Greenhouse Planet: How Rising CO2 Changes Plants and Life as We Know It

Image of Greenhouse Planet: How Rising CO2 Changes Plants and Life as We Know It
Release Date: 
October 18, 2022
Columbia University Press
Reviewed by: 

This is an exceptionally important and readable book addressing vastly underreported topics: the effect on plants of rising CO2 and the crucial importance of science for human survival.

Lewis H. Ziska’s book is about the separate effects of CO2 at different levels of atmospheric concentration and the interacting effects of CO2 and temperature change on plants. How does climate change interact with the biological necessity for healthy food? Ziska, associate professor of environmental health sciences at Columbia University, is a highly experienced and ethical agriculture scientist who writes engagingly for the public. Ziska resigned his decades-long position at the U.S. Department of Agriculture to protest interference by the Trump administration. His book is all the more timely because of the underestimated impacts and simplistic thinking about climate change over the last decades, leading to ever worsening conditions. He is clear that there is astonishingly little funding for agriculture research to even define and answer basic questions. 

He focuses on the dangerous and unexamined proposition that rising CO2 enhances plant production. Ziska writes that this idea has been uncritically accepted because it is partly true, partly due to scientific ignorance, and partly because it is exploited by denialists to promote the idea that increasing carbon emissions are good for plants. In his concluding chapters, he is forthcoming about catastrophic consequences when politics overrides science and reality.

The book is comprehensive and logically organized, starting off with chapters on the importance of plants as food, as drugs, as weeds colonizing entire ecosystems and weeds causing allergies, and a brief history of plants’ place in religion and art. The next section is an in-depth analysis of the theory that “CO2 is plant food,” a scientifically invalid theory based on Stephen Long’s 1991 paper stating that increased plant productivity correlates with increased CO2 concentration in the atmosphere.

As a prelude to his own research and his challenge to “CO2 is plant food,” he powerfully invokes science, the method of discerning what’s real by asking thorough, probing questions.  Knowledge is complex. How complicated can plants be? Plant studies involve many specialties like agronomy, aquaculture, botany, chemistry, physiology, ecology, entomology, genetics, and pathology. How will all these plant functions be affected by increasing carbon in the atmosphere? Proponents of “CO2 is plant food” do not look at any of these functions and do not ask questions.

The book is a compendium of fascinating and crucially important facts, and Ziska is persuasive about the imperative need for scientific research. Here are a few examples that will hopefully encourage reading his book.

He divides the first part of his book into three sections: How CO2 Is Good for Plant Food, The Ways It Is Bad, and the “OMG.” He asks: What do we know? What else is essential to know? and What does more CO2 mean for human existence and all of nature? Isolating the effects of CO2 alone is complex. He describes measuring CO2 concentrations at increments of 100 parts per million, from 300ppm to 700ppm which is the possible concentration by the end of this century. Experiments involve infusing CO2 into the roots of selected plants in greenhouses and in fields. 

One important question is whether there are specific varieties of the major food plants that respond to increased CO2 with increased seed production. For example, findings could result in improving food security for the billions of people who depend on rice for protein. How will these plants then interact under the real climate conditions that accompany increased CO2, such as heat, the availability of water, the unpredictability of seasons, and the reductions in plant and insect biodiversity? Does increasing CO2 also affect plant chemistry? For example, will there be chemical changes in the weed Sweet Annie, source of the most powerful anti-malarial substance?

On the bad side, more CO2 increases growth in some good food plants, but it also increases even more growth of weeds. Ziska includes in his research how CO2 concentration changes plants and their sensitivity or resistance to herbicides. Weeds exploit environmental disturbances and colonize disorders following storms, floods, earthquakes. They colonize forests, rangelands, and wetlands, and they threaten human use of the land. To provide food for billions of people, unwanted plants by the billions must be removed. Arising from WWII, weed killers proliferated, some to be used in wars such as the defoliation of Vietnam rainforests and mangroves. 

Ziska researches the effects of increasing CO2 on cultivated rice and on weedy rice. He found that more CO2 may increase herbicide resistance among the weedy rice varieties that do the most damage to crop production. The rapid increase in the number of resistant weeds is also seen in glyphosate applications. This was also found in the effect of CO2 on potassium levels in cheatgrass, increasing its flammability and also its digestibility to mule deer, their primary herbivore. 

“The worst things more CO2 could do in terms of fire would be to make it less palatable to deer and to decrease the potassium content.” With cheatgrass, fires can occur now every couple of years when before they occurred every 40 or 50 years. More CO2 also increases kudzu, one of the most rapidly invasive weeds. Why? Invasive species are kept in check principally by pest pressures, so increasing growth means that kudzu quickly moves into new areas with no pests, no enemies. All these parameters of CO2 effects  must be researched. 

And the OMG findings? As CO2 stimulates growth and yield, it diminishes nutritional quality.  The nitrogen concentrations of foliage and roots is consistently lower in plants grown at elevated levels of CO2, and nitrogen reflects something even more important: protein concentration. 

Also, additional CO2 was found to change the mineral composition of important grains. Iron and zinc are indispensable for human health. Zinc is necessary for proper immune system function, cell division, cell growth, healing wounds, carbohydrate metabolism, for the senses of smell and taste, and it enhances the action of insulin.

CO2 concentrations also led to significant declines in a range of vitamins, including the B vitamins. About 600 million people get 50% or more of their daily calories from rice, often the staple food for the poorest people. Ziska describes the incredible strides scientists have made in documenting the negative impact of more CO2 may have on plant-based nutrition. 

Other changes in plant-breeding that increase productivity show declines in the concentration of vitamins and minerals. In goldenrod, a non-bred plant, increases in CO2 show decline in the protein content. Also, if CO2 reduces the protein content of the pollen, this will affect the health of bees and other species within the food chain. This needs to be understood as “likely all animals from grasshoppers to cows will be impacted.” What is the correlation between nitrogen and CO2 as it affects protein production? CO2 produces different results in leaves, roots, flowers, seeds. It affects insect-plant interactions. 

This is a wake-up call. “All life will be affected by increases in CO2 and that merits an OMG, but the 2019 National Institute for Food and Agriculture (NIFA), the institute that supplies about a billion dollars in grants to agriculture universities in the United States, there is no mention of CO2. None. For that matter, the phrase ‘climate change’ isn’t included either, except for a few euphemisms like ‘climate uncertainty.’” Ziska is not shy about calling out pseudo-science, especially when it comes to preserving life.

Going back to the 1991 paper claiming that CO2 is good for plants which was based on Long’s only looking at leaves in his assessment of photosynthesis, “it turns out to be more complicated (shock!). As it happens plants consist of more than just leaves. . . . They also consist of seeds and fruit—and pollen, which once again provides an interesting contrast.” Ziska describes observations and experiments and questions directed at understanding the entire complexity. The world’s most important food crops are vulnerable to pollen sterility and decline in seed yield due to interacting CO2 and temperature. Study after study shows that when temperature and CO2 increase together, there may be a decline in seed yield in the major food crops. “Looking at the leaf level is not always a good predictor of what happens at the flower level; looking at flowers doesn’t tell us about root biology; root biology doesn’t necessarily tell us about what the entire plant is doing, and what the plant is doing doesn’t predict how the ecosystem might respond, and so on.”

Ziska’s writing is clear, personal, and expressive. His last section is Politics and Pleas. “We need to know more, much more. Why don’t we?” The irresponsibility of people in positions of power and influence is extreme, and Ziska is clear and direct about this. He quotes the “most over-the-top” and shameless verbiage of William Happer, a senior director at the National Security Council and an emeritus professor of Physics at Princeton: “The demonization of carbon dioxide is just like the demonization of the poor Jews under Hitler. Carbon dioxide is actually a benefit to the world, and so were the Jews.” Ziska’s response: “Uh-huh. Who knew that being against ‘CO2 is plant food’ is the same as committing genocide?”

Ziska’s last word of advice: “Vote for science.”    

Read his book.