Transcript LESSON3 Distribution and hotspots

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.