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.Page 1For 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 ledsome 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 primary productivity in the ocean will decrease and in turn a reduction in resources such as fisheries. Page 2Coral reefs are projected to be among the most sensitive ecosystems to long-term climate change.Corals are especially sensitive to elevated sea surface temperatures.When physiologically stressed, the critical balance that maintains their symbiotic relationship is lost. The coral may lose some or more of their algae, a major source of nutrition and colour.
In this state corals appear white and are referred to as “bleached.” In some species, tissue growth is halted, skeletal accretion is stopped, and sexual reproduction is suspended. Corals survive if the stress is brief, but will die if prolonged.However, even a sublethal stress may make corals highly susceptible to infection by a variety of opportunistic pathogens. Disease outbreaks may result in significant coral mortality. Once mortality occurs, the coral’s soft tissue becomes a food source for scavengers, making the increasingly bare skeleton a feasible site of attachment for rapidly growing seaweeds and other opportunistic organisms.Coral bleaching is most often associated with a significant rise in sea surface temperatures.
Water temperatures of even one degree Celsius above normal summer maxima lasting for at least two or three days appear to provide a potentially useful predictor of consequent bleaching. Stress-related bleaching can also be induced if corals are subjected to a reduction of marine salinity, intense solar radiation, exposure to the air, sedimentation, or xenobiotics ( chemical contaminant). Often, these conditions are at least an indirect consequence of extremes in weather (such as hurricanes and typhoons) which may be proceeded by or occur concurrently with elevated sea surface temperatures. As a consequence, multiple factors may act in concert to cause bleaching.The geographic ranges of many aquatic and wetland species are determined by temperature. Average global surface temperatures are projected to increase by 1.
5 to 5.8oC by 2100 (Houghton et al., 2001). Projected increases in mean temperature in the United State are expected to greatly disrupt present patterns of plant and animal distributions in freshwater ecosystems and coastal wetlands.
For example, cold-water fish like trout and salmon are projected disappear from large portions of their current geographic range in the continental United States, when warming causes water temperature to exceed their thermal tolerance limits. Species that are isolated in habitats near thermal tolerance limits (like fish in Great Plains streams) or that occupy rare and vulnerable habitats (like alpine wetlands) may become extinct. In contrast, many fish species that prefer warmer water, such as largemouth bass and carp, will potentially expand their ranges in the United States and Canada as surface waters warm.
The productivity of inland freshwater and coastal wetland ecosystems also will be significantly altered by increases in water temperatures. Warmer waters are naturally more productive, but the particular species that flourish may be undesirable or even harmful. For example, the blooms of “nuisance” algae that occur in many lakes during warm, nutrient-rich periods can be expected to increase in frequency in the future. Large fish predators that require cool water may be lost from smaller lakes as surface water temperatures warm, and this may indirectly cause more blooms of nuisance algae, which can reduce water quality and pose potential health problems.
Overall, these conclusions indicate climate change is a significant threat to the species composition and function of aquatic ecosystems. However, critical uncertainties exist regarding the manner in which specific species and whole ecosystems will respond to climate change. Indeed, as climate change alters ecosystem productivity and species composition, many unforeseen ecological changes are expected.(Words: 1576)BibliographyWilliam P. CunninghamPrinciples of Environmental ScienceMary Ann CunninghamFakhir A. Bazzaz Eric D.
Fajer Plant Life in a CO2 Rich WorldAmy Mathews-AmesTurning up the heat: How Global Warming ThreatensEwann A. BerntsonLife in the SeaWebsites:www.google.comwww.yahoo.com