In this article we will discuss about the climate changes in technology based agriculture.
The weather is the one factor with which people are familiar that profoundly affects the growth of plants. Everyone knows that to grow plants need sunlight and rain and that both are quite variable around the world.
Weather-defined as short-term (less than a few weeks) variations in the atmosphere-affects the year-to-year yield of crops. The longer-term variations that comprise climate determine the geographic conditions where crops can grow at all.
Short-term variations caused by the weather that affect crop yields occur even in the modern era of technology-based agriculture:
1. Moisture stress is caused by insufficient, too much, or ill-timed rainfall. Plants often have precise water requirements, in terms of both amount and time. If these requirements are not met, yields and/or quality suffer.
2. Temperature stress occurs commonly when the temperature is either too low or too high for optimal growth. A short period of stress can severely depress growth later. Sudden cold snaps injure plants because they do not have enough time to become acclimatized to the cold weather. Moisture stress often accompanies high-temperature stress.
3. Natural disasters occur, such as cyclones, hurricanes, and hailstorms. Although these are more common in such Asian countries as Sri Lanka and Bangladesh, they can also cause severe damage in developed countries by physically harming crops and the soil that supports them.
Yields of many crops vary considerably year to year in many locations. The probability of a staple crop yielding the same year after year can be quite low. Over much of North Africa and the Middle East, for example, yields fall significantly below expectations in half of the crop years. A similar situation exists in the countries of the former Soviet Union.
Complex statistical models, proposed to explain crop yield variability in other situations, show that in many cases climate is the major factor. When things go well (the yield trend is a smooth upward or constant curve), it is because the weather is unusually benign. Different regions of the world are affected differently by climatic variation.
Some of these effects are as follows:
1. Temperate Regions:
The north and south temperate regions produce 75% of the world’s wheat and maize. The most prominent climatic factors affecting yield are moisture stress and temperature extremes. Wheat and soybeans are more drought resistant than maize.
2. Humid Tropics:
Ranging from fertile valleys to jungles to floodplains, these regions are heterogeneous and show great variability of year-to-year yields. The major determining factor here is rainfall. There are pronounced wet and dry seasons, with the wet season often being in the form of a monsoon, with very heavy, sustained rainfall.
But the unpredictability of the intensity of the monsoon, combined with poor water-holding capacity of soils and high rate of evaporation, lead to unstable water supplies for agriculture. In addition, torrential rains on lowland areas, such as river deltas, inundate the crops.
3. Semiarid Tropics:
These regions (for example, the Sahel south of the Sahara, in Africa, and much of India) have a long history of periodic crop failures and resulting famines. The major problem here is rainfall or, more precisely, the lack of it.
Most of the rain falls in a two-to five-month period (April-October in the Northern Hemisphere, October-April in the Southern Hemisphere), when temperatures are at their yearly peak. This leads to extensive evaporation and less water availability.
The sequence of events in growing a crop here is exquisitely sensitive to the annual rainfall cycle. Farmers time the growth of the crop to coincide with the maximum available water. If this period is very short, so is the growing season. In these areas farmers often plant two crops: one that will yield some food if the rains fail to come, and one that will yield abundantly if they do come.
This relationship of agricultural practices to climate is an ancient one. Every culture has its deities and stories relating the cycle of the seasons to food production. Human activities can substantially alter the global environment and thereby negatively impact our ability to grow crops.
The public is now keenly aware of the effects of pollution on society, and generally considers industry to be the main source of pollutants. However, in the past 30 years agriculture has also become an important environmental polluter.
The book Silent Spring, written by biologist and science writer Rachel Carson in 1962, first awakened public opinion to unintended effects that pesticides can have on the environment.
Although organochlorine insecticides then used have since been phased out, they did considerable damage both in developed and developing countries. These pesticides prevented crop damage by insects, but in Asian rice paddies pesticides kill fish, shrimp, and crabs, important sources of protein for poor people.
Burning vegetation to clear forestland or to encourage grass growth in savannahs is an important source of global air pollution. When vegetation burns, some nutrients (potassium, phosphate, and calcium) return to the soil, but nitrogen, sulphur, and carbon disappear into the atmosphere as gases. In addition, burning releases particulates into the air.
The sulphur dioxide and nitrogen oxides, in combination with those same two gases released from the burning of fossil fuels, help acidify soil via acid rain. In Europe and North America acid rain is killing some forests, and in China it has shrunk rice and wheat harvests, with most of the damage occurring at the beginning of the rainy season.
Burning biomass (vegetation) annually releases about 1 to 2 billion tons of carbon into the atmosphere as carbon dioxide. This amount adds to the 2 billion tons of carbon released by burning fossil fuels. Carbon dioxide is a greenhouse gas, which means it contributes to warming of Earth.
Anaerobic decay of organic matter in marshes produces methane, another greenhouse gas. Rice paddies are an important source of methane worldwide, and increased rice cultivation in Southeast Asia has much increased methane production.
These gases are responsible for the greenhouse effect, which warms the surface of Earth. If greenhouse gases were completely absent from the atmosphere, Earth’s surface would be a chilly -18°C. Their presence maintains Earth at a higher temperature, making human life possible.
The temperature of the planet has been rising slowly- about 0.3 to 0.6°C during the past 100 years, and is expected to rise another 0.4 degrees C by 2020. A2°-C rise by the end of the 21st century is possible.
Although this slow global warming could be a natural phenomenon, most experts believe it is the direct consequence of the rise in emissions of greenhouse gases. A likely result of global warming is greater variability in the weather and more extreme weather conditions.
Rainfall may be more variable, making crop production even more variable than it is now. Other gases, especially nitrous oxides and the now banned chlorofluorocarbons formerly used as refrigerator coolant, destroy the protective ozone layer in the upper atmosphere. Ozone shields Earth from destructive ultraviolet solar radiation.
Closer to Earth, nitrous oxides emitted from cars or released by burning vegetation help create photochemical smog, of which ozone is a significant component. Even at quite low concentrations, ozone inhibits plant growth and recent experiments suggest that the ozone levels around cities and in some rural areas are now high enough to impair crop yields.
Scientists may need to take this into account when breeding new crop varieties.