Biodiversity
Why we worry about the number of
species in an area
1. What is biodiversity?
- The number of genes, species or ecosystems in a region.
- Biodiversity is lost when a species becomes extinct - all
individuals of that kind die.
2. Genetic Diversity
- Number of different kinds of genes
- High = many different types of individuals, different abilities
- Low = most individuals are similar, similar abilities
- Problem if low: fewer answers to challenges from the environment
3. From where does genetic diversity come?
- Mutations
- change in DNA
- Some lethal, individual dies
- Some neutral, nothing changes in individual
- Some positive, individual more successful
- Migration
- Sexual reproduction: unique combination may be more successful
- Population size important
- Selective breeding of domestic stock
4. Species Diversity
- Definition: measure of the number of different species present in
an area
- Species richness: # of species
- Influences
- History: more time = more species
- Migration -> introductions may be + or -
- Size of area: bigger islands = more species
- Human activities
5. Ecosystem Diversity
- Definition: measure of the number of kinds of ecosystems present
in a given area
- Influenced by
- Topography: mountains, lakes, streams
- Disturbances create patches: volcanic activities, floods, fires
- Geography: Climate, latitude, altitude
- Microhabitats: the larger the area studied, the more kinds of
ecosystems present
6. Biodiversity Hot Spots:
http://www.biodiversityhotspots.org/xp/Hotspots/Pages/default.aspx
7. Extinction is forever
- No techno fix, no Jurassic Park reprieve.
- Extinction is a natural and common event.
- Concern is over the high rate of extinction directly connected to
human activity
- Human activities have increased the species extinction rate as
much as 1000X above background
8. How many species are there?
Robert May’s estimates **
- 1.5 million, +/- 10%
- 70,000 species of fungi
- 270,000 plants
- 40,000 algae
**Pimm, 2001. The World According to Pimm
9. How many animals (May’s estimates again)?
- 15,000 species of nematodes (tiny worms, some parasitize plants
and animals)
- 70,000 mollusks (snails, clams, squid, etc.)
- Arthropods (jointed legged animals)
- 75,000 arachnids (spiders, scorpions, mites)
- 40,000 crustaceans (shrimp, crabs)
- 720,000 insects (beetles, moths, ants, flies)
10. Humans have increased the extinction rates?
- Using fossils, a typical species exists for about 1 million years.
- So… only 1 species in 1 million should go extinct naturally in a
given year.
- For birds, the global catalog has about 10,000 species.
- The background extinction should be about 1 bird extinction in
100 years.
11. How far above background extinction in birds are we?
Hawaiian example --
- Polynesians introduced pigs to the islands
- colonized the Pacific from New Zealand to Easter Island ~ a few
thousand years ago
- May have driven from 1000 - 2000 species of birds to
extinction
- = Estimate about 1 extinction every few years, not one species
per century
- Europeans began colonizing in 1778, deforested, brought cattle,
goats
- 18 species of birds now known only from museum specimens
- = estimate about 1 extinction/decade for last 200 years
12. How bad is it?
- 10 - 30% of mammal, bird and amphibians threatened with extinction
- 20% of world’s coral reefs lost, 20 % damaged
- 35% of mangroves lost
- We don’t know about some groups because we haven’t ID’d them all
yet.
13. We are loosing Ecosystem Services
- Definition: services that healthy ecosystems provide and
that humans value
- Examples
- Air and water purification
- Survival of fishery stocks
- Regulation of regional and local climate
- Regulation of natural hazards (floods, erosion)
- Regulation of pests
14. Table 11.1: Probability of becoming extinct
15. How do humans cause extinction?
- We modify the world
- Habitat destruction
- Habitat fragmentation
- Invasive species introductions
- Over harvesting of fisheries and other biological resources