Crops in planetary stress test

The massive forest fires, heatwaves, and flooding of recent months have driven home just how serious the effects of climate change can be. But even when the land is not burning, scorching, or drowning, the anthropogenic greenhouse effect is impacting nature and agriculture. How does climate change affect plants?

Leister: The effects encompass many levels, from processes inside plant cells to global cycles. At first glance, more CO2 would seem to be advantageous for plants. But when there’s drought, the extra CO2 is of no use. Without water, nothing works. The same goes for nutrients in the soil. Moreover, plants can suffer from heat stress. From a geological perspective, two degrees of warming are no big deal. There have been much more dramatic fluctuations in the history of the Earth. The problem is the speed with which the changes are happening. I’m not sure whether our natural landscapes can adapt quickly enough.

Fader: Extreme weather events such as droughts, floods, storms, and fires are becoming more frequent and we have seen them destroy ecosystems and farmland on a broad scale. The distribution of pests and pollinators is changing. Climate change is causing habitats to shift geographically. If this happens too quickly, it leads to losses in biodiversity. Moreover, the length of the growing period changes. In agriculture, this affects when and where farmers can sow and harvest certain crops, how quickly a plant matures, and of course how high the yield is.

Do we have to intervene and give the crops a helping hand?

Leister: Agriculture is artificial in any case, a system in which humans intervene in every conceivable manner: when it comes to irrigation, fertilization, pest control, etc. The crops we breed are not natural. And when something is artificial – that is, only maintained by human manipulation – you can respond to changes by further adapting the system.

If plants were black

How can we further optimize crops?

Leister: One of the main starting points for my work is photosynthesis. It is the most important process for life on Earth. Without it, there would be no oxygen, no biomass, no humanity. Everything we eat, everything we are, is ultimately a product of photosynthesis.

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However, crops have not evolved to give us maximum yield. In the course of evolution, they have never needed to be highly efficient. Plants are green because they do not use green light. Our crop plants contain this natural inheritance. There is much scope for optimization here. With a black plant capable of utilizing the entire spectrum of sunlight, you could use 50, 60, or 100 percent more wavelengths.

And this could help make agriculture more sustainable?

Leister: From the poles to the deep ocean, there is no spot left on the Earth that is not touched by humans in some way. The less space we utilize, the better. Therefore, we must try to reduce the area we use for agriculture. We want to develop crops that use more energy and can therefore be planted much closer together. Then we would need less space for arable farming, freeing up areas for nature.

Fader: Mr. Leister is broaching a debate here between two different approaches: land sparing and land sharing. In general, there are two options: The first is to make agriculture highly efficient and thus more spatially concentrated. Then we would have more space to set aside for extensive natural ecosystems. The second option is to have larger agricultural areas that are embedded in and intertwined with natural landscapes – systems that are no longer optimized for efficiency, but for low-intensity land use. Much of the professional discourse around planetary limits hinges on the question as to in which areas one or the other of these systems is the more sustainable. There is no one-size-fits-all answer to this question, and a combination of both can be the solution.

Is there the danger that cultivated areas will not shrink despite crop optimization, but that monocultures will continue to grow?

Fader: We can observe just this effect in action in the Mediterranean area in relation to water use. The farmers there switched from surface to drip irrigation, which is much more efficient. Unfortunately, however, they took the water they could have saved and used it to expand production. And so no water was ultimately saved. Such rebound effects can also arise in relation to land use. But that isn’t a geographical or biological problem so much as a sociological and societal one. For all the brilliant insights science can deliver, we cannot achieve sustainability until politics and society recognize its global importance.

What would happen if we were to abandon monocultures?

Can we feed the world’s population with a return to more natural agricultural systems?

Fader: There is a lot of research being undertaken into this question. Soon, we plan to simulate the use of mixed cultivation in a large-scale ecosystem model. This involves planting several field crops together instead of monocultures. One of these crops is usually a nitrogen-fixing plant, so that less fertilizer is needed. Alongside the planting of mixed crops, the approach also involves extensive working of the fields by means of conservation plowing and water-conserving measures in the soil. We’re investigating whether we can obtain yields with such nature-friendly agricultural practices that are comparable to current yields from monocultures. There are a lot of indications that we could reap a lot of benefits if we returned to more natural forms of cultivation.

Leister: When you ruin the soil and dirty the water, you end up harming yourself in the long run. It’s great when you can avoid this through conservation farming methods. At the same time, such business models may necessitate the use of sophisticated technology, making their produce more expensive. In current monocultures, you just have to fling enough fertilizer over the fields and you can grow crops very cheaply, at least in the short term. And here we touch on a social dimension of the topic, as many people rely on cheap food products. We need decision-makers who are in receipt of good economic advice and who can find viable long-term solutions.

Could synthetically modified plants outcompete natural systems if they escaped from farmers’ fields into the countryside?

Leister: Interestingly, I rarely hear this concern in relation to animal breeding. Nobody is afraid that a modern high-yielding cow will break loose and populate the Alps. Breeding for agriculturally desirable characteristics comes at the expense of general fitness, and most domestic pets and livestock would not be able to survive in the wild without human assistance. It’s a similar story with crop plants. Even a plant with improved photosynthesis would probably have to be nursed and coddled if it is to survive. I cannot imagine that such a crop would spread like a weed.

Fader: This discussion tends to be overly focused on what potentially dangerous organisms we could create in the laboratory. But at least equally important is the question as to the state of our natural ecosystems. If they are generally weakened, they become more susceptible to intrusions and lose the ability to resist. Climate change, deforestation, and pollution are stress factors that can knock a system out of equilibrium. Furthermore, systems are becoming more brittle due to biodiversity loss. We shouldn’t just talk about synthetic dangers from the lab, but about how we can preserve natural structures.

Some people have misgivings about modern genetic engineering. Are we crossing a line here?

Leister: With currently accepted methods, scientists aren’t creating anything completely new. Rather, we slightly modify existing genes by replacing individual amino acids. This is a process that occurs in nature every day. In essence, I’d characterize my work as sustainable genetic engineering. Plants with a generation time of at least one year need thousands of generations to adapt. This takes far too long for lab experiments. Cyanobacteria create a generation within a few hours.

What is the benefit of this rapid breeding?

Leister: We work on these bacteria and algae and get them to adapt to certain conditions. Then we look at how the adapted generation differs genetically from its ancestors. Only once we translate our findings to plants do genetic engineering methods come into play. We’ve already managed to introduce a point mutation discovered in the bacteria into plants, where it also led to improved stress tolerance.

Genetic engineering on the one hand and the return to more natural farming practices on the other: Aren’t these approaches contradictory?

Fader: I’m fundamentally open to different approaches, although genetic modification certainly divides opinions. In many respects, agriculture is already something very artificial. If we can combine nature-friendly systems with sustainable cultivation and technological innovations, forging a path together to successful climate adaptation, then why not? I see great potential here for mutually complementary endeavors.

Leister: Distinguishing between synthetic and natural in the context of farming makes no sense. Rather, it’s about sustainability in the sense of feeding humanity while minimizing any collateral damage. We can draw inspiration from nature and develop clever solutions. Genetic engineering is really just the further development of breeding, but with more scientific know-how. There can be nothing bad in making crops more resistant and efficient. It is artificial, certainly, but sustainable nonetheless.

Are we capable of successfully adapting to climate change?

Leister: I’m generally optimistic as regards human ingenuity. What concerns me is the heterogeneity of nations, societies, and interests. It seems that suffering will be very unevenly distributed globally. Countries that lack the requisite resources and infrastructure to adapt are already suffering now.

Fader: The Earth system possesses a certain plasticity, and human societies are also adaptable, as history has shown. Depending on where we lay the emphasis, however, we must acknowledge that some things are already beyond saving. The so-called tipping points in the climate system are a key factor. If these thresholds are exceeded, it’s likely that even nature-friendly farming with synthetically optimized crops will not be enough to save us.

Prof. Dr. Marianela Fader is Chair of Physical Geography and Nexus Research at LMU. Having studied geography at the University of Göttingen, Fader completed her doctorate with a dissertation at the Potsdam Institute for Climate Impact Research. She has worked as a researcher at the Potsdam institute and at the Mediterranean Institute of Marine and Terrestrial Biodiversity and Ecology (IMBE) in Aix-en-Provence, France. Moreover, she was Deputy Director of the International Centre for Water Resources and Global Change in Koblenz. She has done consulting work for clients such as the World Bank and various German government ministers and UN agencies (FAO, WMO, UNESCO, UNEP)..

Prof. Dr. Dario Leister is Chair of Botany with a focus on Plant Molecular Biology at LMU. Born in 1967, Leister studied biochemistry at the University of Tübingen and received his doctorate in genetics for a dissertation at the Max Planck Institute for Plant Breeding Research in Cologne. He also worked as a postgrad there as well as at the Sainsbury Laboratory (John Innes Centre) in Norwich, England. He obtained his habilitation degree in genetics before coming to LMU in 2005. Leister is spokesperson for the German Research Foundation (DFG) Collaborative Research Centre “The Green Hub: Central Coordinator of Acclimation in Plants” and for the ERC Synergy Grant consortium “Redesigning the Photosynthetic Light Reactions (PhotoRedesign).”

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