Human impacts on biodiversity depend in part on population size - PowerPoint PPT Presentation

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Human impacts on biodiversity depend in part on population size. Today’s estimate: 6,663,153,207. Human population impacts via:. Food production Water use Energy Urbanization Disease emergence. Human Effects: Climate Change.

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Human impacts on biodiversity depend in part on population size

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Human impacts on biodiversity depend in part on population size l.jpg

Human impacts on biodiversity depend in part on population size

Today’s estimate:


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Human population impacts via:

  • Food production

  • Water use

  • Energy

  • Urbanization

  • Disease emergence

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Human Effects: Climate Change

  • If the climate is changing, why aren’t we seeing the effects?

    • 12 years ago: ‘The effects are just starting, but tough to see within natural variance.’

    • Now: The effects are seen everywhere.

  • Does it matter to biodiversity?

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“Biodiversity” includes a lot:

Species (richness)

Genetic variability within species

Population structure across space

Communities – species across space

Ecological processes (competition, predation, symbiosis)

Abiotic processes that maintain the first 5

Biological phenomena – large migrations, species aggregations

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  • Biomes = largest spatial scale ecologically recognized

  • Driven by climate











Mean Annual Temperature (ºC)

0 50 100 150 200 250 300 350 400 450

Mean Annual Precipitation (cm)

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Note: effects are not uniformly distributed; some places are cooling

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Reminder: climate is not just temperature

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Evidence of climate change

  • Surface temperature 

  • Melting glaciers & permafrost

  • Mountain peak air temperature records

  • Sea level rise

    • atolls disappearing under water

  • Freezing elevations in the tropics have risen

  • Crop production

    • growing season 11 days longer in Europe, 1959-93

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Even if temperatures increase a few degrees, what’s the big deal?

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Last time Earth 3oC warmer





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Effects on Wildlife

  • Frogs & toads on tropical mountain tops in cloud forest (Monteverdi, Costa Rica)

  • 20/50 species went extinct

  • Due to global warming,  cloud elevation = decreasing habitat

  • Also allowed fungal pathogen to invade

Pounds et al. 1999

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Coral reef bleaching

= expelling algal symbiont

  • low or high sea temperatures can induce bleaching

  • Occurs naturally – occurrence rate 

  • leads to  photosynthesis, failure to grow, death

  • seaweed overgrowth due to inability to compete

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Range & Phenology Shifts

(Parmesan & Yohe, 2003, Nature)

  • Range = where species live; phenology = timing of events (return of birds in spring, flowers emerging)

  • Reviewed literature on effects of climate change on biodiversity

  • >1700 species

    • woody plants, herbaceous plants, birds, amphibians, fish, invertebrates

  • Looked for:

    • range shifts

    • advancement of spring events

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  • range shifts averaging 6.1 km / decade towards the poles

  • mean spring advancement by 2.3 days / decade

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Speckled wood




Range shift towards poles in many butterflies

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Exotic species invasion

Number of exotic species

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Disrupting Ecological Processes

Beetle damage to white spruce in Alaska – warmer winters kill fewer beetles

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Disrupting Food Chains

pied flycatcher



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pied flycatcher

(Both & Visser, Nature 2001)

National Geographic 9/04

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Disrupting Ecological Processes

  • Disaster At Sea As Global Warming Hits Seabirds

    • The Independent – UK 7/04

  • Hundreds of thousands of Scottish seabirds have failed to breed this summer in a wildlife catastrophe which is being linked by scientists directly to global warming.

  • a rise in sea temperature is believed to have led to the mysterious disappearance of a key part of the marine food chain - the sandeel, the small fish whose great teeming shoals have hitherto sustained larger fish, marine mammals and seabirds in their millions.

  • the sandeel stocks have been shrinking for several years, and this summer they have disappeared: the result for seabirds has been mass starvation.

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Black-billed magpie

Egg laying date




a=corn bunting


c=black-billed magpie

earlier egg laying in temperate birds

  • 20 species, avg. 8.9 days (range = 4-17 days)

Tree Swallow

Crick, et al. 1997. Nature 388:526.

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For doubters that humans are the primary cause of global climate change,

given observed climate change & its effects,

if human-caused emissions are not the primarycause of climate change,

should our response be different than if human-caused emissions are the primary cause?

"I hate to say we told you so, but we told you so." J. Cosimo, NASA researcher, Goddard Space Flight Center 9/06

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