Lecture 14:Interactions between global change drivers and invasions Flashcards
Darwin Plus: Antarctic Research in South Georgia
Major invasive species in South Georgia Antarctica (at present)
Perna viridis (mussel)
Wasmannia auropunctata (crab)
Rattus norvegicus (rat)
Prosopis juliflora (shrub)
*Species introductions across biogeographic barriers continue to accumulate as a result of trade and transport
*Some species establish, increase in abundance and distribution, and have negative biodiversity impacts: invasive
*Remote islands are especially vulnerable to invasions: depauperate; vacant niches; naïve prey; weak competitors
See for reference: Marine traffic of the day on: marine traffic.com
Invasions in the future:
*Introductions will continue, but how will invasions respond to climate change?
-Altered fitness & outcomes of interactions with other species
-Range shifts of established species
-Changes in climate suitability for arriving species (and extant species)
*Rapid warming in (sub-)polar regions, including sub-Antarctic islands
See: Global surface temperature anomalies (compared to 1951-1980 baseline). Credit: NASA
South Georgia
South Georgia is an isolated, sub-Antarctic island, with multiple glaciers and fjords
Vegetation largely restricted to peninsulas
South Georgia species
Include globally important bird and marine mammal colonies and endemic species
Human impacts in South Georgia
*Historically, home to several whaling stations
*Introductions: Rats, mice, reindeer; plants from the N Hemisphere; predatory carabid beetles from the S Hemisphere
*Introduced mammals eradicated; 8 introduced plants are now too well-established to remove entirely
*Marked temperature increase and deglaciation, reconnecting isolated peninsulas and bare ground (increasing access for invasives to areas with naive species)
How can climate change effect South Georgia invasions?
1.Colonisation and dominance of deglaciated ground
2.Increased competitive ability of introduced over native plants
3.Further spread of predator beetles to new peninsulas
4.Increasing climate suitability for species likely to arrive on South Georgia from sub-Antarctic region
Colonisation of deglaciated islands
Transect surveys will identify plant and invertebrate colonists, and quantify relative frequency
Surveys at different times since deglaciation will reveal early community development
Expect plant colonisers to be dominated by introduced species
Plant competition under future temperatures
*Climate chamber experiment: current SG summer temperatures, vs temperatures expected with intermediate GHG emissions by 2081-2100 (SSP Scenario 2: +2.1-3.5 °C) to see how warming impacts germination and growth
*Compare proportion of community biomass belong to invasive species in each climate
*Introduced plants have native ranges in warmer temperate regions; more likely to increase growth than (sub-)polar natives
Invasive carabid spread
*Trechisibus antarcticus; Merizodus solidadinus (flightless beetle)
-Flightless, predatory ground beetles
-Distribution unclear, though evidence of spread to new sites between 1995/6 and 2006/9
*Surveys of northern Peninsulas to establish current extent
*Assess abundance of potential prey species in relation to carabid presence
Future climate horizon scan
*We know the pathways and origins of introduction to South Georgia
*Species most likely to arrive as transport stowaways or contaminants
*Species present in Falklands, Tierra del Fuego and sub-Antarctic islands
*We will assess climate suitability of SG for these species in a 2081-2100 climate (SSP 2)
Summary
*Climate change will be most rapid in polar and sub-polar regions
*Deglaciation and warmer temperature may promote introduced species over cold-adapted native species- consequence for community composition and function: novel communities
*Experimental and modelling work needed to understand which species are likely to be the ‘winners’ of climate change, and to avoid introducing in future
How will climate change affect the likelihood of invasions globally?
Higher levels of trade between nations lead to greater numbers of invading species
How will the effects of trade be moderated by warming?
Predicted changes in mean annual temperature and precipitation, 2020-2029 compared to 1950-2000; ECHAM5-Global Circulation Model under the A1B-climate change scenario (Roeckner et al., 2003; IPCC, 2007) Seebens et al. (2015) Global Change Biology 21: 4128-4140
Invasion model
Altered to account for changes in environmental similarity under future climate scenario:
see equation in notes
Adapted from: Seebens et al. (2015) Global Change Biology 21: 4128-4140
How will other global change drivers affect invasions?
Habitat destruction and disturbance:
*Disturbance trigger invasions, particularly r-selected/dist-adapted spp (plants)
*Extreme weather -> more disturbance -> invasion
Habitat fragmentation
*Isolation- like an island, more prone to invasions? Why?- edge effects, e.g. light levels may suite pioneer invaders; invaders might be high in number in the matrix (high propagule)
*Less connectivity (patchiness), impede invasions?
Urbanisation
*Increased disturbance promoting invasions?
*Increased importation of species (colonisation and propagule pressure). Intentionals, ornamental plants (gardens)- unintentional release (pet trade)
*Increased resource availability (animals and plants-> promote nutrient-demanding spp)
*Urban heat island effects
Nutrient deposition:
*N enrichment might benefit n-demanding competitive plant species, native plants requiring low nutrients-> get outcompeted. Decrease in biodiversity
*More invasions in freshwater ecosystems due to eutrophication (algae, macrophytes);
*May see global patterns, with emerging economies going through rapid industrialisation and increase in fertiliser use may see biggest rise in nutrient-related invasions.
