Change in Land Use: Impacts for Global WarmingAmanda M. BarrDr. Liang YangFall 2006INTRODUCTIONGlobal warming has the potential to have a world-wide impact, and be impacted upon, in a variety of ecosystems. There is a distinct interconnectivity between changing land use, global warming, and future land use. Humans will be affected, as well as virtually all living species of animals and plants. Although research has been conducted regarding the response of various environments and species to global warming, there is much to be done. Variables that can affect environment and/or specie success include atmospheric temperature, atmospheric composition, ocean temperature, ocean composition and increased levels of ultraviolet (UV) radiation as a result of a thinning ozone layer. Naturally, as the changing earth shifts its use of land and resources, different environments will be influenced in distinct and characterized ways. The influence of and on forests, deserts, croplands, and urban environments will be the primary focus of this literature review.Clouds, ice and oceans are only a few of the components of the climate system that are difficult to make detailed climate predictions, but a consensus of scientists agree that the release of fossil fuels will prevent increasing percentages of outgoing thermal energy from permanently leaving the surface of the earth. (ALLEN 2001) In 2001, the Intergovernmental Panel on Climate Change (IPCC) found that the earth will continue to warm over the course of the next 100 years due to the imbalance of incoming solar radiation and outgoing thermal radiation. This will result in several global changes including the melting of polar ice caps, aggressive global weather patterns, sea level increases, and increasing vegetation. (IPCC 2001)FORESTSCarbon dioxide is the second leading greenhouse gas, and is directly responsible for much of the warming trends we are already seeing today. Human use of fossils fuels is directly responsible for a 31% increase in the concentration of carbon dioxide in the atmosphere since the Industrial Revolution. (Malhi 2002) This excess carbon dioxide also has ecosystem and land use consequences for forests. Today, forests are regularly cleared to make room for agricultural land. As of 2002, 45% of the carbon dioxide increase in the atmosphere has been attributed to the loss of forest cover. (Malhi 2002)Source: Y Malhi, P. Meir and S. Brown, 2002The above three graphs illustrate the carbon dioxide increase over long and short time scales. Notice the second graph shows a sharp rate of increase since the 1800’s (IndustrialRevolution). Finally, the third graph shows periodic/seasonal variation of carbon dioxide concentration, with a steady increase in the past 40 years. Approximately half of photosynthesizing reactions of the world takes place in forests. (Malhi 2002) Additionally, biomass sequestered in forest from both the vegetation and soil can account for considerable carbon storage. Thus, changes in global carbon cycles and sinks can greatly influence forest ecosystem. Since about 7000BC, human societies haveprogressively cleared forest land, resulting in large quantities of available carbon. The figure below describes the available carbon release as a function of land use change for specific countries and continents. Three major land use changes can influence the release and/or storage of carbon: permanent removal of forest land for agricultural or ranch use, urbanization, logging, and neglect of designated re-growth forest areas. (Malhi 2002)Source: Y Malhi, P. Meir and S. Brown, 2002Naturally, some areas of re-growth coupled with sound forest management techniques have succeeded. However, the net forest area is in a steady decline, resulting in a net increase in release of carbon.The overall impact that forest decline has had on the atmospheric contribution of carbon is significant. It is surprising to learn, however, the degree to which the fossil fuel contribution competes with deforestation contributions. Below is a figure that illustrates the combined carbon dioxide emissions vs. fossil fuel change and land use change.Notice that land use change only exceeded fossil fuels in the mid 1970’s. Today, however,fossil fuels account for approximately 75% of carbon dioxide emissions. Future options to mitigate the effects of forest degradation are to prevent deforestation, encourage reforestation, reducing carbon loss by changing harvesting methods that require less logging, changing in tilling practices, and increased use of altnerative fuels. (Malhi 2002) Proper land use management should encourage these objectives.DESERT ECOSYSTEMSDesert ecosystems also respond to future warm climate scenarios as predicted by the greenhouse effect. They have the potential to provide major carbon sinks in both theirsoils and vegetation. (Lioubimtseva and Adams, 2004) Specific species will of course be influenced in different ways. Although deserts have relatively low organic carbon storage per unit area, some studies suggest that deserts and semi-desert regions may be one of themost responsive to elevated levels of carbon dioxide and the resultant changes due to thegreenhouse effect. (Lioubimtseva and Adams, 2004) Deserts and semi-deserts comprise approximately 37% of the proportion of the global land surface. Some studies predict that, with a 50% increase in carbon dioxide, plant production could be enhanced as much as 70% in desert systems. Furthur, higher levels of atmospheric carbon dioxide can also decrease the influence of salinity on plant growth. (Lioubimtseva and Adams, 2004) For this reason, potential agricultural uses of land near desert areas could produce more productive crops and further enhance soil organic matter.Indirect effects of global warming are also possible in desert regions. Changing patterns of precipitation and distribution of temperatures could change current land use practices of the desert area. Global Circulation Models (GCMs) vary widely on their prediction in this area. Several GCMs predict that some desert areas will receive enhanced precipitation, while others will become even drier. (IPCC 2001) It is important to keep in mind, however, that evapotranspiration will also increase with increased temperatures, and thus offset any enhanced precipitation. Alternatively, some desert regions have anthropogenic origins such as soil erosion, relatively permanent loss in vegetation, and deterioration of