ESS: Systems, Models, and Ecosystems

• Environmental Systems and Societies (ESS) is an interdisciplinary subject area

Systems and Models

• A system is a set of inter-related parts working together to form a complex whole
• Systems can be open, closed, or isolated
• Open systems exchange both matter and energy with their surroundings
• Closed systems exchange energy but not matter with their surroundings
• Isolated systems exchange neither matter nor energy with their surroundings
• Transfers involve a change in location
• Transformations involve a change in chemical nature, state, or energy
• Models are simplified representations of reality
• Models can be physical, mathematical, or conceptual
• Strengths of models include ease of use and understanding and display of complex systems
• Limitations of models include oversimplification and reliance on assumptions

The ecosystem

• An ecosystem is a community of interdependent organisms and the physical environment they inhabit
• Ecosystems can be aquatic or terrestrial
• A biome is a collection of ecosystems sharing similar climatic conditions
• Biosphere is the part of the Earth inhabited by organisms
• Abiotic factors are the non-living components of the environment
• Biotic factors are the living components of the environment
• Species is a group of organisms sharing common characteristics that interbreed and produce fertile offspring
• Population is a group of individuals of the same species living in the same area at the same time
• Community is a group of populations living and interacting with each other in a common habitat
• Habitat is the environment where a species normally lives

Ecology

• Ecology is the study of relationships between living organisms and between organisms and their environment
• The main processes in an ecosystem are photosynthesis, respiration, feeding and nutrient cycling
• A food chain shows the flow of energy from one organism to the next
• A food web is a network of interconnected food chains
• Trophic level is the position an organism occupies in a food chain
• Producers are autotrophs that make their own food through photosynthesis
• Consumers are heterotrophs that obtain energy by feeding on other organisms
• Decomposers break down dead organic matter
• Ecological pyramids are graphical models of quantitative differences between trophic levels
• Types of ecological pyramids include numbers, biomass, and productivity
• Bioaccumulation is the build-up of persistent pollutants within an organism
• Biomagnification is the increase in concentration of persistent pollutants along a food chain
• The pyramid of numbers records the number of individuals at each trophic level
• The pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square meter (g m−2) or Joules per square meter (J m−2)
• The pyramid of productivity shows the rate of generation of biomass at each trophic level measured in units of biomass or energy per area per time
• The flow of energy through ecosystems is not efficient
• Only about 10% of the energy in one trophic level is transferred to the next level
• Solar radiation is the primary source of energy for most ecosystems

Biomes

• A biome is a collection of ecosystems sharing similar climatic conditions
• Climate and geography influence the distribution of biomes
• Examples of biomes include tundra, taiga, temperate forests, rainforests, grasslands, and deserts
• Tundra is characterized by low temperatures, short growing seasons, and permafrost
• Taiga is a coniferous forest characterized by long, cold winters and short, mild summers
• Temperate forests have moderate temperatures and rainfall
• Rainforests have high temperatures and rainfall
• Grasslands are dominated by grasses and have moderate rainfall
• Deserts have low rainfall

Nutrient cycles

• Key elements such as carbon, nitrogen, and phosphorus cycle through ecosystems
• The carbon cycle involves photosynthesis, respiration, decomposition, and combustion
• The nitrogen cycle involves nitrogen fixation, nitrification, denitrification, and assimilation
• The phosphorus cycle involves weathering, absorption by plants, consumption by animals, and decomposition
• Human activities can disrupt nutrient cycles

Water

• Water is essential for life
• The water cycle involves evaporation, transpiration, condensation, precipitation, and runoff
• Human activities can affect the water cycle
• Water availability varies geographically

Sustainability

• Sustainability is the use and management of resources that allows full natural replacement of the resources exploited and full recovery of the ecosystems affected by their extraction and use
• Natural capital is the natural resources that have a value to humans
• Natural income is the yield obtained from natural resources
• Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs
• Environmental indicators are used to assess sustainability
• Examples of environmental indicators include biodiversity, pollution levels, and resource depletion
• Carrying capacity is the maximum number of a species or 'load' that can be sustainably supported by a given environment

Threats to Biodiversity

• Habitat loss, invasive species, pollution, overexploitation, and climate change are major threats to biodiversity
• Habitat loss is the destruction or fragmentation of habitats
• Invasive species are non-native species that can outcompete native species
• Pollution is the contamination of the environment with harmful substances
• Overexploitation is the unsustainable harvesting of resources
• Climate change is the alteration of global weather patterns, primarily due to increasing atmospheric carbon dioxide levels

Conservation

• Conservation efforts aim to protect and restore biodiversity
• Strategies include habitat restoration, species recovery programs, and protected areas
• In situ conservation involves protecting species in their natural habitats
• Ex situ conservation involves protecting species outside their natural habitats

Pollution Management

• Pollution management strategies include reducing, reusing, and recycling
• Reducing pollution can be achieved through changes in lifestyle and technology
• Reusing materials can reduce waste
• Recycling materials can conserve resources
• Pollution control technologies can reduce emissions

Climate Change Mitigation and Adaptation

• Mitigation strategies aim to reduce greenhouse gas emissions
• Adaptation strategies aim to help people and ecosystems cope with the effects of climate change
• Examples of mitigation strategies include renewable energy, energy efficiency, and carbon sequestration
• Examples of adaptation strategies include building seawalls, drought-resistant crops, and early warning systems

Environmental Value Systems

• An environmental value system (EVS) is a worldview that shapes how people perceive and evaluate environmental issues
• EVSs are influenced by cultural, religious, economic, and socio-political contexts
• Types of EVSs include ecocentric, anthropocentric, and technocentric
• Ecocentrism emphasizes the intrinsic value of nature
• Anthropocentrism emphasizes the value of nature for human benefit
• Technocentrism emphasizes the ability of technology to solve environmental problems

Energy Resources

• Renewable energy resources are replenished naturally, while non-renewable resources are finite
• Examples of renewable energy resources include solar, wind, hydro, and geothermal
• Examples of non-renewable energy resources include fossil fuels (coal, oil, and natural gas) and nuclear
• The use of energy resources has environmental impacts
• Fossil fuels contribute to climate change and air pollution

Soil Degradation

• Soil degradation is the decline in soil quality
• Causes of soil degradation include erosion, nutrient depletion, and contamination
• Soil conservation practices can prevent soil degradation
• Examples of soil conservation practices include terracing, contour plowing, and crop rotation

Human Population

• Human population growth has environmental impacts
• Factors influencing population growth include birth rates, death rates, and migration
• Population pyramids show the age and sex structure of a population
• Demographic transition model describes the stages of population growth
• The carrying capacity for humans is uncertain

Food Production Systems

• Food production systems can be intensive or extensive
• Intensive systems rely on high inputs of resources
• Extensive systems rely on natural processes
• Impacts of food production systems include deforestation, water pollution, and greenhouse gas emissions
• Sustainable agriculture practices can reduce environmental impacts

Waste Management

• Waste management strategies include reducing, reusing, recycling, and composting
• Landfills are used for waste disposal
• Incineration is the burning of waste
• Waste management can have environmental impacts

Aquatic Food Production Systems

• Aquaculture is the farming of aquatic organisms
• Wild fisheries are the harvesting of wild fish populations
• Overfishing can deplete fish stocks
• Aquaculture can have environmental impacts

Atmospheric Pollution

• Air pollutants include particulate matter, ozone, sulfur dioxide, and nitrogen oxides
• Sources of air pollution include industrial emissions, transportation, and agriculture
• Air pollution can have human health and environmental impacts
• Pollution management strategies can reduce air pollution

Water Pollution

• Sources of water pollution include industrial discharge, agricultural runoff, and sewage
• Water pollutants include pathogens, nutrients, and toxins
• Water pollution can have human health and environmental impacts
• Pollution management strategies can reduce water pollution

Biodiversity Loss

• Biodiversity refers to the variety of life on Earth
• Biodiversity loss is the decline in the number and variety of species
• Causes of biodiversity loss include habitat loss, invasive species, pollution, overexploitation, and climate change
• Biodiversity provides ecosystem services
• Conservation efforts can protect biodiversity

Human Impacts

• Environmental impacts resulting from human activities can affect the viability of populations and habitats along with the cycling of nutrients
• The scale of environmental damage can be affected by human population size and level of human consumption