wk 8a and 8b

• In this session: Methods of studying and predicting impacts of climate change, Example of how climate change impacts on insects, The value of ecological data

  
• Global temperatures

  • Rising
  • UK temperature has increased

  
• Annual change from 1961-2006

  Greatest warming is in the south-east

  
• Seasonal changes from 1961-2006

  Greatest warming is in the summer and winter

  
• Predicted future rises in summer mean temperatures for the 2050s, 50% probability level under high and low emissions scenarios
• Predicted future changes in annual precipitation for the 2050s, 50% probability level under high and low emissions scenarios
• Climatic variability and extreme events

  • Climate will become more variable
  • Increased frequency of extreme events
  • Carbon dioxide levels will also affect organisms
• Rate of growth and development

  Climate can determine both the rate of growth and development of organisms, and act as a mortality factor
• Increased temperature may increase rate of development for invertebrates
• Field and lab studies have been carried out across a wide range of temperatures

  • Aphid parasite of citrus trees
  • Increase in fecundity, development and development rate with increasing temperature – but only to a point
• Distribution


  • Distribution of species are expected to move polewards or to higher elevations
  • 3oC increase relates to a shift in isotherms of approximately 300-400 km polewards or 500 m in elevation
  • Species distributions are not solely dictated by climate, e.g. may be land use patterns
  • Species will hit barriers (e.g. the ocean) they cannot cross
• 2/3rds of species shifting north had a stable southern range, 1/3rd showed a retreating southern range too, Northward shifts ranged from 35-240 km
• Large skipper butterfly predicted range for different temperature regimes in the current, 2020s high scenario, and 2050s high scenario
• Used climate models to estimate probability of extinction for sample regions (20% of Earth's surface) under a mid-range climate scenario for the 2050s, predicted 15-37% of taxa would be 'committed to extinction', greater than extinction through habitat loss, pollution etc.

  
• Herbivores need a food source

  We do not just need to understand what effects climate will have on invertebrates, but also their food sources
• Phenology


  Timing of regularly occurring events (e.g. key life cycle events) in relation to climate
• Insect herbivore life cycles often need to be in close synchrony with plants, climate change can affect this markedly (especially for spring-feeding species)
• Different species use different timing mechanisms (e.g. day length, average temperature, both etc.)
• Lamium album flowered 55 days earlier on average in 1991 to 2000 than in 1954 to 1990
• Bombus terrestris audax, a common subspecies of bumblebee in the UK


  • Was regarded as being a species that was inactive in winter, since 1991 winter activity has been recorded in the UK, this has become increasingly common and there is now a winter-active population, attributed to warming
• Pedunculate Oak and Winter Moth


  Optimum hatching date for the moth is at peak bud burst from the tree, if caterpillars hatch too early they may starve or have poorer quality food
• Reduction in synchrony between peak caterpillar date and peak food demand by chicks is seen in multiple species of passerines, there is also now a mismatch between the hatching date of sparrowhawks and peak availability of fledging passerines to feed their chicks, multiple species at different trophic levels affected
• Adaptation


  • Difficult to predict, short generation times in invertebrates, high intraspecific variation, some evidence e.g., selection for greater leg length in bush crickets allowing them to be better dispersers and move to more suitable environments, may be changes in behaviour and use of microhabitats with differing conditions
• Insect herbivores and warming

  • The species least affected: eat many different plant species, have a wide geographic distribution, are not tied in to plant host phenology, have the potential to adapt to warming, high capacity for dispersal, but average warming is less of a problem than increased climate variability, responses will be species specific – very hard to generalise
• Studying responses to climate change


  • Experimental manipulations
  • Modelling
  • Observational / correlative studies
  • Use of altitudinal or latitudinal gradients
  • Long term data sets available
  • Correlations between distribution and local climate
• Open topped chambers provide passive warming that is not well controlled, but are inexpensive and good for remote locations. They have unwanted boundary effects like reduced wind.
• Heating cables provide controlled warming at the soil level, but the set-up is labour intensive and expensive to run.
• Night-time warming uses passive warming at night when the plots are covered by material that keeps in heat. It is inexpensive compared to heating but uses sensors and motors to move the covers.
• Rainfall and water availability can also be manipulated but can be difficult and expensive.
• FACE (Free Air CO2 Enrichment) actively adds higher levels of carbon dioxide to plots that can then be monitored.
• The non-agricultural FACE network is uneven, with no sites in Asia, South America or Africa.
• In a long-term CO2 enrichment experiment in Florida, leaf miner abundance was measured on tree species in an oak forest, showing reduced abundance (-22%), increased relative consumption (+17%), increased development time (+4%), and reduced pupal weight (-5%) under elevated CO2.
• Across multiple studies, herbivores showed reduced abundance (-22%), increased relative consumption (+17%), increased development time (+4%), and reduced pupal weight (-5%) under elevated CO2, regardless of feeding mode. Plants showed increased size (+38%), increased C/N (+27%) and tannins (+30%), and decreased nitrogen (-16%).
• Other factors that can impact insects include habitat loss, habitat fragmentation, pollution, biological invasions, and nitrogen availability.
• It is difficult to predict future climate, especially variability, and the impacts on insects will include changes to growth, development, distribution, and phenology, which may be species-specific. Good ecological data is needed.