A new metric called “suitable plant growing days” helps address an argument often made by climate skeptics: since carbon dioxide promotes plant growth – especially at middle and high latitudes – anthropogenic carbon dioxide emissions will increase agricultural yields and carbon sequestration across the world’s forests. The relationship is not so simple, however. Other factors influenced by climate change (e.g., temperature, water availability, solar radiation) strongly affect plant growth and survival as well. The interactions between all these simultaneously changing climate variables make it challenging to predict how plants will ultimately fare in a rapidly changing world.
New research by Mora and colleagues in PLoS Biology sheds light on the issue by combining the key variables affecting plant growth into the new metric, “suitable plant growing days.” The metric assesses the number of days per year that temperature, soil moisture, and solar radiation fall within thresholds for plant growth across different biomes. The authors compared the number of suitable plant growing days per year between the periods 1996-2005 and 2091-2100 (as predicted from multiple climate models across three greenhouse gas emissions scenarios). Using the “business as usual” emissions scenario, they found that areas in Russia, China, and Canada will gain suitable plant growing days as climate change progresses, but that the rest of the world will lose growing days. In the most extreme case, some tropical areas could lose up to 200 suitable plant growing days per year by the end of the 21st century. The authors predict that such shifts in plant growth could severely impact 2.1 billion of the poorest people on the planet as plant-related goods and services decline. Using scenarios in which greenhouse gas emissions are curbed over time, the authors show that the impacts will likely be less severe. This research highlights the importance of reducing emissions soon so that the most vulnerable human populations will not be disproportionately affected by climate change.
Mora, C., IR Caldwell, JM Caldwell, MR Fisher, BM Genco, SW Running (2015) Suitable days for plant growth disappear under projected climate change: potential human and biotic vulnerability. PLoS Biology, 13, e1002167.