Transcript Geography of Extinctions

Biodiversity Crisis
• Two centuries of warnings from scientists of
anthropogenic losses of species
• Since 1600s:
• 129 species of birds
• 83 species of mammals
• 21 species (including 100 subspecies) reptiles
• 7 species amphibians
Biodiversity Crisis
• Freshwater
• 40 species N. American fish during latter part
of 20th century
• Worldwide – 20% fish in jeopardy or extinct
• Molluscs – 7% of 297 recognized species
presumed extinct; another 65% endangered,
threatened, or candidates for listing
• Plants last 400 yr, 600 species (176 in US)
Number of Plants Globally
Percent Fish Threatened
Examples from Major Faunal Groups
Linnaean Shortfall
• 1.7 million species described
• Estimated 5 – 30 million species
• Species will go extinct before are known to
science
Hotspots of Diversity
• Patterns of diversity and endemism provide
clues for locating rare and endangered
species. Questions:
• What are the locations of hotspots for
particular taxonomic groups?
• Do hotspots of taxa overlap?
• Example – Endemic bird areas (EBAs) –
where range of at least two restricted-range
species present. Their pattern is not random
Is evidence for overlap of some groups
*
*
Overlap of hotspots for fish, coral, lobsters,
and snails
Prehistoric Extinctions
• Permian
• Cretaceous
• Migration and radiation following linkages
between continents
– Formation of Pangaea
– Laurasia
– Great American Interchange
• Pleistocene (climate-driven, at least partly)
Prehistoric Extinctions – last 2 million years
• New world megafauna and human
colonization
• Aboriginal application of fire in Australia
and Americas – broad range of plants and
animals
• Africa exception to human effects; species
there evolved with humans and were able to
adapt
Recent Historical Record of Extinctions
• Insular extinction rate
greater than
continental rate
Human-related Species Introductions
• Similar to continental convergences?
• Most common species: common rabbit, cats,
rats, house mice, pigs, cattle, goats, dogs
• Part of “naturalization”; bring along a piece
of home
• Most common carnivores (19%) and
artiodactyls (31%; deer and related
ungulates)
• Only represent 7% of fauna
Human-related Species Introductions
• Mammal introductions to islands – 118
species, 30 families, and 8 orders
• Birds – 212 species, 46 families, and 16 orders
• Australia has received most introductions per
unit area for continents
Habitat Fragmentation
• Breaking up of large parts of ecosystems for
agriculture and urbanization
• Puts species in peril (details later)
• Hardest hit are tropical rain forests
• 7% Earth’s surface; 50% species
• Madagascar – 7% left
• Brazil Coastal Forest – 1% left
• Singapore - <1%
Causes of plant endangerment in US
Ecological Effects of Fragmentation
• Reduction in total area, resources, and
productivity of native habitats
• Increased isolation of remnant fragments and
their local populations
• Significant changes in environmental
characteristics of fragments, including solar
radiation, wind, and water flux
Stages of Biotic Collapse
• Stage 1: Initial exclusion – some populations
not included in remnant patches
• Stage 2: Extirpation due to lack of essential
resources
• Stage 3: Perils associated with small
populations – genetic, demographic,
stochastic problems
Stages of Biotic Collapse
• Stage 4: Deleterious effects of isolation:
rescues by recruitment diminished
• Stage 5: Ecological imbalances: loss of
interactions (mutualism, parasitism,
commensals) and biotic regulation
(predation, competition)
Biogeography of Climate Change
• Periods of warming from greenhouse gas
accumulation before
• Difference is time over which it took place
• Human activities have greatly escalated
greenhouse gas concentrations over last 50 yr
• Temp – Projected increase 1.5 – 6°C; mean
~2.5°C; 0.7°C since 1860
• End of Wisconsin – Temp incr. 4.5°C over 5000
yr (<1°C/1,000 yr); raised sea level 100 m
Pattern of CO2 last 160,000 yr
Changes in Greenhouse Gases
Change in Global Temperatures (2000-2003)
Departures from Average Temperature
Biogeography of Climate Change
• Biogeography helps predict changes in
distributions, corridors, geographic isolation
of species, and extinctions
• Range change IS NOT just going to be
temperature
• Other abiotic factors must be in place
• Just as in other events, e.g., Pleistocene, must
be able to disperse and adapt to new
conditions
Changes in Elevational Gradients of Habitat
Species-area relationship to predict change in
species richness of boreal mammals in isolated
mountain ranges of Great Basin (3°C increase
Freshwater Biota
• 4°C increase in temperature
• Increase mean annual runoff 9 – 21%
• Shifts temporal runoff patterns (increase
precipitation winter and spring, decrease
summer and fall)
• Lead to changes in water quality
Marine Biota
• Latitudinal and vertical shifts in water
temperature; warm waters toward poles and
greater depths
• Alters horizontal and vertical mixing of
currents
• Salinity near equator and higher latitudes will
decrease (increased precipitation in those
regions)
Connectivity and Corridors
• Redistribution and loss of habitats will create
new barriers for dispersal
• Will also tend to increase isolation of patches
in increasingly fragmented habitats (refer to
human effects earlier)
Tools of Biogeography Used to Create Models and
Provide Answers to These and Other Conservation
Questions