A recent paper from the University of Arizona claims “Grasses across the globe may be unable to keep pace with a changing climate, threatening some of the world’s most critical food sources, according to new research by University of Arizona ecologists.”
The study compared “past rates of niche change in 236 species of plants in the grass family with projected rates of climatic change by 2070, the team led by Alice Cang and John Wiens found that the rate of future climate change may dramatically outpace the capabilities of grasses to change their niches and survive.” (Read press release here and the full paper here.)
I see two problems with the claim:
- Past rates of niche change reflected existing conditions at the time and does not prove that plants cannot adapt at a faster rate if they had to. The authors admit this deep in the paper.
- The rate of warming projected by modeling has “dramatically outpaced” reality.
This is not the first time this claim has been made. There are hundreds of papers which have studied plant productivity from the near and distant past, and also conducted experiments on plant productivity. Most show that plant productivity is enhanced by warming, especially with increasing atmospheric carbon dioxide.
Many of these papers have been reviewed and summarized by the Center for the Study of Carbon Dioxide and Global Change. (http://www.co2science.org/) That organization provides summaries and reviews of scientific papers. Here are the conclusions of their summary studies of plant productivity:
- http://www.co2science.org/subject/b/bioprodhistoric.php (Distant and historic past)
- In conclusion, in spite of claims that rising atmospheric CO2 concentrations and unprecedented global warming since the inception of the Industrial Revolution are destroying (or will destroy) the productivity of the biosphere, the terrestrial vegetative biomass of the globe as a whole continues to rise; and it appears to be doing so at a remarkable rate. As for why is this so, it may well be that the twin evils of the radical environmental movement (rising temperatures and atmospheric CO2 concentrations) are not the evils they are made out to be, but actually blessings in disguise … blessings that are fueling the biosphere!
- http://www.co2science.org/subject/b/bioproductivity.php (Recent past)
- In spite of climate-alarmist claims that the temperatures of the latter part of the 20th century and on through the present were unprecedented over the past one to two millennia (which is highly debatable) and that atmospheric CO2 concentrations were the highest they had been for several hundred millennia (which is true), as well as the fact that mankind yearly harvests and/or destroys much of the planet’s natural vegetation, the total yearly production of terrestrial vegetative biomass for the globe as a whole continues to rise, and at a remarkable rate.
- http://www.co2science.org/subject/b/bioprodfuture.php (Projection for the future)
- Throughout the course of the current century, even the severe warming predicted by current climate models will not likely be detrimental to plant growth and productivity. Rather, it will likely be a major benefit, enhancing plant growth and soil organic carbon storage, which (in addition to their own virtues) will provide a significant negative feedback to global warming as the Greening of the Earth continues!
The studies above are on plant productivity in general. More specific studies on food crops show enhanced growth with warming temperatures and increases of carbon dioxide.
A review of papers on grasslands finds “as the air’s CO2 concentration continues to increase, grassland species should respond positively by exhibiting increased rates of photosynthesis. In addition, such increases in photosynthesis will likely occur even under unfavorable growing conditions characterized by less-than-adequate soil moisture, inadequate soil nutrition, elevated air temperature, and physical stress imposed by herbivory. Thus, earth’s grassland species will likely grow ever more robustly in the future, thanks to the ever increasing atmospheric CO2 concentration produced by the burning of ever larger quantities of fossil fuels.”
A review of papers on food crops is not summarized. Individual papers show that food crops such as wheat and rice will benefit from warming and increases carbon dioxide because the latter extends the temperature range of the plants and make them more water efficient.
In my opinion, the UofA paper does nothing to advance science. It serves only to propagate alarmism. The paper ends with this sentence: “These results support our inferences from grasses that niche shifts may generally be too slow to save populations from rapid anthropogenic climate change.”
History shows that crises in food production occurred during cool periods such as “the little ice age.”
One other thing: Let’s suppose that plants cannot adapt fast enough to survive the projected warming. A solution would be to design cultivars of plants that would be more drought and heat tolerant. Oh no, GMO!
Note to readers: