Effects of climate change on agriculture
There are numerous effects of climate change on agriculture, many of which are making it harder for agricultural activities to provide global food security. Rising temperatures and changing weather patterns often result in lower crop yields due to water scarcity caused by drought, heat waves and flooding.[5] These effects of climate change can also increase the risk of several regions suffering simultaneous crop failures. Currently this risk is regarded as rare but if these simultaneous crop failures did happen they would have significant consequences for the global food supply.[6][7] Many pests and plant diseases are also expected to either become more prevalent or to spread to new regions. The world's livestock are also expected to be affected by many of the same issues, from greater heat stress to animal feed shortfalls and the spread of parasites and vector-borne diseases.[5]: 746
For contributions of agricultural activities to climate change, see Greenhouse gas emissions from agriculture.
The increased atmospheric CO2 level from human activities (mainly burning of fossil fuels) causes a CO2 fertilisation effect. This effect offsets a small portion of the detrimental effects of climate change on agriculture. However, it comes at the expense of lower levels of essential micronutrients in the crops.[5]: 717 Furthermore, CO2 fertilisation has little effect on C4 crops like maize.[8] On the coasts, some agricultural land is expected to be lost to sea level rise, while melting glaciers could result in less irrigation water being available.[9] On the other hand, more arable land may become available as frozen land thaws. Other effects include erosion and changes in soil fertility and the length of growing seasons. Also, bacteria like Salmonella and fungi that produce mycotoxin grow faster as the climate warms. Their growth has negative effects on food safety, food loss and prices.[5]
There has been extensive research on the effects of climate change on individual crops, particularly on the four staple crops: corn (maize), rice, wheat and soybeans. These crops are responsible for around two-thirds of all calories consumed by humans (both directly and indirectly as animal feed).[10] The research investigates important uncertainties, for example future population growth, which will increase global food demand for the foreseeable future.[11] The future degree of soil erosion and groundwater depletion are further uncertainties. On the other hand, a range of improvements to agricultural yields, collectively known as the Green Revolution, has increased yields per unit of land area by between 250% and 300% since the 1960. Some of that progress will likely continue.[5]: 727
The scientific consensus is that global food security will change relatively little in the near-term. 720 million to 811 million people were undernourished in 2021, with around 200,000 people being at a catastrophic level of food insecurity.[12] Climate change is expected to add an additional 8 to 80 million people who are at risk of hunger by 2050. The estimated range depends on the intensity of future warming and the effectiveness of adaptation measures.[5]: 717 Agricultural productivity growth will likely have improved food security for hundreds of millions of people by then.[13][11] Predictions that reach further into the future (to 2100 and beyond) are rare. There is some concern about the effects on food security from more extreme weather events in future.[14][15][16] Nevertheless, at this stage there is no expectation of a widespread global famine due to climate change within the 21st century.[17][18]