Updated climate change data suggests the threat to harvests to increase

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TWH – Climate change consists of more than extreme weather events and steadily rising sea levels. Changes in climate and weather can threaten food harvests.

Crop damage from flooding (U.K.- 2007) Image credit: Bob Embleton, CC BY-SA 2.0

Scientists, like Cynthia Rosenzweig and those at the Agricultural Model Intercomparison and Improvement Project, have studied those potential threats. As part of that research, the journal Nature published an updated version of a 2014 study of those threats.

Disruptions to the corn harvest will become noticeable before 2040 in certain areas. Those areas include Central Asia, the Middle East, southern Europe, the western U.S., and tropical South America. By 2099, those disruptions will have spread to, China, Mexico, North America, and West Africa.

These projections refer to the harvest of crops. Agriculture forms a key part of the globalized market in goods. Extreme weather events will disrupt global maritime trade. Some harbors will fail to survive rising sea levels.

Not all agriculture participates in the global market. Throughout the world, subsistence farmers grow crops for their own consumption. If their crops fail, subsistence farmers will have to choose between slow starvation or forced migration. It may be more accurate to call climate migrants, “climate refugees.”

Technical issues

Predicting the future has many uncertainties. Yet, to prepare for known looming disasters, scientists have to attempt it. The amount of greenhouse gases in the atmosphere has increased since the 2014 study, which requires updates. The updates predict more food disruptions than the 2014 study did. They also predict that those disruptions will occur earlier.

Farming in drought conditions – Image credit: John Sutton, CC BY-SA 2.0

Scientists based their predictions on three key variables about food crops.

First, crops have limits to the temperatures in which they can thrive. Second, crops require constant access to a water source, either rain or irrigation. Third, increases in available carbon dioxide form a major component of climate change.

Carbon dioxide is the major input in photosynthesis. This could be beneficial, but it might also disrupt the natural cycle in which plants evolved. Any of these variables would have a significant impact on the nutritional value of the food crop.

Existing data tells scientists how climate factors have affected crops in the past. Scientists input different amounts of greenhouse gas in the atmosphere. Then, they input its impact on the climate. From that input, they can develop models of how those different rates will affect crop growth.

High-powered computers allow scientists to plot relevant variables in a variety of models which allows them to compare the results. High agreement between models leads to higher levels of confidence in those results.

The models examine how the impact of climate change would affect the harvest of four crops: corn, rice, soybean, and wheat.

The Nature article reported, “These four main crops contribute 90% of today’s global caloric production of all cereals and soybean.”

The models have substantial agreement about corn and wheat. While corn harvests will decrease, wheat harvests will increase. In contrast, they show much less agreement about the rice and soybean harvests. This article will only discuss estimates of the productivity of corn and wheat.

High agreement on conditions worsening

The updates to 2014 predictions show conditions worsening. Current models show increases in from 927 to 1,122 parts per million of carbon dioxide by 2099. Current models predict higher global temperature rises of about 0.3o C (0.54o F) than in earlier models. In corn-dominant regions, scientists expect increases of more than 0.5o C (0.9 o F).

These increases may not seem that large, but corn-dominant regions, however, include large parts of the Tropics. In that area, temperatures tend to be very high. More critically, high heat increases evaporation, and also increases the risk that a lack of water would kill the plant.

Corn and Wheat Harvest

Climate models had the highest agreement on decreasing corn harvests.. The Nature article describes corn as the “most important global crop in terms of total harvest and food security in many regions.”

Some TWH readers may be surprised to read claims of corn being the most important crop. In the past, corn has had prominence in Latin American diets. It lacks that prominence in Asian or traditional Euro-American diets. As Mexican cuisine and its food products enter into the “typical” Euro-American diet, that lack of prominence is declining.

Cornfield (UK 2010) – Image credit: Ian Paterson, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=104835583

Corn has a major indirect impact on Euro-American diets, and also forms the source of many other products. Those products include bourbon whiskey, cornstarch, grits, high fructose corn syrup, and polenta. Corn also makes up a large part of cattle feed.

Additionally, some industrial products, like plastics, use corn products as a component. Disruptions to the corn harvest would threaten the supply chains for these other products as well.

The current models predict worsening corn harvests more than the 2014 models did. Corn is grown mainly in more southern latitudes. These latitudes already have some of the highest temperatures on the globe.

Extreme temperatures in this region could soar past the threshold for crop viability. If extreme temperatures co-occur with droughts, crops could fail on a massive scale. Throughout the Americas, Indigenous people and subsistence farmers rely on corn. Those groups will suffer the most from any decline in the corn harvest.

The scientists in Nature reported that wheat had the second most importance after corn. The models predicted that wheat harvests would show an increase from 2014 estimates.

Current models predict increases in wheat harvest “at the global level.” In one model, the impact of climate change on the wheat harvest would become noticeable as early as 2023. Within all models, it would become noticeable within 20 years. The models suggest increases would level off by midcentury.

Wheat species may differ in how climate change would affect them. By 2050, spring wheat harvests would have begun to decline in Mexico, South Asia, the southern U.S., and parts of South America. In contrast, winter wheat harvests would increase in the U.S. and Canada.

In general, wheat harvests should increase in Australia, Central Asia, the Middle East, and the plains of north China.

Intersecting crises already drive famine in the Horn of Africa

Climate change co-occurs with other threats to harvests. Several other factors contribute to declining harvests.

Recently, Inside Climate News reported on the difficulties in disentangling the “intersecting crises of climate change, biodiversity loss, poverty, and poor governance.” It also reported that by 2050, the planet will have 2 billion more people to feed.

Horn of Africa countries – Public Domain 

A four-year drought has ravaged the Horn of Africa. The number of critically hungry people in that area has reached 23 million. In the Horn of Africa, someone dies of hunger-related issues every 48 seconds.

In that region, droughts have become longer and more severe. Rain seldom comes, but when it does it is short and violent. Somalia and Northern Ethiopia are in a drought but slide into a famine. Kenya already has already moved into a famine.

Mark Lowcock, former U.N. undersecretary-general, linked Kenya’s famine to climate change.
Lowcock said, “I think what we’ve got is a climate-induced food insecurity problem. It would require very substantial neglect by the government for that to be allowed to turn into a famine.”

Everyone depends on food harvest, but not everyone will suffer equally. By definition, the most vulnerable and least powerful will likely suffer first and probably the most.


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