Why does global warming affect crop yields?

Answer 1

Global warming may increase crop yields in some places, but it will seriously reduce crop yields in others.

Colder countries may be able to grow warmer climate crops. However, much of Africa will become too hot and dry for the traditional crops that people rely on for food.

If global warming continues, then even countries like Canada, which will be fruitful for a time, will then become too hot to be productive.

A: There are three things that crops need more than anything else to produce the best yields. Those three things are warmth, water, and carbon dioxide. Let us examine each of these in turn.

Warmth, obviously, is in more abundance during global warming. In many areas that are now too cold to grow crops, higher temperatures will make it possible, thus greatly increasing the acreage available for growing crops. Much of this area has never been cultivated, and therefore has not been subjected to the depletion of nutrients that traditional cropland has seen, so, with fertilizers, these soils will be more fertile than those in traditional crop-growing areas. Meanwhile, in the traditional crop-growing areas, temperatures are also going up (but, it must be noted, not as much as in colder latitudes). Temperatures will get warm earlier and cold later, extending the growing season, which means higher yields. There is, however, some concern that temperatures will get TOO warm in traditional crop-growing areas. While it is true that, beyond a certain maximum temperature (around 90oF for most crops) higher temperatures do not help crop growth and development, neither do these excessive temperatures, in and of themselves, retard crop growth and development. It is only when these excessive temperatures occur simultaneously with a lack of water that crops are harmed. (And as you will learn in the next paragraph, lack of water will not be an issue.) As long as there is plenty of water, temperatures could soar to 120oF and crops would continue to grow and develop at the fastest possible rate. Also, because temperatures get warm earlier, crops can be planted earlier to take advantage of warmer late-winter temperatures, and could be harvested before the hottest part of the year. It is even conceivable that, with a warmer spring and a warmer fall, farmers could get TWO crops each year on the same acreage. By the way, small grains like wheat, oats, barley, and rye, are often planted in the fall and harvested long before the hottest part of summer. Even if high temperatures were harmful to crops, there is no conceivable way they could harm these small grains. So, we could, if we had to, limit production of corn, soybeans, and other "summer" crops to cooler latitudes, and grow the small grains in the warmer latitudes, during the fall, winter, and spring.

Water will also be more abundant under global warming conditions. Higher temperatures will result in more evaporation of water from oceans and other bodies of water. This puts more water vapor into the atmosphere. This in turn means more rainfall. And rainfall benefits crops. There is some concern that global warming will force a shift in weather patterns, causing long-term drought in some areas that historically had plenty of rainfall. But it cannot be denied that, under global warming conditions, total precipitation across the entire planet will increase. So some traditional crop-growing areas will dry up. Fine. The soils there will have a chance to recover from centuries of overcultivation, and be ready to go when the warming trend ends. Meanwhile, the areas that will be, for the first time, receiving enough warmth and rain to grow crops will more than make up for the loss of acreage. OR we could build a system of canals to transport water from those areas that get too much rainfall to those areas that don't get enough. Expensive? Yes. But not nearly as expensive as the measures we will have to enact to stop global warming.

Carbon dioxide is to plants like oxygen is to us. Plants need it to survive, and the more of it they have, the faster they will grow. Growers of greenhouse plants often inject carbon dioxide into their greenhouses, up to 3 times the normal atmospheric concentration, to aid in growth and development, and the results are unequivocably positive. Lack of carbon dioxide has been shown, time and time again, to be the number-one limiting factor in crop yields. To my knowledge, no one has ever discovered a level of carbon dioxide that is "too high" for plants. Now, excess carbon dioxide is, supposedly, the cause of global warming. So, if global warming continues, it must be because of increased carbon dioxide. And increased carbon dioxide is good for crop yields.

However, all that said... even if global warming is occurring, even if it continues, and even if we are causing it by burning fossil fuels, there is absolutely no way that it can be bad for crops. In fact, I believe that global warming, if it continues, will be the best thing to happen to crop yields since the invention of the mechanical harvester, and will cause the amount of arable land to increase well over any level ever seen. Taking both effects into account, I suspect that potential food production will DOUBLE.

A: It is difficult to predict the future, but in 2001 the United Nations InterGovernmental Panel on Climate Change (IPPC) issued a Report: Climate Change 2001: Working Group II: Impacts, Adaptation and Vulnerability(See the link below).

Here are some of the suggested impacts:

• Climate change will affect crop yields and irrigation demands.
• Water Resources will be affected: water supply, quality and competition for water.
• Moderately warmer weather and increased CO2 in the atmosphere may help some crop growth (up 30% in the case of rice, soy and wheat), but with increased temperatures the grain yield drops 10% for every 1Ë�C rise above 26Ë�C.
• Agricultural areas may suffer erosion from increased wind and water from short term changes in weather.
• The growth of agricultural pests (weeds, insects and pathogens) under climate change is being studied with varying results. For example, higher temperatures increase the severity of rice leaf blast epidemics in cool subtropical zones, but in warm humid subtropics higher temperatures lower the severity of the epidemics.
• Farm animals are affected by warmer temperatures, influencing their performances in growth, milk and wool production, reproduction, health and well-being.
• Increased temperatures may lead to increased demand for water from agriculture and wildlife, including farm livestock. It may also lead to reduced water availability.
• Adaption costs for agriculture, including retraining farmers for new practices, as well as the provision of new irrigation may be considerable.
• The cost of basic food will rise, especially with temperature rises of more than 2.5Ë�C, as agriculture will not be able to absorb increased costs.
• "Africa is projected to experience marked reductions in yield, decreases in production, and increases in the risk of hunger as a result of climate change."