Ecology The Human Population is disrupting chemical cycles

Ecology -The Human Population is disrupting chemical cycles throughout the biosphere -Depletion of the Atmospheric Ozone

Nutrient Enrichment Humans remove nutrients from one part of the biosphere and adding them to another The movement of nutrients from one area to another may result in nutrient depletion in one area, excesses in another, and the disruption of the natural chemical cycles of both locations Humans have also added toxic new materials to the environment All of the changes caused by humans must be considered when observing an environment

Agriculture After natural vegetation is cleared from an area, the existing reserve of nutrients in the soil is sufficient to grow crops for some time without nutrient supplementation In agricultural ecosystems, a substantial fraction of nutrients is not recycled, but it is exported from the area in the form of crop biomass Crops’ free period: When there is no need to add nutrients to the soil. It varies greatly.

Nitrogen Cycling Nitrogen is the main nutrient lost through agriculture. The nitrogen cycle is greatly effected by agriculture Plowing and the mixing of the soil both increase the decomposition rate of organic matter, releasing usable nitrogen that is then removed from the ecosystem when the crops are harvested. Industrialized synthesized fertilizer may then be used to make up for the loss of usable nitrogen Studies show that human activities have approximately doubled the Earth’s

Contamination of Aquatic Ecosystems Critical Load: the amount of added nurtient, usually nitrogen or phosphorus, that can be absorbed by plants without damaging the ecosystem integrity. This is the key problem with excess nitrogen. Nitrogenous minerals in the soil that exceed the critical load eventually leak into groundwater or run off and directly Cultural Eutrophication: Human intrusion has disrupted freshwater ecosystems Human disruption of the environment in water ecosystems leads to a massive overload of photosynthetic organisms.

Acid Rain The burning of wood and coal and other fossil fuels releases oxides of sulfur and nitrogen that react with the water in the atmosphere, forming sulfuric and nitric rain. This eventually forms into what we call acid rain. Acid precipitation lovers the p. H level of aquatic ecosystems In terrestrial ecosystems, the change in the soil p. H due to acid rain causes calcium and other nutrients to leach form the soil The entire United States has been effected by acid precipitation

Toxins in the Environment Humans release an immense variety of toxic chemicals, including thousands of synthetics previously unknown in nature, with little regard for the environment along with nutrients and water Some of the poisons are metabolized and excreted Some become more concentrated in successive trophic levels of a food web ^ This is known as Biological Magnification Many toxins cannot be degraded by microorganisms and consequently persist in the environment for years or even decades

Atmospheric Carbon Dioxide Rising Atmospheric CO 2 –The concentration of CO 2 in the air has been increasing in the air due to combustion of fossil fuels and the burning of enough quantities of wood removed by deforestation Increased productivity by vegetation is one predictable consequence of increasing CO 2 levels

F. A. C. T. S. -I How elevates CO 2 Affects Forest Ecology: The FACTS-I Experiment – Forest-Atmosphere Carbon Transfer and Storage experiment in 1995 In this experiment manipulated a single environmental factor, the concentration of CO 2, to which tracts of forest are exposed. All other factors (temperature, precipitation, wind speed, and direction) varied for both experimental plots This experiment is testing how elevated CO 2 influences tree growth, carbon concentration in souls, insect populations, soil moisture, the growth of plants in the forest understory, and other factors over a ten year period

Greenhouse Effect Much of the solar radiation that hits the earth is reflected back into space Although CO 2 and water vapor in the atmosphere are transparent to visible light, they intercept and absorb much of the reflected infrared radiation This then reflects back toward earth. This process retains solar heat. It is known as the Greenhouse Effect

Global Warming Global warming is the rise of the temperature of Earth’s atmosphere. The worst thing that could happen regarding global warming is that it reaches the poles. This would result in a rise in sea levels. Global warming would also cause abnormal distribution of precipitation

Depletion of the Atmospheric Ozone The ozone layer protects earth from UV radiation, preventing much of it from reaching organisms in the biosphere Observations show that over time, the Ozone Layer has gradually been deteriorating This destruction can be directly linked to the accumulation of chlorofluorocarbons CFC’s- used in refrigeration, pesticides, aerosol cans, and in certain manufacturing processes. The Chlorine in these products reacts with the ozone, reducing it to molecular O 2. Consequences of Ozone Depletion: Skin cancer, cataracts, unpredictable effects of crops and natural communities, especially phytoplankton

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