When genetically modified organisms (GMOs) have affected agricultural ecosystems, it has been through indirect effects rather than direct impact. That is, it has not been the modified trait of the crop itself that has been observed to affect the environment. The cultivation of specific GM crops has resulted in increased use of a certain weed control agent or has changed the tillage management, and this in turn have had effects on the environment. This is concluded in a review of the scientific literature in the field.
New GMOs with new traits might influence ecosystems directly, but in order to find out, extended studies on these traits are required.
– One step towards a sustainable utilization of our natural resources is to understand how the specific traits that are modified affect agricultural ecosystems. This knowledge increases the possibility of creating production systems that utilize resources such as water and nutrition efficiently but at the same time has a reduced negative impact on the environment, says Anna-Karin Kolseth researcher at the Department of Plant Production Ecology, SLU, and co-author of the study.
That the crops’ traits can have an effect on the environment (direct or indirect) is not specific to GM crops, but also applies to crops that have been developed with traditional plant breeding methods.
In the study, the researchers reviewed scientifically published results and evaluated how genetically modified plants, animals and microorganisms can affect agricultural production, nutrient cycling, greenhouse gas fluxes, biodiversity and trophic interactions (who eats who). They note that the focus in the reviewed research has been on risk assessments of GMOs at species level, not ecosystem level.
– For example, it has been studied how the cultivation of a certain GM crop affects a certain insect species or a certain type of weed. We have to study the traits of genetically modified organisms in more complex systems, says Anna-Karin Kolseth.
Kolseth, A. K., D’Hertefeldt, T., Emmerich, M., Forabosco, F., Marklund, S., Cheeke, T. E., Hallin, S., & Weih, M. 2015. Influence of genetically modified organisms on agro-ecosystem processes. Agriculture, Ecosystems & Environment 214: 96-106
A barley variety that takes up more nitrogen compared to the varieties of today would be more climate friendly thanks to (1) a higher yield, (2) an increased storage of carbon in the plants due to more biomass, and (3) a reduced emission of of the greenhouse gas nitrous oxide.
To be able to grow crops more effectively and get higher yields, with lower or sustained inputs, goes hand in hand with lower emissions from agriculture.
– A nitrogen efficient crop cannot save the Baltic Sea by itself, but it can be an important tool in combination with other actions that are used, or discussed, says Pernilla Tidåker, one of the researchers behind the study.
How can barley, wheat, rice and other crops be tailored to take up nitrogen more efficiently? One strategy is to develop varieties with a denser and deeper root system. Another strategy is to use biotechnology to alter the activity of the enzymes that affect the uptake of nitrogen in plants.
Today there are no commercial varieties available that have been made nitrogen efficient though biotechnology, but research and pre-breeding is underway. In Mistra Biotech we develop potato varieties with increased nitrogen uptake.
In the absence of commercial nitrogen efficient crops and long-term field trials, the researchers have instead used three simulation models (SOILN, SOILNDB and ICBM) to estimate the effects of an introduction of barley varieties with improved nitrogen uptake. They investigated the effects on yield, nitrogen leaching and carbon storage. The simulations were based on conditions typical for barley cultivation in the south of Sweden and areas close to the lakes Hjälmaren and Mälaren.
– A nitrogen efficient crop would have most effect in the south through reduced nitrogen leaching. Our study indicates that the increased biomass, and thereby the carbon storage, has a large impact on whether a crop is climate friendly or not. When evaluating the environmental impact of a crop, we should focus more on what is returned to the soil after we have taken out what we wanted, in this case the grain, and emphasize the total biomass, not only the grain yield, says Pernilla Tidåker.
She also points out the risk that a crop with a higher nitrogen uptake efficiency could result in farmers using more nitrogen fertilizer.
– That does not mean that there will be an increased nitrogen leaching. But if a crop is very efficient in taking up nitrogen initially, it might suffer from nitrogen deficiency later on if more nitrogen is not added. If we should introduce such a crop,we might also need incentives for farmers to keep nitrogen application rates maintained, says Pernilla Tidåker.
Tidåker, P., Bergkvist, G., Bolinder, M., Eckersten, H., Johnsson, H., Kätterer, T., & Weih, M. 2016. Estimating the environmental footprint of barley with improved nitrogen uptake efficiency - a Swedish scenario study. European Journal of Agronomy 80: 45-54
The classic science on plant nutrition states that plants acquire nitrogen from the soil as nitrate or ammonium, or as nitrogen gas if the plant forms symbiosis with nitrogen-fixing bacteria. Today we know that there are plants that also can make use of organic nitrogen, but the consensus has been that it only applies to certain mycorrhiza-forming plants growing in nutrient-poor soils. Together with colleagues from Austria and Australia the SLU researchers show that a plant that does not form mycorrhiza acquires organic nitrogen when grown in nutritious agricultural soil.
The findings show that the plant is dependent on a specific protein for this to work. The protein is an amino acid transporter, and the researchers have performed a number of experiments on genetically modified thale cress (Arabidopsis thaliana) that either lack the transporter or over produces it.
Torgny Näsholm is Professor in ecophysiology at the Swedish university of agricultural sciences in Umeå, and he led the study.
– We grew the plants in greenhouses in agricultural soil, and could follow the way of the amino acid glutamine from the soil into the plant by labelling the glutamine with carbon and nitrogen isotopes. It turned out that the uptake of the amino acid is much more efficient in plants that overproduce the amino acid transporter, and very low in plants lacking the transporter, he explains.
Additionally, the plants that were lacking the transporter had the lowest carbon/nitrogen ratios, and the plants overproducing the transporters had the highest ratios. Theoretically the amino acids should result in a higher carbon concentration, which indicates that the plants have been taking up organic nitrogen from the soil continuously.
– This study is a milestone in our research. With the use of genetically modified model plants we have been able to show that amino acids in soil are used as nitrogen sources by plants. We also aim to increase the plant capacity to take up nitrogen from the soil, and our results show that an optimization of organic nitrogen uptake is a possible way to achieve this, says Torgny Näsholm.
Thale cress is not an agricultural crop, but a model plant which is often used to predict the effects of genetic modifications in agricultural plant species. The research group now investigates how the uptake of organic nitrogen can be improved in potato.
– We are now testing if it is possible to use the same strategy to increase the uptake of organic nitrogen in an agricultural crop. We have propagated modified potato clones to see if we get the same increase in potato as in thale cress.
Ganeteg, U., Ahmad, I., Jämtgård, S., Aguetoni-Cambui, C., Inselsbacher, E., Svennerstam, H., Schmidt, S., and Näsholm, T. 2017. Amino acid transporter mutants of Arabidopsis provides evidence that a non-mycorrhizal plant acquires organic nitrogen from agricultural soil. Plant, Cell & Environment, 40: 413–423. doi: 10.1111/pce.12881.
Which is best for the environment, animal feed based on genetically modified (GM) soy or GM-free soy? It depends on how you look at the matter. Researchers have developed a comprehensive picture of how it would affect the environment if Swedish farmers began to give their animals feed based on imported GM soy, which is common in many other European countries, instead of using 100 percent GM-free soy as Sweden does today.
The study showed that there are no significant environmental gains from importing non-GM soy, instead of GM soy, when comparing the two parallel supply lines. However, when the researchers use a more holistic approach and include the market effects of a shift from the more expensive GM free feed to the cheaper GM feed in the analysis, a different future scenario appears. The cheaper GM based feed would lead to increased demand for soy which could lead to deforestation to release new farmland. At the same time, the demand for Swedish protein crops would decrease.
– In the study, we have taken into account that GM soy is getting cheaper and thus outcompeting other protein feeds. It is certainly logical that the production moves to where it is cheapest, but lower prices can also make us start consuming more, requiring increased production that can bring more negative consequences for the environment than the actual shift of production site, says Mattias Eriksson, one of the researchers behind the study.
On the other hand, the global warming potential and the freshwater ecotoxicity are higher from non-GM import than import of GM soy, per imported amount of soy. However, increased imports of soy would replace our domestic protein production, and thereby demand more land and cause more environmental impact in South America. In addition, transportation and waste has increased as a result of the fact that we keep the two supply chains separated altogether.
– Because the non-GM soy needs to be kept free from contamination of GM soy, segregated transports and production lines are required. Controls and certifications also need to be separated to ensure that the different types of soy are not mixed. This makes the GM-free soy more expensive, but smaller volumes also contribute to higher prices, explains Mattias Eriksson.
Earlier environmental impact assessments of soy production and trade did not distinguish between GM and non-GM soy, in spite of the fact that the import of the different soybeans to EU in done through separate supply lines.
In the current study, the researchers did a detailed mapping of the various stages of events taking the soy feed from the farms in South America to the animal farmers in Europe. Then they made a life cycle assessment (LCA) for GM soy and for non-GM soy.
– Since Sweden stands out in a European perspective, as only GM free soy is sold here, it is interesting to analyze the possible environmental impact of becoming more like our neighboring countries. And as we can see, it's not the production itself that is the main problem, but production is projected to increase if the prices fall, says Mattias Eriksson.
The GM soybeans are allowed for use throughout the EU, but in Sweden there is an agreement in the field of agriculture that the meat industry should not use GM based animal feed.
The results of the study point out that the most environmentally friendly option would be to develop protein-rich plants that can grow in the Nordic climate through plant breeding, and then use them as animal feed to replace soy that is now being imported.
Eriksson, M., Ghosh, R., Hansson, E., Basnet, S., & Lagerkvist, C. J. 2017. Environmental consequences of introducing genetically modified soy feed in Sweden. Journal of Cleaner Production 176 (2018) 46–53.
Potatoes with higher amylose content take up more nitrogen than regular potatoes. It can be seen as another benefit of this potato, as long as it does not requires increased fertilization and the risk of eutrophication.
"If you focus on the amount of the final product, amylose, produced per unit of nitrogen in the soil, then I think that the genetically altered potato will be more nitrogen efficient compared to the potato without this genetic change." That is ecology professor Martin Weih’s comment on the results of a study where he and his colleagues studied how much nitrogen the amylose potato, or GI potato as it is also called, takes up (GI, glycemic index).
Starch consists of amylose and amylopectin. The amylose potato produces starch with more fiber-like properties than regular potato. The amylose molecules have fewer branches than the amylopectin, and that is what makes the starch fibrous. The new starch is well suited to use in the production of environmentally friendly packaging materials, and it has a low GI which makes the potatoes healthier to eat.
The researchers developed the amylose potato by silencing two enzymes that affect how the starch branch, using the method of RNA interference (RNAi).
Martin Weih’s research is about how plants absorb and utilize the nitrogen found in the soil. He became interested in finding out if the genetic changes that led to the increased amylose content would also lead to changes in nitrogen uptake or nitrogen efficiency in the potato plants.
– That's why we did this study where we grew both the potato with and the potato without the genetic change, he says.
It was found that the genetic change affected nitrogen uptake and lead to a significantly higher amylose production. It remains to be ascertained whether the higher nitrogen uptake capacity of the amylose potato poses a greater need for nitrogen and whether it is compensated by the higher starch content.
Pourazari, F., Andersson, M. & Weih, M. 2018. Altered tuber yield in genetically modified high-amylose and oil potato lines is associated with changed whole-plant nitrogen economy. Frontiers in Plant Science 9: 342