biology - chp 6 - humans in the biosphere - powerpoint
TRANSCRIPT
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
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
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