Environmental Change - Quaternary and Anthropocene Flashcards
ESD
Messinian Salinity Crisis (2.96-5.33Myr) end of the Miocene -> Mediterranean Sea desiccated due to tectonic activity closing the Gibraltar Strait via the Tethys Seaway
evidence in the form of evaporites across the basin -> orbital forcing led to the rapid warming as well
Messinian Salinity Crisis -> only extremophiles could cope with the suboxic and anoxic water -> flora and fauna recomposition particularly across the Mediterranean Islands
Betic Seaway formed (landbridge) -> interchange of mammals e.g. camels, mice and elephants (Gilbert et al., 2013)
Zanclean Flood (5.33MA) -> Atlantic Ocean reconnected with the Mediterranean Sea via a 200km channel which flooded causing incisional erosion -> Mediterranean filled at 10m/day
biogeography reset as a result
Man-made Suze Canal -> connected the Mediterranean Sea and Red Sea = Lesspsian Exchange -> saltier regions act as a filter for biota
core periods of exchange 2010 and 1956 -> canal was widened temporarily during these periods decreasing salinity -> imbalance of migration as Red Sea species better competitors as they are use to harsher environments (Lomolino et al., 2016)
The Great American Biotic Interchange (2.8-2.4Myr) -> Isthmus of Panama closed (Bartoli et al., 2005) = interchange of organisms but asymmetrical filter -> mainly N.A to S.A.
N.A. species = better dispersers, speciators, competitors and therefore niches in N.A already saturated AND landbridge formed during dry period -> birdge was grassland which favoured N.A species, evidence = sloths and anteaters from S.A. found in tropical rainforest in S.Mexico but did not move further north (Lomolino et al., 2016)
reptiles were the only species that
moved from S.A. to N.A (Lomolino et al., 2016)
GABI earlier theories -> landbridge formed via volcanic island formed by Pacific Plate subducted under the Carribbean Plate jioned by volcanic sediment (Cody et al., 2010) -> Gaarlandia was never a complete bridge and was previously a peninsula
evidence -> plant stem nodes identified that some plants migrated from Central to S.A. prior to the closure (Cody et al., 2010) -> ground sloths from S.A. present 9Myr in N.A but the isthmus closed in 3Myr - floated across? (Bacon et al., 2016)
Climate during the LGM (20ka) -> ice sheets across NH + Antarctica and mountain glaciers, Beringia refugia, 134m drop in sea levels, increased aridity, tropical rainforest at lower latitudes replaced with savanna (Barry and Chorley, 2009)
species diversity higher during LGM across the 3 European peninsulas -> refugia regions -> lots of species in one region (Petit et al., 2003)
Late Pleistocene megafauna extinctions -> globally lost except Africa which only lost 5-18% (Mann et al., 2018) -> modelling revealed that 96% of extinctions were human driven (Smith et al., 2018).
2/3rds of mammals with a body mass > 44kg went extinct (Barnosky and Lindsey, 2010)
Stripes and Plaid Hypothesis -> environments constantly shifting due to climatic changes producing plaid environments which species favoured
Holocene halted climatic shifts and environments became striped and more stable -> limited the range of megafauna making them vulnerable to human hunting (Mann et al., 2018)
Stripes and Plaid Hypothesis works for Africa -> country retained megafauna as they developed alongside humans
ITCZ, monsoonal precipitation patterns and 23,000yr procession events maintained Africa as a plaid environment (Mann et al., 2018)
Broken Zig-Zag Hypothesis
arrival of humans into S.A. disrupted the savanna vs tropical rainforest expansion and contraction relationship and human activity targeted the species populations that tended to be weaker through the environmental conditions (Miotti et al., 2018)
Climatic changes as the cause of Late Pleistocene megafauna extinctions (Steward et al., 2021) e.g. Younger Dryas (12.5kyr) – global, rapid cooling is what influenced megafauna but species persisted through other shifts, so the argument is less favourable
human activity exacerbated extinctions through the YD -> 24 genera went extinct during the period in N.A and clovis hunters entered the region at this time (Press-Pulse Theory – extinctions more likely when 2+ ecological impacts are taking place) (Barnosky and Lindsey, 2010).
Blitzkreig theory/overkill hypothesis -> arrival of humans times with the extinction of 30 species in N.A and 30 in S.A. -> led to the extinction of the giant ground sloth and mammoths (Anderson et al., 2010)
but Smilodon and Cantonyx remained in S.A 1.5-2.9ka after human arrival (Barnosky and Lindsey, 2011) and assosciational critique -> not enough scavenging/kill sites for all the species lost (Grayson et al., 2021) but this as a criticism was deconstructed by Wolfe and Broughton (2021)
Humans transmitting disease as the cause of the Late Pleistocene megafauna extinctions
Fasciola hepatica came from Europe to S.A. in humans and infected deer and camelids leading to their extinction (Pérez and Agnolin, 2021) -> also thought that anthrax and tuberculosis were to blame entering the New World around 10-20ka (Pérez and Agnolin, 2021)
Responses to climate change
phenology -> species shift to realign to seasons e.g. flowering in a different period, behaviour = adaptions e.g. amphibians move into water when it is too hot, acclimatisation = phenotypic plasticity as other phenotypes emerge to deal with the environmental conditions (Piglucci et al., 2006) and morphological = structural change to enable the organism a better change at survival (Bellard et al., 2012)
Refugia in Eurasia during the LGM -> hedgehog, grasshoppers and Brown Bair -> shifted to the Balkans and S.Italy during glaciations
allopatric speciation of the hedgehog as hybrid zones formed -> led to the western and eastern hedgehog across Europe (Steward and Stringer, 2012)
Europe (in 1971) had a phenology network to understand future changes to species, but it shut in 2000 due to a lack of funding
analysed 524 plant species and 19 animal species.
Responses to climate change - positive
Yellow-Bellied Marmot -> climate had led to an earlier hibernation and an earlier weaning of the young = longer growing season and the marmot growing.
climatic shifts on hominin development -> pulsed climate variability hypothesis (currently accepted theory) -> regular but rapid periods of climate change and longer periods of cooling led to the development of hominins across Africa -> three different proposed routes of the movement of species to Gibraltar, then to the Arabian Peninsula via the Nile valley and to the Arabian Peninsula via the southern Red Sea (Lomolino et al., 2016)
125-70ka -> movement out of Africa, 70-20ka movement into Australasia and Eurasia, 20-10ka -> movement into the America and 10-0ka -> movement around the rest of the globe (Smith et al., 2018).
Anthropocene -> sixth mass extinction is taking place as extinction rates far surpass background rates of extinction (Barnosky et al., 2011)
Maslin and Lewis (2015) -> Colombian Exchange with the Orbis Spike -> CO2 decrease detected in the Law Dome Ice Core from E.Antarctica
Wilson (2010) HIPPO
Habitat Loss, Invasive Species, Pollution, Human Population, Overharvesting/Overexploitation -> worrying since without biodiversity humanity will likely collapse (Pievani, 2014).
Sea LeveL Rise along the Great Barrier Reef
extinction of the Australian Rodent in 2019 (Tuvey and Cress, 2019)
bioclimatic modelling/envelope modelling -> using current environmental conditions to determine species distributions and from this project future distributions on projected environmental change
sensitive to the variable and so can often be inaccurate -> land use, projected climate (good GCM), dispersal rates -> often fail to consider metapopulations and disease outbreak (Thomas et al., 2004)
