Human Impact on the Environment
(including succession)
•Changes in complexity
•Effects of intensive food production
•Effects of increased energy production
•Pollution
Changes in complexity
Ecosystems change naturally over time.
The change is gradual, repeatable and may take
years or centuries.
These processes are known as succession.
•Autogenic (primary and secondary)
•Allogenic (climax disturbed)
•Degradative (heterotrophic)
Autogenic Succession
Changes in ecosystem species composition is brought
about by the biological processes of the organisms
themselves.
Primary succession
Takes place on ground where no soil has formed
and no organisms have been present before
Secondary Succession
Takes place on previously occupied ground where
soil is present
Primary succession
Primary succession
e.g bare rock, concrete, sand dunes
•First colonisers (pioneer species) include lichens followed
by mosses as the lichens break down surface.
•Decaying plant matter and rock pieces create early soil
layer which annual plant seeds can germinate in
•Further decaying material creates enough soil for grasses
and small shrubs to grow in.
•Many years sees soil deep enough to support trees of the
climax community like pines and oak.
•Climax communities are relatively stable, show many food
chains and show high biodiversity.
couch grass
sea buckthorn
marram grass
sycamore
Secondary Succession
•Existing area with soil is colonised by plants like a bare
field, forests destroyed by fire.
•Soil usually has organic matter.
•Pioneer species are often annual plants.
•The process is much quicker than primary succession.
•All communities make it less favourable for themselves
and more favourable for other species until the climax
community.
Allogenic Succession
Is secondary succession in an area that has
a climax community established but it is disturbed
by climate change, forest fire etc.
Degradative (Heterotrophic) Succession
Are the changes that take place when an organism dies
and decomposes. A similar sequence of organisms will be
seen and does not involve plants.
Bacteria and fungi, insects including flies and then beetles
(eggs and larvae), spiders that eat the insects.
Used by forensic scientists to judge decomposition
Succession progression
•show an increase in the complexity of food webs.
•show an increase in the biodiversity.
•show an increase in habitats and niches.
•show an increase in stability
•show an increase in productivity
Human influences on succession
• Monoculture
• Eutrophication (algal bloom)
• Toxic pollution
• Habitat destruction
All these activities will reduce the complexity
in ecosystems and will have a detrimental
overall effect on the ecosystem.
Intensive food production (monoculture)
Growing of one or two species over large areas of land
Mainly to produce food or raw material
Effects soil condition.
Effects field size.
Effects habitats and shelter
Use of pesticides and chemical fertilisers on these
monocultures further affects species diversity and
stability of the ecosystem
Monoculture
Advantages
•reduces competition for nutrients, light, space.
•increased profit from high yields.
Disadvantages
•pathogenic micro-organisms spread more easily.
•pests spread more easily and increase.
•soil can erode due to lack of root systems.
•adverse weather can destroy whole crop.
•very unstable, low biodiversity.
•increased use of fertilisers, pesticides, herbicides and
fungicides
Increases in Energy Needs
Energy sources
Non renewables.
Finite - coal, oil, natural gas and nuclear.
Create significant pollution.
Renewables (alternative).
Infinite - solar, wind, hydro electric,
wave, tidal, geothermal, biofuels
Create much less pollution.
Reality - energy requirements are increasing and present
finite energy sources will not meet demand.
Oil - 50 years, Coal - 200 years
Present problems caused by energy use:
Global warming and the greenhouse effect
gases from burning fuels are carbon dioxide and water.
gases build up in layer around earth
more reflected heat is trapped and earth warms
effects on weather patterns, ice distribution, climate,
distribution of organisms
Other gases contributing to the greenhouse effect are
methane, nitrous oxide and CFCs.
Corals are polyps (animals) that
secrete calcium carbonate to
create skeleton.
corals appear
white (bleached).
zooxanthellae algae
(symbiosis) in corals
leave as result of
warmer waters.
Bleaching hotspots around the world
Present problems caused by energy use:
Acidic precipitation
burning fossil fuels produces sulphur dioxide,
nitrous oxide and carbon dioxide.
water in the atmosphere combines with these gases.
precipitation (rain) is acidified.
soil and water is acidified.
plants and aquatic organisms particularly are effected.
Areas in Europe at risk of Acid rain
Effects of acid rain
What can be done?
• Use less non renewable fuels for energy.
• Use other more renewable energy sources.
• Change the mind-set of the whole human
population from being reliant on oil.
Pollution
Pollution is the negative effect of a harmful substance
on the natural environment.
All environments are effected by pollution.
Aquatic (fresh water and salt water)
Air
Land
Pollution occurs as a result of human activities
Pollution
Effects of pollutants on species include:
• appearance/disappearance of species
• community function and structure changes
• behaviour and demography changes
• energy flow, production and nutrient cycling changes
Pollution
Tars, solvents, pesticides, domestic rubbish, lead,
mercury, copper, zinc, iron, arsenic
All dumped onto the land or released into
the atmosphere on a daily basis.
Landfill sites are a cocktail of dangerous
chemicals, many leach into ground water sources.
Fresh Water
Naturally contains:
•dissolved salt ions sodium, potassium, magnesium
•gases oxygen, carbon dioxide, sulphur dioxide
•solids soil dust, pollen
Pollution added:
•sewage (domestic and industrial)
•farm waste
•industrial waste
Many are biodegradable organic pollutants but they
will cause changes in the water quality.
Fresh Water
Monitoring water quality for:
Colour
pH
Turbidity
detergent level
Odour
Temperature
suspended solid level
dissolved oxygen level
biochemical oxygen demand (BOD)
ammonia, nitrate, chloride and phosphorus levels
Fresh Water
Biochemical oxygen demand (BOD)
Is a measure of how much biodegradable material there
is in a water sample.
Oxygen is essential for this activity.
The BOD is the mass of oxygen removed from a
water sample at 20oC in the dark in grams per cubic
metre.
The oxygen level in water directly effects the
living organisms found there.
High BOD = high level of organic matter and vice versa
Fresh Water
Biological monitoring using indicator species.
These give an indication of the state of an ecosystem
depending on their presence or absence.
Invertebrate species are often used.
Indicators of clean water
caddis fly larva and may fly
larva. They need high
oxygen levels to flourish
Indicators of water polluted with
organic matter. Low oxygen
levels mean sludge worms and
rat tailed maggots can flourish
Biological monitoring
Advantages:
•detects intermittent pollution.
•provides early warning.
•accumulation of toxic chemicals mean. detection of
low levels otherwise not easily detected.
Disadvantages:
•natural variation exists in invertebrate communities.
•indicators may tolerate one pollutant but be susceptible to
another.
•expertise in identification is essential.
Biotransformations
• Chemicals once released in to the
environment undergo changes.
• Leaching of ions increases with acidic conditions.
• Oligotrophic conditions in lakes is caused by
changes in nitrates caused by leaching aluminium
ions.
• Chemicals can be made more toxic in the environment.
Biomagnification / Bioaccumulation
• Living organisms can build up chemicals in their
systems.
• These quantities start small but as the food chain
progresses through the trophic levels they increase
in concentration.
• These higher concentrations can cause problems
• Examples include chlorinated hydrocarbons such as:
pesticide DDT and industrial chemical PCBs
(polychlorinated biphenol)
DDT (Dichlorodiphenyltrichloroethane)
• used to kill mosquitos (1940s and 50s)
• stable in environment
• accumulates in fats (bioaccumulation)
• changes to DDE which thins egg shells
• birds of prey particularly effected
• resistance has been built up by mosquitos (35 species)
• DDT occurance spread to areas not used e.g. Canada
and Greenland
• does not biodegrade
Mercury Poisoning
• Japan 1969 Minimata Bay
• Mercury dumped into bay by chemical plant
• Bacteria converted mercury to methyl mercury
• Very toxic
• Biomagnified in food chain
• Humans ate fish from Bay
• Caused neurological disorders, organ failure and deaths (68)
Favoured and susceptible species
• Species occupy different environments, some are
more tolerant of pollution than others.
• Favoured species are less sensitive and can tolerate
a wider range of environmental conditions.
• Susceptible species are very sensitive and
cannot tolerate changes in the environment.
Indicators of clean water
caddis fly larva and may fly
larva. They need high
oxygen levels to flourish
Indicators of water polluted with
organic matter. Low oxygen
levels mean sludge worms and
rat tailed maggots can flourish