Interview: Plants and their fungi to slow down climate change

César Terrer, participant in the IIASA 2016 Young Scientists Summer Program, and PhD student at Imperial College London, recently made a groundbreaking contribution to the way scientists think about climate change and the CO2 fertilization effect. In this interview he discusses his research, his first publication in Science, and his summer project at IIASA.

Conducted and edited by Anneke Brand, IIASA science communication intern 2016.

César Terrer ©Vilma Sandström

César Terrer ©Vilma Sandström

How did your scientific career evolve into climate change and ecosystem ecology?
I studied environmental science in Spain and then I went to Australia, where I started working on free-air CO2 enrichment, or FACE experiments. These are very fancy experiments where you fumigate a forest with CO2 to see if the trees grow faster. In 2014 I moved to London for my PhD project. There, instead of focusing on one single FACE experiment, I collected data from all of them. This allowed me to make general conclusions on a global scale rather than a single forest.

You recently published a paper in Science magazine. Could you summarize the main findings?
We found that we can predict how much CO2 plants transfer into growth through the CO2 fertilization effect, based on two variables—nitrogen availability and the type of mycorrhizal, or fungal, association that the plants have. The impact of the type of mycorrhizae has never been tested on a global scale—and we found that it is huge. I think it’s fascinating that such tiny organisms play such a big role at a global scale on something as important as the terrestrial capacity of CO2 uptake.

How did you come up with the idea? One random day in the shower?
Long story short, researchers used to think that plants will grow faster, and take up a lot of the CO2 we emit. They assumed this in most of their models as well. But plants need other elements to grow besides CO2. In particular, they need nitrogen. So scientists started to question whether the modeled predictions overestimated the CO2 fertilization effect, because the models did not consider nitrogen limitation. To find out, I analyzed all the FACE experiments and indeed I saw that in general plants were not able to grow faster under elevated CO2 and nitrogen limitation. However, in some cases plants were able to take advantage of elevated CO2 even under nitrogen limitation. I grouped together the experiments where plants could grow under nitrogen limitation and after a lot of reading I saw what they had in common: the type of fungi! It turned out that one type of mycorrhizae is really good at transferring large quantities of nitrogen to the plant and the other type is not.

How did that feel?
Awesome! When I saw the graph, I knew: this is going to be important. Of course, after this, my coauthors helped me to polish the story. Without them, the conclusions would not be as robust and clear.

So how does this process work? Where do the fungi get the nitrogen from?
Particular soils might have a lot of nitrogen, but the amount available for plants to absorb might be low. Also, plants have to compete with non-fungal microorganisms for nitrogen. So if there is not much there, the microorganisms take it all. It’s called immobilization. Instead of mineralizing nitrogen, they immobilize it so that plants cannot take it up, at least not in the short term. Some types of fungi are much more efficient in accessing nitrogen, and associated with roots they allow plants to overcome limitations.

Nitrogen mobilization abilities of different types of fungi. Growth of plants associated with fungi not beneficial for nitrogen uptake (illustrated as grass roots on the left) could be limited by low nitrogen availability in soil. Other plants have the advantage of increased nitrogen uptake due to their beneficial association with certain types of fungi (illustrated as yellow mushrooms connected to the roots of the tree on the right). ©Victor O. Leshyk.

Nitrogen mobilization abilities of different types of fungi. Growth of plants associated with fungi not beneficial for nitrogen uptake (illustrated as grass roots on the left) could be limited by low nitrogen availability in soil. Other plants have the advantage of increased nitrogen uptake due to their beneficial association with certain types of fungi (illustrated as yellow mushrooms connected to the roots of the tree on the right). ©Victor O. Leshyk.

What is the impact of your findings?
Plants currently take up 25-30% of the CO2 we emit, but the question is whether they will be able to continue to do so in the long term. Our findings bring good and bad news. On the one hand, the CO2 fertilization effect will not be limited entirely by nitrogen, because some of the plants will be able to overcome nitrogen limitation through their root fungi. But on the other hand, some plant species will not be able to overcome nitrogen limitation.

There was a big debate about this. One group of scientists believed that plants will continue to take up CO2 and the other group said that plants will be limited by nitrogen availability. These were two very contrasting hypotheses. We discovered that neither of the hypotheses was completely right, but both were partly true, depending on the type of fungi. Our results could bring closure to this debate. We can now make more accurate predictions about global warming.

What will you do at IIASA and how will you link it to your PhD?
I want to upscale and quantify how much carbon plants will take up in the future. If we are to predict the capacity of plants to absorb CO2, we need to quantify mycorrhizal distribution and nitrogen availability on a global scale. We are updating mycorrhizal distribution maps according to distribution of plant species. We know for instance that pines are associated with ectomycorrhizal fungi and always will be. To quantify nitrogen availability we use maps of different soil parameters that are available on a rough global scale.

© Adam Edwards | Dreamstime.com

© Adam Edwards | Dreamstime.com

About César Terrer
Prior to his PhD, Terrer studied at the University of Murcia in Spain and the University of Western Sydney in Australia.

Currently he is a member of the Department of Life Sciences at Imperial College London, UK. For this study he collaborated with researchers from the University of Antwerp, Northern Arizona University, Indiana University and Macquarie University.

In the IIASA Young Scientists Summer Program, Terrer works together with Oskar Franklin from the Ecosystem Services and Management Program and Christina Kaiser from the Evolution and Ecology Program.

Further reading

 

Note: This article gives the views of the interviewee, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.

Emission rates of VW models in Europe as high as in the USA

© kichigin19 | dreamstime.com

© kichigin19 | dreamstime.com

By Jens Borken-Kleefeld, IIASA Mitigation of Air Pollution and Greenhouse Gases Program

Earlier this week, Volkswagen admitted fraudulent software causing high exhaust emissions of nitrogen oxides (NOx) from several of its diesel car models during normal driving. That diesel cars emit many times more NOx in normal driving than their legal limit has been known for more than a decade in Europe. The surprise to me is that the enforcement of these legal limits is pursued now from the USA and not from a European authority, and that – in the face of a public outcry – the automaker admitted the same software was not only in US models.

Following this announcement, I took a second look into the on-road emission data from Europe and compared it with data collected by colleagues in the USA. We find that VW diesel cars in Europe emit as much NOx as the incriminated models in the USA, as shown in the chart for VW Golf, Jetta and Passat models model years 2009 to 2013.

emissions

On-road data US: Peter McClintock, remote sensing campaign by Envirotest Inc. for Colorado (2013). On-road data Europe: Jens Borken-Kleefeld, analyzing remote sensing campaigns by AWEL Zurich (2009-2013). Each filtered for normal driving conditions.

We measured significant differences between manufacturers, yet on the whole the gap between officially certified and real-driving NOx emissions from diesel cars in Europe has been growing. The few models with low emissions are by far outnumbered by cars with high NOx emissions. Yet, VW’s emission levels are not even the worst in class.

References:
US EPA Notice of Violation, 18 Sept 2015. http://www3.epa.gov/otaq/cert/documents/vw-nov-caa-09-18-15.pdf

Announcement by VW: http://www.volkswagenag.com/content/vwcorp/info_center/en/news/2015/09/Volkswagen_AG_has_issued_the_following_information.html

Chen and J. Borken-Kleefeld, “Real-Driving Emissions from Cars and Light Commercial Vehicles – Results from 13 Years Remote Sensing at Zurich/CH,” Atmospheric Environment 88 (May 2014): 157–64. http://dx.doi.org/10.1016%2Fj.atmosenv.2014.01.040

Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.

A futuristic view of farming

Within the next  few decades, the world will need to increase food production to support a growing population also striving for higher shares of animal protein in their nutrition. But food production always affects the environment: Nitrogen runoff from fertilizer has led to major pollution of waterways around the world, while deforestation to extend cropping areas and methane emissions from livestock increase the amount of greenhouse gases in the atmosphere, adding to the problem of climate change.  In order to increase food production, without further increasing nitrogen pollution and greenhouse gas emissions, agricultural systems will need to innovate.

In a recent study, IIASA researcher Wilfried Winiwarter explored the range of solutions for future agriculture, researching current literature for ideas and innovations, and examining their feasibility and potential.

“I call this a science fiction paper,” says Winiwarter. “It’s not about what exists and can be implemented immediately, but about the possible innovations that could conceivably be developed in the long-term.”

The study focused on innovations ranging from seemingly simple behavioral changes to radical technological fixes as discussed in more detail below. It reviewed existing scientific literature, mostly peer-reviewed, including design studies that quantified potential environmental effects of such innovations.Laboratory Plant

Precision Farming
Precision farming refers to technological solutions to improve yields and reduce waste in farming. On the one hand, precision farming can refer to the mechanization of agriculture that may not be environmentally benign, but on the other side, to optimized processes that reduce losses and impacts on the environment.

“Much is already happening,” says Winiwarter. For example, milk production in Europe now occurs mainly in large sheds, with indoor cows, not with free-ranging cows in idyllic meadows. While this industrial approach to agriculture makes food cheaper and more abundant, it also raises questions about animal welfare, and the massive scale of such operations can lead to increased greenhouse gas emissions.

Precision farming can also be used to reduce the amounts of fertilizers or irrigation used, for example, using soil sensors or other high-tech infrastructure to detect exactly what is needed and apply no more than necessary.

Genetic Modification
Genetic modification (GM) of crops allows scientists to equip organisms with certain traits in a much more directed way than traditional breeding. It presents the potential to increase yields, provide drought or pest resistance, or introduce additional nutrients to foods that lack them. GM is already widely used in some crops (mostly to increase pesticide resistance and thus also pesticide application), but in Europe the subject is controversial and GM foods are viewed negatively

Winiwarter notes that the side effects of genetic modification are in general not well understood, and thus possible impacts are quite unpredictable.

Urban Gardening
The study looked into the growing popularity of urban gardening, the “green” trend to grow food in individual gardens inside cities. While urban gardening is generally considered environmentally benign due to small-scale, low transport needs and high personal motivation, Winiwarter notes that it doesn’t have the potential to produce staple food required to feed large populations. One key background study calculated that urban gardens had the potential to produce 10% or less of the food needed in a given city.

“You need space to produce food,” says Winiwarter.

Vertical Farming
As people move to cities and land becomes scarcer, one logical concept is to construct skyscraper “farms” with multiple levels of vegetables growing in hydroponic or aeroponic tanks – like giant, multistory greenhouses. “Compared to an open field, you could produce 200 times as much food on the same space,” explains Winiwarter. “In a city like Vienna, you could conceivably produce all the food for the city within city limits.”

Another advantage of vertical farming is that it could be organized to avoid  waste: whereas fertilizer in a field runs off or percolates through the soil into the water table, a vertical farm would employ nutrient solutions that could be contained and recycled.

However, the sunlight needed for photosynthesis could not so easily be multiplied. Instead, the process would require artificial light, which means enormous amounts of energy – even if efficient LED lighting could be employed.  “The question is where you would get that energy,” he says.

C

Cultured meat can now be grown in laboratories – but will it ever make sense on a large scale?

Cultured Meat
Another radical idea for food production is to take meat production off the farm, and instead culture animal cells in petri dishes to grow artificial meat in a laboratory in a nutrient solution. Indeed, the first hamburger from cultured meat was produced in 2013. But Winiwarter notes that meat from the laboratory may not be less resource-intensive than the real thing, since it would need energy, heat, light, and nutrients, which all would make the process extremely expensive, even under ideal conditions. He says, “Upscaling such a process may come with a number of negative surprises – from sanitary issues to pollution as a side-effect of tackling potential health threats. Little is known on the potential environmental effects in a life cycle.”

Dietary Changes
“In general, meat has a higher environmental footprint than a vegetarian diet,” says Winiwarter. “It takes more area to produce feedstock for an animal than it would to produce vegetarian food for humans.”

Europe in particular has a high level of meat consumption, Winiwarter explains, so cutting meat consumption in the region has a large potential. In much of the highly populated areas of Asia, people consume a mostly vegetarian diet. As these countries become richer, increased consumption of meat and milk production is observed when people tend to copy European lifestyle. If Europeans were able to cut down on meat consumption and treat themselves with a more healthy diet, positive environmental effects may even spread to world regions where European food patterns may serve as an example.

Agriculture, like a high-tech industry, will continue to develop dynamically in the future. Many paths of development can be imagined, and have been described in scientific or other literature. “There is no ‘silver bullet’ to resolve the environmental damage of agriculture”, Winiwarter says. Instead, future innovations will need to be carefully monitored and evaluated for potential environmental effects, in order to minimize damage of nitrogen pollution and maintain livelihood on earth.

Reference
Winiwarter W, Leip A, Tuomisto HL, Haastrup P. 2014. A European perspective of innovations towards mitigation of nitrogen-related greenhouse gases. Current Opinion in Environmental Sustainability. http://www.sciencedirect.com/science/article/pii/S1877343514000396

By Katherine Leitzell, IIASA Science Writer

Interview: The problems with phosphorus

In a new commentary (subscription required) in Nature Geoscience, IIASA researchers Michael Obersteiner, Marijn van der Velde,  and colleagues write about the problems facing the world’s food supply as we exhaust our supplies of phosphorus. Projections show that phosphorus supplies could run out in the next 40 to 400 years.  In this interview, Obersteiner and van der Velde give more background on the “phosphorus trilemma.”

field of wheat

Fertilizers containing phosphorus are vital for crop production – but phosphorus is limited in availability and growing scarcer.

Why is phosphorus so important?

MV:  Phosphorus is essential for life on Earth. It is a key component of DNA and cell membranes, and vital for cellular energy processes. Crops need phosphorus to grow. And to maintain crop production, and to make sure that soils remain productive, we have to add extra nitrogen and phosphorus as fertilizer. This is one of the food security issues in Africa where soils are suffering from nutrient depletion without replenishment.

Where do we get phosphorus and why is that supply in danger?

MO: Phosphorus is ubiquitous in the Earth’s crust. However, most of it is strongly bound in the soil , where plants cannot access it. Modern agriculture (which made human population explode) essentially began when we found ways to extract nitrogen from the air and phosphorus from minerals to make fertilizers for agricultural purposes.

The problem is that minable phosphorus is geographically concentrated in very few places. For example 75% of known reserves are located in Morocco and these reserves are limited. If, for example, political turmoil restricted access to the mines of Morocco, we would be in danger of short-term shortages that could lead to rising food prices or food insecurity in poor countries.

What problems do you expect as phosphorus becomes even more limited?

MO: The biggest problem we face is limited or no access to phosphorus fertilizers by the poor and food insecure.

MV: At the same time, rich countries apply excess fertilizers causing eutrophication to their lakes and rivers, while the poor cannot afford fertilizers.

What can be done about these problems?

MV: More efficient fertilizer application would make fertilizers cheaper to poor farmers, and at the same time help address the environmental problems. But in the long run we need to figure out how to produce food in a way that recycles nutrients at minimum loss rates.  (This also includes losses from human excrement!)

To better solve the issues around long-term phosphorus availability and equitable use we also need better data on how much phosphate rock is remaining in the world and where it is located. Countries will need to be persuaded to collaborate on both these issues to ensure equity.

How does IIASA research inform this debate?

MV:  In a paper we published earlier this year in PLOS ONE we showed the importance of soil phosphorus and the significant increases in yields that could be achieved in Africa with balanced micro-dosed applications of nitrogen and phosphorus. Available phosphorus in soils is generally low, especially in older weathered soils in the tropics where a lot of the phosphorus can be locked up in iron and aluminum complexes. We are currently investigating what application rates of nitrogen and phosphorus would be optimal for a range of soils and climates. This can then lead to better soil and nutrient management.

MO: In addition researchers in the Mitigation of Air Pollution and Greenhouse Gases program have been very active in finding solutions to the problem. For example: http://www.iiasa.ac.at/web/home/resources/multimedia/Podcasts/Our-Nutrient-World—Wilfried-Winiwarter-on-Reality-.en.html

What should people to know about this issue?

MO: Many things in nature that we like or depend on for our livelihood are substitutable. But phosphorus is in everything we eat and cannot be substituted by any element. If we continue business as usual we will squander this resource and thereby potentially compromising the wellbeing of our daughters and sons.

Further Reading

M. Obersteiner, J. Peñuelas, P. Ciais, M. van der Velde, and I.A. Janssens, 2013The phosphorus trilemma. Nature Geoscience, 6, 897-898, doi:10.1038/ngeo1990 [COMMENTARY].

M. van der Velde, L. See, L. You, J. Balkovič, S. Fritz, N. Khabarov, M. Obersteiner and S. Wood, 2013.Affordable nutrient solutions for improved food security as evidenced by crop trials. PLoS ONE 8(4): e60075. doi:10.1371/journal.pone.0060075 [OPEN ACCESS].

Marijn

Marijn van der Velde is a Research Scholar with IIASA’s Ecosystems Services and Management (ESM) Program

Michael Obersteiner at IIASA conference 2012

Michael Obersteiner is the leader of IIASA’s Ecosystems Services and Management (ESM) Program.