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Defining Biodiversity
What is the nature What is the nature and value of biodiversity?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 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
Biodiversity is low where there are climatic extremes
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
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 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
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.
Alterations in
ecosystem composition
Climate Change
Habitat loss and
destruction
Over exploitation
Pollution
Invasive species
Threats to Biodiversity
MadagascarReasons for High Biodiversity:
Signature Species:
Threats:
ChinaSpecific Hotspots:
Reasons for High Biodiversity:
Signature Species:
Threats:
Galapagos IslandsReasons for High Biodiversity:
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.