This is a follow up to my post debunking the “CO2 is life” talking point. Whereas the general flaw in logic was previously examined and the broad assertion that “more CO2 is good” was exploded, here the specific question- whether anthropogenic CO2 emissions will be a boon to the biosphere- is weighed.
Image courtesy of flickr user A guy with A camera used under Creative Commons
Are Business As Usual CO2 emissions good for “Life”? The short answer is an emphatic no. While there will be some initial benefits to certain crops in certain areas due to increased levels of CO2 and warmer temperatures, even these isolated benefits are negated beyond a doubling of CO2 and 3C of warming. The claim that increasing CO2 will be a benefit to the biosphere ignores three very obvious problems- the climatic change that accompanies such an increase; the lack of science convincingly linking increased CO2 to tangible net benefits for crops in the real world; the devastating impact ocean acidification will have on marine life and ecosystems.
The global increase in temperatures and resulting alteration of climatic norms under an unchecked emissions scenario are discussed at length elsewhere. Those that make the case that CO2 will be good for the planet as a rule fundamentally reject the scientific basis of anthropogenic driven warming. As such, discussing the alteration of climate and its effect on the biosphere becomes counterproductive when taking on the claim that CO2 is “plant food”. Therefore I will ignore this issue and focus instead on CO2 effects on crops and ocean acidification. The relevant arguments can be found in the IPCC AR4 and CCSP reports linked to below for those interested.
Impact on crops:
The simple “more CO2 means better crops” line of reasoning that is often expressed as “CO2 is plant food” ignores the evidence that CO2 may not provide net benefits to crop production. The IPCC AR4 and the U.S. Climate Change Science Program reports show that on the balance, increased CO2 will negatively impact crop production while boosting undesired plant growth among weeds and pests. Even a cursory glance at the recent literature demonstrates that the “more CO2 is good for crops” axiom is false:
- Photosynthesis, productivity and yield of maize are not affected by open-air elevation of CO2 concentration in the absence of drought (Leakey et al. 2005)
- Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentrations (Long et al. 2006)
- Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2 (Mohan et al. 2006)
- Crop Models, CO2, and Climate Change (Ewert et al. 2007)
- Crop Models, CO2, and Climate Change – Response (Long et al. 2007)
- Anthropogenic increase in carbon dioxide compromises plant defense against invasive insects (Zavala et al. 2008)
This alone renders the “CO2=life” argument moot. Ocean acidification is pushing an already stressed group of ecosystems to their breaking points. Unchecked emissions will alter the pH balance of the oceans by an amount and speed unknown for a million years or more. The effect this would have on oceanic ecosystems is almost unimaginable:
- Anthropogenic carbon and ocean pH (Caldeira and Wickett 2003)
- Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms (Orr et al. 2005)
- The Dangers of Ocean Acidification (Doney 2006)
- Coral Reefs Under Rapid Climate Change and Ocean Acidification (Hoegh-Guldberg et al. 2007)
- Corals in deep-water: will the unseen hand of ocean acidification destroy cold-water ecosystems? (Turley et al. 2007)
- Impacts of ocean acidification on marine fauna and ecosystem processes (Fabry et al. 2008)
- OCEANS: Carbon Emissions and Acidification (Zeebe et al. 2008)