What might disrupt ecosystem processes? - Rawlins A-level ...
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? 50% energy loss at each level from respiration and decay 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 point at which people harvest or catch them. 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 dont 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 shipe.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?
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