Biosphere Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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The term biosphere refers to the totality of life on earth and its interdependency on abiotic environmental factors. It encompasses the interactions between the atmosphere, hydrosphere, and lithosphere to support the entirety of earth’s organism through climate (temperature and precipitation), soil formation, hydrology (surface water, ground water, and soil moisture storage), solar energy input (variation in intensity and daily and seasonal accumulation with latitude), and the cycling of energy and nutrients through food webs. The biosphere is the highest level of the ecological hierarchy.

The lowest level of the ecological hierarchy focuses on individual species, with a single individual of a species at the lowest level of classification, and moving upward to a population of that species (the total number of individuals of a species in a given area) and metapopulations (the total number of individuals of a species across the total number of disjunctly distributed populations). Above the species level of classification is the community, which is concerned with the number of species co-occurring in a given location. Emphasis is placed strictly upon the species that are present and the nature of their competitive or mutualistic interactions in creating stable or unstable species compositions.

Above the community level, the ecosystem level is concerned with both the specific community composition in addition to environmental factors of nutrient and energy input as well as the cycling of these nutrients through food webs. At this level, both biotic and abiotic factors are considered to be components. At broader spatial scales, the abiotic inputs are grouped according to climatic patterns and their support of terrestrial ecosystems whose vegetation have similar physiognomic structure, giving the biome level of classification. For example, the tropical rainforest biome is characterized by high biomass and broadleaf evergreen trees forming multiple canopy layers, although the actual species composition and nutrient cycling specifics (i.e., ecosystems) will differ between the tropics of the various continents. Above the biome level is the globally inclusive classification of the biosphere, in which the interconnectedness of global climatic systems forms a principal analytical focus.

Human-Biosphere Interaction

Environmental concerns at the biosphere level focus on human-environment interactions, especially as these interactions contribute to global climate change and mass extinction of species. Ecologists consider the contemporary period of history, especially after the mid-20th century, to be unique in the history of the planet, in that human activity is altering the environment on a global scale. Furthermore, environmental management efforts are being targeted at the biosphere level as well.

Current extinction rates of known species exceed the background extinction rate by 40 times, but could be as high as 400 times the background rate based on estimates of total species. For this reason, many biologists consider these extinctions to be the beginning of a major extinction event. Ecologists have identified habitat loss as being the primary cause of these extinctions, as extractive activities (forest clearing for timber and agriculture, urban sprawl), with the introduction of nonnative species (either by direct human introduction or accidentally through transportation networks), pollution, and direct exploitation of species contributing greatly to these extinction rates. Regions of the world with highly specialized species and endemics are particularly at risk of extinctions, and identified as “biodiversity hotspots.” Due to high rates of endemism, many islands environments and Mediterranean shrubland ecosystems have been identified as biodiversity hotspots.

Global climate change is also a human-driven aspect of environmental change that affects the entire biosphere. Although scientists debated for years whether observed warming trends were normal climatic variations or the result of interglacial warming as opposed to being anthropogenically driven, by 2001 the persistence of increasing carbon dioxide levels in the atmosphere, in conjunction with results from analyzing the dissolved gas content in ice core samples taken from Antarctica and Greenland, have settled the debate in favor of human causes for the phenomenon. The data from the ice cores provide a record of environmental change extending back 900,000 years, and indicate that the rate of carbon dioxide accumulation since the beginning of the Industrial Revolution has been at an unprecedented high. Carbon dioxide concentrations in the atmosphere currently have reached their highest levels during this 900,000 year period, and temperatures are expected to rapidly follow. The polar regions have been warming more rapidly than models have predicted, causing many arctic species to be threatened with extinction.

If climatic conditions change more rapidly than species can adapt or disperse, then climate change could have severely adverse effects on the entire biosphere. The solutions require coordinated political action between international governments, but multilateral cooperation has proven difficult to achieve. Industrialized nations invariably consume the greatest amount of the worlds’ resources, especially fossil fuels that produce greenhouse gases, while many of the world’s developing nations do not, but view increased consumption of fossil fuels as being necessary for economic development.

For example, the newly industrializing countries of south and east Asia, in conjunction with their high populations and rates of growth, are expected to consume more fossil fuels in the near future. Political tensions have thus arisen around perceived inequalities in both consumption and economic impacts to emissions reductions. The Kyoto Protocols, an international agreement setting goals for reductions of greenhouse gas emissions, became international law in March of 2005, despite the United States and Australian delegations not participating.

Habitat loss tends to occur on a more local scale, but is greatly affected by social, political, and economic linkages in the global economy. The articulation of precapitalist modes of production with market economies tends to increase the amount of cultivated land required to meet a household’s needs, as well as exacerbate gender and age differences within the household mode of production. Developing countries rely heavily on primary production of agricultural and timber products, driving deforestation and often putting various social groups into conflict.

Bibliography:

Raymond Bryant and Sinead Bailey, Third World Political Ecology (Routledge, 1997);
Robert W. Cristopherson, Geosystems (Pearson Prentice Hall, 2006);
Glen MacDonald, Biogeography: Space, Time and Life (John Wiley & Sons, 2003);
Tom McKnight and Darrel Hess, Physical Geography (Pearson Prentice Hall, 2005).