Appendix 2.

Some examples of ecological tolerances and thresholds
in relation to climatic variables and global change


Climate Change and Biodiversity Conservation



BIOME


REGION/
COUNTRY/
AUTHOR


THRESHOLD

EFFECTS

OTHER FACTORS

Tidal coastal marsh

NE USA/
Connecticut

Warren & Niering (1993)


Relative sea-level rise: 10.0-12.5 cm/century

Change in plant community structure. Replacement of Juncus geradi-Spartina patens complex

Storms, sediment supply, human alterations

Coastal Mangroves

Oceanic islands (Pacific,Indian Ocean, Atlantic)

Ellison and Stoddart (1991)


Relative sea-level rise: 9-12 cm/century

Mangroves not receiving significant levels of sediment input will be stressed, and at rates of sea-level rise greater than 12 cm/century, will begin to retreat

Sediment supply

Coral reefs

Indo­Pacific

Smith and Buddemeier (1993)


Temperature: ­2 day exposures of 3­4oC above the normal maximum. Or several weeks of temperatures 1­2oC above normal

Can cause temperature induced bleaching. Mortality can be more than 90% at 4oC above normal maximum for even a few hours. Recovery is normal for bleaching induced by changes of less than 2oC

Irradiance (visible and UV). Variable according to taxa. Related to long­term,, site­historical mean temperature of warmest month. ther human impacts

Marine

East coast/USA

Ray, McCormick­Ray and Potter (1993),


Water temperature: 13­18oC

Shad (Alosa sapidissima) track water temperatures within this range, and spawning peaks at 15oC. Temperature changes could reduce number of repeat spawners and reduce success

Overfishing

Riverine wetlands

Mississippi River, Illinois/USA

Janzen (1994)

Mean July temperature:
Increase of 4oC

Elimination of production of male offspring in a population of painted turtles (Chrysemys picta)

Bogs

Wales/Germany/
Ireland/
Netherlands

Schouten, Streefkerk and van der Molen (1992)


Mean annual temperature:
11oC

11oC appears to be the limiting temperature for formation of ombrotrophic bogs in NW Europe

Drought and moisture stress

Heathland

South coast & Lancashire/UK

Gates (1992)


Daily average sunshine hours:
Not less than 6.5 hours through May

The 6.5 hour May isohel limits UK distribution of sand lizards

Alpine

Austrian and Swiss Alps

Grabherr (1994)


Mean annual temperature:
Increase of 1­1.5oC. over the last 100 years

Rates of upslope migration for Alpine plants is between 3 and 12 feet per decade,, but would need to be 30 feet to keep up with rate of warming

Animal movements, CO2 concentrations

Alpine

Yellowstone/
USA

Romme and Turner (1991)


Summer drought stress:
Increases may lead to upward shift in lower timberline of 460m

This scenario would reduce available habitat for whitebark pine in Yellowstone National Park by 90%. Whitebark pine is a key food source for grizzly bears and Clark's nutcrackers

Tropical montane forest

Luquillo/ Puerto Rico

0'Brien et al. (1992)


Hurricane frequency:
Greater than once every nine years,

Model experiments for the Tabonoco rainforest predict a trend towards early successional forest types, reduced biomass and declining populations of large commercial species including Dacroydes excelsa and Sloanea berteriana

Increase in destructive potential of hurricanes, size, and possibly in multiple land­falls

Caves

Indiana/USA

Richter et al. (1993)


Mean winter temperature:
Cave roost sites 5oC higher than normal

Increased winter body mass loss (42% more than control) during hibernation of Indiana bats (Myotis sodalis). High mortality. Warm caves may act as metapopulation sinks

Temperate forest

Northern Rocky Mountains/North America

Mean fire return frequency:
40 years

Rapid decline of Whitebark pine stands (over 200 years)

(Using FIRESUM model)

Temperate forest

Southern Appalachia/USA

Clinton,, Boring and Swank (1993)


Drought length:
Severe, prolonged, drought from 1985 through 1988. Annual precipitation averaged 24% below normal, peak deficit was 31% below normal in 1986

66% of all canopy gaps surveyed in 1988 in a mid­elevational mixed­oak forest were created after 1986. 44% of gaps were formed by scarlet oak (Quercus coccinea). Canopy turnover rate based on 1988 rates would be 8 times faster (66 years) than in 1985 (526 years)

Scarlet oak decline can be linked to drought­induced infection with the shoe­string fungus, Armillaria mellea

Temperate zone

UK

Dennis (1993)


Ambient temperature:
Prolonged summer chilling (less than 4oC)
Ambient temperature above 33oC


Prolonged chilling is lethal to the small white butterfly (Pieris Brassicae).
Eggs laid at ambient temperatures over 33oC are infertile


Arctic

Circumpolar

Sveinbjornsson (1992)


Ambient temperature:
<Treeline is correlated with mean temperature of 10oC for the warmest month and a minimum of 30 days with a mean daily temperature above 10oC

Warming would cause northward migration of tree line

Arctic/Alpine

Norway

Holten (1993)


Winter temperature:
Increases of 4oC or more

Warming threatens the group of Norwegian plant species limited by a January isotherm of ­10oC or lower,, including Campanula uniflora,, Draba alpina,, Luzula arctica,, Poa arctica,, Ranunculus nivalis,, Stellaria crassipes, and Carex capitata

Warm desert

USA

Nobel (1985)


Minimum winter temperature:
Below freezing

Carnegia gigantica is restricted to regions where freezing temperatures do not exceed 24 hours. Four Opuntia spp. die at temperatures below ­8oC. Only 3 of the 65 species of arborescent ceroid cacti occurring in the Sonoran desert are found north of the frost line


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