Understanding Earth: Basics and Impact of Human Activities on Ecosphere

1. Introduction to the Earth Basic Terminology and Concepts Spring 2012 , Lecture 1

2. Ecosphere • That part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere

3. Atmosphere • The gaseous layer which surrounds the earth, and which is held by gravitational attraction. It consists of layers, the bottom ones of which are: • Thermosphere > 80 km • Mesopause • Mesosphere 45 - 80 km • Stratopause • Stratosphere 12 - 45 km • Tropopause • Troposphere 0 -12 km

4. Hydrosphere • Earth's water, in any physical state – • Gaseous • Liquid • Solid

5. Lithosphere • The outermost part of the solid earth, consisting of the entire crust and the upper mantle, from the surface to a depth of about 70 kilometers (km) • It is stronger and mechanically more rigid than the asthenosphere (70 - 250 km), which lies under it

6. Interior of the Earth • Crust – • Continental (0-40 km, to a maximum of 100km) • Oceanic (0-10 km) • Mantle – • Upper (bottom of crust to 700 km, and includes the transition zone (350 to 700 km) • Lower (700 - 2900 km) • Core – • Outer (2900 - 4980 km - liquid iron-nickel) • Inner (4980 - 6370 km - solid)

7. Biosphere • Interface layer between earth's crust, atmosphere, and hydrosphere where life is found • Includes the total ecosystem of the earth

8. Ecosystem • Community of interacting organisms, of all species • Includes interactions of this community with the chemical and physical systems of earth

9. Human Activities • Interact with the natural world, causing changes in the ecosystem • Changes vary in magnitude and temporal scale

10. Environmental Issues • Changes in the ecosphere caused by: • Natural processes • Human activities • Often cause change • Affect the rate at which change occurs • Or both

11. Changes By Other Species • Humans are not the only species to cause environmental change • Cyanobacteria, the first organisms capable of photosynthesis, gradually changed the atmosphere of earth from one without oxygen to one with the present 21% oxygen content

12. So What Makes Humans Different? • Humans are the first species to be aware of their influence • Humans assume, to some extent, responsibility for wise management of the planet • Humans affect change at rates unprecedented in the geological record

13. Technology Improvements • During the last fifty years • Have greatly contributed to our awareness of environmental change • Especially contributing to our knowledge of global scale processes • Greatly enhanced out knowledge of the temporal scale of global change

14. Examples of Technological Change • Satellite observations • Computational power • Rapid communication (Internet)

15. Changes to the Ecosphere • Many examples of modification of ecospheric components have been described • Representative examples of these modifications are shown on the following slides

16. Atmospheric Modifications • Depletion of ozone (O3) in the ozone layer (stratosphere) which affects UV light absorption • Ozone “hole” • Leads to increased rates of skin cancer • Acid deposition – introduction of pollutant gasses into the atmosphere leads to the formation of “acid rain”

17. Atmospheric Modifications cont. • Modification of the climate system by the introduction of “greenhouse” gases • Major gases are carbon dioxide, freons, methane, nitrous oxide • Are leading to a warmer earth, and will increase number and severity of major storms • May affect short and medium term climate, and may modify the areas in which food can be grown • May create climate refugees

18. Hydrological Modifications • Diagram shows a local example of the hydrological cycle

19. Hydrological Cycle Modifications • Withdrawal of water • Pollution of water • Impoundment of water (dams) • Modifications in erosion and depositional rates • Silting of rivers and estuaries • Increased erosion below dams • Changes in form of precipitation – rain rather than snow

20. Biosphere Modifications • Mobilization and redistribution of chemical elements • Most important carbon (C), nitrogen (N), and oxygen (O) • Results in enrichment and depletion of various parts of the system, leading to problems like red tide, depletion of soil productivty, etc.

21. Biosphere Modifications cont. • Human activities change natural environment • Often results in changes in species distribution, especially in loss of biological diversity (biodiversity) • Rapid expansion of urban and suburban areas decreases available habitat • Deforestation • Expansion of farming into marginal environments • Land use that is insensitive to long term changes • Salinization

22. Results of Environmental Change • Species reduction • Mass mortality - a large number of individuals die, which may lead to a new equilibrium distribution, with a smaller number of individuals of the species in question, or the original equilibrium may be approximately restored, to precatastrophe levels • Extinction - A complete elimination of a species. Extinction can and does occur naturally - Man's activities have increased the rate of extinction

23. Natural Events • Natural events often lead to mass mortality in many species - extinction may occur in severely geographically restricted species • Examples: • Earthquakes • Volcanoes • Tsunamis • Hurricanes • Small meteorite impacts

24. Large Scale Extinction • Large meteorite impacts can result in mass extinctions • Example: Cretaceous-Tertiary event that wiped dinosaurs, and many other species, from the face of the earth • Large scale nuclear war would probably have the same effect

25. Environmental Action • Awareness of environmental change does not always translate to actions favorable to the stabilization of the ecosystem • Why?

26. Political Problems • Politicians make most policy decisions, yet relatively few politicians have any training in science or technology • Some overcome this by relying on science/technology advisors • Political considerations may cause them to rely more heavily on political or economic advisories, whose perspective is usually focused on a much smaller time scale

27. Economic Gain • Short term economic gain is a powerful motive • Example: Drilling for oil in the Arctic Wildlife Preserve will provide profit, and will very temporarily stave off the decline in oil production • This may make the final decrease in petroleum even more difficult for humans, since we will have built more automobiles, power plants, etc. • It will also create immense difficulties for many Arctic species

28. Sources of Pollution • Pollution may occur from a variety of sources • Generally we can divide pollution sources into two types: • Point sources – pollution emanating from a single source, such as a power plant smokestack • Non-point sources – pollution derived from a variety of sources, such as smog from automobile exhaust

29. Scope of Environmental Problems • Environmental problems are generally split into one of three groups, with the possibility of overlap between groups • Local – effluent introduced into a stream from an industrial plant • Regional – acid rain in the northeastern U.S., extending into Canada • Global – Greenhouse gas warming of the planet