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.