United Nations Secretary-General António Guterres called the Sixth Assessment Report, released by the Intergovernmental Panel on Climate Change (IPCC) in August, a “code red for humanity” (IPCC, 2021). With improved knowledge of climate processes, paleoclimate evidence, and increasing radiative forcing (change in the energy flux in the atmosphere caused by climate change), some uncertainties in climate model parameters have been reduced. With greater confidence in the modeling, this report cuts the estimate threshold of crossing 1.5°C of global warming by a decade, to the early 2030s. As carbon dioxide rises, ocean and land carbon sinks will become less effective at slowing the accumulation of carbon dioxide in the atmosphere. Unless we decarbonize to net-zero greenhouse gas emissions (GGEs), global warming of 1.5–2.0°C will be exceeded in the 21st century (IPCC, 2021).
As plant scientists, how can we contribute to mitigating GGEs? We can think of our impact in at least three major arenas—decarbonization of agriculture, decarbonization of materials, and growth of a sustainable bioeconomy.
If there is any good news from the IPCC, it is that scenarios with low or very low GGEs, including reductions in methane and nitrous oxide, would produce discernible differences in trends of global surface temperature, within two decades, above the background of natural variability. The carbon cycle is asymmetric for pulse emissions or removals, which means that carbon dioxide emissions are more effective at raising atmospheric carbon dioxide than carbon dioxide removals are at lowering it. Although direct air capture of carbon dioxide by natural or synthetic means is an important goal, we need to offset additions of GGEs to the atmosphere.
A recent report from McKinsey & Company pointed out the surprisingly large contribution that agriculture makes to GGEs: over one-quarter of all GGEs (Ahmed et al., 2020). If cattle were a country, their methane emissions would be higher than those of China. Nitrous oxide from fertilizer use is 264-fold more potent than carbon dioxide as a greenhouse gas. Beyond powering farm equipment and processes with renewable resources, including biofuels, major strategies to reduce the carbon footprint of agriculture could include
- transitioning from meat to plant-based proteins, because production of ruminant animals is almost 30 times more carbon intensive than production of vegetable protein;
- mitigating the one-third of food we produce that is lost in the supply chain or as food waste at the retail and consumption stages; and
- managing forest resources and natural carbon sinks to capture about 7 gigatons of carbon dioxide equivalents from reforestation, avoided deforestation, and natural forest management.
To achieve a pathway that limits warming to 1.5°C will also require next-horizon technologies, such as the ability to modulate plant and soil microbiomes for optimized plant health, perennialization of row crops, and genetic engineering to enhance carbon sequestration in roots (Ahmed et al., 2020). The Plant Science Decadal Vision 2020–2030, spearheaded by ASPB, outlines a comprehensive set of recommendations for research, technology, and human capital (Henkhaus et al., 2020).
Even as climate change affects the global water cycle and arable land diminishes with desertification, global population increase will drive a 70% increase in demand for food production by 2030. The past five years, 2016 to 2020, were the hottest five-year period in the instrumental record (IPCC, 2021), and the National Oceanic and Atmospheric Administration reported that July 2021 was the hottest month recorded to date. The frequency and intensity of extreme weather events have increased relative to the baseline of 1850, and there is compelling evidence for the relationship between anthropogenic climate change and events of extreme precipitation, droughts, tropical storms, and compound extremes, including weather created by wildfires (IPCC, 2021). On less land, with lower inputs of water, fertilizer, and energy, we must increase productivity. To meet future demands for food, feed, fiber, and fuel, all of our crops must be high yielding, growers must benefit from diversification of plant products, and we must utilize every single carbon atom trapped as photosynthate into target molecules—in other words, more acres in production, more plants per acre, higher value per plant, and higher efficiencies of converting photosynthate to useful products.
On its present course, global population increase is expected to triple the demand for materials by 2050. Materials comprise fossil fuels, metal ores, minerals, and biomass and are the raw resources from which we derive our homes, vehicles, and other possessions. For example, plastics currently use 6% of global oil consumption, a proportion that is expected to increase to 20% by 2050. Material use is tightly coupled to energy use, GGEs, land and water use, and waste flows. We will not meet the projected needs in a sustainable manner for quantity and quality of materials if we can’t design fit-for-purpose bio-based and bio-hybrid materials that are energy efficient across their entire life cycle. One example is the development of “superwood,” a material 10 times stronger than natural wood (Chen et al. 2020). Our challenge is to redesign materials for structure or for novel functions that can displace or improve the properties of the materials we currently use in every aspect of our modern lives.
Historically, a country’s economic prosperity, measured as gross domestic product, has been tightly coupled to its consumption of fossil fuels. Decoupling economic growth from fossil fuel consumption can be achieved by growing a sustainable bioeconomy. McKinsey & Company evaluated 400 test cases, products that could be made using existing reaction pathways, and concluded that 60% of physical inputs to the global economy could be produced biologically, even on a timescale of a few decades (Chui et al., 2020). Their report made me think of how we might
- co-opt plants to synthesize homopolymers, heteropolymers, and composite materials;
- displace structural concrete and steel with new materials like superwood or develop novel functionalized materials with biological properties such as self-repair;
- simplify production systems with the components of cells or make biohybrid materials outside an intact organism; and
- design our genetic circuits to adapt to external conditions that plants experience moment by moment and to allow valuable transgenic organisms to be identified and tracked.
The interconnected crises of climate change and increasing demand for food and energy by a growing global population are front and center in the global consciousness. As individuals and as a research community, we need to use our passion and creativity to set a trajectory for the next decades that preserves the biodiversity of plant life, climate proofs our agricultural systems, and delivers sustainable prosperity for all. It’s a code red emergency, and we need to respond.
Thanks to Nick Carpita and Crispin Taylor for their insights and edits on this and previous President’s Letters.
References
Ahmed, J., Almeida, E., Aminetzah, D., et al. (2020). Agriculture and climate change: Reducing emissions through improved farming practices. New York: McKinsey & Company. http://bit.ly/McKinseyClimate
Chen, C., Kuang, Y., Zhu, S., et al. (2020). Structure–property–function relationships of natural and engineered wood. Nature Reviews Materials 5: 642–666. https://doi.org/10.1038/s41578-020-0195-z
Chui, M., Evers, M., and Manyika, J. (2020). The bio revolution: Innovations transforming economies, societies, and our lives. New York: McKinsey & Company. https://mck.co/3mo05iU
Henkhaus, N., Bartlett, M., Gang, D., et al. (2020). Plant Science Decadal Vision 2020–2030: Reimagining the potential of plants for a healthy and sustainable future. Plant Direct 4(8): e00252. https://doi.org/10.1002/pld3.252
Intergovernmental Panel on Climate Change. (2021, August 7). Climate Change 2021: The physical science basis. Cambridge University Press. https://www.ipcc.ch/report/ar6/wg1/#FullReport