Today –finish biodiversity (Chapter 23) –start conservation biology (Chapter 25) Wednesday –conservation biology Friday –quiz! –conservation biology Monday –historical biogeography (Chapter 24) Wednesday –ecosystem management (outside reading)

Conservation Biology - a mission- oriented science that focuses on protecting and restoring biodiversity Biodiversity 1.All forms of life 2.All levels of organization (subpopulation to biosphere) 3.All interactions among forms of life and the environment

Where is the biodiversity? Endemic species – restricted to a small region –isolated areas (islands, mountain ranges) –product of unique habitat, climate features

Biodiversity hotspots - areas with a high concentration of endemic species, experiencing rapid habitat loss

Hotspots: –1.4% of the land area –44% of vascular plant species –35% of terrestrial vertebrate species But… –20% of the human population, which is… –growing at 1.8% per year (vs. 1.3% worldwide) –each hotspot has already lost 70% of its vegetation

Current Status of Biodiversity 1.4 million described species, possibly 10 million in total Background extinction rate – rate of species loss in the absence of human activities –fossil record: species survive 1-10 million years –one year: one species has a 1 in 1-10 million chance of going extinct –total: 1 extinction per year

Mass extinction – loss of large number of species –usually due to catastrophic volcano or meteor impact –very rare (5 times in 3 billion years) Current rate of extinction???

Some estimates for current rate: –1 species per hour –1 million species total, so far –10% of all species so far –8.8% of all species –27,000 species per year –20% of neotropical plant species –100 to 10,000 times the background rate

Numbers of threatened/endagered species: –5,188 vertebrates (9%) –1,992 invertebrates (0.17%) –8,321 plants (2.89%) –2 lichens (0.02%) Since 1600, ~1000 species have gone extinct (probably many more)

Why do species go extinct? 2 separate processes: 1.Something causes a large population to decline. 2.Small populations go extinct.

Causes of species declines 1.Habitat destruction and fragmentation 2.Introduced species 3.Exploitation and overharvesting 4.Pollution 5.Climate change

USA

1.Habitat destruction and fragmentation Fragmentation – disruption of extensive habitats into small, isolated patches

Relaxation – loss of species from isolated habitats over time Area S

Edge effects – negative impacts adjacent to habitat boundaries Forest edges: –more sunlight –drying –high winds –tree mortality –invasive species –more predators

Core area Edge area Core area – part of a patch not impacted by edge effects Patch size is not always the best predictor of patch quality

2.Introduced species Humans are constantly moving species between continents, islands –deliberate or accidental Most serious impacts on islands –low species diversity –few native predators –animals lack anti-predator defenses, resistance to diseases

Characteristics of invasive species –pioneer species –high dispersal rates –found in disturbed habitats, but… –some can invade undisturbed communities Why are invasives successful? –no diseases, herbivores, parasites, predators –better competitors than native species

Introduced diseases – exploit lack of evolved resistance –Dutch elm disease – American elm –Chestnut blight – American chestnut –avian malaria – Hawaiian birds –Rinderpest – African ungulates –chytrid fungus – amphibians

Net result of invasive species –homogenize ecological communities around the world –drive native, endemic species extinct

3.Exploitation and overharvest Direct exploitation for food –overfishing –“bycatch” in fisheries – killing non-target species (birds, marine mammals) –“bush meat” – harvest of wild animals for food can be sustainable, but often not threatens many large mammals, primates

Global trade in wildlife –birds, orchids, cactus, primates –captured for gardens, pets, zoos, etc. Many species driven extinct before hunting/harvest regulations were in place –passenger pigeon, island tortoises, marine mammals

Exam Definitions, compare-contrast – 5 points each (20 points per page) 5 questions – 12 points per question bonuses – 3 points each dropped the question with the lowest score Average grade = 86

Causes of species declines 1.Habitat destruction and fragmentation 2.Introduced species 3.Exploitation and overharvesting 4.Pollution 5.Climate change

4.Pollution Most important for aquatic systems –chemical pollutants –acid precipitation Bioaccumulation – process by which toxin concentrations increase in living tissues –concentrations increase through the food chain

5.Climate change

Why do small populations go extinct? Demographic stochasticity – chance events that occur at small populations size –failure to breed or survive –failure to find a mate –skewed sex ratio

Dusky Seaside Sparrow

Environmental effects – unpredictable events that reduce survival or reproduction –droughts, floods, fires, storms Genetic effects at small population size –inbreeding –genetic drift –random mutations

Extinction vortex – combination of genetic, environmental and demographic factors that drive a small population to extinction

Heath hen 1700 – throughout the northeast coast 1907 – 50 left on Martha’s Vineyard 1915 – 2000 birds 1916 – fire 1917 – goshawk invasion 1920’s – poultry disease 1927 – 13 birds, mostly males March 11, 1932 – last known sighting

Minimum viable population – smallest population has a specified probability of surviving for a certain time –usually 95% chance of surviving for 100 years How big? –at least 50 individuals to avoid demographic stochasticity –at least 500 individuals to avoid genetic effects –realistically > 1000 but varies by species

Reasons for protecting biodiversity 1.Intrinsic – valuable for its own sake 2.Instrumental – beneficial to humans

Instrumental Reasons for Protecting Biodiversity 1.Economic benefits –food –drugs –cultivated crops –ecotourism

2.Ecosystem services – quantifiable services that an ecosystem provides to humans –often very valuable economically Examples: –moderating climates –mitigating floods and droughts –eliminating waste and toxins –pest control –pollination

Pollinators Insects pollinate 2/3 of crop species –~25% of foods consumed U.S.: $20 to 40 billion in agriculture Evidence that many pollinators are declining –bats –honeybees hummingbirds

3.Maintenance of ecosystem function How many species can you safely remove? How do you ensure maximum productivity in managed or natural ecosystems?

More diverse ecosystems are more stable

Diversity-productivity relationship How are plant species richness and primary productivity related? 3 possibilities:

Why would productivity increase with richness? Greater odds of encountering a super- productive species Complementarity – use of different resources by different species