climate change part two: demographic mechanisms (lecture 11) Flashcards Preview

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1

What mechanisms drive local colonisation and extinction?

- local colonisations/extinctions drive range shifts

- mechanisms matter (bioclimatic model)
- biophysical threshold - foraging duration
- life history - winter survival, summer recruitment
- recruitment and foraging energetics

2

What are the direct impacts of heat and drought stress?

McKechnie and Wolf, 2010
- small birds peak water requirements increase 150-200% increasing risk of massive die offs

Williams, 2012
- forest die backs
- forest drought stress index (FSDI)
- relationship with negative impacts on trees
- decreased growth rate

Jiguet et al., 2006
- birds in france after heatwave
- bigger temperature anomaly = bigger reduction in population size
- species adapted to warmer temperatures maintained population size better
- heat impacts of climate change may really affect european bird populations in the future

3

Which species will be most impacted?

-northern latitudes will experience more warming
- species that occupy these areas will have the most impacts
e.g. drosophila
- species closer to the equator have smaller safety margins
- equator species may be more vulnerable

- species' specific physiology
e.g. lizards
- increasing average body temperatures negatively impacts performance
- how species interacts with others
- lizards species doing poorly in the open country will move into the forest habitat
- out compete the forest species
- eventual extinction of forest species

4

How is climate change affecting phenology?

- spring events getting earlier
- adaptive response due to phenotypic plasticity
- indicated by first event/mean timing
e.g. bud burst, egg lay

- can lead to trophic mismatches
- Thackery et al., 2010
- Climate Sensitivity Profile - primary producers most sensitive then primary consumers then secondary consumers

5

How is climate change creating a trophic mismatch in caribou and spring green up?

Caribou migration/breeding becoming unaligned to spring green up (Post and Forchhammer, 2008)
- signal to migrate given by winter habitat
- but winter habitat not giving signal to move earlier even though spring green-up is getting earlier
- calfs not born earlier
- decreased calf production/increased mortality

6

How is climate change creating a trophic mismatch in breeding birds and food availability?

- woodland birds may suffer the most from trophic mismatch
- fewer insects
- later peak caterpillar availability = better maintenance of bird populations
- linked to temperature

7

Are migrants more vulnerable to trophic mismatch?

- birds species that don't alter phenology of their migration dates to match with climate have maintained or increased population trends
- phenological changes could adversely impact populations

8

What are the adverse impacts of assymetrical warming + maladaptive shifts in phenology on large birds

- rate of warming varies through spring/summer
- negative impacts for large birds

- longer egg incubation period
- chicks hatch in cooler & wetter conditions than usual
- higher mortality

9

How to test for carry-over and trophic mismatch in breeding migratory birds?

-simultaneously assess influence of winter, passage & breeding climate on breeding performance

methods
- compare breeding phenology with breeding performance
- compare with climate events/conditions
- breeding conditions can partly influence breeding timing + performance

- no evidence that wintering ground conditions are causing population decline
- climate impacts on food abundance can be more important
- population size may not be regulated by breeding success

signs of trophic mismatch
- diet switches: feeding young on different types of food
- nesting in different vegetation

10

How do environmental change drivers interact?

- sheffield study on long term effects of nitrogen deposition
- high nitrogen plot lost 3x more of its vegetation during drought than control
- N deposition made plot more sensitive to drought