This blog is intended to go along with Population: An Introduction to Concepts and Issues, by John R. Weeks, published by Cengage Learning. The latest edition is the 12th (it came out in 2015), but this blog is meant to complement any edition of the book by showing the way in which demographic issues are regularly in the news.

If you are a user of my textbook and would like to suggest a blog post idea, please email me at: john.weeks@sdsu.edu

Monday, February 25, 2013

Climate Change and Agriculture: New Bad News

As global climate change came into sharper focus in the 1990s, many people thought that this might actually work to the advantage of agriculture--leading to longer growing seasons at the same time that more carbon dioxide in the atmosphere might actually help to fertilize plants and heighten productivity. However, a report just released by the Global Development and Environment Institute at Tufts University offers little enthusiasm for that positive view of the effects of climate change.
First, newer experimental studies have sharply reduced older estimates of carbon fertilization effects. Second, the effect of temperature on many crops has been found to involve thresholds, above which yields rapidly decline; the number of hours above the threshold is typically more important than the average temperature. Third, climate change will bring significant changes in precipitation; in a number of important areas, decreases in precipitation may cause declines in agricultural production. Simple,
aggregated economic analyses of climate change have often omitted these crucial effects of precipitation.
The report is especially critical of economists (e.g, Julian Simon, although he is not mentioned by name) who have believed that technology will always lead to the substitution of expensive inputs for less expensive ones.
It should not be surprising that even a little climate change is bad for agriculture. The standard models and intuition of economic theory emphasize options for substitution in production – less steel can be used in making cars, if it is replaced by aluminum or plastic – but agriculture is fundamentally different. It involves natural processes that frequently require fixed proportions of nutrients, temperatures,  precipitation, and other conditions. Ecosystems don’t make bargains with their suppliers, and don’t generally switch to making the same plants out of different inputs.
The bottom line is that as population continues to grow, it is going to be increasingly difficult to grow the food we need. Sitting on our hands waiting for something to happen isn't going to cut it.
Global warming is now causing unprecedentedly rapid changes in the climate conditions that affect agriculture – much faster than crops can evolve on their own, and probably too fast for the traditional processes of trial-and-error adaptation by farmers. At the same time, the world’s population will continue to grow through mid-century or later, increasing the demand for food just as climate change begins to depress yields. To adapt to the inescapable early states of climate change, it is essential to apply the rapidly developing resources of plant genetics and biotechnology to the creation of new heat resistant, and perhaps drought-resistant, crops and cultivars.

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