Chapter 6Chapter 6

Humans in the BiosphereHumans in the Biosphere

6 – 1 A Changing Landscape

• What type of human activities can affect the biosphere?

Earth as an Island• All of the organisms, including

humans that live on Earth share a limited resource base and depend on it for their long term survival

• To protect these resources we need to understand how humans interact with the biosphere

Human Activities• Since we depend on the

ecosystem for resources we must be aware that human activities can change the local and global environments

• Among human activities that affect the biosphere include

Hunting and Gathering

Agriculture

Urban Development

The Tragedy of The Commons

The tragedy of the commons is a dilemma arising from the situation in which multiple individuals, acting independently and rationally consulting their own self-interest, will ultimately deplete a shared limited resource, even when it is clear that it is not in anyone's long-term interest for this to happen. This dilemma was first described in an influential article titled "The Tragedy of the Commons," written by ecologist Garrett Hardin and first published in the journal Science in 1968.

6 – 2 Renewable and Nonrenewable Resources• How are environmental resources

classified?

• What effect does human activities have on natural resources?

Renewable resource • Can regenerate if they are alive or

be replenished if they are non-living

• A renewable resource is not necessarily unlimited

Ex.) water

Nonrenewable resource• Cannot be replenished by natural

processes

Sustainable development

• A way of using natural resources without depleting them and without causing long-term environmental harm

• Human activities can affect the quality and supply of renewable resources such as land, forests, fisheries, air, and fresh water

Land Resources• If managed properly, soil is a

renewable resource

• Soil, however can be permanently damaged if it is mismanaged

Soil erosion • The wearing away of surface soil

by water or wind

Desertification

• When once productive areas are turned into deserts

• Caused by:

• Farming

• Overgrazing

• Drought

Sustainable Solutions to guard against these practices

• Contour plowing

• Leaving stems and roots of the previous years crop in place

• Planting an unused field with rye

Forest Resources

• Provide wood• Are considered the

lungs of the earth• Store nutrients• Provide habitats• Provide food

• Moderate climate

• Limit soil erosion

• Protect freshwater supplies

• Forests are important because they

Deforestation• Loss of forests

• Can lead to severe erosion

Sustainable Solutions for Forest Management

• Harvest mature trees selectively

• Tree farms

• Tree geneticists

Fishery Resources• Fishes and other animals that live

in water are a valuable source of food for humanity

Overfishing

• Harvesting fish faster than they can be replaced by reproduction

Sustainable Solutions for Fisheries

• The US National Marine Fisheries Service uses data on fish populations to create guidelines for commercial fishing

• Aquaculture – raising aquatic animals for human consumption

Air Resources• Air is a common resource that we

use every time we breathe

• The condition of air affects peoples health

• The preservation of air quality remains a challenge to modern society

Smog

• A mixture of chemicals that occurs as a gray-brown haze in the atmosphere

Pollutant• A harmful material that can enter

the biosphere

• Many combustion processes, such as the burning of fossil fuels, releases nitrogen and sulfur compounds

• When these compounds combine with water in the atmosphere they produce nitric and sulfuric acids - which fall to the earth as acid rain

Freshwater Resources• Americans use billions of liters of

freshwater everyday• Although water is a renewable

resource, the total supply of freshwater is limited

• For this reason, protection of water supplies from pollution is a major priority

Sustainable Solutions• Protect natural systems involved

with the water cycle

Ex.) wetlands and forests

• Water treatment facilities

• Drip irrigation

Protect natural systems involved with the water cycle

Ex.) Wetlands and Forests

Water Treatment facilities

Drip irrigation

6 – 3 Biodiversity• What is the value of biodiversity?

• What are the current threats to biodiversity?

• What is the goal of conservation biology?

6 – 3 Biodiversity• Variety is the spice of life

• But variety in the biosphere gives us more than just interesting things to look at

• Human society takes place in local and global food webs and nutrient cycles

• For that reason, out well being is closely tied to the well being of a great variety of other organisms

Biodiversity• (Biological diversity) – the sum

total of the genetically based variety of all organisms in the biosphere

Types of Biodiversity• Ecosystem diversity – the variety

of habitats

• Species diversity – the variety of species

• Genetic diversity – the variety of genetic info carried by all the organisms

The Value of Biodiversity• Biodiversity is one of Earth’s

greatest natural resources • Species of many kinds have

provided us with…• Food• Industrial products• medicines

Gum Tree

Rosy Periwinkle

Threats to Biodiversity• Human activity can reduce

biodiversity by:

Altering habitats

Hunting species to extinction

Introducing toxic chemicals

Introducing foreign species

Endangered Species • A species whose population is

declining and is in danger of becoming extinct

Extinct• When a species disappears from

the biosphere

Habitat Alteration• When land is developed, natural

habitats are destroyed

Habitat fragmentation • When development split

ecosystems into pieces

Demand for Wildlife Products

• Throughout history, humans have pushed some animal species to extinction by hunting them for food or other products

• Today, endangered species are protected by laws

• Unfortunately it is difficult to enforce laws in remote wilderness areas

Pollution• Many forms of pollution can

threaten biodiversity

• One of the most serious problems occurs when toxic compounds accumulate in the tissues of organisms

Ex.) DDT

Biological magnification • When concentrations of harmful

substances increase in organisms at higher trophic levels in a food chain

Introduced species• One of the most important threats

to biodiversity today is introduced species

Invasive species • Plants and animals that live in

environments they are not native to

Zebra mussel

Leafy Spurge

Mile-a-minute

Nutria

Phragmites

Purple loosestrife

Q: Why do invasive species reproduce rapidly and quickly take over their new habitat?

A: Their new habitat lacks the predators and parasites that control their populations “back home”

Conservation• The wise management of natural

resources including the preservation of habitats and wild life

Strategies for Conservation

1. Managing of a single species

Ex.) captive breeding

Strategies for Conservation

2. Protecting entire ecosystems

Ex.) setting land aside

Conservation Challenges• Protecting resources for the future can require

people to change the way they earn their living

• The challenge is to maximize benefits while minimizing economic cost

• But an ecological perspective tells us that if we don’t take some difficult steps today, some resources may disappear and jobs that depend of that resource will be lost permanently

6 – 4 Charting a Course for the Future

• What are two types of global change of concern to biologists

6 – 4 Charting a Course for the Future

• For most of human history, environmental change was a local affair

• Today, most of Earth’s land surface has been altered by human activity

• In order to plan a sound environmental strategy for the 21st century, we need data provided by research

Ozone Depletion

Ozone layer

• Part of the atmosphere that contains a relatively high concentration of ozone gas (O3)

• The ozone layer absorbs a good deal of harmful ultraviolet or UV radiation from sunlight before it reaches the Earth’s surface

• Over exposure to UV rays causes:

• Sunburn

• Cancer

• Damage to eyes

• Decreased resistance to disease

Early evidence• Satellite images in the 1970’s first

showed the hole in the ozone layer over Antarctica

• Evidence also showed that chlorofluorocarbons or CFC’s could change the ozone layer

One Solution• Reduce the use of CFC’s

• Many CFC’s are now banned

Ex.) Montreal Protocol signed 1987

Global Climate Change• All life on Earth depends on climate

conditions such as temperature and rainfall

• That’s why many ecologists are concerned about strong evidence that Earth’s climate is changing

• Since the late nineteenth century, average atmospheric temperatures on Earth’s surface have risen about 0.6 degrees Celcius

• Since 1980 average temperatures have risen .2 and .3 degrees Celcius

• The 1990’s were the warmest decade on record

• 1998 was the warmest year since record keeping began

Global Warming• Increase in the average

temperature of the biosphere

Evidence of Global Warming• If is believed that the current warming is related

to human activities that are adding CO2 and other greenhouse gases to the atmosphere

• The burning of fossil fuels combined with cutting and burning of forests worldwide is adding carbon dioxide to the atmosphere faster than the carbon cycle removes it

• As a result, the atmosphere’s natural greenhouse effect is intensified causing the atmosphere to retain more heat

Possible Effects of Global Warming

• Computer models based on the trends seen in the data suggest that average global surface temperatures will increase by 1 to 2 degrees Celsius by the year 2050

Q: What might this mean?A:• Sea levels may rise enough to flood some

costal areas• More droughts in North America• New organisms will be able to live in places

where they once could not• Other organisms may become threatened or

extinct in areas they once thrived

The Value of a Healthy Biosphere

• Human society depends on healthy, diverse and productive ecosystems because of the environmental and economic benefits they provide

• People can help maintain the health of the biosphere without drastically changing their lifestyles if they make wise choices in the use and conservation of resources

The Future of the Biosphere

• Studies of human impact on the environment are not about predicting disaster

• You have seen how research has lead to action which is fixing the mistakes of the past

• Remember, the biosphere is strong and we humans are clever. Both humans and natural ecosystems can adapt to change of different kinds