The fertilization effect or carbon fertilization effect is the increased rate of photosynthesis in plants that results from increased levels of carbon dioxide in the atmosphere. The effect varies depending on the plant species, the temperature, and the availability of water and nutrients. However, enhanced rates of photosynthesis in plants due to fertilization are only partially transferred to enhanced plant growth and any hypothesized CO2 fertilization response is unlikely to significantly reduce the human-made increases in atmospheric CO2 concentration over the next century. From a quarter to half of Earth's vegetated lands has shown significant greening over the last 35 years largely due to rising levels of atmospheric carbon dioxide. Studies led by Trevor Keenan from the Department of Energy's Lawrence Berkeley National Laboratory show that, from 2002 to 2014, plants appear to have gone into overdrive, starting to pull more carbon dioxide out of the air than they have done before. The result was that the rate at which carbon dioxide accumulates in the atmosphere did not increase during this time period, although previously, it had grown considerably in concert with growing greenhouse gas emissions. Keenan concluded “Unfortunately, this increase is nowhere near enough to stop climate change.” Theory predicts the tropics to have the largest uptake due to the fertilization effect, but this has not been observed. The amount of uptake from fertilization also depends on how forests respond to climate change, and if they are protected from deforestation.
Free-Air CO2 Enrichment (FACE) experiments
The ORNL conducted FACE experiments where levels were increased above ambient levels in forest stands. These experiments showed:
Increased root production stimulated by increased, resulting in more soil carbon.
FACE experiments have been criticized as not being representative of the entire globe. These experiments were not meant to be extrapolated globally. Similar experiments are being conducted in other regions such as in the Amazon rainforest in Brazil.
Empirical evidence shows that increasing levels of result in lower concentrations of many minerals in plants tissues. Doubling levels results in an 8% decline, on average, in the concentration of minerals. Declines in magnesium, calcium, potassium, iron, zinc and other minerals in crops can worsen the quality of human nutrition. Researchers report that the levels expected in the second half of this century will likely reduce the levels of zinc, iron, and protein in wheat, rice, peas, and soybeans. Some two billion people live in countries where citizens receive more than 60 percent of their zinc or iron from these types of crops. Deficiencies of these nutrients already cause an estimated loss of 63 million life-years annually.
