NASA Climate Study Predicts Agricultural Impacts Within the Next Decade

As I read the latest NASA climate change study and the implications of its conclusions regarding future food security, I wondered how many political leaders and policymakers attending COP26 in Glasgow, have taken the time to look at this document and consider their country’s future options.

I’ve read a number of previous climate change impact studies that looked at extreme weather event costs, sea-level rise, and other consequences of atmospheric warming, but one that talked about the substantial disruption to staple crops almost in our immediate future raised my level of concern. What are we humans doing to our home planet?

The latest NASA study is “markedly more pessimistic” in looking at the impact of atmospheric warming on staple crops such as corn (maize), soybeans and rice. It appears that these three, and particularly the first, are going to be negatively impacted by increased atmospheric warming as early as the end of this decade. Only wheat, it would seem, will gain a temporary advantage from higher concentrations of carbon dioxide (CO2) in the atmosphere. Why the latter will see a short-term gain. Because the areas where itAgMIP can be grown will expand as warmer temperatures march poleward.

The NASA study is published in the journal Nature Food and was released on November 1, 2021. It arrived at its projections by assessing climate and crop model simulations that looked at multiple variables related to atmospheric warming and its consequences from rising greenhouse gas emissions (GHGs). The Agricultural Model Intercomparison and Improvement Project (AgMIP), an international partnership headed up by Columbia University, provided crop models.

These crop models simulate how key staple crops grow and respond to changes in temperature, precipitation, and atmospheric CO2. How wheat, corn, soybean and rice plants are impacted by these types of variables gave the researchers the means to create as many as 240 global climate-crop model simulations for each type of crop. These were then mixed and combined with 5 different climate models and then run through a supercomputer to complete the analysis. The result, states the report, is a reliable indicator of both the near future and what will happen throughout this century, minimizing the uncertainties raised by previous climate and crop studies.

Alex Ruane, from the Goddard Institute for Space Studies, is a co-author of the study. In a NASA press release, he states, “What we’re doing is driving crop simulations that are effectively growing virtual crops day-by-day, powered by a supercomputer, and then looking at the year-by-year and decade-by-decade change in each location of the world.”

What Ruane and his co-researchers didn’t address is how human behavioural changes in agricultural practices could alter their projections. Nor did their study look at new varieties bred or genetically altered that could make staple crops more adaptable to changing climate circumstances. They note that a future study will address such factors.

What the study concludes is, that based on what we are growing now, and the present pace of atmospheric warming projected through the coming decades, we are going to see a discernible decline in crop yields for corn, soybeans, and rice. Although wheat as a temperate climate crop will see production range grow in places like the Northern United States, Canada, Northern China, Central Asia, Southern Australia, and East Africa, it too will eventually see per hectare yields decline by mid-century and beyond.

Singling out corn as an example, it is grown today pretty much all over the planet from the mid-latitudes to the equator. Corn is more temperature-sensitive than wheat and the hot tropics of Central and South America and Africa will see crop yields impacted as the atmosphere warms. The same is true for Central Asia where higher atmospheric temperatures will have a negative impact on this crop. What this implies is populations in the Developing World countries of these regions will be at greater risk of growing food insecurity. What are the numbers? Based on projections the decline will begin within this decade and by late in the century will see a 24% drop in yields per hectare.

For climate change deniers who talk about how higher levels of CO2 are greening up the planet over the last few decades, this result, visible when viewed from Earth observation satellites or the International Space Station, has a downside. Although more CO2 positively impacts photosynthesis and water retention in plants, it has an opposite effect on nutritional content. This is more noticeable in wheat than in corn and the study accurately assesses the scientific implications in terms of the nutritional quality of the food we grow and eat.

Other factors feeding the climate and crop models covered in the 240 simulations include:

• assessing the rate of atmospheric temperature climb,
• changes to rainfall patterns whether excessive extreme precipitation events or extended droughts,
• the frequency of heatwaves and their duration,
• and changes to the growing season with impacts on the rate at which the plants mature.

The latter point is one I had not thought a lot about. Why would this be a factor when considering crop yields? Ruane states, “You can think of plants as collecting sunlight over the course of the growing season…They’re collecting that energy and then putting it into the plant and the grain. So, if you rush through your growth stages, by the end of the season, you just haven’t collected as much energy.” Those results note Ruane, mean that our crops will produce less grain than they would under current conditions. It turns out that growing faster because of a warmer atmosphere and more CO2 has negative consequences.

Lead author on the study, Jonas Jägermeyr, at the Potsdam Institute for Climate Impact Research in Germany, is quoted in the NASA release stating, “Even under optimistic climate change scenarios, where societies enact ambitious efforts to limit global temperature rise, global agriculture is facing a new climate reality…And with the interconnectedness of the global food system, impacts in even one region’s breadbasket will be felt worldwide.”

I hope that those gathered in Glasgow pay heed to Jägermeyr’s words and to the implications contained within this study that points to a near-term consequence of our unwillingness to treat anthropogenic climate change as the existential crisis of our time.