Staying MouseAlert, not MouseAlarmed, this Christmas

Sure, he might look cute, but this fella and his friends can cause a whole lot of trouble when they get together.

Sure, he might look cute, but this fella and his friends can cause a whole lot of trouble when they get together.

By Leon Braun 

“’Twas the night before Christmas, when all thro’ the house
Not a creature was stirring, not even a mouse …”

CSIRO scientists are keeping their eyes peeled for more than just Santa Claus this Christmas. With unusually high numbers of mouse sightings in Victoria this spring, CSIRO ecologist Peter Brown and colleagues at various Australian and New Zealand research agencies are monitoring mouse populations to see whether 2015 will bring a sigh of relief or send people scurrying for cover under a deluge of tiny, furry bodies.

While taken individually, mice can be rather cute (think Mickey, Mighty and Danger), en masse they can be absolutely devastating. In 1993, Australia’s worst ever mouse plague caused an estimated $96 million worth of damage, destroyed thousands of hectares of crops, blighted piggeries and ravaged poultry farms. The whiskered marauders chewed their way through rubber and electrical insulation, damaged farm vehicles, ruined cars and buildings. Another plague in 2010/11 was almost as bad, affecting 3 million ha of crops in NSW’s central west and the Riverina, as well as parts of Victoria and South Australia.

Eww.

This photo is named ‘Mice Mound”. There’s not much more we can add to that.

Along with economic hardship and disease, plagues bring severe psychological distress for people living through them.

“The sheer stress of dealing with mice in your kitchen every night takes its toll,” Peter says. “They’re everywhere: chewing, defecating, breeding.”

The good news is that with sufficient warning it is possible to prepare for mouse plagues, and to minimise the damage they cause, through early baiting and removing food supplies and cover. Over the years, our scientists have become increasingly accurate at predicting mouse plagues (they got it right in 1994 and 2001-2003) and have developed an ever more sophisticated range of tools to assist them. The latest weapon in their arsenal is “MouseAlert“, a citizen science website where keen-eyed rodent reporters can notify CSIRO about mouse sightings. The website is optimised for mobile phones, and Peter and his team hope to have an app out soon.

A recent mouse monitoring map. Marvelous!

A recent mouse monitoring map. Marvelous!

“Numbers are everything when you’re trying to predict a plague,” Peter says. “Traditionally we’ve used traps and chew cards [thin pieces of cardboard soaked in vegetable oil], but they have disadvantages, not least the fact that we’re not physically able to put them everywhere. MouseAlert allows us to capture data over a much wider area and potentially spot a plague well before it becomes a problem.”

Equally important as sightings, Peter says, are reports of where mice haven’t been.

“The jump from zero sightings to one or two can be an important indicator that mouse numbers are increasing,” he says. “By participating in citizen science, the public can help us identify these trigger points.”

So how are things looking this year? A little ominous, actually. Unusually high numbers of mice were seen in western Victoria in September. Depending on how much rain we get, they could build up to plague proportions by March or April next year. That’s why Peter wants mouse watchers to keep their eyes peeled:

“If it looks like there’s going to be a plague, we want to be able to give farmers plenty of time before sowing to prepare – or else put their minds at ease if it looks like there isn’t.”

So if you do see a mouse this Christmas Eve – stirring or not – get over to MouseAlert and report it. The pantry you’re saving could be your own!


Explainer: what is raw milk and why is it harmful?

There is no evidence that the health benefits of milk are compromised by pasteurisation. jacqueline/Flickr, CC BY-NC

There is no evidence that the health benefits of milk are compromised by pasteurisation. jacqueline/Flickr, CC BY-NC

By Edward Fox, CSIRO and Narelle Fegan, CSIRO

Milk is a highly nutritious food, and an important source of amino acids and minerals such as phosphorus and calcium, which contributes to bone health.

Historically, milk was prone to contamination by bacteria from cows that could cause severe illness in humans. This remains the case with raw (unpasteurised) milk. The tragic death of a Victorian toddler this week is a stark reminder of these risks.

Pasteurisation involves heating the product to 72°C for 15 seconds. The method was originally employed to destroy bacteria in wine and beer that caused these products to spoil. It was quickly realised that this process could also be applied to milk to destroy harmful bacteria, and make milk safer for human consumption.

Pasteurisation was first introduced in Australia in the late 1950s and remains a legal requirement for milk produced for human consumption in Australia.

Nowadays, some of the important bacteria that pasteurisation targeted, such as those that cause tuberculosis, are no longer as problematic. So why do we continue to pasteurise milk?

The animals we use for milking can sometimes carry other pathogenic organisms that are capable of causing disease in humans. They can be found on hides or shed in the faeces.

Even healthy animals may be a source of organisms that are harmful to people. Such pathogens may be present in the farm environment, including soil, water, on pasture and in animal feeds. These pathogens can enter the milk during milking and if such milk is consumed, it can cause disease.

The most common pathogens found in association with dairy farms and milking animals include bacteria such as Escherichia coli (E. coli), Campylobacter and Salmonella, but other pathogens such as parasites like Cryptosporidium, a type of gastro, may also be present.

As soon as milk is secreted from the udder, it is at risk of contamination by many different bacteria. cheeseslave/Flickr, CC BY

As soon as milk is secreted from the udder, it is at risk of contamination by many different bacteria.
cheeseslave/Flickr, CC BY

Campylobacter and Salmonella can cause severe diarrhoea and certain types of E. coli, particularly those known as Shiga toxin-producing E. coli (STEC), can cause very severe disease which impairs kidney function and may result in death.

Milk is highly nutritious to bacteria. Bacteria can quickly proliferate if their growth is not inhibited. Stopping the growth of bacteria in milk requires either heating to kill the bacteria, or chilling, which will not kill the bacteria but will slow down their growth.

E. coli, for instance, can go from ten cells to 100 million cells in just over six hours at 30°C. Only ten cells may be required to make someone ill. If such an organism is likely to be present, it’s important that any potential growth is stopped.

These harmful bacteria have caused outbreaks and disease associated with the consumption of raw milk in many countries. Data from the United States indicates that over a 13 year period to 2011, there were 2,384 illnesses, 284 hospitalisations and two deaths associated with the consumption of raw milk.

In Australia, raw milk contaminated by bacteria such as Campylobacter and Salmonella caused at least nine outbreaks of disease between 1997 and 2008, leading to 117 cases of illness.

So why do people choose to drink raw milk?

Advocates of raw milk often claim improved health benefit and nutritional value, or desiring a product which has not undergone further processing, retaining bacteria naturally present in milk.

But there is no evidence that the health benefits of milk are compromised by pasteurisation.

The defining difference between pasteurised and raw milk is the bacteria that are present. As soon as milk is secreted from the udder, it is at risk of contamination by many different bacteria as it makes its journey to our table. This includes harmful bacteria. These bacteria can lead to severe illness in humans, particularly children and the elderly.

For these reasons, raw milk continues to have a far higher risk of causing illness. Pasteurisation remains an important step in ensuring we can continue to enjoy safer, nutritious milk.

Further reading: Bath milk crisis must prompt better cosmetic safety regulation

This article was originally published on The Conversation.
Read the original article.


World Soil Day: a chance to worship the ground we walk on

By Leon Braun

It’s downtrodden, underfoot and often under appreciated, yet so crucial to our existence that one of our scientists describes it as “the complex natural medium that supports all life on Earth”. It holds our crops, stores and purifies our water, and provides habitat for amazing creatures like the giant Gippsland earthworm, which can reach up to 3 m in length. But most of us only think about it when we’re trying to get it out of footy socks on laundry day.

It’s soil – and today (and all next year) it gets a bit of long-overdue recognition. December 5 is World Soil Day, and the United Nations has declared 2015 to be International Year of Soils. That’s a good thing, because globally, soils are under threat: from erosion, poor land management and urbanisation. At the same time, we need soils more than ever to produce the food we need for a growing population, to help manage climate change and to ensure ecosystem health.

Cracked soil at Chowilla, South Australia.

Cracked soil at Chowilla, South Australia.

Luckily for Australia’s soils, they have CSIRO looking out for them. We started researching soils in 1929, published the first soil map of Australia in 1944, and have been working hard ever since to improve our understanding and management of soils. We’re looking at ways to make agricultural soils more productive and to ensure they’re used sustainably, so future generations can continue to reap their bounty. And we’re working internationally too, so it’s not just Australia that benefits.

Our latest achievement (with allies from around the country) is the Soil and Landscape Grid of Australia, a digital map of Australia’s soils with two billion ‘pixels’ of about 90 by 90 metres, down to a depth of two metres below the surface. It contains information such as water holding capacity, nutrients and clay, and has applications for everyone from farmers deciding where to plant their crops to conservationists looking for habitats for endangered native species. You can read more about it here.

We’re also home to the Australian National Soil Archive, which has just gotten a new home in Canberra. The archive contains about 70,000 samples from almost 10,000 sites across Australia, the oldest dating back to 1924. Each sample represents a time capsule of the Australian landscape at the time it was collected, so we can measure things like caesium dispersal from the British nuclear tests at Maralinga and the impact of phosphate-based fertilisers on agricultural land. The archive is a vital national asset for soil researchers and industry, and has even been used by the Australian Federal Police to examine the potential of new forensic methods. Finally, data from the archive powers our first official app, SoilMapp, which puts information about Australian soils at your fingertips. This is incredibly useful, whether you’re growing canola on a farm in Western Australia or planning a major roads project in Victoria.

So as you go through your day today, eat your lunch, wipe your shoes, just remember: it takes 2000 years to form 10 centimetres of fertile soil suitable for growing our food, but just moments for that soil to blow away or get covered in a layer of asphalt. Something to think about next time you sit down to a meal – or do your laundry.


Go with the grain: technology to help farmers protect crops

 

Tractors may have revolutionised farming but to protect biosecurity, farmers could do with some extra help. Ben McLeod/Flickr, CC BY-NC-SA

Tractors may have revolutionised farming but to protect biosecurity, farmers could do with some extra help. Ben McLeod/Flickr, CC BY-NC-SA

By Paul De Barro, CSIRO and Grant Smith, Plant Biosecurity Cooperative Research Centre

New technology to tackle biosecurity challenges down the track is one of the five megatrends identified in today’s CSIRO report Australia’s Biosecurity Future: preparing for future biological challenges.

As manpower in the agriculture and biosecurity sectors declines, we must look to technological innovation to protect crops. Monitoring and surveillance, genetics, communication and data analysis have been identified in today’s report as future work priorities, along with developing smaller, smarter, user-friendly devices.

But this is easier said than done. There are a number of potential barriers that need to be addressed to make sure that appropriate technologies are used to maximum effect. It might sound obvious, but making sure farmers can – and want to – use new technology is a crucial step.

Declining workforce

With an ageing population and fewer young people entering agriculture, we are seeing the loss of the wealth of knowledge and experience held by long-time farmers.

Many farmers have a deep understanding of the day-to-day activities that can protect properties and reduce the spread of pests and diseases across the country, and this on-farm biosecurity knowledge may be lost.

Farming a wide brown land means there’s a lot of ground to cover … and monitoring devices can make a farmer’s job much easier. Ed Dunens/Flickr, CC BY

Farming a wide brown land means there’s a lot of ground to cover … and monitoring devices can make a farmer’s job much easier.
Ed Dunens/Flickr, CC BY

 

We are also seeing a decline in specialists in areas crucial to biosecurity management such as taxonomy, plant pathology and entomology. This is prevalent throughout the biosecurity landscape, reducing our overall pest and disease response capability.

With fewer people training in taxonomy, we’ve estimated that 50% of Australia’s diagnostics capability will be lost by 2028.

Without adequate surveillance in place, pests can cripple emerging industries. In recent seasons, we have seen two new diseases devastate local farmers in the Northern Territory:

  1. the recent invasion of banana freckle, which authorities are working to eradicate
  2. the cucumber green mottle mosaic virus (CGMMV) infected melon crops near Katherine this year. Lack of CGMMV knowledge meant a delay identifying the disease and starting treatment.
Banana freckle. Scot Nelson/Flickr, CC BY-SA

Banana freckle.
Scot Nelson/Flickr, CC BY-SA

 

Surveillance is critical to the delivery of effective biosecurity, both for early detection of a disease and for effective response. Yet delivery of effective surveillance faces a growing challenge which becomes greater in the more remote parts of Australia.

Constraints on surveillance include declining investment among jurisdictions, declining expertise or limited availability of personnel, expense and occupational health and safety requirements.

Technology innovation

In response to these challenges there is a strong drive to draw on technological innovation to deliver biosecurity previously provided by people.

Research is already underway with new applications of technology for surveillance and detection, sensitive diagnostics, as well as preventative pre-border technologies.

Access to low-cost sensors and development of automated systems are opening up opportunities for rapid identification and response to pests and diseases. Sensors smaller than a pea can, for example, help monitor the health of oysters in real time.

sr320/Flickr, CC BY-SA 

sr320/Flickr, CC BY-SA


 

Pestpoint, a mobile device application being developed by staff of the Plant Biosecurity Cooperative Research Centre (PBCRC) provides access to an online community of people working in the agricultural sector who need to identify plant pests in order to make decisions about how to manage those pests.

By using genetic techniques, scientists with the PBCRC are developing rapid tests using molecular sequences for identifying pests and diseases. The next phase is to transfer these tools to biosecurity practitioners, including diagnosticians and port inspectors.

Sounds great … but there are barriers

The adoption of a new technology hinges on how easily it can be incorporated into the existing biosecurity system, which means that the technology needs to be integrated into a human system:

  1. the connection to institutional arrangements governing biosecurity regulation, response and compliance
  2. the social acceptability of deploying smart technologies and information systems.

The Queensland Biosecurity Strategy: 2009–14 highlighted that biosecurity risks are inherently social, and that a better understanding of human behaviours, values and attitudes has the ability to improve engagement.

Similarly, the 2007 New Zealand Biosecurity Science Strategy indicated that the application of social research could increase biosecurity compliance and reporting, and support post-border invasion response programs.

Farmers and indigenous communities in remote and regional Australia are currently working together on a project to understand how each group decides to manage plant pests and diseases, and to increase their capacity to engage in biosecurity surveillance activities.

In the face of declining resources and investment, science and technology offer opportunities to create greater efficiencies in biosecurity while at the same time driving competitive advantage in primary industries.

The Conversation

Paul De Barro receives funding from the Bill and Melinda Gates Foundation and the Cotton Research and Development Corporation.

Grant Smith is a co-PI on the PBCRC bacterial diagnostics project described in this article. He is a member of various organisations including Australasian Plant Pathology Society (APPS), the Royal Society of New Zealand (MRSNZ) and the Project Management Institute (PMI).

This article was originally published on The Conversation.
Read the original article.


Australian farmers face increasing risk of new diseases: report

Honeybees pollinate a third of Australia’s food crops. Losing them due varroa might would cost the economy billions of dollars. David McClenaghan, Author provided

Honeybees pollinate a third of Australia’s food crops. Losing them due to varroa might would cost the economy billions of dollars. David McClenaghan, Author provided

By Gary Fitt, CSIRO

A nationwide outbreak of foot and mouth disease; an invasion of a devastating wheat disease; our honeybees completely wiped out. These are just three possible disastrous scenarios facing Australia; they’re considered in the Australia’s Biosecurity Future report published today by CSIRO and its partners.

Intensifying and expanding agriculture, biodiversity loss, and more people and goods moving around the world are the “megatrends” driving what we have called “megashocks” — new outbreaks of diseases and pests.

These three events alone could not only cost Australia’s economy billions of dollars, but would also devastate our agricultural industries and environment and severely alter our way of life.

How well prepared is Australia, and how would our biosecurity system cope with such a situation?

Cucumber Mottle Mosaic Virus, currently affecting cucumbers in the NT. USDA Forest Service/Wikimedia Commons, CC BY

Cucumber Mottle Mosaic Virus, currently affecting cucumbers in the NT.
USDA Forest Service/Wikimedia Commons, CC BY

For example, governments and farmers near Katherine in the Northern Territory are mounting an emergency response to deal with an outbreak of a new disease — Cucumber Green Mottle Mosaic Virus — and while this virus is not likely to create headlines, it is devastating crops, severely affecting the NT farming community financially and threatening industries elsewhere in Australia.

An ever-hungrier world

As part of the drive to help feed the world, Australia will have to increase agricultural production — both through intensification and expansion. Both of these processes could expose new biosecurity challenges.

The United Nations Food and Agriculture Organization (FAO) has forecast that food production will need to increase by 60% (compared to 2005/2007 levels) to meet demand in 2050.

This 2050 scenario could see the value of Australian food exports increasing by 140% compared to 2007 levels.

However, Australia’s agriculture sector is already constrained by limited soil and water resources and future intensification will bring its own challenges through herbicide resistance and more intensive animal production systems. These factors could all increase the impacts of a biosecurity incident, and reduce the industry’s ability to sustainably meet demand.

In 1973 Australia’s wheat production industry was devastated by an outbreak of wheat stem rust, causing an estimated A$200-300 million in damages. While wheat stem rust has been under control since that time, there are new threats on the horizon.

Currently sweeping the world is the even more virulent Ug99, and without stepping up our biosecurity, it is likely to reach Australia. Luckily in this case we have time to prepare by developing varieties resistant to Ug99, but we may not always have such forewarning.

A researcher investigates the wheat rust Ug99 in Kenya. International Maize and Wheat Improvement Center/Flickr, CC BY-NC-SA

A researcher investigates the wheat rust Ug99 in Kenya.
International Maize and Wheat Improvement Center/Flickr, CC BY-NC-SA

Expanding into new areas

Intensifying food production alone may not be sufficient to meet global demand. We may also have to expand into new or previously marginal areas. This could expose agriculture to new biosecurity threats, some that we may not fully understand, through new pathways or new hosts for pests and diseases.

For example, there is considerable government and industry interest in increased agricultural development in Northern Australia. Various reports, including the recent Green Paper on Developing Northern Australia suggest that northern agricultural production could increase substantially through targeted use of soil and water resources.

But this could expose Australia to new biosecurity threats. There are already a number of established pests and diseases in NT. And, importantly, these small areas of northern irrigated agriculture could act as a target for exotic pests and as a bridge for exotic pests to enter, establish and spread southwards.

This could have more severe consequences for established agricultural systems in southern Australia. In 1998 sugarcane smut appeared in the Ord, Western Australia. It then spread to Queensland in 2006, ultimately costing a 10-30% reduction in gross margins thanks to loss of yield, and the cost of planting resistant sugarcane varieties.

So biosecurity needs to be explicitly considered in any plan to expand agriculture in northern Australia – we need to anticipate future threats and mitigate them where possible.

Diversity dilemma

Invasive species are one of the most significant known threats to biodiversity and ecosystem services around the world. In Australia invasive vertebrates such as rabbits, feral cats, pigs and camels impose severe impacts on Australian habitats and wildlife.

But biodiversity is also important in underpinning the ecosystem services for agriculture and the economy. Healthy soil function, pollination, and natural pest control are all driven by biodiversity within agricultural landscapes. Over the past century, crops have lost 75% of their genetic diversity, making them potentially more susceptible to new pathogens or pests.

A varroa mite on the head of a bee nymph. Gilles San Martin/Flickr, CC BY-SA

A varroa mite on the head of a bee nymph.
Gilles San Martin/Flickr, CC BY-SA


We rely on some species for the services they provide, such as the European honeybees which pollinate our largely non-indigenous crops. Australia is fortunate to be the only continent not yet affected by the devastating bee pest, varroa mite. There is very real potential for it to arrive and spread in Australia.

Elsewhere in the world, varroa mite is driving a complex of factors leading to a global decline of honeybees, and native pollinators are also threatened through pesticide use and habitat loss.

Losing these pollination services, would severely impact the 30% of food crops which are dependent on honeybees, particularly many fruits and vegetables. The impact on our economy would be in the order of A$4-6 billion each year.

On the move

The increased movement of people, goods and vessels around the globe increases the chance of biosecurity threats hitting our shores. That’s why our biosecurity border protection is so important.

Inadvertent spread of exotic organisms in shipping containers such as European house borer in Western Australia, on contaminated equipment or carried by people such as the introduction of fire ants, as well as the spectra of deliberate introductions which haven’t yet happened in Australia show the scale and breadth of the issues we have to deal with.

An outbreak of foot and mouth disease in Australia livestock could cost tens of millions of dollars. Marc Dalmulder/Flickr, CC BY

An outbreak of foot and mouth disease in Australia livestock could cost tens of millions of dollars.
Marc Dalmulder/Flickr, CC BY

An outbreak of an exotic pest or disease, such as foot and mouth disease (FMD) in Australia, which affects cloven hoofed animals such as cattle, pigs and sheep, could close down export markets overnight or make other countries more competitive.

An FMD outbreak in Australia could lead to industry-wide revenue losses for livestock producers of around A$6 billion for a small outbreak and A$50 billion for a large multi-state outbreak over a 10-year period. Additional costs related to disease control, such as labour, decontamination, slaughter, disposal and facilities, would be expected to range from A$60 million to A$373 million.

Pre-empting the threat

As an island nation, Australia has been able to maintain an enviable biosecurity status, keeping out many of the world’s worst pests and diseases. This means we have market access for a vast array of export produce, a status which will be increasingly valuable in a growing and highly competitive global market for food.

To ensure we maintain this status, the management of Australia’s biosecurity will require a step change towards smarter and more efficient strategies that are ideally ahead of the pace of change around the world. Smarter technologies, strengthened integration across governments and industry and great commitment will be needed. If we do this, we are surely better able to protect our farmers, communities and environment from the impacts of exotic pests and diseases.

Clearly, we can’t afford to become complacent with our nation’s biosecurity measures. As is true of any threat, it is much better to pre-empt and avoid than have to deal with the costly consequences.

The Conversation

The CSIRO Biosecurity Flagship receives funding from government and industry R&D bodies and works in collaboration with many research and industry partners..

This article was originally published on The Conversation.
Read the original article.


World Food Day – let’s make it every day

Wheat rust on a wheat stem. Image: Evans Lagudah and Zakkie Pretorius.

Wheat rust on a wheat stem. Image: Evans Lagudah and Zakkie Pretorius.

It’s World Food Day, and this year’s focus is on the role smallholder farmers play in feeding the world.

Food production is at record levels, yet 842 million people are estimated to be suffering from chronic hunger and under-nourishment. Many of these are themselves small family farmers.

We’re trying to do our bit to help subsistence farmers grow more productive crops, combat plant diseases, farm seafood sustainably, develop climate change adaption strategies and grow coffee more sustainably.

One plant we’re working on is cow peas (one of the staple crops in parts of Africa). We recently got a Gates Foundation grant to further our research on improving their productivity.

On a broader scale, we’ve also cracked a problem with a globally-significant crop: wheat. With colleagues from the Sydney and Adelaide Universities, we’ve identified a gene that confers resistance to wheat rust – probably the biggest enemy of wheat crop yields worldwide.

Seafood is a major source of protein in both the developed and developing worlds, and we’ve found a way to farm the most delectable kind of all – prawns – more sustainably. Our Novacq™ fishless prawn food is now licenced for use in several South-East Asian countries. It makes use of the marine microbes at the base of the food chain to produce a prawn food that has the added benefit of increasing their growth rate by around 30 per cent.

Climate change is a pressing problem for us all, but some of the people most at risk are farming communities in countries in southern and south-eastern Asia. We’re collaborating with farmers in parts of Cambodia, Laos, Bangladesh and India to identify, select and test climate change adaptation options that are both viable and suitable for local communities. One of the things we’re aiming to do is develop and test new crop and water management practices for rice-based cropping systems that will outperform existing farming practices and can accommodate future climate variability and climate change.

There are about 400 000 PNG households involved in coffee production

There are about 400 000 PNG households involved in coffee production

After all that work, we might be tempted to celebrate with a good cup of coffee. Maybe a PNG blend. There are more than 400 000 households involved in coffee production in PNG, and it’s that country’s most important export cash crop.

With our Australian and international partners, we’re developing new ways for farmers and researchers to learn from each other and identify ways to improve the sustainability of PNG’s coffee industry. We hope to identify the points in the coffee-food farming system that can be targeted for the best possible result in retaining and reusing scarce nutrient resources.


Plants absorb more CO2 than we thought, but …

Plants doing the photosynthesis thing

A new study shows plants may absorb more carbon than we thought. Jason Samfield/Flickr, CC BY-NC-SA

By Pep Canadell, CSIRO

Through burning fossil fuels, humans are rapidly driving up levels of carbon dioxide in the atmosphere, which in turn is raising global temperatures.

But not all the CO2 released from burning coal, oil and gas stays in the air. Currently, about 25% of the carbon emissions produced by human activity are absorbed by plants, and another similar amount ends up in the ocean.

To know how much more fossils fuels we can burn while avoiding dangerous levels of climate change, we need to know how these “carbon sinks” might change in the future. A new study led by Dr. Sun and colleagues published today in PNAS shows the land could take up slightly more carbon than we thought.

But it doesn’t change in any significant way how quickly we must decrease carbon emissions to avoid dangerous climate change.

Models overestimate CO2

The new study estimates that over the past 110 years some climate models over-predicted the amount of CO2 that remains in the atmosphere, by about 16%.

Models are not designed to tell us what the atmosphere is doing: that’s what observations are for, and they tell us that CO2 concentrations in the atmosphere are currently over 396 parts per million, or about 118 parts per million over pre-industrial times. These atmospheric observations are in fact the most accurate measurements of the carbon cycle.

But models, which are used to understand the causes of change and explore the future, often don’t match perfectly the observations. In this new study, the authors may have come up with a reason that explains why some models overestimate CO2 in the atmosphere.

Looking to the leaves

Plants absorb carbon dioxide from the air, combine it with water and light, and make carbohydrates — the process known as photosynthesis.

It is well established that as CO2 in the atmosphere increases, the rate of photosynthesis increases. This is known as the CO2 fertilisation effect.

But the new study shows that models may not have quite right the way they simulate photosynthesis. The reasons comes down to how CO2 moves around inside a plant’s leaf.

Models use the CO2 concentration inside a plant’s leaf cells, in the so called sub-stomatal cavity, to drive the sensitivity of photosynthesis to increasing amounts of CO2. But this isn’t quite correct.

The new study shows that CO2 concentrations are actually lower inside a plant’s chloroplasts — the tiny chambers of a plant cell where photosynthesis actually happens. This is because the CO2 has to go through an extra series of membranes to get into the chloroplasts.

This means that photosynthesis takes place at lower CO2 than models assume. But counterintuitively, because photosynthesis is more responsive to increasing levels of CO2 at lower concentrations, plants are removing more CO2 in response to increasing emissions than models show.

Photosynthesis increases as CO2 concentrations increase but only up until a point. At some point more CO2 has no effect on photosynthesis, which stays the same. It becomes saturated.

But if concentrations inside a leaf are lower, this saturation point is delayed, and growth in photosynthesis is higher, which means more CO2 is absorbed by the plant.

The new study shows that when accounting for the issue of CO2 diffusivity in the leaf, the 16% difference between modelled CO2 in the atmosphere and the real observations disappear.

It is a great, neat piece of science, which connects the intricacies of leaf level structure to the functioning of the Earth system. We will need to reexamen they way we model photosynthesis in climate models and whether a better way exists in light of the new findings.

Does this change how much CO2 the land absorbs?

This study suggests that some climate models models under-simulate how much carbon is stored by plants, and in consequence over-simulate how much carbon goes into the atmosphere. The land sink might be a little bigger — although we don’t know yet how much bigger.

If the land sink does a better job, it means that for a given climate stabilisation, we would have to do a little bit less carbon mitigation.

But photosynthesis is a long, long way before a true carbon sink is created, one that actually stores carbon for a long time.

About 50% of all CO2 taken in by photosynthesis goes back to the atmosphere soon after through plant respiration.

Of what remains, more than 90% also returns back to the atmosphere through microbial decomposition in the soils and disturbances such as fire over the following months to years — what stays, is the land sink.

Good news, but not time for complacency

The study is a rare and welcome piece of possible good news, but it needs to be placed in context.

The land sink has very large uncertainties, they have been well quantified, and the reasons are multiple.

Some models suggest that the land will continue to absorb more carbon all throughout this century, some predict it will absorb more carbon up to a point, and some predict that the land will start releasing carbon — becoming a source, not a sink.

The reasons are multiple and include limited information on how the thawing of permafrost will effect large carbon reservoirs, how the lack of nutrients could limit the further expansion of the land sink, and how fire regimes might change under a warmer world.

These uncertainties put together are many times bigger than the possible effect of the leaf CO2 diffusion. The bottom line is that humans continue to be in full control of what’s happening to the climate system over the coming centuries, and what we do with greenhouse emissions will largely determine its trajectory.

The Conversation

Pep Canadell receives funding from the Australian Climate Change Science Program.

This article was originally published on The Conversation.
Read the original article.


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