No ecosystems are completely isolated although the physical boundaries are not always obvious.

Transcription

1 Ecosystem Changes

2 No ecosystems are completely isolated although the physical boundaries are not always obvious. Natural changes in the physical environment of an ecosystem happen all the time. Ex. volcanic eruption forms a new island - sets off a process of colonization and ecosystem development.

3 Ecosystems change through the process of succession. Succession on newly formed habitat is called primary succession. It can take years from sand dune to forest. No remaining organisms or soil Examples, lava flow, sand dune, glacier retreat

4 Small, fast growing plants move in first - pioneer organisms,, such as moss, lichens. These species are r-selected r organisms. These do not persist because their pioneering efforts make the area more hospitable for other organisms to invade. This process continues with each group of inhabitants paving the way for a new group to better compete in the environment.

5 Succession in a previously inhabited area is called secondary succession. Much shorter period of time years or so. Some organisms and soil remain examples are fires, abandoned fields During succession, one set of species replaces another until a community is reached that is self- sustaining and persists over time - climax community

6 Primary succession example exposed rocks lichens and mosses small herbs and shrubs heath mat jack pine, spruce, aspen white spruce, climax

7 Secondary Succession Example annual weeds perennial weeds and grasses shrubs young pine forest mature oak-hickory forest

8 Is there only one climax community possible per location? Originally, it was thought --> > YES Now, we think-- --> > No There are many possible climax communities in an area - it depends upon original pioneer species, climate and interaction among later species. No two succession sequences are exactly alike but will tend toward similar communities in similar physical environments.

9 HUMAN IMPACT ON THE ENVIRONMENT

10 Global Change The Earth faces unprecedented environmental problems ranging from global changes in the atmosphere to loss of topsoil. Human-induced environmental changes that affect ecosystems worldwide are referred to as global change.

11 ACID RAIN Burning high sulfur coal creates acid precipitation. Sulfur introduced into air combines with water vapor to form H 2 SO 4 ; precipitation carries acid back to earth. Acid rain is any precipitation with higher than normal acidity. Acid rain is caused by the interaction between pollutants and water in the atmosphere.

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13 High smoke stacks are supposed to release gases high into the atmosphere where wind will dilute and disperse them In the 1970 s, scientists began to report that these stacks were not eliminating the problem - only shifting it.

14 In No. Europe decrease in species diversity trees in Black Forest is dying In North America - eastern U.S. and Canadian forests also damaged

15 Acid Rain breaks down limestone buildings and sculpture

16 Average ph of precipitation in U.S. in 1989 was 5.6 except in New England where it is 3.6 (100x higher!!) Possible solutions capture emission with scrubbers ; very expensive Clean Air Act of 1990 helped in US Polluters and recipients of pollution are far apart on the issue - no one wants to pay for another s problem tragedy of the commons

17 OZONE LAYER The ozone layer of the upper atmosphere ( miles above sea level) absorbs 99% of the UV radiation that reaches the earth (good ozone) Ozone also forms in the lower atmosphere when emissions from cars and factories react with sunlight where the ozone then becomes a corrosive reactive substance (bad ozone)

18 In the past, CFCs, an ideal heat exchanger, were used as coolants in air conditioners and propellants in aerosol containers In 1985, it was noticed that the ozone layer over Antarctica had decreased 30% over 10 years - satellite images revealed a hole Destruction of the ozone layer is caused by chlorofluorocarbons (CFCs) and several other kinds of chemicals.

19 Ozone Depletion High ozone values are yellow-red in color, while low total ozone values are blue-purple in color. Note the distinct differences in ozone between the earlier years and later years in the Arctic region.

20 CFC s stick to frozen water vapor and catalyze the conversion of O 3 O 2

21 One chlorine atom can destroy 100,000 ozone molecules! As ozone levels,, amount of UV radiation leading to an increase in skin cancer rates, cataracts and malignant melanomas. Every 1% in ozone levels a 6% in skin cancer rates Ozone depletion affects crops such as soybeans, rice, corn

22 Many marine algae are very sensitive to UV levels O 2 production Ozone levels in lower atmosphere irritates and damages lungs & eyes, suppresses the immune system and aggravates respiratory and heart diseases

23 In 1996, 93 nations agreed to stop production of CFCs but those already in atmosphere can remain for the next century! The good news is that CFC levels should have begun to decrease in 1998 and should be close to normal by 2045

24 GLOBAL WARMING The Greenhouse Effect: Much of the light that hits the surface of the earth and is reflected as heat is trapped by gases in the upper atmosphere (water vapor, methane carbon dioxide & nitrous oxide). This results in an earth that is habitable Global Warming: Humans are increasing the concentrations of greenhouse gases such as carbon dioxide with the burning of cheap fossil fuels. This is resulting in a higher surface temperature

25 Greenhouse Effect

26 Temperature records of the last 50 years support this fear that temperatures are

27 Ecosystem Damage Two serious environmental problems are a)pollution b)destruction of non-replaceable resources. Unlike other organisms, the human population has the capacity to increase the carrying capacity of the Earth. Since the Industrial Revolution, people have thought that the environment could absorb unlimited pollution.

28 Many types of pollution involve toxic or carcinogenic chemicals - ex. mercury, pesticides, oil (Exxon Valdez leaked 11 M gallons of oil in effects still being felt)

29 Three non-renewable resources in particular danger are top soil, ground water and species. TOP SOIL Soil has three layers- the top has the most organic material (a.k.a. humus) Originally the prairie had top soil to a depth of >1M Now it is much less

30 GROUND WATER Ground water = water trapped beneath soil (much of it in porous rock) in reservoirs called aquifers Much of this water is polluted by run off from fertilizers, chemical wastes, etc.. It is being wasted on lawns, washing cars, fountains, etc.. Once pollution enters ground water there is no effective way to remove it.

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32 EXTINCTION OF SPECIES During the last 50 years, 50% of the world s tropical rain forests have been destroyed. As they disappear, so do their inhabitants - the most species diverse biome on the earth It is estimated that 1M species (20% of world total) will become extinct during the next 50 years.

33 Extinction

34 In addition to the problems of pollution and consumption, a more fundamental problem is the rapid growth in the human population.the number of people the Earth can support is unknown. World population now over 6B Expected to double every 40 years (or less)

35 Solving Environmental Problems One of the most encouraging developments in the 1990 s has been a world wide effort to reduce pollution. International agreements to stop CFC production Restriction of DDT, dioxin and asbestos in the U.S. emissions of SO 2, CO and soot 30% Number of secondary sewage treatment plants 72% Businesses spending approximately 100B/yr on pollution controls

36 In our economy, pollution can be profitable because the environmental damage caused by pollution and/or health consequences are not usually not factored into the price of products. There are two ways to factor the costs of environmental damage into the prices of goods and services. One way is to require pollution devices. The other is to tax products or services that create pollution.

37 Environmental problems must be documented and understood before they can be solved. There are five components to solving environmental problems: assessment, risk analysis, public education, political action and follow-through.