Biodiversity I
ES 118 Spring 2008
What is biodiversity?

Today
– What is biodiversity?
– Where it is found?
– Where and how is it threatened?

Wednesday
– How do we value biodiversity?
– What are strategies to protect it?
Incentives
Values
Information
Biological diversity

The sum total of all living things
–
–
–
–
–
–
Genes
Species
Populations
Communities
Ecosystems
Landscapes
Biodiversity indicators

Genetic diversity: within
the population or species
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Ecosystem diversity: a
diversity of habitats

Species diversity: number
of species & abundance
How many species?

1.75 million described
– 300,000 fossil

Estimates range from 10-50 million
Indian (Asian) Elephant
Elephas indicus
African Elephant
Loxodonta africana
Photo: Jonathan and Angie
Orangutan
ORDER: Primates
SUPERFAMILY: Hominoidea
FAMILY: Pongidae
GENUS: Pongo
SPECIES: pygmaeus
SUMATRA (Pongo pygmaeus abelii)
BORNEO (Pongo pygmaeus pygmaeus)
© 2001 Michael Nichols
Photographer: Rod Brindamour
Panthera tigris
Where is biodiversity
Similar patterns emerge for elevation as for latitude
Groom et al. 2006
Habitats of Richest
Diversity
Tropical rain
forests
 Coral reefs
 Large tropical
lakes
 Deep sea

Mammal Species Richness
Endemic species
Definition: Species found in
one area and no place else
Extinction is the most irreversible of all
environmental calamities. With each
plant and animal species that
disappears, a precious part of creation is
callously erased.
Michael Soulé, 2004
The Oxford Dodo
Passenger
pigeon
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

Most common bird in
North America
Flocks would darken
sky
Extinct by 1914
1898 Photograph of a
Passenger Pigeon
Stephen Island wren


Flightless, nocturnal
insectivore, endemic
to small Stephen’s
Island near New
Zealand
Entire population
killed off in 1894 by
"Tibbles”the
lighthouse keeper's
cat
The Grail Bird:
The Ivory-billed wood
pecker
Extinction rates

Extinction rates now 1,000x or more
beyond “background” rates
– 10-30% of mammal, bird, and amphibian
species threatened with extinction
– 20% of world’s corral reefs lost, another
20% damaged
– 35% mangroves lost

Sixth “mass extinction” episode
7
7
6
People and biodiversity
6
5
Billions of People
5
4
3

20-30% of net primary productivity
co-opted by humans
4
– 60-80% of regional NPP in North
America and Europe
3
2
2
1
1
500,000
10,000
8,000
6,000
Years Before Present
4,000
2,000
0
Extent of cultivated
systems
Human footprint
Sanderson et al. 2002
The Last of the Wild (WCS)
http://wcs.org/humanfootprint
Threats to Biodiversity
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Habitat degradation
Overexploitation
Invasive species
Disease
Climate change and pollution
Habitat degradation
 Habitat loss
– Conversion of natural
ecosystems for human use
 Habitat fragmentation
– Dissection of natural habitat
by human activities
 Matrix quality
– Overall integrity of the
landscape
Examples of degradation

Habitat degradation
Overexploitation
Invasive species
Disease
Climate change &
pollution
Forest systems: ½ the world’s forest
cover has been removed
– In 25 countries no forest remains
– In 29, 90% has been lost

Grasslands: In North America, 97% of
tallgrass prairies and 60% of
mixedgrass and shortgrass prairies
have been converted since mid-1800s
Deforestation along the
Trans-Amazonian
highway
Approximately 47% of the
world's largest rainforest
has either been settled,
totally deforested, burned
or is being used for mining,
logging or agriculture
Picture taken November 17, 2004
Photo by STRINGER
Picture from www.planetark.org. © 2004 Reuters Limited.
Fragmentation

Increase in edge
– High edge to area ratio
– Center of patch closer to edge
Habitat degradation
Overexploitation
Invasive species
Disease
Climate change &
pollution
Habitat degradation
Overexploitation
Invasive species
Disease
Climate change &
pollution
Edge effects
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Can change physical gradient like
temperature, moisture, and light
Increased risk of fire
Increased risk of disease
Biological Dynamics of
Forest Fragment Project,
Brazil
Edge Effects

Increase vulnerability to
predators and exotic pest
species
– Parasitic cowbirds
decimating song bird
populations
Overexploitation

Habitat degradation
Overexploitation
Invasive species
Disease
Climate change &
pollution
Humans have always exploited wild
animals and plants
– Timber extraction
– Non-timber forest products
– Commercial and subsistence hunting
Bushmeat in Africa

+/-30 million people live within forested regions of
Central Africa, 40-60% live in cities and towns, most
rely on wildlife as primary source of animal protein
– 1 million metric tons of wildlife killed for food/year

In West Africa, wildlife populations so depleted by
years of unsustainable hunting that bushmeat no
longer most important source of protein
Invasive Species

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Habitat degradation
Overexploitation
Invasive species
Disease
Climate change &
pollution
Exotic species: Species that occur outside
their range because of human activity
Invasive species: Exotic species that
establish themselves in new area at
expense of native species
–
–
–
–
Human colonization
Horticulture and agriculture
Accidental transport
Biological control
Cane Toad, Australia
Invasive Species
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Est. $137 billion per
year in US alone
Examples include:
– Purple loosestrife
– Fire ants
– Japanese
honeysuckle
– Brown tree snakes
Disease
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Habitat degradation
Overexploitation
Invasive species
Disease
Climate Change &
pollution
Major threat to many species
Rinderpest in Africa
– 19th Century introduced from livestock
– Killed 75% of wild animals in some areas

Canine distemper
– 25% of lions killed at Serengeti NP

Chestnut blight
– Wiped out chestnut trees in eastern US
Climate change &
pollution
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Habitat degradation
Overexploitation
Invasive species
Climate change
Disease
Climate Change &
pollution
Phenological shifts
Range shifts
Increasing CO2
Ecosystem processes
Pollution can affect habitat quality and
kill or reduce the fitness of organisms
Case of amphibians

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Amphibian populations are in decline in many areas
of the world
In US, amphibian malformations (extra limbs,
malformed or missing limbs, and facial
malformations) documented in 44 states and 60
species
– In some local populations, up to 60% of amphibians exhibit
malformations

Multiple Stressors: Compelling evidence for habitat
loss, climate change, UV radiation, contaminants
and pollutants, disease, habitat degradation, and
predation by invasive species as possible causes
Probability of going extinct

More likely
– Low population
density
– Found in small
areas
– Specialized “niche”
– Low reproductive
rates

Less likely
– High population
density
– Found over large
areas
– Generalized “niche”
– High reproductive
rates
Special case of islands
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Small islands lose species faster and
have fewer total species than big islands
Islands remote so harbor many endemic
species
Introduction of new species can have
rapid and devastating consequences
MacArthur and Wilson’s
Equilibrium theory of island biogeography
More Species
Mainland
Fewer Species
Distance from Mainland
Island Size
Species diversity on islands
Figure from E.O. Wilson and
W.H. Bossert. 1971. A primer
of population biology.
Sinauer Associates, Inc.
Sunderland, MA
Mammal extinction in parks