Title: Human Impact on Ecosystems
1Human Impact on Ecosystems
2Humans in the Biosphere
- The human population is still growing, but the
earth is not, and this places increasing demands
on Earths air, water, land, and living things - Understanding how humans interact with the
biosphere is crucial to protecting these
resources - Industry technology give humans a strong
advantage in competing w/ other species for
limited resources - Human activity uses as much energy as all of
Earths other multicellular species combined - Hunting and gathering, agriculture, industry and
urban development have significantly transformed
the biosphere - Human activities can change the flow of energy in
an ecosystem and reduce the ability of ecosystems
to recycle nutrients.
3The Green Revolution
- The green revolution was introduced in the 1950s
by the government as an effort to greatly
increase the yields of rice, wheat, and other
crops - Using highly productive varieties of certain
crops - Using monoculture large fields cleared, plowed,
and planted with the same crops year after year - Relied on pesticides, fertilizers, and large
equipment to support large growing areas - Benefits increased food production
- Problems depletion of energy and water
supplies, pest species enabled to reproduce on a
vast scale, pesticides can be potentially
harmful, fertilizers can interfere with food webs
and biogeochemical cycles
4The Industrial Revolution
- The era known as the Industrial Revolution was a
period in which fundamental changes occurred in
agriculture, textile and metal manufacture,
transportation, economic policies and social
structure (1760-1850). - Dense human communities
- Human waste products
- Reduction in habitats
- Pollution
- Overuse of wildlife products
5Environmental Resources
- Environmental resources can be classified into 2
types renewable and nonrenewable - Renewable Resources can regenerate and are
therefore replaceable (trees) - Nonrenewable resources one that cannot be
replenished by natural processes (coal, oil, and
natural gas) - Renewable resources are NOT NECESSARILY
unlimited! Fresh water is renewable but can
become limited by drought or overuse. - Fossil fuels form over hundreds of millions of
years from deeply buried organic materialswhen
they are depleted, they are gone forever!!!!
6Sustainable Use
- Sustainable use is a way of using natural
resources at a rate that does not deplete them - Land resources
- Forest resources
- Ocean resources
- Air resources
- Water resources
- A sustainable system operates without causing
long-term harm to the ecological resources on
which it depends - Example alternative methods of pest control
that do not involve harmful chemicals
7Land Resources - Renewable
- Provides space for cities, etc. Important for
the soils where crops are grown. If managed
properly, soil is renewable. - Plowing removes the roots that hold soil in
placewhich increases the rate of soil erosion
(wearing away of surface soil by water wind). - In dry climate parts of the world, a combination
of farming, overgrazing, and drought has turned
once productive areas into deserts (a process
called desertification). - Prevention contour plowing (plowing across
slopes of land to reduce erosion, leaving stems
roots of previous crops to help hold soil)
8Forest Resources
- Forests are dubbed the lungs of the earth b/c
they remove CO2 and produce O2. They also store
nutrients, provide habitats and food for
organisms, limit soil erosion, and protect
freshwater supplies. - Forests can be renewable or non-renewable
depending on the type. For example, an old
growth forest is considered non-renewable because
of the amount of time it would take to replace
the forest. - Deforestation can lead to severe erosion and loss
of nutrients and habitats - Prevention harvest mature trees to promote the
growth of saplings, utilize tree farms
9Ocean Resources
- The ocean is a vast source of species and food
supply! In addition, some 75 of the earths
available oxygen is produced by ocean species. - The increased rate of commercial fishing has had
a severe impact on the worlds ocean species!
Pollution of water systems is also an increasing
concern! - Prevention limit catching of certain types of
fish prevent pollution dumping from industry
10Air Resources
- Air is used every time we breathe!
- Smog (mixture of chemicals appearing as a
gray-brown haze) in cities results from
automobile exhaust. - A pollutant is a harmful material that can enter
the biosphere through the land, air, or water! - The burning of fossil fuels is a major
contributor to the earths pollution problem and
can lead to acid rain (gases combined with water
vapor in the air and form drops of nitric and
sulfuric acid)can drift for miles before falling
as acid rain.
11Water Resources
- Although fresh water is a renewable resource, the
total supply of fresh water is limited! - Pollution threatens water in several ways
- Protections of the natural systems involved in
the water cycle are essential for maintaining
safe, fresh water sources.
12Biodiversity
- Biodiversity is the sum total of the genetically
based variety of all organisms in the biosphere - Biodiversity is one of the Earths greatest
natural resources food, industrial products,
medicines - Ecosystem diversity includes the variety of
habitats, communities, and ecological processes
in the living world - Species diversity is the number of different
species in the biosphere - Genetic diversity is the sum total of all the
different forms of genetic information carried by
all organisms living on Earth today
13Human Threats to Biodiversity
- Habitat Alteration Fragmentation
- Development often splits ecosystems into pieces
(habitat fragmentation). - Creates habitat islands.
- Fewer species can survive here and they are more
vulnerable to further disturbances or climate
changes.
14Human Threats to Biodiversity
- Demand for Wildlife Products
- Endangered species are now protected from being
hunted in the US. This is still a problem in
other parts of the world, such as Africa, South
America, and Southeast Asia.
15Human Threats to Biodiversity
- Introduced Species
- the accidental or intentional introduction of new
plants animals into an area. - invasive species -a new species able to reproduce
rapidly because their new habitat lacks the
natural population controls they face in their
old habitat. - Cane Toads in Austraila
- Kudzu in America
- African Bees in South America
16Kudzu
17Conserving Biodiversity
- Today, conservation efforts focus on protecting
entire ecosystems as well as single species - Most often, the need to protect biodiversity is
greatest in countries that are least able to do
so. These are known as hot spots immediate
danger of extinction of species as a result of
human activity - Example rainforests are found in developing
countries
18Biological Hot Spots
- In an effort to locate problem areas and set up a
list of conservation priorities, conservation
biologists identify hot spotsplaces where
significant numbers of habitats and species are
in immediate danger of extinction as a result of
human activity.
19Changing the Future
- Many biologists are now concerned about the
biological effects of 4 types of global change - The thinning, or depletion of the ozone
- Global warming
- Acid Precipitation
- Biological Magnification
20A Thinning Ozone
- Our atmosphere contains a concentration of ozone
gases called the ozone layer. Ozone molecules
consist of 3 oxygen atoms. - Function absorbs harmful UV radiation before it
reaches Earths surface (global sunscreen). - Studies suggest that the ozone has been gradually
thinning since 1975. - The problem of thinning ozone is caused by CFCs
(chlorofluorcarbons) used as propellants in
aerosol cans, to produce plastic foam, and as
coolants in a/c systems. In cold atmospheres
such as in space, CFCs allow UV to break apart
ozone molecules. - The US has joined other countries in phasing out
the use of CFCs.
21Ultraviolet Radiation
A threat to the continuation of life
Visible
Infrared (IR)
UV
Humans DNA damage Cancer Crops Productivity
decrease Ocean plants Death?
22Ultraviolet Radiation
stratospheric ozone layer
UV
destroy
CFCs refrigeration electronics foam
packaging spray propellants
1996 CFC decrease noticed 2006 stabilization?
23Size of the Antarctic Ozone Hole
North America
30
20
Antarctica
Average Area millions sq km
10
0
1979
2001
Prediction 50 years to return to 1980 size
24Global Warming
- Earths temperatures remain within a range
suitable for life because of the biospheres
natural insulating blanket the atmosphere - Carbon dioxide, methane, water vapor, and other
gases trap heat energy and maintain Earths
temperature range - The function of these gases is similar to glass
in a greenhouse they trap the heat energy of
sunlight inside Earths atmosphere. - The natural situation in which heat is retained
by this layer of greenhouse gases is called the
greenhouse effect. - These greenhouse gases allow solar energy to
penetrate the earths atmosphere, where much of
the sunlight that hits the Earths surface is
converted to heat energy and reflected back into
the atmosphere. - The same greenhouse gases do not allow the heat
to readily escape the atmosphere, but instead,
trap it inside. The Earth is heating up!
25Global Warming
- Human activities may be causing climate change by
increasing carbon dioxide concentration in the
atmosphere! - Rising atmospheric CO2 - since the Industrial
Revolution, the concentration of CO2 in the
atmosphere has increased greatly as a result of
burning fossil fuels. - Human-produced greenhouse gases include carbon
dioxide CO2 , methane CH4, nitrous oxide N2O - The predicted consequences of global warming
include - sea level rise
- increased plant primary productivity
- increased storm severity
- changes to patterns of rainfall
- changes to ocean circulation patterns
26Acid Rain
- The burning of wood and of fossil fuels,
including coal and oil, releases oxides of sulfur
and nitrogen that react with water in the
atmosphere, forming sulfuric and nitric acid,
respectively. - The acids eventually fall to Earths surface as
acid precipitation rain, snow, sleet, or fog
that has a pH of less than 5.2. - This acid precipitation lowers the pH of streams
and lakes and affects soil chemistry and nutrient
availability. - The main causes of acid rain are emissions from
ore smelters and electrical generating plants.
27Ecological Effects from Acid Rain in Lake System
- Changes begin to occur as soon as a lake starts
to lose it natural bases or alkalinity. - A large reduction in the number of plankton
invertebrates. - The rate of decomposition of organic matter
decreases - Direct effects on fishes reproductive cycles.
- A calcium deficiency in fish leads to bone
malformation. - Fish can suffocate as their gills become clogged
with aluminum hydroxide. - Songbirds are effected by eating insects
contaminated with toxic metals.
28Biomagnification
In biomagnification, there is a tendency for
pollutants to concentrate as they move from one
link in a food chain to anothertop level
carnivores suffer the most harmful effects of
biomagnification.
29Biomagnification DDT
- Dichlorodiphenyltrichloroethane (DDT)
- Used as a pesticide from 1939-late 1960s fat
soluble compound - it is not broken down by
metabolic processes in bacteria, plants, or
animals - When DDT is picked up by organisms, they do not
eliminate it from their bodies. As a result,
something unexpected happens. DDT is picked up,
concentrated, and stored by aquatic plants and
algae. - When herbivores eat those plants, they
concentrate DDT to levels ten times higher than
levels found in plants! When carnivores eat
herbivores, the toxic substance is concentrated
further in a process called biological
magnification. - The worlds production has substantially
decreased since it was banned in the West - Detected in mud of deep sea and snow ice of
Antarctica