Chapter 23Chapter 23

Humans and the EnvironmentHumans and the Environment

The Biodiversity CrisisThe Biodiversity Crisis

A Global ConnectionA Global Connection Convection cell- patterns of rising and falling Convection cell- patterns of rising and falling

airair Groups of convection cells form the system of Groups of convection cells form the system of

global air circulation that helps determine global air circulation that helps determine climateclimate

UpwellingUpwelling In the southern Pacific Ocean, the usual pattern of In the southern Pacific Ocean, the usual pattern of

convection cells creates a wind that blows from east convection cells creates a wind that blows from east to west and pushes warm surface water from South to west and pushes warm surface water from South America toward Australia.America toward Australia.

Along the South American coast, cold water rises Along the South American coast, cold water rises from deeper in the ocean and replaces the warm from deeper in the ocean and replaces the warm water.water.

This rising current is called an upwelling and it brings This rising current is called an upwelling and it brings with it organic material and nutrients that support an with it organic material and nutrients that support an abundance of plankton. abundance of plankton.

The plankton in turn supports an abundance of fish.The plankton in turn supports an abundance of fish.

El NinoEl Nino

The Peruvian economy along with sea birds depends The Peruvian economy along with sea birds depends on normal atmospheric conditions.on normal atmospheric conditions.

But sometimes, usually in December, the normal east-But sometimes, usually in December, the normal east-to-west winds do not form over the Pacific Ocean.to-west winds do not form over the Pacific Ocean.

Instead, winds push warm water eastwards toward the Instead, winds push warm water eastwards toward the coast of South America.coast of South America.

When these conditions occur, the warm surface water When these conditions occur, the warm surface water cuts off the upwelling of nutrients.cuts off the upwelling of nutrients.

The event is called El Nino.The event is called El Nino.

Consequences of El NinoConsequences of El Nino

The fish populations decline and Peruvian anchovy The fish populations decline and Peruvian anchovy exports decrease because of the halted upwelling.exports decrease because of the halted upwelling.

Fewer anchovies mean fewer birds and reduced Fewer anchovies mean fewer birds and reduced guano population.guano population.

Peruvians need guano for fertilizer.Peruvians need guano for fertilizer. Northeastern Australia can suffer summer drought Northeastern Australia can suffer summer drought

leading to reduced grain production there.leading to reduced grain production there. The southeastern United States gets higher rainfall in The southeastern United States gets higher rainfall in

El Nino years, boosting agriculture while also El Nino years, boosting agriculture while also decreasing forest fires.decreasing forest fires.

Declining OzoneDeclining Ozone Ozone is a naturally occurring gas in the upper Ozone is a naturally occurring gas in the upper

atmosphere that is vital to life on Earth.atmosphere that is vital to life on Earth. Ozone protects life from deadly ultraviolet rays.Ozone protects life from deadly ultraviolet rays. Humans if exposed to UV light can suffer skin cancer Humans if exposed to UV light can suffer skin cancer

and cataracts.and cataracts. Several kinds of human-made chemicals are Several kinds of human-made chemicals are

diminishing the ozone shield.diminishing the ozone shield. A major chemical that destroys the ozone is A major chemical that destroys the ozone is

chlorofluorocarbons or CFC’s.chlorofluorocarbons or CFC’s. CFC’s are used in coolants in fridges, air conditioners CFC’s are used in coolants in fridges, air conditioners

and in aerosol cans.and in aerosol cans.

Consequences of Ozone DepletionConsequences of Ozone Depletion

Due to the ozone depletion, UV rays are Due to the ozone depletion, UV rays are negatively affected life on Earth.negatively affected life on Earth.

Plants and algae are also damaged by UV rays.Plants and algae are also damaged by UV rays. The rise in skin cancer indicates the ozone The rise in skin cancer indicates the ozone

layer is still thinning.layer is still thinning. A global agreement has been reached that has A global agreement has been reached that has

cut CFC’s by 75%.cut CFC’s by 75%. Hopefully, the ozone will recover within 50-Hopefully, the ozone will recover within 50-

100 years.100 years.

Increasing Carbon DioxideIncreasing Carbon Dioxide

Carbon dioxide or COCarbon dioxide or CO22, is a naturally occurring gas , is a naturally occurring gas

that is the raw material of photosynthesis and a that is the raw material of photosynthesis and a byproduct of respiration.byproduct of respiration.

It is released when fossil fuels are burned.It is released when fossil fuels are burned. This includes, natural gas, coal and petroleum.This includes, natural gas, coal and petroleum. Around the middle of the 19Around the middle of the 19thth century, humans began century, humans began

to use fossil fuels more frequently.to use fossil fuels more frequently. Carbon dioxide levels and global temperatures have Carbon dioxide levels and global temperatures have

risen as a result of the increased use of fossil fuels.risen as a result of the increased use of fossil fuels.

Effects of Rising COEffects of Rising CO22 Levels Levels

There is a correlation or cause and effect There is a correlation or cause and effect relationship exists between global relationship exists between global temperatures and carbon dioxide levels.temperatures and carbon dioxide levels.

As carbon dioxide levels increase due to As carbon dioxide levels increase due to increased use of fossil fuels, global increased use of fossil fuels, global temperatures will rise causing drastic changes temperatures will rise causing drastic changes to our environment.to our environment.

Future Population GrowthFuture Population Growth

The human population is currently just above The human population is currently just above 6 billion and growing at a rate of about 90 6 billion and growing at a rate of about 90 million per year. million per year.

The United Nations estimates that by the year The United Nations estimates that by the year 2050 the world’s population could be more 2050 the world’s population could be more than double.than double.

How would the doubling of the human How would the doubling of the human population affect the environment?population affect the environment?

The Biodiversity CrisisThe Biodiversity Crisis

Biodiversity- the variety of organisms in a Biodiversity- the variety of organisms in a given area; can be measured different waysgiven area; can be measured different ways

Evenness- the number of individuals Evenness- the number of individuals belonging to particular speciesbelonging to particular species

Genetic diversity- amount of genetic variationGenetic diversity- amount of genetic variation Genetic diversity is an important measure of Genetic diversity is an important measure of

biodiversitybiodiversity Species richness is the number of different Species richness is the number of different

types of species.types of species.

Measuring Earth’s BiodiversityMeasuring Earth’s Biodiversity

Biologists estimate that there are at least 10 Biologists estimate that there are at least 10 million species on Earth and possibly as much million species on Earth and possibly as much as 30 million.as 30 million.

Mammals are actually a small portion of the Mammals are actually a small portion of the Earth’s biodiversity.Earth’s biodiversity.

Most species are insects, plants and Most species are insects, plants and crustaceans.crustaceans.

Reducing BiodiversityReducing Biodiversity Biologists estimate that up to 20% of existing species Biologists estimate that up to 20% of existing species

may become extinct by the year 2030.may become extinct by the year 2030. There have been 5 major extinctions in the past and There have been 5 major extinctions in the past and

the 6the 6thth is currently happening. is currently happening. The 6The 6thth extinction is different in that it is being caused extinction is different in that it is being caused

by humans instead of natural causes.by humans instead of natural causes. The greatest threat to biodiversity is destruction of The greatest threat to biodiversity is destruction of

habitats.habitats. Since the discovery of agriculture 10,000 years ago, Since the discovery of agriculture 10,000 years ago,

more than ½ of the world’s tropical rainforests have more than ½ of the world’s tropical rainforests have been destroyed.been destroyed.

Rainforests contain the most biodiversity so their Rainforests contain the most biodiversity so their destruction is especially damaging to the world.destruction is especially damaging to the world.

Ways to Save BiodiversityWays to Save Biodiversity Many countries that have tropical rainforests Many countries that have tropical rainforests

are some of the economically poorest nations are some of the economically poorest nations on Earth.on Earth.

In a process called debt-for-nature swap, richer In a process called debt-for-nature swap, richer countries or private conservation organizations countries or private conservation organizations pay off some of the debts of a developing pay off some of the debts of a developing country in exchange for the country to protect country in exchange for the country to protect their biodiversity.their biodiversity.

This could be setting up a preserve, launching This could be setting up a preserve, launching educational programs, or promoting educational programs, or promoting ecotourism.ecotourism.

Importance of BiodiversityImportance of Biodiversity

Utilitarian value- thinking of economic Utilitarian value- thinking of economic benefits that biodiversity provides humansbenefits that biodiversity provides humans

Some species are valuable as sources of Some species are valuable as sources of medicines.medicines.

Nonutilitarian value- life-forms have value Nonutilitarian value- life-forms have value simply because they exist apart from any simply because they exist apart from any human uses.human uses.

Many people have both reasons to preserve Many people have both reasons to preserve biodiversity.biodiversity.

Essential QuestionsEssential Questions Why is the upwelling on the coast of Peru Why is the upwelling on the coast of Peru

important to that country?important to that country? Describe the consequences of El Nino?Describe the consequences of El Nino? How have CFC’s affected the atmosphere? How have CFC’s affected the atmosphere?

How might this change affect humans?How might this change affect humans? Describe some possible effect of a continued Describe some possible effect of a continued

increase in the human population.increase in the human population. Explain how species richness and evenness Explain how species richness and evenness

differ.differ. What is genetic diversity?What is genetic diversity?