A new book launched by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) highlights the importance of climate change as a matter of significant economic, environmental and social concern in Australia.

Climate Change: Science and Solutions for Australia provides the latest information on international climate change science and potential responses.

According to CSIRO Chief Executive Dr Megan Clark the book seeks to provide a bridge from the peer-reviewed scientific literature to a broader audience of society while still providing the depth of science that climate change demands.

“This publication draws on the latest peer-reviewed literature contributed by thousands of researchers in Australia and internationally,” Dr Clark says.

“It also provides a synthesis of CSIRO’s long history of publicly funded research into climate change.”

The book’s 168 pages provide scientific insights including:

•     Evidence from many different sources shows human activities are contributing to the Earth’s changing climate

•     Some of the impacts of climate change on Australia are already apparent

•     We are committed to some degree of climate change as a result of past greenhouse gas emissions, so we will need to adapt on a far more extensive scale than is currently occurring

•     Energy saving technologies, demand reduction and distributed power generation will help to lower national carbon emissions

•     Agriculture and forestry hold great potential for mitigating greenhouse gas emissions through afforestation, soil-carbon management, and better management of livestock and cropping emissions

•     Action within the next decade to lower greenhouse gas emissions will reduce the probability and severity of climate change impacts.

You can download the full book as a PDF here or read it online, chapter by chapter at the CSIRO website.

Whether they live in trees, underground or at the bottom of the ocean, no creature or plant  will be able to hide for much longer, following the development of a new online encyclopaedia of all living things in Australia.

The Atlas of Living Australia has been developed to build a better picture of the Australian biosphere and already holds 23 million records of the distribution of Australia’s fauna and flora, including information, maps and images for each record.

Members of the public are invited to help build the database by sending in photographs or sightings of species they may have spotted in their backyard, on bushwalks or even hiding in the kitchen.

Local contributions are particularly valuable since one of the most important features of the Atlas is its ability to provide geographic information on how species are distributed across the country.

This will enable scientists to predict areas that could be suitable for a species to live, determine how a species will be affected by a change in climate, the effect of natural disasters on populations and will also contribute to managing biosecurity issues. A new tool currently in development will look to predict the impact of temperature and rainfall increases on specific species’ populations.

For the public, the Atlas is a useful tool for students, teachers and parents to learn more about their own environment and the species nearby.  By simply typing in a postcode, the Atlas can provide a list of every known animal, plant, funghi and micro-organism within a 5km radius.

The Atlas is the result of a five-year Federally funded project to consolidate data and images from more than 60 national collections.  One of these is the National Insect Collection in Canberra which holds more than 12 million specimens and grows by about 100,000 specimens a year – no small task for the Atlas creators to keep up!

The project is the result of collaboration between the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the Australian natural history collections community and the Australian Government.

Now three years into the project, over the next two years the Atlas team will continue to add richer data, more predictive tools, more mobile applications and a new user interface, as well as creating the most comprehensive names list ever developed for Australian species.

People around Australia are encouraged to submit photos and sightings to the Atlas. For more information, visit the sharing section of the Atlas website.

Scientists aboard the Aurora Australis, Australia’s Antarctic Flagship, will be using this summer season in Antarctica to continue a 20-year study that is mapping significant changes in one of the ocean’s tiniest creatures.

One of 80 projects underway this season, the Continuous Plankton Recorder Survey uses a special recorder towed behind a research ship to filter and track tiny plankton and krill.

Over the last twenty years, the project has covered more that 278,000 kilometres and taken more than 30,000 samples to help scientists build a map of the creatures’ distribution in the Southern Ocean.

This ocean plays a huge role in the world’s climate, from absorbing carbon dioxide produced from human activities, to driving deep ocean currents.  The information scientists collect about the conditions in this ocean and how they are changing is vital for monitoring the effects of global climate change.

Project Leader, Dr Graham Hosie, said the research was starting to reveal some interesting trends.

“Since the project began in the early 1990s there have been significant changes in the composition of plankton in our samples,” Dr Hosie said.

“We seem to be catching a lot more smaller plankton compared to krill; notably copepods which, like krill, also graze on phytoplankton. 

“We don’t know what is causing this or if competition for the same food will affect krill. But any change from krill to smaller zooplankton may force animals that are dependent on krill, such as whales and penguins, to change their diet in order to survive.

“We have also observed, at times, sudden very large increases in foraminiferans – a calcareous single-cell zooplankton.  These blooms are short lived, but suppress other zooplankton numbers and again we don’t know if this has a flow-on effect to higher animals.”

While the scientists are still working to discover the exact cause of the differences they are observing in plankton distribution, one thing is for certain – changes in sea-ice and ocean temperature are already starting to have an impact on the complex Antarctic food web.

The team’s hard work over the past 20 years has resulted in the first Zooplankton Atlas, which documents the distribution and abundance of the 50 most common zooplankton species in the Southern Ocean.  The Atlas will serve as a reference for other researchers and monitoring programs.

For a first-hand look at the plankton recording project, watch this video.

Image: This photo was taken by Uwe Kils. It shows an amphipod, a type of plankton. The photo was taken using magnification so users can see the amphipod in detail. In reality, most amphipods are only 1 mm to 140 mm in length. Courtesy of Wikipedia Commons

The summer season in Antarctica has now officially begun and the Australian Antarctic Division is in the midst of coordinating the southward journey of around 500 people, including expedition scientists to investigate 80 different scientific projects.

These intrepid scientists will work on projects from far below the ice, to the unique upper atmosphere in conditions that can be life threatening – the lowest ever recorded temperature was -89.2 degrees Celsius in 1983.

This year, projects will vary from investigations into astronomical robotics to the impact of the calving of 78 km of the Mertz Glacier tongue on global ocean circulation, all in the name of understanding our complex global ecosystem.

One such unique project will explore the impact of the Black Saturday Australian bushfires of 2009 on the atmosphere above Antarctica to learn whether Antarctic ecosystems are more vulnerable than others, and whether bushfire plumes add to the depletion of the protective ozone layer.

Using high quality measurements collected by modern satellite and ground-based instruments, the team will study vertical and horizontal motions of the smoke plume, the chemical composition of this plume, and chemical reactions between various molecules in the plume and other atmospheric gases.

While many people may think Antarctic research focuses only on its environment and climate, groundbreaking research is also being conducted into human health and wellbeing.

While their main focus is on ensuring the immediate health and well being of people living on and visiting the stations, Antarctic doctors are also part of studies on the effect of the unique and extreme environment on the human body.

For example, recent research by Australian Antarctic doctors has shown that the lack of sunlight over the Antarctic winter can lead to vitamin D deficiency.  All Australian Antarctic expeditioners are now offered vitamin D supplements to help protect their bones.

One project this season, titled ‘The role of sleep and circadian phase on crew safety, performance and psychological health during long-term analog space missions’ will study the sleep patterns, health and brain function of researchers based in Antarctica.

It is hoped that the study will provide data necessary for the development of a program to monitor and improve astronaut’s health, safety and psychology during long-duration missions to space.

Antarctic science not only investigates some important processes that influence the world’s climate, such as ice melt, carbon dioxide absorption and deep ocean currents but also provides a history of our planet’s climate by analysing air-bubbles trapped in the Antarctic ice sheet.

Many projects this summer will explore the crucial history trapped in between the ice sheets of Antarctica while others will examine the current and potential future impacts of global warming and other human activities.

To learn more about Antarctic research being conducted this year, visit the Australian Antarctic Division website.

Following a decade of oceanic exploration and the work of 2700 scientists from 80 countries, including Australia, the first ever Marine census is finally complete.

The census presents an unprecedented picture of the diversity, distribution and abundance of all kinds of marine life – from microbes to whales, from the icy poles to the warm tropics, and from our shorelines to the deepest darkest depths of the ocean.

The project resulted in the Ocean Biogeographic Information System which is a database of the names and addresses of all known ocean species as well as exposing the vast areas of ocean that have never been explored.

This will enable scientists to track the future impact of things such as climate change, ocean acidity levels and oil spills on the marine environment.

The project was led by Australian scientist, Dr Ian Poiner who believes the beauty, wonder and importance of marine life are hard to overstate.

“All surface life depends on life inside and beneath the oceans. Sea life provides half of our oxygen and a lot of our food and regulates climate. We are all citizens of the sea,” Dr Poiner said.

“And while much remains unknown, including at least 750,000 undiscovered species and their roles, we are better acquainted now with our fellow travellers and their vast habitat on this globe,” he said.

Former Chief Scientist for Australia Professor Penny Sackett said the census was an outstanding testament to the importance of international collaboration.

“The information in this census is some of the most valuable data available to us in our studies of environmental science, biology and the impact of humanity on our natural resources,” Professor Sackett said.

“Critically, it will also serve as a baseline to measure future change, leaving a legacy for decades to come,” she said.

“I congratulate the international marine science community on this extraordinary effort that will pay dividends far into the future .”

In the abyssal Pacific Ocean at 5000m, a sea cucumber ingests sediments from around a field of manganese nodules. It is a widely distributed deposit feeder that uses its upright 'sail' to use current energy for transport along the seafloor. Credit: Ifremer, Nordinaut cruise 2004

A pink siphonophore, from the Sargasso Sea is actually a colonial organism similar to the Portugese Man O'War. Credit: Laurene Madin, Woods Hole Oceanographic Institution

Flamingo tongue snail was photographed near Grand Caymen, British West Indies, and is listed in the Gulf of Mexico biodiversity inventory. Credit: Kacy Moody

A fathead trawled during the NORFANZ expeditions at a depth between 1013m and 1340m, on the Norfolk Ridge, north-west of New Zealand. Credit: NORFANZ Founding Parties Photographer Kerryn Parkingson

Thumbnail image: Three subarctic sunflower stars crawl along the seafloor in shallow waters off Knight Island in Prince William Sound, Alaska, USA. Credit: Casey Debenham, University of Alaska Fairbanks.

From September 20-24, the World Green Building Council will be promoting sustainable architecture and design in order to raise awareness of green buildings and their benefits for society.

Green buildings incorporate many different innovations ranging from having a ‘living roof’ covered in plants to absorb rainwater and provide insulation, to cutting edge solar panels, which provide green energy on-site.

Whether it’s incorporating recycled materials or maximising the use of natural light, the aim of these designs is always to reduce the environmental impact and to make the building as a whole sustainable, taking into account both its construction and the impact of day to day operations.

Current scientific data shows that the observed increase in global temperatures since the industrial age is due primarily to greenhouse gases released into the atmosphere by human activities. Recent reports have also indicated that around 30 per cent of worldwide greenhouse gas emissions are created by buildings*.

Former Chief Scientist for Australia, Professor Penny Sackett is particularly interested in the crucial role sustainable buildings can play in adapting to the certainties of climate change
 
“Switching to sustainable building practices in both new buildings and in the redesign of existing buildings can play a huge role in managing climate change,” Professor Sackett said.

“Although it may be a great challenge to retrofit existing cities to make them low carbon, livable and sustainable societies, we must not let the opportunity pass for developing new standards and taking action today.”

To help progress the work of the World Green Building Society, Professor Sackett said her office had already begun considering a proposal for a ‘Science and Cities’ conference in Australia to bring together scientists, city planners, engineers and local policy makers.

“I’m interested in starting a discussion about how science in Australia can contribute to sustainable cities for the benefit of our environment, our people and our future generations,” Professor Sackett said.

In Australia, the Green Building Council has introduced a Green Star Rating system to categorise buildings based on their environmental impact.  You can find out more about the green buildings near you through their Project Directory.

As part of creating sustainable cities, green building innovations can be applied at all levels, from big new developments like Doltone House on Darling Island Wharf in Sydney to individual homes like Australia’s first zero-emissions house that was launched this year in Melbourne.

For information on events happening during World Green Building Week, including, check out the World Green Building Council website.

* United Nations Sustainable Buildings and Climate Initiative, 2009. Buildings and Cities.

The image for this story is a photo of the School of Art, Design and Media at Nanyang Technological University in Singapore.

The team is researching the effects of ocean acidification on tiny marine snails, known as pteropods, and planktonic, single-celled, shell-forming organisms called foraminifera. Pteropods are an important food source for marine predators in the Antarctic food web and sometimes replace krill as the dominant zooplankton group in parts of the Southern Ocean. Foraminifera are prey for many small marine invertebrates and fish. Both organisms are indicators of changes in the ecosystem that could have profound implications for commercial fish species, seals and whales.

About 40% of man-made carbon dioxide is absorbed by the Southern Ocean and forms a weak acid (carbonic acid) when it mixes with water. This acid readily releases hydrogen ions, and as acidity is determined by the concentration of hydrogen ions (measured on the pH scale), the more acidic a solution, the more hydrogen ions are present and the lower the pH. Increasing hydrogen ions affect the ability of pteropods and foraminifera to form shells, resulting in thinner, lighter, and pitted or etched shells. As colder water absorbs more carbon dioxide than warmer water, the effects of ocean acidification will be seen first in the Southern Ocean.  According to Dr John Baxter, a scientific advisor to government from the Scottish Natural Heritage who has joined ‘Team Acid’ on the ship, ocean acidity has increased by 30% (a pH change of 0.1) since the beginning of the Industrial Revolution and is already affecting shell-forming marine organisms. Observed effects include thinner shells, fewer pteropods in areas where they were previously common, and an increase in gelatinous organisms such as jellyfish and salps.

Team Acid is undertaking the first study of the effects of ocean acidification on pteropods and foraminifera in their natural environment (previous studies have been conducted in the laboratory or through modelling). ACE CRC pteropod biologist, Dr Donna Roberts, says the team want to establish a baseline of the health of these organisms in the ocean now, so that they can detect changes in the future.

Team Acid leader Dr Donna Roberts (right) and engineer Alex Pentony Vran

To do this they are deploying a ‘rectangular midwater trawl’ (RMT) – a pair of rectangular mesh nets – at different latitudes, from 47– 54°S, along a line from Hobart to Casey. They hope to catch larger pteropods with a 4 mm mesh net, but the main species they’re looking for is the tiny (0.5–1 mm) Limacina helicina antarctica, which will be caught in a 150 micron mesh net. The microscopic foraminifera will also be sieved from the water brought up in the trawl and preserved for later shell integrity analysis.

Team Acid will conduct seven trawls; three in subantarctic waters (45–49°S), two in polar waters (54–56°S) and one in the narrow channel of water where the subantarctic and polar waters meet (51°S). They expect to see a change in the shell weight, size and species of pteropods as we move further south into the colder and more acidified water, and hope to collect a good sample of the common Limacina helicina antarctica.

On the trawl deck the ship’s crew winch the two RMTs into the heaving seas. Each net has a ‘cod end’ attached to it – cylindrical canisters to contain the sample. The nets remain closed until they reach the required depth, between 20 and 200 m below the surface, at which time the team can remotely open the net to collect the sample.

Up in a control room above the trawl deck, the team hover around a pair of monitors displaying information about the temperature, depth, salinity and biomass as the nets descend. This information is relayed from a ‘CTD’ (conductivity, temperature, depth) instrument attached to the nets, and the ship’s acoustic echosounders, which can detect organisms in the water, such as swarms of krill or phytoplankton. When an area of high biomass is reached, dots and blobs appear on the screen and the team open the nets up.

Large Pteropod Clio Recurva

The team has chosen to sample between 20 and 200 m as this is the region where scientists think the pteropods construct their shells. This hypothesis is based on an analysis of pteropod shells collected in ocean sediment traps. These shells contained isotopes (different forms of molecules such as carbon and oxygen) typical of the water column at these depths.

Fifteen minutes after deployment, the RMTs are retrieved.  Team Acid and their accompanying paparazzi crowd into the ship’s ‘wet lab’ and begin bucketing and sieving through the samples. Both cod ends contain a glutinous mass of salps – ‘another bucket of snot’ as one crew member describes it – but this subantarctic sample also yields some surprises – about 12 large pteropods (Clio recurva) and six of the smaller Limacina helicina antarctica. A tiny squid, a large selection of amphipods (small crustaceans) and some translucent predatory worms called chaetognaths, also appear. The huge abundance of salps and other gelatinous creatures is typical of these waters. Some theories suggest an increase in salps is occurring, creating a ‘jellyfish ocean’.

Dr Roberts is surprised at the catch, saying she expected more of the smaller pteropods and less of the larger ones. It will be interesting to see if this trend continues.

At the seventh RMT site at 54°S, Team Acid hit the jackpot. One large Clio recurva shell and a whopping six small Clio pyramidata antarctica shells are captured. Dr Roberts wears a huge grin as she preserves the impressive specimens in ethanol.

The final RMT goes in at 58°S – inside waters managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) – and pulls up an amazing array of species – a magnificent pelagic polychaete (worm), lots of amphipods, juvenile krill, ctenophores (small jellyfish-like creatures), two naked (shell-less) pteropods, small salps and some mysterious, gelatinous, eyeball-like spheres, which someone suggests could be fish eggs.  The naked pteropods are particularly interesting.  Scientific theory suggests that these may become the dominant pteropods in the ocean as ocean acidification increases.

Clio Pyramidata Antarctica

When they return to Australia, team member Alex Pentony Vran, an engineer from the Australian National University, will examine the mechanical properties of the captured pteropod shells to provide definitive evidence that they are becoming more fragile. Previous work has focussed on changes in shell weight and the use of optical microscopy to examine shell thickness. In contrast, Vran will take the shells captured on this trip, apply force to them with an extremely fine diamond-tipped probe, and measure their response to this force.  This will allow him to put a figure on how strong or weak the shells are.

The team has plenty of work ahead of them, but after five days of frenetic activity, they can now enjoy the voyage at a snail’s pace. 

Written by Wendy Pyper, editor of the Australian Antarctic Magazine
For more information, go to: www.aad.gov.au/magazine
Photos supplied by Keith Martin-Smith

For further research on ocean acidifcation, the references below are a great starting point.

For a summary of the issue of ocean acidification for policy makers:

• Howard W Sandford R Haward M Trull T (2008) ‘Position Analysis: CO2 emissions and climate change: ocean impacts and adaptation issues’ ACE CRC 16pp. http://www.acecrc.org.au/uploaded/117/797619_20pa02_acidification_0805.pdf

To read the first paper to demonstrate in nature (not a lab experiment or model) that ocean acidification is already having an impact on marine biota: 

• Moy, A.D., Howard, W. R., Trull, T. W., Bray, S., 2009. Reduced calcification in modern Southern Ocean planktonic foraminifera, Nature Geoscience, v. 2, p. 276-280, doi: 10.1038/ngeo460; http://www.nature.com/ngeo/journal/v2/n4/abs/ngeo460.html

To read an analysis of the policy challenges presented by ocean acidification, how they overlap and how they differ from climate change policy:

• Howard, W. and Sandford, R., 2008, Developing Ocean Acidification Policy, Australian Antarctic Magazine, Issue 15.
  

Reluctance of nations around the world to implement mechanisms that recognise the cost of greenhouse gas emissions will increase the effort required to manage and adapt to the impacts of climate change, according to the country’s top independent science advisor.

“Delays in the reduction of emissions mean that the amount of CO₂ in the atmosphere will continue to increase and continue to compound the greenhouse effect,” Professor Sackett said.

“If no action is taken, this will eventually lead us to dangerous climate change.”

Professor Sackett warned that additional delay meant more stringent emission reduction would be required in future if Australia still planned to meet its portion of the worldwide carbon budget aimed at limiting temperature increases to 2 degrees. A 2 degree change is considered to be the guardrail value that if surpassed, would result in dangerous conditions.

“It is clear that now is the time for action on climate change, and yet we are not acting with sufficient speed to reduce the large degree of risk that climate change poses to our health, our environment and our livelihoods,” she said.

According to the Chief Scientist, not all required action will be taken through national government policy, but nations should show leadership to safeguard a sustainable and economic future for their citizens.

“Combating climate change is not just a matter of policy and government, it’s an issue that affects our society at every level, right down to the individual, and requires systematic change at all levels and in all sectors, not just at policy level,” Professor Sackett said.

“In the face of slow changes at national levels, it is all the more important that forwarding-looking industries, states, individual cities and towns, community groups and family groups continue to network together to reduce their carbon footprints and assess the impact of climate change on their activities”, she said.

“We all recognise that this is a global problem that is not just confined to Australia, but we have an opportunity to do more than our fair share and be international leaders in tackling climate change at national, sectoral, community and individual levels. We must not let that opportunity to make a positive difference pass.”

For more information on Australia’s Chief Scientist, visit http://www.chiefscientist.gov.au/

Click here to download media release

Media Contact: Alexis Cooper, Office of the Chief Scientist, Mobile: 0410 029 407

In 1998 the world saw its hottest year on record up to that point, as measured by average global air temperatures[1]. This has led some to falsely conclude that world has stopped warming ever since.  Global warming has not stopped.  Here are the facts. 

First, climate change (including global warming) is defined as long-term changes in the average parameters of the climate, not shorter year-to-year variability.  Air temperatures were somewhat cooler in the years following the extremely hot year in 1998, largely due to a natural effect called La Niña (see breakout box). But to say that this represents a halt to global warming is like saying that just because we have a cool summer day it is not summer any more. 

Second, when averaging over the decadal time scales that scientists use to study climate change, the past decade was not only warmer than historical averages, it was the hottest on record.  In fact, 8 of the 10 hottest years on record have occurred in the decade after 1998[2].

Finally, the atmosphere (air) in which we live contains only a very small fraction of the total heat associated with the surface of the earth.  The vast majority of the heat, about 85% of it is contained in the oceans, and observations show that ocean heat content has been rising over the past decade[3]. 

[1] World Meteorological Organization (2009) WMO Statement on the status of the global climate in 2008, www.wmo.int/wcc3/documents/1039_en.pdf

[2] World Meteorological Organization (2009) WMO Statement on the status of the global climate in 2008, www.wmo.int/wcc3/documents/1039_en.pdf

[3] Levitus, Antonov and Boyer (2005), Geophysical Research Letters, Vol 32, L02604, ftp://ftp.nodc.noaa.gov/pub/data.nodc/woa/PUBLICATIONS/grlheat05.pdf

Since carbon dioxide is an important greenhouse gas, one strategy that can partially combat global warming and climate change is to increase the amount of carbon stored in plants.  By increasing the amount of plant life on earth, or altering it to plant types that store the most carbon, more carbon dioxide may be pulled out of the air and stored for a period of time. 

Scientists call anything that removes carbon from the atmosphere a ’sink’.  In order to be effective in combating climate change, the sink must be large and the carbon must stay in the sink.  So what is important for climate change is not the amount of carbon exchanged between the atmosphere and plants, but how much carbon stays in the total forest and total grassland ’sinks’. 

Australia has 149 million hectares of forest.  Of this, 147 million hectares is native forest, dominated by eucalypt (79%) and acacia (7%), and 1.82 million hectares is in plantations[i]. Grassland covers around 440 million hectares of land in Australia[ii]. 

The size of the difference in the total carbon storage between grasslands and woodlands depends not just on the amount of land covered by the plants, but on the capacity of the individual ecosystems to store carbon, and the depth to which the carbon sink is tested.   The sinks can be the plant material above ground, below ground (roots), and soil that is enriched in carbon by dead plant material.

Based on data from typical perennial grasslands and mature forests in Australia, forests are typically more than 10 times as effective as grasslands at storing carbon on a hectare per hectare basis.

[i] Bureau of Rural Science, (2008) http://adl.brs.gov.au/forestsaustralia/facts/type.html

[ii] Australian Government, (2007), National Inventory Report Vol 2 Part g,  Department of Climate Changehttp://www.climatechange.gov.au/publications/greenhouse-acctg/~/media/publications/greenhouse-acctg/national-inventory-report-vol-2-part-g.ashx

Carbon in plants

Carbon is continuously exchanged between various elements of the earth: atmosphere, soil, ocean and life, which is predominately plant material.  The length of time it takes for the carbon to be exchanged depends on the process involved.  In the process known as photosynthesis, plants generate their own ‘food’ by absorbing carbon dioxide (CO2), water (H2O) and sunlight to create sugars.  Excess oxygen is released, and carbon is stored in the sugars and starches (particular combinations of carbon (C), hydrogen (H) and oxygen (O) in the plant material.

Forests

The amount of carbon taken up every year by dry forests in Australia depends on the weather conditions and age of the trees.  Science tells us that the range for forests with continuous canopies is about 0.5-2 tonnes of carbon per year for each hectare.  Grasslands may have a similar annual rate of net carbon uptake[i], but the long-term storage of carbon per hectare of grasslands is less than that over an average hectare in woody trees. 

In other words, over the long haul, more carbon stays in the tree sink than in the grass sink.  Some Australian native eucalyptus forests store up to ten times more carbon per hectare than Australian native and introduced grasslands – both above and below ground[ii]. 

The Co-operative Research Centre for Greenhouse Accounting has estimated that Australian forests store about 10.5 billion tonnes of carbon (excluding soil carbon)[iii].  This store of solid carbon has accumulated over an assumed life of 100 years for native eucalypt regrowth.  That translates to our forests storing an amount of carbon equivalent to almost 38.5 billion tonnes of gaseous carbon dioxide from the atmosphere, about 70 times Australia’s annual net greenhouse gas emission. 

Grasses

Using data from a study of semi-arid Australian grasslands by the Queensland Department of Primary Industry[iv] that accounted for the amount of live grass above ground found that about 5 tonnes of carbon could be stored per hectare of perennial grass year, assuming little grazing.  This compares to carbon stocks of mature dry sclerophyll forest that contain about 100 tonnes of carbon per hectare (with wide variability).  A recent ANU study assembling data from Australia’s unlogged, natural eucalypt forests concluded that kind of ecosystem may even hold an average of 640 tonnes of carbon per hectare[v].

So, in order for grasslands to have a greater carbon stock than an equivalent acreage of Australian forest, the roots of a summer pasture grass such as kangaroo grass, panic or weeping grass, would have to contain more than 10 times the mass of the grass that you can see above the ground[vi], which is not the case.

Soil carbon

Carbon can also be stored in the soil itself in the form of old organic matter.  Depending on the depth of soil investigated, the nutrient level of the soil and the availability of water, grassland soil can have either a similar or much lower amount of carbon than does the soil beneath forests.

As an example, studies done in 1999[vii] and again in 2005 show that reducing the amount of tree cover tends to decrease the amount of organic carbon in deep soil sinks[viii].  The 2005 study showed that about 1 metre underground, grassland sites contained only 25 tonnes of carbon in the soil per hectare compared with the soil in treed savannah sites, which stored 30 to 70 tonnes per hectare. 

The NSW Department of Primary Industry has compared soil organic carbon under perennial pasture in high rainfall areas in the mid-north coast of NSW to native hardwood forests within a 100km radius.  They found that for the high-rainfall areas studied, there was no significant difference between soil organic carbon in the pastures and native forests at 20 centimetres depth, with an average storage of 72.9 tonnes per hectare in the pasture versus 76.5 tonnes per hectare in the native forest sites[ix].

[i] Potter KN, Potter SR, Atwood JD and Williams JR, (2004) Comparing Simulated and Measured Soil Organic Carbon Content of Clay Soils for Time Periods Up to 60 Years, Environmental Management Vol. 33, Supplement 1, pp. S457–S461,  http://www.springerlink.com/content/8u6h76lr73p8eh6c/ 

Potter, K. N.; Torbert, H. A.; Johnson, H. B.; Tischler, C. R. (1999), Carbon Storage After Long-Term Grass Establishment on Degraded Soils, Soil Science: October 1999 – Volume 164 – Issue 10 – pp 718-725 http://journals.lww.com/soilsci/Abstract/1999/10000/Carbon_Storage_After_Long_Term_Grass_Establishment.2.aspx

Scurlock, J.M.O.; Johnson, K. and Olson, R.J. (2002). “Estimating net primary productivity from grassland biomass dynamics measurements”. Global Change Biology 8: 736. doi:10.1046/j.1365-2486.2002.00512.x, http://www3.interscience.wiley.com/journal/118961406/abstract?CRETRY=1&SRETRY=0 

[ii] Mackey BG, Keith H, Berry SL and Lindenmayer DB, (2008) Green Carbon – The role of natural forests in carbon storage, A green carbon account of Australia’s south-eastern Eucalypt forest, and policy implications, ANU E Press, http://epress.anu.edu.au/green_carbon/pdf/whole_book.pdf 

Keith H, Mackey BG and Lindenmayer DB, (2009), Re-evaluation of forest biomass carbon stocks and lessons from the world’s most carbon-dense forests, PNAS Early Edition,  http://www.pnas.org/content/early/2009/06/24/0901970106.full.pdf

[iii] Ximenes F, Robinson M, and Wright B, (2007) Forests, Wood and Australia’s carbon balance, Australian Government Forest and Wood Products Research and Development Corporation and Cooperative Research Centre for Greenhouse Accounting , http://www.plantations2020.com.au/assets/acrobat/Forests,Wood&CarbonBalance.pdf

[iv] Christie EK, (1981), Biomass and nutrient dynamics in a c4. semi-arid Australian grassland community,  Journal of Applied Ecology (1981), 18, 907-918, http://www.jstor.org/pss/2402381

[v] Mackey BG, Keith H, Berry SL and Lindenmayer DB, (2008) Green Carbon – The role of natural forests in carbon storage, A green carbon account of Australia’s south-eastern Eucalypt forest, and policy implications, ANU E Press, http://epress.anu.edu.au/green_carbon/pdf/whole_book.pdf 

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