Download What might disrupt ecosystem processes? - Rawlins A

What might disrupt ecosystem
processes?
BIODIVERSITY UNDER THREAT
Learning Intentions:
To understand the factors that affect processes in an ecosystem
Examine the processes in ecosystems and the factors that affect
these
What about the local?
 We have looked at threats which are occurring on a
global scale BUT what threats can you think of that
are occurring on a local level?
Local threats
 In small scale areas, local threats can be numerous and
represent a severe threat to ecosystems and biodiversity.
Localised deforestation;
clearance for farming and
urbanisation
Mining, ranching and overgrazing,
road building leading to
ecosystem fragmentation
Tourism development; trampling,
erosion; urbanisation and
associated pollution; increased
risk of wildfires
Runoff from farms and urban
areas; eutrophication and
heavy metals in rivers, lakes
and seas
Overfishing and harmful
forms of fishing e.g. dynamite
and cyanide
Siltation from runoff;
increased risk of alien
invasive species
What are energy flows?
 Energy Flows – primary
producers (green plants) at
trophic level 1 convert
sunlight into energy by
photosynthesis
 A food chain, or web exists
between the trophic levels.
 Teritary level is usually the
50% energy loss at
point at which people
each level from
harvest or catch them.
respiration and
decay
What is a nutrient cycle?
 Nutrient cycles – the circulation of chemical elements
from the environment to organisms and back again
into the environment
 What three parts does a nutrient cycle have?
 What movement can occur between these parts?
What is a nutrient cycle?
 Functioning ecosystems have a continual
flow of nutrients and energy through
them
 These systems are self-regulating, but
prone to human disruption:
 Deforestation or over fishing depletes the
biomass store in the nutrient cycle
 Climate change may affect precipitation,
runoff, decay rate and weathering rate
 Alien species can disrupt the food web,
changing the balance of predators and
prey
 Eutrophication drastically increases
available nutrients
What is the global movement of a
species?
 As the world becomes more global more species are
moved around the world
 This poses a huge threat to ecosystems
 Why is there movement?
 Alien or exotic species may become established at
any trophic level in the ecosystem
 What features do these species share in order to
survive in an alien environment?
Alien invasive species
 Our globalised world has
increased the threat from
alien invasive species
 These are species which
move out of their natural
habitat and colonise new
areas, as a result of human
activity
 Such species don’t move
because they want to find a
better place to live!
 Some aliens are introduced
deliberately, perhaps as a food
source, predator or
ornamental species, but then
escape into the wild and have
unintended consequences
 Other aliens are accidental
introductions
Successful invaders tend to be:
Capable of rapid reproduction
Able to disperse
Rapid growing
Tolerate a range of environmental
conditions
Able to eat a wide range of foods
What do you already know?
 Which alien species can you think of?
 Were these introduced on purpose or by accident?
Accidental Introductions
 Some alien species arrive by ship…e.g. Zebra Mussel
which arrived to North America from the Caspian Sea
in the ships Ballast water….these eventually ended
up in the Great Lakes. In Lake Erie there were 70,000
per m2. and reduced phytoplankton by 80%
 What will this eventually lead to?
 Air transport introduced snakes to Pacific island of
Guam destroyed food chains
Not all introductions are accidental
 Introduced species can be
difficult to control, they
often spread quickly
 WHY?
 They usually have very
harmful impacts
 E.g. Pheasants, rainbow
trout, Rhododendron
Hedgehogs were introduced to the
Outer Hebridies to deal with garden
slugs. They have since led to ground
nesting birds becoming endangered
Study Figure 3
Explain how human activities have contributed to the
condition of ecosystem goods and services. (10)
Plenary: Fox hunting is now banned what
impact has this
had on the British ecosystem?