ecological footprint

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Current Threats to Biodiversity

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Threats by Taxonomic Group The Sixth Great Extinction

Human caused contemporary extinctions.

The Sixth Extinction •  Currently extinction rates are greater than

speciation rates. •  Current anthropogenic extinction rate greater than

natural background rate. –  Natural background rate 0.0001% - 0.00001% of

species per year. –  Current rate for Birds and Mammals 0.01%.

•  99% of modern extinctions are linked to human causes.

•  Current extinction rates comparable to rates during previous historic mass extinctions.

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Survey of Threats to Biodiversity

Habitat Impacts

Habitat Impacts

Direct Loss Fragmentation Effects

Direct Loss Direct Loss

Organism’s have evolved to do best in particular habitats.

Mortality rates are higher and fertility rates are lower in less

preferred and unsuitable habitat.

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Natural Vegetation •  US - 42%.

–  East and Midwest less then 25%. •  Europe - 15%. •  Thailand, India, and Vietnam - 50%. •  Mediterranean - 10% forest left.

US causes •  Agriculture 38%. •  Commercial Development 35%. •  Water Projects 30%. •  Outdoor recreation 27%. •  Livestock grazing 22%. •  Pollution 20%. •  Infrastructure and roads 17%. •  Disruption of fire ecology 13%. •  Logging 12%.

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Habitats Lost

•  Tropical Forest. –  Madagascar 13% left. –  Rest of world varies from 90% to 5% left.

Habitats Lost

•  Tropical Forest. –  Madagascar 13% left. –  Rest of world varies from 90% to 5% left.

•  Grassland - US 97% lost. •  Wetlands - US 50% lost.

Habitats Lost

•  Tropical Forest. –  Madagascar 13% left. –  Rest of world varies from 90% to 5% left.

•  Grassland - US 97% lost. •  Wetlands - US 50% lost. •  Coral Reefs - 20% lost and at least 20%

degraded. Estimate that up to 95% may be lost by 2100.

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Habitat Fragmentation

Breaking larger contiguous blocks of habitat into smaller

isolated island of habitat.

Fragments tend to have higher extinction rates.

Habitat Fragmentation

Cadiz Township Green County

Wisconsin

1831 - 1950

Fragmentation - Warwickshire England

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Fragmentation Effects - I

•  Increasingly Smaller Patches. •  Increasingly Isolated Patches. •  Changes in Patch Habitat Quality.

–  Increased Edge Habitat. –  Changes do to intensive human use. –  Greater penetration of Invasive Species.

Patch and Matrix

Patch Characteristics and Conservation Biology

•  Size. •  Number. •  Position. •  Edges. •  Corridors. •  Networks of Patches and Corridors.

Patch Size

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Local Extinction Probability Habitat Quality as an Extinction Factors

Large Patch Benefit - Habitat Diversity

Number of Patches

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Habitat Loss

Patch Isolation

Isolation and Extinction

Edges

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Large Patch Benefits – More Interior Habitat Interior Habitat and Species

Change in Edge/Interior Ratio Loss of total vs. Interior Habitat

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Interior Habitat Species – Area Sensitive Species

•  Require large patches of habitat. •  Avoid the edges of habitat. •  Are sensitive to edge effects.

45 Northern Goshawk

Area sensitive species need interior forest

Edge effects - Why do they effect forest interior species?

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Edge effects as a function of distance from the edge.

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Edge effects on microclimate

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Edge Effects

Edge effects on vegetation

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Edge Effects

Edge effects on animals

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Edge Effects Edge Effects

•  Changes in Microclimate. •  Changes in Plant Community. •  Changes in Animal Community. •  Invasion of Interior by Edge Species.

–  Brown-headed Cowbird. –  Invasive Plants.

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Brown-headed Cowbird Habitat Fragmentation Effects II

•  Limits to dispersal and colonization. •  Restricted access to food and mates. •  Disruption of interspecific interactions.