The Anthropocene (HL) (DP IB Environmental Systems & Societies (ESS))

The Anthropocene

What is the Anthropocene?

• The Anthropocene is a proposed geological epoch

  • Scientists have suggested that humans have become a dominant force shaping the Earth’s environment and climate

• The Anthropocene is not yet an officially recognised epoch

  • However, it still highlights the extent to which human activities, like industrialisation, deforestation, and urbanisation, are driving:

    • Rapid environmental change

    • Species extinction

• Human impacts are so significant that they are leaving permanent records on Earth's geology, atmosphere, and ecosystems

Debate over the Anthropocene

• There is debate among scientists about whether the Anthropocene should be considered separate from the current Holocene epoch, which began around 11,700 years ago after the last Ice Age

  • Some scientists argue that human impacts are significant enough to define a new epoch

  • Others believe these changes (e.g. in climate) are part of the natural variability of the Holocene

• The starting point of the Anthropocene is also debated, with different proposals for when it began

Proposed start dates for the Anthropocene

• 1610 carbon dioxide dip:

  • One proposed marker is a dip in carbon dioxide levels around 1610, following the arrival of Europeans in the Americas

  • This drop in CO2 is believed to be caused by the decline of Indigenous populations due to European diseases, warfare, and slavery, which led to the reforestation of previously farmed lands in the Americas

  • These new forests absorbed more CO2, leading to a detectable drop in the atmosphere

  • This is sometimes referred to as the "Orbis spike" and is considered one potential starting point for the Anthropocene

• 1950 spherical fly ash particles:

  • Another suggested marker is the appearance of spherical fly ash particles in the geological record, beginning around 1950

  • These particles were created by the burning of fossil fuels in coal-fired power plants

  • The particles have since spread globally, leaving a clear, human-made trace in the Earth's sediments

  • The 1950s also saw the beginning of the "Great Acceleration", when human impacts on the environment, such as pollution and greenhouse gas emissions, increased dramatically

• 1964 carbon-14 markers:

  • The 1964 spike in carbon-14 in the atmosphere, caused by nuclear weapons testing, is another potential marker

  • Nuclear tests, particularly those conducted during the Cold War, released radioactive isotopes like carbon-14 into the atmosphere

  • These isotopes settled into the Earth’s soils and sediments, creating a distinct signal in the geological record

Awaiting image: Earth system trends 1800-2010

Image caption: Earth system trends of the "Great Acceleration" of the Anthropocene from 1800 to 2010

Awaiting image: Socioeconomic trends 1800-2010

Image caption: Socioeconomic trends of the "Great Acceleration" of the Anthropocene from 1800 to 2010

Human impact on the planetary scale

• Human activity is having a planetary effect on Earth's environment

  • This effect will be detectable in the geological record for millions of years.

  • This means future geologists could look at Earth's layers and see clear evidence of our presence (a bit like how we study fossil records to understand ancient life forms)

Further evidence for the Anthropocene

1. Chemical pollution accumulating in geological strata:

   • Human-made chemicals, such as plastics, pesticides, and industrial waste, are accumulating in soils and sediments around the world

   • Microplastics are a clear example of human pollution that will be preserved in the Earth's strata far into the future

2. Mixing of native and non-native species:

   • Human activities have led to the mixing of native and non-native species through processes like global trade and introduction of invasive species

   • Species that do not naturally interact now share ecosystems

   • In the future, this mixing will be evident in the fossil record

3. Modification of terrestrial and marine sedimentary systems:

   • Human activities, such as agriculture, deforestation, and urbanisation, are altering Earth's natural sedimentary systems

   • These changes lead to:

     • Increased soil erosion (large-scale agriculture and deforestation often leads to soil erosion, where topsoil is worn away by wind or water)

     • Changes to river flows and coastal ecosystems (building cities and roads changes the natural landscape, blocking rivers and coastlines, which affects sediment flow and can lead to unnatural sediment build-up in some areas and erosion in others)

4. Minerals created by human activity:

   • Humans are creating new types of minerals and materials that do not exist naturally

     • E.g. concrete, plastics, and metal alloys

   • These human-made materials will persist in the geological record for millions of years, providing clear evidence of our influence on the planet