Introduction to Ecosystems and the Anthropocene

Posted on Aug 24, 2024 in Geology

Ecosystem: A Dynamic Complex

An ecosystem is a dynamic complex of plant, animal, and microorganism communities and their non-living environment interacting as a functional unit. It is also the network of interactions among the living and non-living elements of the system.

Research on these interaction networks showed the need to consider ecosystems as a whole when studying nature. The science behind these studies is called ecology.

Ecology is not:

  • A political option
  • An ethical approach to nature
  • A social movement

Ecosystem Self-Organization

Ecosystems have self-organization. Their complexity increases without any external drive. Higher complexity means higher resilience.

Scale in Ecosystems

  • Scale is important when dealing with complex systems.
  • We can find systems nested in larger ones.
  • Each of these levels usually has its own properties and is usually related through feedback relationships.
  • Complex system management (conservation) should always be addressed at different scales simultaneously.

Food Chain

A food chain is a linear network of links among different organisms showing how they are related to each other by the food they eat.

  • Food chains start with producers (use radiation from the sun to make their food) and end at apex predators.
  • Include detritivores (earthworms) and/or decomposer species (bacteria, fungi).
  • Each step is a trophic level.

Food Web

  • Energy comes from the sun.
  • Each step loses about 90% of the energy. This energy loss restricts the amount of trophic steps and system complexity.

A food web is a natural interconnection of food chains showing what-eats-what in an ecological community.

  • It should also include non-living elements of the ecosystem.
  • Biogeochemical cycles

Socio-ecological System: For Human Well-being

A socio-ecological system is an ecosystem, the management of this ecosystem by actors and organizations, and the rules, social norms, and conventions underlying this management.

  • The well-being of people all over the world depends on the goods and services provided by ecosystems.
  • Ecosystems need to be healthy to provide those goods and services.
  • However, most ecosystems are under pressure and overexploited.
  • We need a strategy for the integrated management of land, water, and living resources that places human needs at its center.

Management Options

  • Hands-off
  • Adaptive management
  • Natural resource management
  • Command and control
  • Others

Think BIG (Individual Species – Ecosystem)

Marine Turtle

Problem: Longline fishing accidentally kills thousands of endangered sea turtles.

Solution: Working with fishermen, trying and developing a different kind of hook, developing a different kind of bait (fish, for example), changing the fishing depth and the distance from the coast.

How to liberate a captured marine turtle?

  • They remove the hook with an indicated device.
  • If that’s not possible, they cut the thread as close to the eye of the hook as they can.

Planetary Boundaries

These nine processes and systems regulate the stability and resilience of the Earth System (interactions of land, ocean, atmosphere, and life that provide conditions upon which our societies depend.

  1. Stratospheric ozone depletion.
  2. Loss of biosphere integrity (biodiversity loss and extinctions)
  3. Chemical pollution and the release of novel entities
  4. Climate Change
  5. Ocean acidification
  6. Freshwater consumption and the global hydrological cycle
  7. Land system change
  8. Nitrogen and phosphorus flows to the biosphere and oceans
  9. Atmospheric aerosol loading

Four of nine planetary boundaries have been crossed as a result of human activity:

  • Climate change
  • Loss of biosphere integrity
  • Land-system change
  • Altered biogeochemical cycles

Two of these, climate change and biosphere integrity, are “core boundaries”. Significantly altering either of these core boundaries would drive the Earth System into a new state.

Resilience

Resilience is “the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks.

  • Ecosystem’s stability and capability of tolerating disturbance and restoring itself.
  • If the disturbance is of enough magnitude or duration, a threshold may be reached where the ecosystem undergoes a regime shift, possibly permanently.
  • Resilience increases with ecosystem’s complexity

Planetary Boundaries and Resilience

  • Planetary boundaries are resilience thresholds for the Earth.
  • Crossed boundaries, take the Earth to a different state.
  1. Stratospheric ozone depletion.
  2. Loss of biosphere integrity (biodiversity loss and extinctions)
  3. Chemical pollution and the release of novel entities
  4. Climate Change
  5. Ocean acidification
  6. Freshwater consumption and the global hydrological cycle
  7. Land system change
  8. Nitrogen and phosphorus flows to the biosphere and oceans
  9. Atmospheric aerosol loading

Anthropocene: Age of Humans

Scientists have listed the many impacts of human activities on the planet including:

  • Human-induced carbon and sulfur emissions
  • Global runoff of nitrogen fertilizers.
  • Species extinctions
  • Coastal habitats destruction

They declared the Holocene over and the beginning of the Anthropocene. A geologic era is a subdivision of geologic time that divides an eon into smaller units of time.

Recognizing a New Era

These signals have to be global and found throughout the world in different elements:

  • Glacial ice
  • Tree rings
  • Coral growth bands
  • Seafloor and lake sediments
  • Other geological structures

Anthropocene Boundary

  • The most preeminent signal of the boundary was the radioactive fallout from thermonuclear weapons tests.
  • The fallout would reach the stratosphere and be evenly distributed throughout the world in weeks after the test.
  • Plutonium is very scarce, but there is a fine layer in sediments and glacial ice all over the planet.
  • Thermonuclear weapons tests started in 1952 and ended in 1964 (they are tested underground since then).

Anthropocene Signals

Fossil Fuels

  • The use of fossil fuels and carbon emissions has increased sharply since 1850.
  • Carbon dioxide concentration exceeds 400 parts per million.
  • The highest concentration in the last 65 million years
  • Shift in carbon isotopes present in any material