Natural and Human – Induced Environmental Stress Natural Environmental Stress Catastrophic - e.g. droughts and floods Gradual - e.g disease Human-Induced Stress Catastrophic - e.g. deforestation, urbanisation Gradual - e.g overfishing

Human Threats to Biodiversity 1. Species introductions: wipe out endemic flora and fauna by preying on them or competing for food and space, thus affecting the food chain (trophic levels).

2. Habitat Destruction: now the major threat to biodiversity. Areas are converted to human use (technosphere). Involves outright loss of used by species to degradation and fragmentation where native species are deprived of food, shelter and breeding areas and are squeezed onto smaller amounts of land.

3. Hunting: can lead to uncontrolled exploitation of and trade of wildlife. It can decimate species. Once again, this affects trophic levels and food chains/webs. E.g. overfishing – Blue Fin Tuna in the Southern Ocean. In 2009, Australia’s quota was reduced by 30%.

4. Pollution: is a major threat to aquatic and terrestrial ecosystems. e.g. Mexico City and air pollution. It is city surrounded by mountains and as a result, traps in air pollution. It has a population of over 26 million people. One management strategy has been to introduce car number plate and colour days.

Natural Stress Read the case study on p25 – Mt St. Helens (an example of natural stress) Answer the question at the bottom of the page

Human-Induced Stress Read the case study on p 27 ( Great Barrier Reef) Answer questions (2) a,b,c p28. Answer questions (1) a,b,c,d. p28

Greenhouse gas emissions leading to coral bleaching and destruction