Agricultural impacts of climate change

Given that crops and livestock thrive in a relatively narrow set of environmental parameters, it makes sense to explore how climate change will affect agricultural productivity. Factors considered include the impacts of rising temperatures, increased production of carbon dioxide and other greenhouse gases, water supply fluctuations, soil quality variations, sea-level increases, and the introduction of new pests, diseases, and weeds, which could hurt agricultural output. These

One of the ways agriculture contributes to greenhouse gases is by shipping produce hundreds of miles to markets.

changes can have different impacts depending on the geographic scale of analysis. Climatic change will have different manifestations at local, regional, and global scales. Impacts will also vary according to the agricultural products under consideration. Some plant or animal species may be very resilient to environmental changes. Others may not adapt so well to change.

Temperature increases will affect crop and livestock production in various ways. A warming climate will extend the frost-free growing season at higher latitudes. Regions that are too cold to support commercial agriculture in northern Canada, Alaska, Scandinavia, and Russia, may become viable agricultural areas if temperatures increase. On the other hand, temperature-sensitive crops may no longer be commercially viable in regions that become too hot or dry. Also, rising temperatures could increase the heat stress on livestock.

Climatic change models predict that regional temperature variations may alter precipitation patterns and the supply of water for agriculture. Areas that are currently too dry may receive more moisture in the future. Areas that are productive now without irrigation may suffer as temperatures increase, because of increased plant evapo-transpiration. Farmers will have to find ways to offset the rising temperatures and corresponding moisture loss if they are to survive. Furthermore, many meteorologists suggest that weather events such as thunderstorms, tornados, and hurricanes may become more intense and occur with greater frequency. This may bring more rain to some regions. On the other hand, severe storms cause strong winds and flooding, which could cause large-scale crop damage.

Many regions of the world, such as the Indian Subcontinent, the Andes region of South America, Kazakhstan, California, and the American High Plains, rely on melt water from glaciers and heavy winter snows to feed streams and rivers that provide water for irrigation. These high altitude water sources have traditionally been viewed as renewable resources that can be depended upon to provide moisture during the growing season and are then replenished by snow falls during the frigid winters. However, rising temperatures have caused glaciers to shrink or disappear and have been linked to reduced snow pack at high altitudes.

A related problem is that many of the most productive rivers to fuel hydroelectricity are fed from the melt water of high altitude glaciers and snow pack. The Yangtze River in China is important for agriculture, and with the Three Gorges hydroelectric power plant, it is also an important energy producer. However, the Yangtze River, like the Colorado River in the United States and the Ganges River in India, is replenished by melt water from glaciers and snowmelt. This shows the complex impacts of rising temperatures that will reduce water for agriculture, but also produce a renewable form of energy to offset carbon dioxide production from fossil fuels. Melting glaciers may also increase sea levels, which could jeopardize agriculture by flooding and accelerated soil erosion in many low-lying areas around the world.

Global warming is caused by increased concentrations of carbon dioxide, nitrous oxides, methane, and other gases produced by the combustion of fossil fuels. The impact of having more carbon dioxide in the atmosphere is difficult to gauge with certainty. Plants consume carbon dioxide in the production of oxygen through photosynthesis. Theoretically, increased levels of carbon dioxide could spur plant growth because increased atmospheric concentrations of carbon dioxide mean that there is more available for plants to use during photosynthesis. In addition, there is a synergistic relationship between carbon dioxide and water uptake. Plants are more efficient users of water as ambient concentrations of carbon dioxide increase.

Unfortunately, there are many factors that could offset the potential productivity gains to agriculture from increased carbon dioxide concentrations. The conditions that increase the growth of commercial crops also increase the growth of traditional weeds and could accelerate the growth of new invasive plant species. Also, increased temperatures will prompt the growth of plant diseases and insects. In order to reduce the impact of pests and pathogens, farmers will have to apply more pesticides, herbicides, and other chemicals, many of which are manufactured from petrochemicals.

Soil dynamics will also be affected by changing temperature regimes. Rising temperatures will increase the rate at which organic material decomposes and possibly decrease the level of moisture in soils. This will lower soil productivity, thus prompting the increased use of fertilizers. This might be mitigated, though, by the growing presence of nitrogen oxides that are also increasing as a result of fossil fuel combustion. Increased temperatures might also accelerate soil erosion in agricultural areas, rising temperatures increase the severity of thunderstorms. Without appropriate adaptation by producers, soil erosion could accelerate as the increased flow and force of water droplets dislodge soil. This is a problem because soil erosion is itself a cause of carbon dioxide release into the atmosphere.

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