surrounding the condition and stewardship of our freshwater.

With growing interest in the state of New Zealand’s freshwaters and the policy decisions needed to ensure stewardship of the estate, the report aims to provide common understandings of the scientific and technical knowledge on which freshwater ecosystem management should be based. In doing so, the paper acknowledges the many  values New Zealanders place on freshwater and the different diversity of stakeholders.

The report provides an overview of the issues and a technical analysis for those who wish to explore the science further.

“My office started working on this report nearly a year ago, recognising the complexity of decisions and trade-offs that New Zealand faces between conserving our ecosystems and mitigating our agricultural, industrial and urban impacts,” said Sir Peter.

“Because of the Government’s recent ‘Clean Water’ consultation package, which includes proposed new approaches to defining ‘swimmability’, I thought it would be useful to accelerate the release of our report before the end of that consultation phase.”

Sir Peter’s report was developed with the assistance of the Freshwater Group at NIWA. It was reviewed by New Zealand and international academics and by the Departmental Science Advisors from the Department of Conservation and the Ministry for Environment.

The intent was to ensure diverse scientific perspectives on the challenges presented by New Zealand’s varied river catchments, lakes, estuaries and wetlands could be fully explored.

The issues extend from understanding the influence of distinct landscapes and watersheds, climate, and the diversity of uses and values of freshwater systems, to the ecology of our native freshwater plants, fish, insects, and birds. The report explores the impacts of our pastoral agricultural system, urbanisation, industrialisation and climate change, and how these might be managed to maintain and restore New Zealand’s freshwater estate.

“Water is not a trivial issue for New Zealand and New Zealanders,” said Sir Peter.

“Our cultural and economic relationship to our land and water defines us, and I felt the importance of the issues merited a full explanation of all the freshwater science that informs them.”

The report is available on the PMCSA website HERE. 


NIWA team finds native forests are absorbing more carbon dioxide

New research led by NIWA atmospheric scientists Drs Kay Steinkamp and Sara Mikaloff-Fletcher indicates that New Zealand’s forests absorb much more carbon dioxide than previously thought, with much of the uptake occurring in the southwest of the South Island.

Carbon dioxide is a primary greenhouse gas and responsible for most of the human-induced warming in the atmosphere. Globally, carbon sinks, such as oceans and forests, have helped mitigate the effects of climate change by absorbing about half the carbon dioxide emitted by human activities over the past few decades.

New Zealand’s forest carbon uptake played a key role in meeting our commitments under the Kyoto Climate treaty and is expected to play an important role in meeting our COP21 commitments.

The results of the research have just been published in the scientific journal Atmospheric Chemistry and Physics.

Dr Mikaloff-Fletcher and her team used an “inverse” modelling approach to estimate the amount of carbon uptake. This is done by measuring the carbon dioxide present in the atmosphere at a network of sites, and then using high resolution weather models to determine what parts of New Zealand the air has passed over before reaching the site.

Simulations from a land model, run by partners at GNS Science, and ocean carbon data provide additional information. From there, the team calculates the best combinations of sources and sinks to match the data.

 This project included data from NIWA’s clean air station at Baring Head, near Wellington, its atmospheric research station at Lauder in Central Otago, and measurements taken from a ship that collects observations on a line between Nelson and Osaka, Japan.

“The inverse approach integrates information about carbon dioxide sources and sinks from atmospheric data, ocean data and models,” Dr Steinkamp says.

“The story the atmosphere is telling us is that there’s a big carbon sink somewhere in the South Island, and the areas that seem to be responsible are those largely dominated by indigenous forests. However, we cannot rule out an important role for carbon uptake in the hill country or from pasture from our current data.”

Dr Mikaloff-Fletcher says this was a very surprising result mainly because strong carbon sinks are expected when there is a lot of forest regrowth.

“Carbon uptake this strong is usually associated with peak growth of recently planted forests and tends to slow as forests mature. This amount of uptake from relatively undisturbed forest land is remarkable and may be caused by processes unique to New Zealand or part of a wider global story.”

The National Inventory method reported by Ministry for the Environment reports annually on New Zealand’s carbon uptake. This internationally standardised methodology puts the amount of carbon being absorbed by all New Zealand forests at 82 teragrams (Tg) CO2 (A teragram is one millon metric tons) total over 2011-2013, the period studied by Dr. Mikaloff-Fletcher’s team.

Once accounting rule differences are corrected for, the new NIWA measurement approach finds that actual carbon uptake could be up to 60% higher.

The inventory-based method estimates carbon uptake using measurements of tree growth taken from about 100 sampling areas, and extrapolates this to the entire country using statistical techniques and modelling. There is still considerable work to be done in comparing the two independent approaches.

“We need to find out definitively what processes are controlling this unexpectedly large carbon uptake, in order to understand the implications for land management and climate treaties. We need additional measurments to tell us if this is unique to the southern half of the South Island or holds across a wider range of New Zealand.”

Dr Mikaloff-Fletcher says the ability of forests to absorb carbon is a powerful tool to help address the challenge of climate change.

Next steps include incorporating data from NIWA’s newest atmospheric CO2 observing site, Maunga Kākaramea/Rainbow Mountain in the central North Island, deploying two new atmospheric CO2 observing sites and a major improvement to model resolution. This will start to shed light on what’s happening in the North Island and the Canterbury plains.

Significant progress made towards eradication of Hydrilla weed

A recent annual flora and fauna survey conducted by the National Institute for Water and Atmospheric Research shows the Ministry for Primary Industries has made good progress in removing Hydrilla verticillata, a highly invasive aquatic weed from the Tutira, Waikōpiro and Opouahi lakes in the Hawke’s Bay.

For the first time in more than five decades the Hydrilla weed has not been found in the three Hawke’s Bay lakes where it was first found, says Dr Mike Taylor, the ministry’s Manager Biosecurity Response.

“After over seven years of dedicated work, we are well on our way to reaching our goal of eradicating this invasive weed,” he says.

Hydrilla is a submerged, rooted freshwater aquatic plant which grows up to 9 metres. As it grows it becomes very dense and crowds out native aquatic plants, restricts light, and depletes oxygen. It is considered one of the world’s most invasive water weeds.

Hydrilla is one of 9 species currently managed as part of the National Interest Pest Responses, which is an ministry programme focused on responding to organisms that present significant risks to New Zealand’s biodiversity.

In collaboration with the Hawkes bay Regional Council, Department of Conservation, Fish and Game, and local iwi, MPI has been actively working on removing Hydrilla from Hawke’s Bay’s lakes since 2008.

The programme started off with the use of an aquatic herbicide, which was then followed up with the introduction of Ctenopharyngodon idella, the herbivorous grass carp (a type of fish), into the affected lakes in December 2008 and again in 2014.

“This has been successful as Hydrilla is a preferred food plant by grass carp. The carp used will not breed in New Zealand waters, so we aren’t having to deal with an increase of carp numbers in the local waters,” says Dr Taylor.

“Being able to remove Hydrilla from these lakes will remove the likelihood that Hydrilla can be transported to other water bodies.”

Native fauna, such as freshwater mussels, are re-colonising their preferred habitat which was previously smothered by the dense Hydrilla weed beds.

The ministry will be contracting NIWA to conduct a further flora and fauna survey in autumn 2017 to monitor progress.

The 2016 flora and fauna survey report is available here.


Scientists attribute rising methane levels to agriculture

Agricultural practices, not fossil fuel as previously thought, are the likely cause of a global rise in methane emissions over the last decade, according to scientists from NIWA in collaboration with international partners.

The research, led by NIWA atmospheric scientist Hinrich Schaefer, has just been published (see here) in the journal Science. 

The amount of methane in the earth’s atmosphere is estimated to have increased by about 150 per cent since 1750.

NIWA scientists first noticed trends occurring in the data collected at NIWA’s clean air monitoring stations at Baring Head in Wellington and Arrival Heights in Antarctica.

In a press release on the research, NIWA said the scientists had only only Southern Hemisphere data to go on and so began to collaborate with the University of Colorado in the US, and Heidelberg University in Germany whose scientists were taking similar measurements in a number of locations across the world.

“We wanted to put all the data together, then calculate the global average for each year and look at how that has changed over time,” Dr Schaefer said.

Between 1999 and 2006 scientists observed a plateau in the amount of methane in the atmosphere. The amount had been steadily increasing since pre-industrial times but then levelled out for about seven years. After 2006 it began to rise again and continues to do so.

Dr Schaefer said there were three broad questions the scientists sought to answer:

  • Were there methane sources that diminished when the plateau began in 1999?
  • What were they?
  • What has been driving the renewed growth since 2006?

“We found we could distinguish three different types of methane emissions. One is the burning of organic material, such as forest fires. Another is fossil fuel production – the same processes that form natural oil and gas – and the third is formed by microbes which come from a variety of sources such as wetlands, rice paddies and livestock.”

Around the time the plateau in methane emissions occurred, economic collapse in the Soviet Union caused oil production to decline dramatically – a factor that could now be detected in atmospheric analysis but is of no great surprise to the scientists.

But analysis since 2006 rules out fossil fuel production as the source of methane increasing again.

“That was a real surprise, because at that time the US started fracking and we also know that the economy in Asia picked up again, and coal mining increased. However, that is not reflected in the atmosphere,” Dr Schaefer said.

“Our data indicate that the source of the increase was methane produced by bacteria, of which the most likely sources are natural, such as wetlands or agricultural, for example from rice paddies or livestock.”

Previously published studies had determined that the methane originated from an area that includes South East Asia, China and India – regions that are dominated by rice production and agriculture.

“From that analysis we think the most likely source is agriculture.”

“If we want to mitigate climate change, methane is an important gas to deal with. If we want to reduce methane levels this research shows us that the big process we have to look at is agriculture.

“The good news is that if the source was wetlands, we couldn’t do anything about it. But there is ongoing research that is looking at reducing methane production in agricultural practices.”

There is another important consideration in the mix. Naturally produced methane sources are particularly sensitive to changes in climate and Dr Schaefer says wetlands produce more methane if there is more rain and if it is warmer. Thawing permafrost produces methane and methane is also found in ice-like structures in ocean sediments.

This means that global warming could result in more methane being produced from these natural sources, Schaefer says.

“You could have a situation where humans are causing global warming which causes natural methane sources to emit more methane, contributing to further warming.”

“We don’t see that, maybe not yet. Our findings at least give us an angle to tackle the problem.”

But Dr Schaefer stressed it would be wrong to conclude that the study gives fossil fuel a clean bill.

If fossil fuel production picked up again, “that may change the situation dramatically”.


El Niño – and why we should be braced for an unusually dry summer

These observations on El Niño come from Brent Clothier, at Plant and Food Research…

All around the world, people are talking about El Niño. What is El Niño?

At the simplest level, El Niño is when a big puddle of warm water forms in the middle of the Pacific.  And the current puddle is big & warm.  The last comparable El Niño was in 1997/98. And there’s a great video of the inter-comparison at . Here’s a screen grab of the comparison as at 3rd August …

el nino


According to the latest Update from the World Meteorological Organization there is

“… a mature and strong El Niño is now present in the tropical Pacific Ocean and is likely to strengthen further. This year’s El Niño event is the strongest since 1997-1998 and is potentially among the four strongest events since 1950. The peak strength of this El Niño, expected sometime during October 2015 to January 2016.”

What does this oceanic heating that is associated with El Niño do to atmospheric and oceanic flows?

El Nino 3

NIWA says

“…during El Niño, the trade winds weaken, leading to a rise in sea surface temperature in the eastern equatorial Pacific and a reduction of ocean upwelling off South America. Heavy rainfall and flooding occur over Peru, and drought over Indonesia and Australia. The supplies of nutrient rich water off the South American coast are cut off due to the reduced upwelling, adversely affecting fisheries in that region. In the tropical South Pacific the pattern of occurrence of tropical cyclones shifts eastward, so there are more cyclones than normal.”

So what’ll happen next now we’ve a strong El Niño?

We’ll get more westerly winds and NIWA has shown (below)

“…the average rainfall amounts, in percentage of the 1981-2010 normal, that were recorded for the summer season (December – February) during the three strongest El Niño events since 1950 (1972/73, 1982/83, 1997/98). Based on this record, an elevated risk for drought for parts of New Zealand is anticipated later during summer, in particular for eastern parts of both islands as well as northern areas of the North Island.”

El Nino 2

So in prospect we’re in for an unusually dry summer, especially in the north and east of both islands.

This has prompted the Ministry of Primary Industries to issue advice to farmers on how to prepare for this summer’s El Niño. It’s at

This advice includes:

  • Have a plan in place with set dates for decisions depending on climate conditions. Discuss your plan with trusted advisers and update it over time.
  • Make decisions early and take action.
  • Use irrigation water efficiently and plan for water restrictions.

Farmers would know all about the dry summer – but ocean temperatures are up too

Farmers won’t need telling, but rainfall was well below normal (< 50%) or below normal (50-79%) for most parts of the country in January.

It was extraordinarily dry in parts of Northland, Auckland, Taranaki, Manawatu-Whanganui, Kapiti Coast, Wellington, Marlborough, north Canterbury and Central Otago where rainfall totals for the month were less than 10% of their respective January normal.

The information is contained in the the  New Zealand Climate Summary: January 2015 , published today. The full climate summary is here: Climate_Summary_January_2015.pdf

At the same time NIWA has said an international team of oceanographers, including NIWA’s Dr Philip Sutton, has analysed data from ocean-profiling instruments known as Argo floats and found the temperature of the world’s oceans increased steadily between 2006 and 2013.

Continue reading

Let’s talk about the weather

If there’s nothing else to talk about as we return from the summer holidays, there’s always the weather.

The Science Media Centre a href=””>has published a round-up of experts responding to news that 2014 was a near average year for New Zealand weather-wise, although analysis of worldwide data has highlighted increasing global temperatures.

According to the 2014 annual climate summary from NIWA, the nation-wide average temperature for 2014 was 12.8°C (0.2°C above the 1981–2010 annual average), making it the 23rd-warmest year since records began.

The summary draws on data from NIWA’s seven-station temperature series which begins in 1909.

Notably, New Zealand observed its warmest June on record. More national and regional annual climate data covering temperatures, rainfall, wind and significant weather events can be found in the full summary, available here.

The warming trend was noted globally with 2014 officially declared the hottest year on record since global average surface temperatures started being measured in 1891, by the Japan Meteorological Association.

Further global data from NASA and the National Oceanic and Atmospheric Administration are expected to confirm the findings this month.

Last week the Australian Bureau of Meteorology confirmed that 2014 was Australia’s third warmest year on record. According to the Bureau, seven of Australia’s ten warmest years on record have occurred in the 13 years since 2002.

The Science Media Centre post includes commentary collected by the AusSMC and from elsewhere.