Ib biology : Climate change

anthropogenic causes of climate change

• Increase in Carbon dioxide levels

• Increases in methane levels

these have lead to an enhanced greenhouse effect

anthropogenic

caused by human activities

correlation between CO2 levels in atmosphere and temperature

• data from Antarctic ice cores show a positive relationship between atmospheric CO2 concentrations and temperature over time

• however, this shows a correlation, but not a causation

Positive feedback cycles in global warming examples

• release of carbon dioxide from deep ocean (warmer temperatures = lower CO2 solubility)

• increase in absorption in solar radiation due to loss of reflective snow and ice

• acceleration of decomposition of peats (organic soil made from partially decomposed material) and previously undecomposed organic matter in permafrost

• release of methane from melting permafrost

• increases in droughts→ forest fires

climate tipping point definition

a critical threshold where a system undergoes significant and potentially irreversible changes due to a small additional disturbance

climate tipping point example forest

• boreal forests destruction

• vast dense forests which absorb much carbon dioxide for photosynthesis

• but less rainfall → drought → lower forest productivity → lower primary production

• leads to

• forest browning (death of tress)

• increase in frequency and intensity of forest fires → legacy carbon combustion

forests aren’t carbon sinks anymore, they have become net carbon contributors

imate tipping point example polar habitat change

• melting of landfast and sea ice → polar habitat is changing

• loss of breeding ground for the emperor penguin due to early breakout of landfast ice in Antarctic

• loss of sea ice habitat for walruses in Artic

nutrient upwelling

process in which deep, nutrient rich waters rise to the surface of the ocean

effects of changes in ocean currents

• warmer surface water can prevent nutrient upwelling to surface

• this can decrease ocean primary production (phytoplankon receive less nitrogen, phosphorus and iron)

• and therefore decrease energy flow through marine food chains

temperate species

organisms adapted to inhabiting temperate regions, characterised by mild to warm summers and cool to cold winters.

Poleward and upslope range shifts of temperate species

• phenomena in which species gradually shift their distriution towards higher altitudes and elevations

• usually caused by changes in climate conditions

example of upslope range shifts of temperate species

• In mountainous regions of new guinea, upslope shifts in distribution of bird species typically found in tropical zones

• this response is believed to be caused by birds’ need to find a cooler climate, closer to their preferred conditions

example of poleward shift in temperate specie

• in north american, certain tree species exhibit range contraction in their southermost distribution while simultaneously expanding northward

• associated with shifts in climate conditions (rising temperatures and lower precipitations

• impacts forest compostion, carbon sequastrations, and has effects on other species in the ecosystem

threats to coral reefs

• extra CO2 in the atmosphere leads to ocean acidification as CO2 dissolves in water, leads to a decrease in PH

• corals cannot build calcium carbonate skeletons

• increases in temperature can lead to coral bleaching

• death of corals can lead to destruction of the ecosystem

carbon sequestration

strategies and approaches aimed at capturing and storing carbon dioxide

examples of carbon sequestration

• afforestation: intentional planting of trees in non forested lands: trees absorb CO2 during photosynthesis and store it n their biomass

• restoration of peat forming wetlands: they have a lot of potential storage in waterlogged soil

• forest regeneration: the natural or intentional regeneration of tree cover after forest loss, which can be achieved through planting nursery grown seedlings after events which have resulted in the destruction of the forest

Phenology

a scientific field that investigates the timing of biological events and their relationship with seasonal and regional factors

factors which determine timing of bioevents

• photoperiods

• temperature patterns

photoperiod

duration of light exposure during a 24 hour cycle. Serves as a cue for many organisms in determining their timing.

biological patterns which can be studies in phenology

• flowering: as photoperiod increases during spring, plants will flower + precipitation + temperature

• bud burst/ bud set in deciduous trees: same thing + increase in temperature

• bird migration and nesting: photoperiod, temperature, and food availability

examples of climate change affecting phenological events

• mouse ear chickweed in the artic initiates growths too early because of temperature

• however raindeer migration depends on phototiming cues

• so arrival of raindeer might not coincide with availability of chickweed, reducing food sources

• warmer temperatures lead catterpillars to emerge earlier in north european forests

• but great tit breeding cycle remains the same

• so mismatch between food availability and food need

effect of climate change on insect life cycles

• life cycle of insects is shortened due to climate change → temperature increases

• spruce spark beetles, which infest and damage spruce trees

• increase in development, because of increase in metabloic rates, so increased growth and maturation

• can lead to multiple generations produced in a single year

• can challenge ecosystel health, causing death of trees and species that rely on it

example of evolution as a consequence of climate change

Tawny owl: initially brown and grey variant exist, but because of reduction in snow cover, brown owls have an advantage as they can better hide from predators, ie the grey lost their advantage

effect of climate change on populations

selective pressure, which leads to genetic adaptation and evolutionary changes in response to a shift in environmental conditions