Livestock: The answer, not the problem?

Post written by C. Will

Seth Itzkan of Planet-TECH discusses how holistic management can restore grass lands and reverse the effects of climate change in his TEDx talk; “How global warming can be mitigated through holistic management”.

In the video, Seth discusses his experiences in Zimbabwe and how the village herders have changed the way they manage their livestock. Using holistic management, they have replenished grasslands and during the dry season surface water is occurring further upstream than before. Increased availability of surface water has made farming easier and removed the need for water pumps, saving money. Regenerating grasslands also increases soil sequestration, reducing the amount of carbon in the atmosphere.

Holistic management uses livestock in a way that mimics wild herds which were a key component in the ecosystem when grasslands thrived. The wild herds would graze, naturally process the grass, fertilise the ground and then move onto a new area. The villagers are now replicating this process by running livestock in dense packs and moving them regularly just as a wild herd would. They also stick to grazing plans to prevent over grazing.         

Although his focus is on environments that have suffered desertification (the transformation of habitable land to desert), parallels can be made between the framework of holistic management and the way farmers in New Zealand manage their stock. Relative to farmers in Africa though, New Zealand farmers have lower emissions per unit of production and are more efficient. However, even in New Zealand many farmers can apply management strategies other farmers are already using to reduce their environmental impact. A recent Motu working paper, looks at such mitigation possibilities.

Holistic management was a way of managing resources originally developed by Allan Savory. Here Allan offers further discussion on holistic management and “how to fight desertification and reverse climate change”.

A Negotiator’s Perspective: the Future of Agriculture in the UNFCCC Negotiations

Post written by H. Griffin.

With this year’s annual international climate change (UNFCCC) negotiations kicking off in Warsaw on Monday, now is a good time to look at agriculture’s place in the negotiations and where things might be headed in the future. 

Due in part to socio-economic and food security issues, progress in agricultural negotiations within the UNFCCC has been very slow. This is because of the role agriculture plays as a source of employment for many of the world’s poor, and the fact that many developing countries have had recent experiences of drought induced famine.

A new agreement is currently being negotiated and is expected to come into force in 2020 at the end of the Kyoto Protocol’s second commitment period. Whilst the Kyoto Protocol placed mitigation obligations on industrialised nations, the post-2020 agreement will be applicable to all nations. The negotiations are currently in a phase of design and preparation for the post-2020 agreement. It is particularly important that progress on mitigation and adaptation in the agricultural sector is made in preparation for the next agreement.

To give us a better idea about what is going on in the negotiations, Paul Melville from the Ministry for Primary Industries has kindly agreed to be interviewed for this blog. Paul is in Warsaw with the New Zealand government delegation as a negotiator in the area of agriculture.

Q. What is New Zealand hoping to achieve in relation to agriculture at the negotiations in Warsaw?

A. The discussions on Agriculture had a breakthrough at the inter-sessional meeting in Bonn this year. After many years of inconclusive negotiations, Parties agreed to a submission and workshop process as a first step of SBSTA (Subsidiary Body for Scientific and Technological Advice) work on Agriculture. This will be a useful opportunity for Parties to share experiences and lessons learned on agricultural adaptation and adaptation co-benefits. This workshop should facilitate more focussed negotiations on agriculture at Warsaw and future SBSTA sessions.

A successful work programme would aim to provide the UNFCCC with detailed scientific advice on issues relating to agriculture. One workshop will however unlikely deliver this. Though, it is often said that the hardest part of any process is taking the first step. The challenge for COP19/Warsaw is to ensure that Bonn was the first step in a wider process by continuing and building upon this work. If Warsaw was to fail to continue the progress made in Bonn we risk falling back into the previous pattern.

Q. What role can New Zealand play, both within and outside of the negotiations?

A. New Zealand likes to be a flexible thought leader wherever possible, piloting new ideas and working with a broad range of countries. We have expertise and a particular interest in issues related to agriculture, forestry and carbon markets.

Q. How is domestic policy in New Zealand relating to agricultural GHG emissions influenced by the international context?

A. There is a two-way relationship between domestic and international policy: domestic policy in New Zealand influences New Zealand’s international position; and international policy has an influence on New Zealand’s domestic policy.

While there is an influence in both directions, the two remain different. We promote international rules and commitments that are suitable for New Zealand’s domestic circumstances; and once agreed we implement commitments and rules using policies and measures that best suit our domestic policy environment.

Q. In your opinion, what would be the best outcome for agriculture in the post-2020 agreement?

A. The agricultural sector faces unique challenges. Agriculture is responsible for approximately 10–12 percent of global greenhouse gas emissions and is also an extremely vulnerable sector to the impacts of climate change. In addition to the challenge of having to simultaneously manage greenhouse gas emissions while adapting to climate change, it is forecast by the FAO that global agriculture will be required to increase production by 70 percent by 2050 to meet rising demand.

Outlining a best outcome for agriculture is difficult at this early stage of the negotiations as we are still working collectively in the UNFCCC on the design of the post-2020 agreement. However, by focusing on what we do know we can begin to understand what a good outcome for agriculture could look like.

We know the post-2020 agreement will include measures that will be ‘applicable to all’ Parties. We assume it will include, amongst other things, mitigation, adaptation and finance. We know that agricultural systems, including considerations of capacity, scale, culture, environment, efficiency and productivity are extremely varied, and it will probably not be possible to design a one size fits all rule set.

Therefore, in order to remain applicable to all, a key feature of any treatment of agriculture will be a need to adopt an approach with sufficient flexibility to cater for this broad range of national circumstances. In this sense, although agriculture has its own unique features, the broad principle of ensuring Parties are able to take commitments consistent with their specific national circumstances remains relevant here, too. New Zealand has outlined a concept of ‘Bounded Flexibility’ in a number of fora including the below submission which builds on this idea of a flexible framework.

http://unfccc.int/files/documentation/submissions_from_parties/adp/application/pdf/adp_new_zealand_workstream_1_20131015.pdf

Beyond outlining that any treatment will need to be sufficiently flexible to cater for national circumstances, it is very hard to predict or prescribe outcomes for a post-2020 agreement at this early stage.



About Paul:
I am a Senior Policy Analyst in the Ministry for Primary Industries International Policy Team. Our team covers environmental policy related to forestry or agriculture. In addition to agriculture in the UNFCCC, I also have responsibilities related to common metrics in the UNFCCC (global warming potentials), environmental footprinting policy and carbon footprinting policy. Prior to working for MPI I was a member of Fonterra’s Sustainability team. While at university and high school I paid my bills by milking cows and operating a successful calf rearing business on my parent’s dairy farm near Te Awamutu.

New OECD Report: Policy Instruments for Green Growth in Agriculture

Post written by H. Griffin.

An OECD Green Growth report on agricultural policy instruments was released on Monday. The report synthesises the experience of OECD countries in developing and implementing green growth policies in the agricultural sector. In addition to looking at experience in the areas of improved resource-use efficiency and decreased local environmental impact, the report explores policy potential to reduce greenhouse gas emissions. A key conclusion of the report is that whilst a wide range of policies are being used throughout the OECD, the degree of ambition is extremely variable between countries.

Check out the full report here.

Reframing the Policy Approach: Lessons from Niki Harré

Post written by H. Griffin.

Niki Harré’s Psychology for a Better World explores how we can create a society in which governments, organisations and individuals take pride in their efforts to protect the planet and each other. In the video below, Harré summarises the key messages of her book.

In a previous post, we looked at how individual environmental action can be motivated. Harré’s work is not only relevant to individuals, but also to policy-makers. The design and implementation of policy can have a huge impact on its effectiveness. Harré highlights the importance of positivity in encouraging creativity and cooperation. Positive emotions also play a vital role in facilitating behavioural change.

Framing the way agricultural greenhouse gas emissions are addressed in a more positive manner could be very beneficial. Approximately half of New Zealand’s greenhouse gas emissions relate to agriculture. The mitigation of these emissions is particularly challenging because current mitigation options are mostly associated with farm management practices and must be implemented by tens of thousands of farmers. There are currently no ‘silver bullet’ technologies that can be imposed or implemented by agricultural processing/distribution companies on behalf of farmers. Furthermore, incorporating agriculture into the ETS – which has been the focus of public debate – risks generating large wealth transfers. Because of this, it is crucial that communication of the issue is productive in facilitating positive action.
 

Political debate on the issue so far has been polarised, negative and unproductive. Harré shows us that reframing the policy conversation could potentially better equip New Zealand’s agricultural sector to face the challenges ahead.

As explored in this Motu note, New Zealand can play an important role in global climate change mitigation efforts as a policy leader. Positively reframing our policy debate domestically is an important step in enabling New Zealand to play this role.

 Instead of tales of terror, we need to be telling tales of joy. We also need to be designing policy that facilitates the acknowledgement of positive behaviour of farmers. Harré suggests that making positive behaviour more visible to other farmers could have multiplying effects as people tend to copy each other.

The good, the bad and the ugly: how do different greenhouse gases compare?

Which greenhouse gas contributes the most to global warming? The bad news, for those who want a simple answer, is that it really depends on how you define the question. 

One oft-quoted statistic is that three quarters of the world's greenhouse gas emissions are made up of carbon dioxide. Another is that in New Zealand almost half our greenhouse gas emissions come from agriculture. And these emissions aren't carbon dioxide - rather, roughly 2/3 are methane and 1/3 are nitrous oxide. 

But what do these figures mean? Does agriculture produce roughly one out of every two kilograms of gas we emit? Or is agriculture ultimately responsible for roughly half our contribution to global warming? 

Somewhat mysteriously, the answer is – neither. There are three important variables to keep in mind when comparing carbon dioxide, methane and nitrous oxide. The first is the quantity in kilograms of gas emitted - more gas causes more warming. The second is how long gas molecules linger in the atmosphere - and this varies significantly across types of gas. The third is how much energy a kilogram of each type of gas traps in the atmosphere per unit time.

The statistics referred to above don't tell us about the number of kilograms of each gas emitted, nor about the total amount of energy that each type of gas will trap in the atmosphere in the long run. Rather, they are calculated by taking the number of kilograms of each gas that we emit, and multiplying it by a "global warming potential" (GWP). A GWP is the amount of energy that one kilogram of that gas traps in the atmosphere over a 100 year period relative to carbon dioxide. For instance methane's GWP is more than 20, which means that in the 100 years after a kilogram of methane is emitted, it will trap over 20 times as much energy in the earth's atmosphere as one kilogram of carbon dioxide will.

The thing about GWPs is that they only look 100 years into the future. If we care only about the short term, then GWP - or an even shorter term measure - might be the best to use. But if we want to consider the impact of gases more than a hundred years forward, then we might think that GWP over- or understates the effect a gas has on warming. How far ahead should we look? The question remains open for debate.

In this video, Dave Frame from the Victoria University of Wellington Climate Change Institute discusses these differences between the three types of gas. The results might be surprising! Note that Dave’s comparisons are per-kilogram, and don’t necessarily reflect the aggregate contribution to global warming of each gas.

Agricultural Emissions Teaching Materials Released

Last month, we released a brand new short film on agricultural emissions. Today, we are pleased to announce the release of a set of free teaching materials to accompany the film. These consist of an editable presentation, complete with speaking notes, and further information on some of the figures that the presentation contains.

Our intention is that a wide range of people – including teachers, lecturers, farmers or people working with farmers – will be able to use the film and presentation to lead a discussion on what we can do about agricultural emissions. Potential audiences include secondary and tertiary students, as well as consumers and farmers. In other words, anyone who eats!

The materials can be downloaded by following the links below. In addition, we have just released the film in physical copy. If you would like to be posted a free DVD which includes the film and materials, please send your name and address to info@motu.org.nz.

We will be happy to support those who wish to use the film and materials by answering specific questions. We'll collate the questions and answers into an FAQ document which will be available soon on the blog and also on the Motu website. If you have any questions at all, please email them through.

The New Zealand Farming Story presentation (.pdf version)
The New Zealand Farming Story presentation (editable Powerpoint)
The New Zealand Farming Story speaking notes
Notes on figures for emissions from meat consumption in presentation

"Origin Green" - certifying the sustainability of Irish primary products

Rural News recently ran this article about a quality assurance scheme initiated by Bord Bai (the Irish Food Board). Called "Origin Green", the scheme guarantees the sustainability of certified foods to consumers. As the article explains, Beef and Lamb New Zealand Chair Mike Petersen thinks that there is scope for New Zealand to do something similar.

The Irish scheme is very similar to an idea developed within New Zealand by the Agricultural Emissions Dialogue and a version of it is already being developed by one of the members, Mike Barton, through his Taupo Beef programme. Mike discusses Taupo Beef in our short film.

More information on Origin Green is available here.

 

The New Zealand Farming Story: Tackling Agricultural Emissions

Today we are very excited to release our new short film on New Zealand’s agricultural emissions. Although the topic may sound dry (though hopefully not too dry if you visit this blog!) our filmmaker Jess Feast has done an excellent job of making an engaging film on an extremely important topic for the future of our country, our planet, our people and our stomachs. (She also made our films about improving the water quality in Lake Rotorua).

The film covers a wide range of topics, and many of the ideas in it come directly from what we learnt through the AgDialogue process. Importantly, we cover how we might be able to achieve some real reductions in New Zealand’s agricultural GHGs (greenhouse gases). You will get to meet some of the participants and experts from AgDialogue, including two of our star farmers, Mike and Megan.

The film speaks for itself, so you are better off watching it than reading about it. But before you do that, I’d just like to acknowledge all the hard work that went into making the film. To all those in the AgDialogue who gave their time and those who have done related research in the past few years, this film is dedicated to you and the hard work you have done.  Also thank you to our filmmaker Jess and the Ministry for Primary Industries for its support. The work will pay off in creating a more sustainable and prosperous future for us and future generations.

Oh, and if you like the film, please share it far and wide. New Zealand is uniquely placed to be able to make a big difference to levels of agricultural GHGs (greenhouse gases) around the world. And everyone in this country can make a difference.

UPDATE: Teaching materials to accompany the film have now also been released. These can be found here.

Looking forward: what NZ rural land might look like in the coming decades under a carbon price

This blog post is by Motu Research Analyst Zack Dorner.

A couple of years ago, my sister brought her partner to visit New Zealand for the first time. We picked them up in Auckland, and drove down the North Island back to Wellington. He asked “Why are there so many golf courses here?”

Of course, they weren’t golf courses, but the lush, green grassy farmland that New Zealand is so well known for, and that he was not used to.

Motu has just released a new working paper, modelling what our rural land might look like in the coming decades, including with a price on agricultural GHGs (greenhouse gases). Luckily, for our “golf courses”, even with the agricultural sector facing a price on its GHGs, New Zealand probably won’t look much different to the way it does now.

The really cool thing about the model used is that it is based on real world observations of how rural land use in New Zealand has changed in recent decades in response to commodity prices. It is slow to adjust – farmers don’t want to switch immediately to the new best thing for their land (see final graph below), which is understandable. Changing your whole farm can’t be easy or cheap to do, and who’s to say market conditions won’t change again.

Of course, the results in the working paper are just from a model. They do not predict the future, but give us an idea about the types of changes to land use and their magnitude under certain scenarios. There are on-farm mitigation options that farmers may be able to do to reduce their GHGs before changing land use, but to keep things simple, the model does not include these.

The working paper models three scenarios out to 2030: no carbon price, a carbon price ($25) just for forestry, and a greenhouse gas price for forestry and agricultural emissions.

The model shows several interesting things.

First, as I have said, land use change is quite slow. Even with a $25 carbon price on forestry and agriculture, there is actually relatively minimal changes in land use. This provides evidence that our agricultural sector may be able to respond efficiently to a price on carbon without huge disruption to rural life in New Zealand.

However, although changes to land use are gradual and small, they actually make a big difference to our emissions. The extra trees are especially helpful in this regard. From the paper directly:

Under our ETS [emissions trading scheme] scenarios there is substantial reforestation. The extra removals associated with this new planting mean that the additional sequestration in 2024 is from 17.6 to 20 percent of national inventory agricultural emissions in 2008.

That’s a huge amount of emissions, and would help New Zealand immensely in our quest to lower our emissions.

In terms of cows and sheep, we actually see more dairy cows, and fewer sheep and beef farms. This is because dairy farms are so much more profitable, and the balance is tipped even more in their favour once a price is applied to farming emissions. This is already happening to a much larger extent, and only the already marginal sheep and beef farms are converted to dairy or forestry under an efficient response to a carbon price. The overall change is only minor in the scheme of things, and even when you exclude agricultural emissions from a carbon price, this still happens (see the first graph below).

So these results suggest that there are large benefits to having a $25 carbon price in New Zealand for forestry and our country’s emissions profile. As for agricultural emissions, if dairy and sheep and beef farmers face a price on their emissions, the sky won’t fall in, but the adjustments that are already taking place will just continue to a greater extent. By creating an efficient, economy-wide price signal which includes agriculture, we should achieve more mitigation overall (see the second graph below). If on farm mitigation is encouraged optimally, and technologies continue to improve, we might well see less of the minor reduction in farming in the model and instead end up with more efficient farms on our rural land.

Bringing agricultural emissions into the ETS or some other pricing mechanism must occur once farmers are ready and on board. Through research like this, and having a dialogue with all interested parties, we can hopefully move forward together, and work towards future-proofing our golf courses, and our farms.

And now, for those of you who get a kick out of graphs (like me), here are some relevant ones:

This graph above shows the projected change in land use share for each type of land use. The solid lines give baseline projections. Short-dash-dot lines give a $25 carbon price, but not on agriculture. Dashed lines show a carbon price with agriculture. Note the y axis is the same scale for each graph so direct comparisons can be made (page 9).

This graph shows the amount of emissions that are reduced or sequestered. The red line is with just forestry, the blue line shows including agricultural emissions as well increases the emission reductions (page 16).

  

This final graph below shows why sheep and beef farms have been declining over the years, and how land use change is gradual (page 4 of Kerr and Olssen 2012).

Motu's agricultural GHG emissions research in the news

"We can't design systems assuming we're going to fail. Let's assume we're going to succeed and what the world will look like in 30-50 years given that we have succeeded."

There was an interesting article in the Timaru Herald’s Central South Island Farmer feature last week, which discussed a speech Dr Suzi Kerr gave to the New Zealand Institute of Agricultural and Horticultural science. The article is a good summary of many of Motu’s conclusions from the AgDialogue group, stressing rewarding farmers who make changes towards best practice guidelines for reducing emissions and making long-term, carefully considered policy decisions instead of rushing into dramatic changes.

The article can be found here.

Biological Farming and soil carbon – green wash or climate saviour?

This blog post is by Motu Research Analyst Zack Dorner.

Earlier this year, AgDialogue participant Rick Braddock sent us through this article, written Clayton Wallwork from the Carbon Farming Group, about Biological Farming. Rick Braddock is Operations Director of Farming New Zealand, an agricultural investment fund established to aggregate large pastoral farms under a New Zealand ownership model, as well as a trustee of the Carbon Farming Group.

Biological Farming is a farming practice that is still being developed and aims to use natural rather than synthetic fertilisers. We at Motu decided to ask some soil scientists about the potential for Biological Farming to store soil carbon, as a way of removing carbon dioxide from the atmosphere.

As noted in the Carbon Farming Group article, evidence to date around Biological Farming is largely anecdotal, and each farm has different Biological Farming techniques applied to it, based on its unique circumstances.

Troy Baisden from GNS Science told us about what may cause changes in soil carbon in traditional intensive farming system, and how this might differ under a Biological Farming system. Biological Farming systems may be less prone to losing soil carbon compared with traditional intensive systems, but Troy emphasises there is no clear evidence Biological Farming will gain soil carbon. Therefore more research is needed before it can claim to be a reliable way of helping to address climate change.

Troy explained to us that it is almost impossible to store carbon in soil without nitrogen, typically at a ratio of around ten carbon particles to one nitrogen particle. Therefore, understanding the amount of nitrogen being stored in the soil is important for understanding how much carbon is stored in the soil (see image below).

This image was pulled from this useful article in NZ Science Teacher magazine

With intensive farming, by trying to push more nitrogen through the system (by using more nitrogen fertiliser or importing more feed to produce more product), farm nitrogen budgets show that despite increasing nitrogen inputs, many farms lose more nitrogen than they gain. Counter intuitively, it seems that cycling more nitrogen faster and faster through the soil might eventually start to cause the overall level of nitrogen and carbon in the soil to drop. 

Troy says “We’ve been surprised at the level of losses that seem to be occurring, and at the observation that large N [nitrogen] losses seem to be taking carbon out of the soil as well.” Unfortunately it remains difficult to understand why these losses are occurring and work out the exact numbers without long-term experiments that run for decades. The one long term study to date provides some evidence that almost three quarters of a tonne of carbon per hectare per year are lost on traditional intensive dairy farms (Schipper et al. 2010).

In terms of Biological Farming, Troy says:

...the main argument [is] that you’re trying to work with a system that regulates itself better. So it will simply tell you “no” when you try and push it too hard. ... That’s the magic of it. ... One of the reasons why you can’t [push the system] is you’re not going to add bag nitrogen fertiliser.

By relying on natural nitrogen fixation, such as through clover in the soil, the soil is prevented from becoming saturated with nitrogen to the point where it loses more than it is gaining, and the total level of nitrogen in the soil starts to drop. The natural nitrogen fixers shut down when the system is being run too hard, though of course this will also place a limit on the total output of the farm. Though this might mean a Biological Farming system isn’t losing soil carbon, it’s unclear whether Biological Farms actually gain soil carbon.

There is very limited evidence that organic farming systems (which are similar to Biological Farming systems) limit nitrogen losses much better than a conventional farming system, but we still don’t understand fully why that might be (and Troy is not aware of this evidence having been published).

So, Biological Farming could be better at managing stores of carbon if it is better at managing stores of nitrogen. But the jury is still out.

Jacqueline Rowarth, Professor of Agribusiness at Waikato University who holds a PhD in soil science, is even less positive about Biological Farming. It’s a very complicated picture, as carbon has many ways into and out of the soil within a farm system. For example, Jacqueline points out that drought could be the major cause of loss in soil carbon in the Schipper et al. (2010) study, given the study’s period and the effects of drought during that time.

There are a number of ways in which carbon will find its way onto and off of a farm. Like any plant, the grass will naturally remove carbon from the atmosphere and use it to form its structure as it grows, including its roots in the soil. On a dairy farm carbon is regularly being exported in milk tankers, having been removed from the soil and grass through grazing, and turned into part of the milk by livestock, rather than being put directly into the atmosphere (this also applies to nitrogen). Less carbon will be exported less regularly from a sheep and beef farm, through removal and slaughter of animals.

Carbon is also being added through any inputs brought into the farm, including extra feed such as palm kernel (though of course this may have climate impacts elsewhere). Fertilisers such as urea will only add nitrogen directly to the soil, and not carbon.

Another dimension within a farming system is level of grazing. The growth of grass on soil can have a bearing on the amount of carbon in the soil. More grass on the surface supports more litter in the soil, which increases soil carbon. Also, different types of grasses will support different levels of carbon being stored in the plants and soil.

With lower levels of production from Biological Farming, and little evidence to support the claims around it, Jacqueline says that proponents of Biological Farming, though well meaning, may be heading down the wrong track. Strong scientific backing is vital to informing decisions around farming systems and environmental impacts.

With all the mysteries surrounding soil carbon, we are a long way off measuring and rewarding those storing carbon in their soil (see this Parsons and Rowarth 2009 article on measuring soil carbon under Kyoto on pages 2, 5 and 6). So, if you wanted to start Biological Farming only to store carbon in your soil, then perhaps you should wait for more evidence. And you need to be careful who you decide to listen to. Though Jacqueline is sceptical, Troy Baisden thinks that there’s a reasonable chance that Biological Farming doesn’t lose soil carbon, even if we may not be sure whether it would gain soil carbon.

In terms of switching from an intensive farming system to a biological farming system then, it’s a big risk to do it just to store more carbon in your soil. To decide to become a Biological Farmer, you would have to be convinced by some the other arguments outlined in the Carbon Farming’s document, attached to this post. No doubt, as evidence starts to accumulate, the debate on Biological Farming will continue for some time.

Many thanks to Rick Braddock, Troy Baisden, Jacqueline Rowarth and Louis Schipper for their help in putting this post together.

Reference

Schipper, L.A.; Parfitt, R.L.; Ross, C.; Baisden, W.T; Claydon, J.J.; Fraser, S. (2010) Gains and losses in C and N stocks of New Zealand pasture soils depend on land use. Agriculture Ecosystems and Environment. 139: 611–617. doi:10.1016/j.agee.2010.10.005.

Further reading

Parsons, A.J.; Rowarth, J.S., Newton, P.C.D. (2009) Managing pasture for animals and soil carbon. Proceedings of the New Zealand Grassland Association. 71: 77-84.

Thorrold, Bruce (May 2012) The Biological Farming Debate. Grassland News. New Zealand Grassland Association. 2-3.

http://www.nature.com/nature/journal/v485/n7397/full/nature11069.html