Introduction lecture Flashcards
Defining the ‘Anthropocene’
The Anthropocene = human dominated epoch
^ the final epoch?
Officially we are in the Holocene era but many ecologists argue that we must now acknowledge we are now in a new human dominated epoch – the Anthropocene – as humans are an integral part of Earth’s systems. However geologists do not acknowledge the Anthropocene as an official epoch.
What defines an epoch
Geological time can be divided into epochs – units (usually) measuring millions of years
Epochs are contained within periods (current = Quaternary)
Periods are within eras (current = cenozoic)
From ~11,700 we have been in the Holocene – before this was the Pleistocene (2.58 Mya)
the transition from Pleis. To Holo. Was linked to climate change at the end of the ice age. Resulting in increased atmospheric CO2 and 18 O – water which is heavier than the more common 16 O water isotope resulting in reduced evaporation and earlier precipitation at lower lat. And temp.
NGRIP2 ice core confirmed the shift at the end of the Pleistocene
Iridium dust evident at the cataclysm point when the dinosaurs were wiped out
When did the Anthropocene begin?
Debatable
Circa 1610 the Old World – New World collision ‘discovery’ of the Americas
Global trade and biotic exchange
Increasing urbanisation and land use change
CIrca 1950 the ‘Great acceleration’
an uptick observable in socio-economic trends in early 20th century – reflected in Earth system trends with a matching uptick in atmospheric NO, C02, Methane + fishing, forest loss, surface temp, ocean acidification etc.
Circa 1950’s stratigraphic signatures
Manufactured materials in sediments (Technofossils)
C, N, and phosphorous deposition
Atmospheric CO2 and methane, climate and sea level rise
Biotic exchange and extinctions
Radionuclide spikes from nuclear weapon fallout ( can still be used for dating matter)
Technofossils
The rise of plastics
Ocean currents and gyres concentrate plastics in the water column forming large ‘patches’
Photo-degredation – leads to distribution of plastic particles
^ Persistent and widespread in ocean sediments
plastic production has increased to ~300Tg yr-1 produced at present
98% of all aluminium produced after 1950
Concrete – invented by Romans, 500,000 Tg >50% total produced after 1995
These materials are near ubiquitous and will form a persistent technofossil record
see: http://www.bbc.co.uk/news/scienc
e-environment-36233567
&
Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622
Mineral extraction and changes in sedimentation
Mineral extractions alone accounts for 57000Tgyr-1 of sediment displacement per year
^ equivalent to 9500 egyptian pyramids
Carbon
SCP and black carbon (soot) increasing since Ind. Rev
Accelerated since 1950 – globally near synchronous (SCP)
* Mineral extraction alone accounts for 57,000 Teragrams
yr-1 of sediment displacement (57,000,000,000,000 kg)
That’s 3 times the amount of sediment
moved by Earth’s rivers
In UK: 50 tg material yr-1 moved by rivers
688 Tg yr-1 shifted by us
see: Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622; Douglas et al. (2000) J Industrial Ecology 4: 9-33.
Nitrogen
Haber-Bosch process:
-used for fixation of atmospheric Nitrogen since 1913
-Produces Ammonia which can be converted into inorganic N fertiliser
-production accelerated after 1950 - that’s a 120% increase in reactive N
Marked by declines in 15N - Preferential reduction of the lighter 14N isotope in N fixation/NOx
see: Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622
Fallout radionuclides from nuclear weapons
GSSP
Peak in radioactive Plutionium and Carbon14 in 1964 following peak in nuclear weapon testing
Not a ‘golden spike’ (not directly linked to Earth system level change)
Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622
CO2 – climate change
Increase in late Pleist. And gradual increase through Holo.
Rise in 13C mid holocene preferential 12C uptake in biosphere, ocean release
Burning of coal, oil and gas resulted in decrease of atmospheric 13C and increase in 12C atmospheric
Overall cooling trends in last 2000 years
Temp quirks have occurred in the past e.g. medieval warming period (MWP) and Little Ice Age (LIA) but not on the scale of modern climate change
Temperatures in S hemisphere and tropics already exceeding Holocene variation
- N Hemisphere following suit
see: Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622; Wanner et al. (2015) J Geological Society London 172:254-263.
Biotic exchange and homogenisation
Unprecedented levels of species transport both intentional and accidental
Resulting in invasives
Even remote islands e.g. St Helena have a high proportion of non-native species
Extinctions
Current rates far exceed natural rates and have since 1800’s
Loss of species from the fossil record
Gain of ubiquitous species through introduction – hence why the anthropocene is referred to as the ‘age of the chickens’ as 71% of bird life globally is now farmed
Waters et al. (2016) Science 351 (6269), DOI: 10.1126/science.aad2622
The case for Anthropocene starting circa 1950
is still up for debate
The Working Group on the Anthropocene
- Part of the Subcommission on Quaternary Stratigraphy of the International Commission on Stratigraphy
Case for the new Epoch, and its start date (1950) put to the International Geological Congress: 29.08.2016
2021: neither the International Commission on Stratigraphy (ICS) nor the International Union of Geological Sciences (IUGS) has officially approved the term as a recognised subdivision of
geologic time
Arguments for and against continue…
Whether we name it or not:
– we humans are continually impacting and changing our environment
– transforming biomes from natural -> anthropogenic
Humans as ecosystem engineers
Destruction and transformation
Restoration and novel ecosystems
Novel evolutionary trajectories
Why does the new Epoch matter for ecology?
Remaining wilderness 22% of the world mostly located in 20 countries
Watson et al. (2018) Nature 563: 27-30
At all spatial scales species interactions must now take into account human influence
Summary
- The case for defining the Anthropocene as a new Epoch has gained momentum, but remains controversial - Coincides with the ‘Great Acceleration’ ~1950
- Impacts of human activity are global in scale, and will leave a persistent geologic signal
- Many impacts involve massive changes to the biosphere: ecology and evolution of life on Earth is no longer independent of human activity
