Download Ch 6 Humans in the Biosphere

Chapter 6
Humans 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 selfinterest, 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 nonliving
• 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
• Forests are important because they
• Provide wood
• Are considered
the lungs of the
earth
• Store nutrients
• Provide habitats
• Provide food
• Moderate climate
• Limit soil erosion
• Protect
freshwater
supplies
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