Environmental impacts of climate change: Agriculture

By Matt Burdett, March 2018

On this page, we look at the impact of climate change on agriculture, including crop yields, limits of cultivation, and soil erosion.

  • Anti-Atlas Mountains, Morocco: Agriculture in this arid region survives within a complex and sensitive hydrological balance. The dew on the ground in the morning is an important source of liquid water for grass crops. Even limited climate change could have significant impacts.

What is agriculture?

Agriculture is the process of growing food and other products from plants and animals. Climate change is closely linked to agriculture, not least because changes in land use from natural forest to commercial agriculture are part of the causes of enhanced greenhouse gas emissions. It is also linked because agricultural productivity is likely to decrease in the future due to climate change. Decreased productivity will have an impact on food security as well as agricultural-related economies, as shown in the diagram below.

  • The main links between climate and agriculture. The width of the red lines reflects the amount of research conducted on the issue. Source: IPCC, 2014 (page 490).

Crop yields

The yield of a crop refers to the total amount of production. In general crop yields are expected to decrease for most of the current staple crops. Staple crops are the main crops grown such as rice and maize (corn). The IPCC (2014) research suggests that there has already been a decrease in the yield of four of the world’s most important crops.

  • Summary of estimates of the impact of recent climate trends on yields for four major crops. Source: IPCC, 2014 (page 492).

This doesn’t mean the total yield has actually gone down. In fact, the world is producing more food than ever before, because of better agricultural techniques and an extension of the amount of land under cultivation. But, if the techniques weren’t changed and no new land was used for farming, the IPCC summary suggests that yields would have gone down due to climate change.

The reduction in yield is predicted to continue in most parts of the world, and especially for tropical regions, as shown on the graph below. Tropical regions (between the Tropic of Cancer and the Tropic of Capricorn) are already towards the upper end of the growing temperatures for the crops shown, so these regions will struggle to keep growing crops if temperatures rise further. But temperate regions (those with mild temperatures, such as the plains of North America, much of Europe and large parts of China) might see a small increase in yields because warmer temperatures could help faster growth. Even so, a warming of above 4℃ would be too much for these crops to grow well.

  • Percentage simulated yield change as a function of local temperature change for three major crops and for temperate and tropical regions.Source: IPCC, 2014 (page 498).

The yield changes are likely to keep reducing the longer the climate continues to warm up. The graph below shows the percentage of researchers’ projections that suggest yield changes due to climate change. For the period 2010-2029, there are roughly the same number of projections suggesting that yields will go up as go down. But for the period 2090-2109, most projections suggest a significant drop in yield.

  • Summary of projected changes in crop yields, due to climate change over the 21st century. Source: IPCC, 2014 (page 504).

One counter-argument is that the increase in carbon in the atmosphere will mean that there is more carbon for plants to absorb and use for growth. It has been suggested that crops such as sugarcane could get a growth boost from the increased concentration of carbon in the atmosphere. However, the reduced availability of water and suitable temperatures is likely to have a bigger impact on overall yields.

Limits of cultivation

‘Limits of cultivation’ refers to the extent of the area that can be successfully farmed. The map below shows the approximate area that is currently suitable for growing arable crops. White areas are generally too dry, too hot or too cold for commercial-scale agriculture. Note: pastoral farming (raising cattle and other animals) can occur on a small scale in many areas that are coloured white on the map.

  • The suitability of land for growing crops. Source: Ramankutty, Foley, Norman and McSweeney, 2001.

With an increase in temperatures, some areas that can currently be farmed will be too hot or dry for agriculture. This problem is already occurring in areas such as the Sahel in Africa which is experiencing desertification. However, some areas that are currently too cold or dry for agriculture might become available, such as parts of Russia and Canada.

The suitability of an area for growing crops varies significantly on a local scale – one part of a small country might remain suitable while another might change completely. It also depends on the crop. The IPCC (2014) found many examples of studies suggesting changes for specific crops and areas, including the following:

  • Negative yield impacts of climate trends for perennial trees, including apples in eastern Washington and cherries in California
  • Reductions in suitability for grapevine are expected in most of the wine-producing regions in Europe, USA and Australia, although it could be a benefit in Portugal and British Columbia in Canada
  • Sugarcane and coffee are expected to migrate toward more favorable zones in the south of Brazil
  • Suitability for coffee crops in Costa Rica, Nicaragua, and El Salvador will be reduced by more than 40%
  • Suitability for potato crops is expected to increase in very high latitudes and high tropical attitudes toward 2100

The IPCC’s most important conclusion is that “global arable area is projected to increase from 2007 to 2050…Countries at northern latitudes and under the current constraint of low temperature may increase cultivated area…[but] the generally lower nutrient quality of soils

and the lack of necessary infrastructure required to convert virgin land into productive arable land make estimates of cropping area increases highly uncertain” (IPCC, 2014).

Soil erosion

As with the limits of cultivation, the impact of climate change on soil erosion is highly debatable. The table below outlines some of the arguments.

Soil erosion will increase

Soil erosion will decrease

Temperature increase

With higher temperatures, soils could dry out and be eroded by wind.

Rainfall decrease

With less rainfall overall, soil will be less likely to be eroded by water.

Extreme weather event increase

With more storms, sudden flooding may erode soil quickly.

More intensive land use

If less land is suitable for farming (or more food is required), poor agricultural practices might lead to greater soil erosion.

Greater investment

With more profit to be made from farming, farmers can invest in better techniques to maximise yields while protecting soils.

The IPCC recognises this lack of consensus in the research so far. They state:

“In summary, there is limited evidence and low agreement that anthropogenic climate change has made a significant contribution to soil erosion, sediment loads, and landslides. The available records are limited in space and time, and evidence suggests that, in most cases, the impacts of land use and land cover changes are more significant than those of climate change.” (IPCC, 2014)


Sources

IPCC, 2014. Climate Change 2014: Impacts, Adaptation, and Vulnerability – IPCC Fifth Assessment Report. https://www.ipcc.ch/report/ar5/wg2/

Ramankutty, Foley, Norman and McSweeney, 2001. The global distribution of cultivable lands: current patterns and sensitivity to possible climate change. Global Ecology and Biogeography. https://nelson.wisc.edu/sage/data-and-models/atlas/maps.php?datasetid=19&includerelatedlinks=1&dataset=19


Environmental impacts of climate change: Agriculture: Learning activities

Questions

  1. What is meant by ‘agriculture’? [1]
  2. Define ‘yield’. [1]
  3. Describe the likely impact of climate change on the yield of one crop for both tropical and temperate regions. [4]
  4. Describe the current global distribution of areas suitable for agriculture. [3]
  5. Explain why there is disagreement over whether the total area under cultivation will increase or decrease in the future. [4]
  6. Give three pieces of evidence that climate change will be harmful to agriculture, and two pieces that suggest it will be beneficial. [5]
  7. Describe the role of climate in the erosion of soil. [3]
  8. Explain why the IPCC is unable to give a definitive prediction on the future of soil erosion due to climate change. [2]

Other tasks

Use this page to compile a spider diagram of the impacts of climate change on agriculture. Colour code each part to identify positive and negative changes.


© Matthew Burdett, 2018. All rights reserved.

All secondary material on this site is clearly referenced and may be subject to copyright restrictions by the original authors. All original material on this page is subject to copyright.

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