Climate Change

Global climate change has positive and negative effects on marine and terrestrial ecosystems. The cause of global climate change is said to be because carbon dioxide is being emitted through the large scale burning of oil, coal and gas, with an additional contribution coming from clearing of tropical forests and woodlands which results in wildlife life destruction. The carbon dioxide traps heat from the sun in the earth's atmosphere and prevents it from being sent back out into space. The heat that stays trapped in the atmosphere causes the global temperature to increase. Globally, average temperatures are expected to increase between 1.5 to 6.1 degrees Celsius in the next hundred years.

Climate change will have significant impacts on the global temperature such as an increase in temperature, change in weather patterns and sea-level rise. Sea-level is expected to rise 95 cm by the year 2100, with large local differences due to tides, wind and atmospheric pressure patterns, changes in ocean circulation, vertical movements of continents etc; the most likely value is in the range from 38 to 55 cm. The relative change of sea and land is the main factor: some areas may experience sea level drop in cases where land is rising faster than sea level.

Indirect factors are generally listed as the main difficulties associated with sea-level rise. These include erosion patterns and damage to coastal infrastructure, salinization of wells, sub-optimal functioning of the sewerage systems of coastal cities with resulting health impact, loss of littoral ecosystems and loss of biotic resources.

Plants grow through the well-known process of photosynthesis, utilizing the energy of sunlight to convert water from the soil and carbon dioxide from the air into sugar, starches, and cellulose. CO2 enters a plant through its leaves. Greater atmospheric concentrations tend to increase the difference in partial pressure between the air outside and inside the plant leaves, and as a result more CO2 is absorbed and converted to carbohydrates. Crop species vary in their response to CO2. Wheat, rice, and soybeans belong to a physiological class called C3 plants that respond readily to increased CO2 levels. Corn, sorghum, sugarcane, and millet are C4 plants that follow a different pathway. The latter, though more efficient photo-synthetically than C3 crops at present levels of CO2, tend to be less responsive to enriched concentrations. These effects have been demonstrated mainly in controlled environments such as growth chambers, greenhouses, and plastic enclosures.

Higher levels of atmospheric CO2 also induce plants to close the small leaf openings known as stomatas through which CO2 is absorbed and water vapor is released. Thus, under CO2 enrichment crops may use less water even while they produce more carbohydrates. This dual effect will likely improve water-use efficiency. At the same time, associated climatic effects, such as higher temperatures, changes in rainfall and soil moisture, and increased frequencies of extreme meteorological events, could either enhance or negate potentially beneficial effects of enhanced atmospheric CO2 on crops. Meteorological Events such as hurricanes and heavy storms damage trees and hence reduce productivity. Droughts disrupt crop rotation, many plants are not adapted to such environments and are therefore unable to survive hence productivity is reduced.

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For interior regions, there might be beneficial gains in agricultural production resulting from the indirect effects of a warmer climate and adequate precipitation, especially in higher latitudes across Canada and Russia. The increased carbon dioxide might also directly increase plant growth and productivity as well. In fact, this theory, known as the Carbon dioxide Fertilization Effect, has led

some scientists to controversially suggest that the Greenhouse Effect might be a blessing in disguise. Laboratory experiments have shown that increased carbon dioxide concentrations potentially promote plant growth and ecosystem productivity by increasing the rate of photosynthesis, improving nutrient uptake and use, increasing water-use efficiency and decreasing respiration, along with several other factors.

In middle and higher latitudes, global warming will extend the length of the potential growing season, allowing earlier planting of crops in the spring, earlier maturation and harvesting, and the possibility of completing two or more cropping cycles during the same season. In warmer, lower latitude regions, increased temperatures may accelerate the rate at which plants release CO2 in the process of respiration resulting in less than optimal conditions for net growth. When temperatures exceed the optimal for biological processes, crops often respond negatively with a steep drop in net growth and yield. Another important effect of high temperature is accelerated physiological development, resulting in hastened maturation and reduced yield.

Higher air temperatures will also be felt in the soil, where warmer conditions are likely to speed the natural decomposition of organic matter and to increase the rates of other soil processes that affect fertility.

An expected increase in convective rainfall caused by stronger gradients of temperature and pressure and more atmospheric moisture may result in heavier rainfall when and where it does occur. Such "extreme precipitation events" can cause increased soil erosion.

As global temperature rises, atmospheric circulation patterns are likely to change with alterations in the frequency and seasonality of precipitation and an overall increase in the rate of evaporation and precipitation. Coupled with the associated general rise in temperature, such changes in the water cycle will affect infrastructure planning, natural habitats, water availability and agricultural activity will decrease.

Marine ecosystems are likely to be affected by global climate change in many ways. Summer stratification is a normal part of the seasonal pattern of the ocean. Human induced climate change will affect ocean stratification and primary productivity which is the synthesis of organic matter from inorganic nutrients, and is the foundation of the food chain. Temperature increases will warm the surface waters beyond normal seasonal temperatures and the warm layer of the surface water will be thicker and more strongly stratified. Wind forcing and upwelling will be less able to break through the warm surface waters to bring nutrient rich water to the surface. There will therefore be reduction of available nutrients in the surface layer for the phytoplankton to utilize, hence