Ecosystem ChangesEcosystem Changes

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

Natural changes in the physical environment of an Natural changes in the physical environment of an ecosystem happen all the time. Ex. volcanic ecosystem happen all the time. Ex. volcanic eruption forms a new island eruption forms a new island -- sets off a process of sets off a process of colonization and ecosystem development.colonization and ecosystem development.

Ecosystems change through the process of Ecosystems change through the process of successionsuccession..

Succession on newly formed habitat is called Succession on newly formed habitat is called primary successionprimary succession. .

It can take 1000+ years from sand dune to forest.It can take 1000+ years from sand dune to forest.No remaining organisms or soilNo remaining organisms or soilExamples, lava flow, sand dune, glacier retreatExamples, lava flow, sand dune, glacier retreat

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

Succession in a previously inhabited area is Succession in a previously inhabited area is called called secondary successionsecondary succession. .

Much shorter period of time Much shorter period of time -- 100 years or so.100 years or so.Some organisms and soil remainSome organisms and soil remainexamples are fires, abandoned fieldsexamples are fires, abandoned fields

During succession, one set of species replaces During succession, one set of species replaces another until a community is reached that is selfanother until a community is reached that is self--sustaining and persists over time sustaining and persists over time -- climax climax communitycommunity

Primary succession examplePrimary succession example

exposed rocks

lichens and mosses

small herbs and shrubs

heath mat

jack pine, spruce, aspen

white spruce, climax

Secondary Succession ExampleSecondary Succession Exampleannual weeds

perennial weeds and grasses

shrubs

young pine forest

mature oak-hickory forest

Is there only one climax Is there only one climax community possible per location?community possible per location?

Originally, it was thought Originally, it was thought ----> YES> YESNow, we thinkNow, we think----> No> NoThere are many possible climax communities in There are many possible climax communities in an area an area -- it depends upon original pioneer species, it depends upon original pioneer species, climate and interaction among later species. climate and interaction among later species. No two succession sequences are exactly alike but No two succession sequences are exactly alike but will tend toward similar communities in similar will tend toward similar communities in similar physical environments.physical environments.

HUMAN IMPACT ON THE HUMAN IMPACT ON THE ENVIRONMENTENVIRONMENT

Global ChangeGlobal Change

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

ACID RAINACID RAIN

Burning high sulfur coal creates acid precipitation.Burning high sulfur coal creates acid precipitation.Sulfur introduced into air combines with water vapor Sulfur introduced into air combines with water vapor to form Hto form H22SOSO44; precipitation carries acid back to ; precipitation carries acid back to earth.earth.Acid rainAcid rain is any precipitation with higher than is any precipitation with higher than normal acidity. Acid rain is caused by the interaction normal acidity. Acid rain is caused by the interaction between pollutants and water in the atmosphere.between pollutants and water in the atmosphere.

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

In No. Europedecrease in species diversitytrees in Black Forest is dying

In North America - eastern U.S. and Canadian forests also damaged

Acid Rain breaks down limestone buildings and sculpture

Average pH of precipitation in U.S. in 1989 was 5.6 Average pH of precipitation in U.S. in 1989 was 5.6 except in New England where it is 3.6 (100x higher!!)except in New England where it is 3.6 (100x higher!!)Possible solutionsPossible solutions

capture emission with “scrubbers”; very expensivecapture emission with “scrubbers”; very expensiveClean Air Act of 1990 helped in USClean Air Act of 1990 helped in US

Polluters and recipients of pollution are far apart on Polluters and recipients of pollution are far apart on the issue the issue -- no one wants to pay for “another’s no one wants to pay for “another’s problem”problem”

tragedy of the commonstragedy of the commons

OZONE LAYEROZONE LAYER

The ozone layer of the upper atmosphere (11The ozone layer of the upper atmosphere (11--16 16 miles above sea level) absorbs 99% of the UV miles above sea level) absorbs 99% of the UV radiation that reaches the earth (good ozone)radiation that reaches the earth (good ozone)Ozone also forms in the lower atmosphere Ozone also forms in the lower atmosphere when emissions from cars and factories react when emissions from cars and factories react with sunlight where the ozone then becomes a with sunlight where the ozone then becomes a corrosive reactive substance (bad ozone)corrosive reactive substance (bad ozone)

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

Ozone DepletionOzone 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 betweenthe earlier years and later years in the Arctic region.

CFC’s stick to frozen water vapor and catalyze the conversion of O3 → O2

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

Many marine algae are very sensitive to UV Many marine algae are very sensitive to UV levelslevels∴∴OO22 production production ↓↓Ozone levels in lower atmosphere Ozone levels in lower atmosphere ↑↑ irritates irritates and damages lungs & eyes, suppresses the and damages lungs & eyes, suppresses the immune system and aggravates respiratory and immune system and aggravates respiratory and heart diseasesheart diseases

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

GLOBAL WARMINGGLOBAL WARMING

The The Greenhouse EffectGreenhouse Effect::Much of the light that hits the surface of the earth and is Much of the light that hits the surface of the earth and is reflected as heat is trapped by gases in the upper reflected as heat is trapped by gases in the upper atmosphere (water vapor, methane carbon dioxide & atmosphere (water vapor, methane carbon dioxide & nitrous oxide).nitrous oxide).This results in an earth that is habitableThis results in an earth that is habitable

Global WarmingGlobal Warming::Humans are increasing the concentrations of greenhouse Humans are increasing the concentrations of greenhouse gases such as carbon dioxide with the burning of cheap gases such as carbon dioxide with the burning of cheap fossil fuels.fossil fuels.This is resulting in a higher surface temperatureThis is resulting in a higher surface temperature

Greenhouse EffectGreenhouse Effect

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

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

Many types of pollution involve toxic or Many types of pollution involve toxic or carcinogenic chemicals carcinogenic chemicals -- ex. mercury, pesticides, ex. mercury, pesticides, oil (Exxon Valdez leaked 11 M gallons of oil in oil (Exxon Valdez leaked 11 M gallons of oil in 1989 1989 -- effects still being felt)effects still being felt)

Three nonThree non--renewable resources in particular danger renewable resources in particular danger are top soil, ground water and species.are top soil, ground water and species.

TOP SOILTOP SOILSoil has three layersSoil has three layers-- the top has the most the top has the most organic material (a.k.a.organic material (a.k.a.humus)humus)

Originally the prairie hadOriginally the prairie hadtop soil to a depth of >1Mtop soil to a depth of >1M

Now it is much lessNow it is much less

GROUND WATERGROUND WATER

Ground water = water trapped beneath soil Ground water = water trapped beneath soil (much of it in porous rock) in reservoirs called (much of it in porous rock) in reservoirs called aquifersaquifers

Much of this water is polluted by run off from Much of this water is polluted by run off from fertilizers, chemical wastes, etc..fertilizers, chemical wastes, etc..It is being wasted on lawns, washing cars, It is being wasted on lawns, washing cars, fountains, etc..fountains, etc..Once pollution enters ground water there is no Once pollution enters ground water there is no effective way to remove it.effective way to remove it.

EXTINCTION OF SPECIESEXTINCTION OF SPECIES

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

ExtinctionExtinction

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

Solving Environmental ProblemsSolving Environmental Problems

One of the most encouraging developments in the One of the most encouraging developments in the 1990’s has been a world wide effort to reduce 1990’s has been a world wide effort to reduce pollution. pollution.

International agreements to stop CFC productionInternational agreements to stop CFC productionRestriction of DDT, dioxin and asbestos in the U.S.Restriction of DDT, dioxin and asbestos in the U.S.emissions of SOemissions of SO22, CO and soot , CO and soot ↓↓ 30%30%Number of secondary sewage treatment plants Number of secondary sewage treatment plants ↑↑ 72%72%Businesses spending approximately 100B/yr on pollution Businesses spending approximately 100B/yr on pollution controlscontrols

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

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