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Transcript
Defining Biodiversity What is the nature and value of biodiversity? Learning Objectives – • • • Describe the global distribution of biodiversity Define the term ‘hotspot’ Describe the global distribution of hotspots Describe the pattern! Think at different scales : latitudes; continents; countries LATITUDES •The pattern is strongly correlated with latitude – highest levels usually in the tropics •There is a gradual decrease in higher latitudes CONTINENTS •South America •Asia •Oceania – Australia is unusually high due to ‘endemism’ COUNTRIES •Mostly found in developing countries •Brazil is ranked 1st According to levels of biodiversity Brazil comes out on top. 750 species of tree 400 types of bird 100 types of reptile 1500 species of flowering birds Biodiversity is low where there are climatic extremes Biodiversity is greatest in the tropics Biodiversity is generally greatest in the southern hemisphere Seventy per cent of the world's species is found in just 12 countries: Australia, Brazil, China, Colombia, Costa Rica, Ecuador, India, Indonesia, Madagascar, Mexico, Peru and Democratic Republic of Congo Marine hotspots are essentially coral reef areas in the tropics (contain 24% of world’s coral reefs yet cover 0.017% of oceans) Terrestrial and marine hotspots are often adjacent to each other e.g. Cape Floristic Province, South Africa Such choropleth maps give an overview of biodiversity distribution by country but this can hide the real picture What’s this about? Is there a link to biodiversity? Def: An area containing a huge number of species, a large % of which are endemic • Described as ‘the most remarkable places on Earth and the most threatened’ • They (25 hotspots) cover <2% of the Earth’s surface yet contain 44% of the World’s plant species and 35% of the World’s animal species* • • *Conservation International has recently updated this analysis 34 identified hotspot areas which are home to 50% of the World’s plants and 77% of the terrestrial vertebrates Species richness Level of threat to species Endemic richness Biodiversity hotspot • Continental Hotspots • Large Island Hotspots • Small Island Hotspots • Marine Hotspots ATLANTIC FOREST AUSTRALIA MADAGASCAR CORAL REEF The top 25 land-based hotspots are divided into 3 categories 1. Continental hotspots (richest in terms of biodiversity) 2. Large island (or continental island) hotspots (contain diverse & distinctive species inc relict fauna extinct elsewhere) 3. Small island hotspots (low in species no’s but high in proportion of endemics so at great risk of being wiped out) The location of hotspots does not correlate exactly with the location of greatest biodiversity. For example, France does not have a particularly high biodiversity but yet its southern shores are part of the Mediterranean Basin Hotspot. The tropical distribution of both types of hotspot is due to an absence of limiting factors which allows maximum primary productivity. In the tropics high temperatures, high humidity, abundant rainfall, and plentiful nutrients all encourage luxuriant growth of rainforests and reefs Invasive species Alterations in ecosystem composition Pollution Threats to Biodiversity Climate Change Over exploitation Habitat loss and destruction China Specific Hotspots: Reasons for High Biodiversity: Signature Species: Threats: Galapagos Islands Reasons for High Biodiversity: Signature Species: Madagascar Reasons for High Biodiversity: Threats: Signature Species: Threats: Has ensured that the ‘best bits’- areas with the highest levels of biodiversity, substantial levels of endemism (unique/rare species) are conserved and protected. Areas under threat are commonly in the tropics and in developing countries where conservation costs are much lower (cheap labour) – idea of value for money. Hotspots now covers marine area under threats in addition to terrestrial ecosystems Even with the additions of marine hotspots under 2% of the earth and 0.017% of oceans are protected by this approach The distribution of areas protected is very uneven. Most hotspots lie in the tropics e.g. rainforests. Many ecosystems such as Tundra, Taiga and Temperate Forest are not included. Huge areas of the world are not covered including many areas under great threat e.g. Arctic Ocean, or many outstanding smaller regions such as Galapagos . These are not protected because they do not meet all three criteria to be a hot spot. Polar bears subsequently face extinction. Hotspots tend to follows protectionist approach. This entails removing people and their activities from areas under threat. This has occurred in tropical countries where indigenous people have been forced off their land in favour of creating big reserves.