# Increased CO2 and Food Quality

*Published:* 2007-08-22
*Author:* Lisa Moore

*This is Part 1 of a three-part series on **Food and Farming**.*

*1. Increased CO2 and Food Quality  
2\. [Farm Animals and Methane](https://blogs.edf.org/climate411/2007/09/10/livestock_methane/)  
3\. [“Food Mile” Complexities](https://blogs.edf.org/climate411/2007/10/11/food_miles/)*

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*The author of today’s post, [Lisa Moore, Ph.D.](http://www.environmentaldefense.org/page.cfm?tagID=404), is a scientist in the Climate and Air program.*

When people talk about the harmful effects of fossil fuels, they usually focus on global warming. But as I explained in my post about [nitrogen pollution](https://blogs.edf.org/climate411/2007/08/17/nitrogen_pollution/), and Bill discussed in his post about [ocean acidification](https://blogs.edf.org/climate411/2007/08/17/nitrogen_pollution/), fossil fuel use has other unintended consequences.

Here is yet another example: increasing levels of carbon dioxide (CO2) can affect the food chain. There’s a lot to be concerned about, but today I’ll focus on livestock.

This issue got some coverage last week, when [Grist described some of the effects](http://gristmill.grist.org/story/2007/8/14/14546/1396) of CO2 on food quality, based on [a news story in *Nature*](http://www.nature.com/news/2007/070730/full/448526a.html) (paid subscription required).

As Grist and *Nature* described, plants grown in high-CO2 conditions contain less nitrogen and other nutrients. From an animal’s perspective, this can be a problem because these plants have less protein and are less nutritious.

For example, researchers at Kansas State University have been [analyzing the effects of rising CO2 on ruminants](http://spuds.agron.ksu.edu/fq3.html) (animals like cattle, sheep and goats). In one study, they exposed sections of a tallgrass prairie to CO2 levels that could easily be reached later this century. Then they measured the nutrient content of the plants and found that the plants were less digestible, with lower nitrogen and protein content. The change in forage quality was bad enough that, according to the scientists’ calculations, beef cattle grazing on prairie in a high-CO2 future would not gain as much weight as today’s cattle, even if they ate as much grass. More than that, the authors pointed out that cattle tend to eat less in warm conditions. So the higher temperatures coming with global warming would mean that cattle gain even less weight.

The *Nature* article mentioned the possibility that fertilizer might offset some of the effects of CO2 on crop quality. Setting aside for a moment [the unintended ecological and health effects of fertilizer use](https://blogs.edf.org/climate411/2007/08/17/nitrogen_pollution), not to mention the expense and logistics of fertilizing large pastures, would that even work for ranchers? [A study in Colorado’s shortgrass steppe](http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T3Y-4GRH6S3-1&_user=10&_coverDate=12%2F01%2F2005&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e07fb6849a10c71473c27c0858d97813) addressed this question, and the conclusion was that no, “nitrogen fertilization did not ameliorate the negative effects of elevated CO2“.

One final thought: the consequences of decreased plant nutrition won’t be confined to domesticated animals. Scientists anticipate that many wild animals, from insects to antelopes, will feel the effects. In case we needed yet another reason to cut carbon pollution from fossil fuels, keeping food quality high is a good one.