Environmental Science: Human and Natural Systems

Understanding Environmental Science

• Environmental Science studies the interactions between human and natural systems, focusing on human-caused (anthropogenic) problems.
• It uses an integrated approach, drawing from fields like geology, atmospheric chemistry, climatology, and ecology.
• The goal is to find sustainable solutions to environmental problems caused by human activities.
• A comprehensive understanding of environmental problems is needed before proposing solutions.

Anthropogenic Problems

• Defined as problems caused by human activities, such as pollution and resource depletion.
• Understanding these is crucial for developing effective solutions, as humans are primary agents of environmental change.
• Examples include burning fossil fuels, contributing to climate change and air pollution.

Integrated Approach to Solutions

• It involves cross-disciplinary collaboration to address environmental issues holistically.
• Environmental scientists analyze problems from multiple perspectives for comprehensive solutions.
• This approach is essential for complex issues like climate change, which cannot be solved by one discipline alone.

Core Concepts of Sustainability

• Sustainability is maintaining ecological balance while meeting human needs.
• Human systems (transportation, agriculture, manufacturing) depend on natural systems (sunlight, water, soil).
• Unsustainable practices deplete these resources.
• The use of non-renewable resources, like fossil fuels, indicates unsustainable practices.

Environmental Indicators

• Metrics used to assess the health of ecosystems and the sustainability of human activities.
• Examples include biological diversity, sea level change, and water quality.
• Environmental indicators determine the impact of human activities on the environment.
• Environmental scientists can evaluate whether practices like fracking are sustainable.

The Ecological Footprint Model

• Quantifies the impact of human activities on the environment, measuring resource consumption and waste production.
• It helps individuals and societies understand their environmental impact and identify areas for improvement.
• This model is crucial for assessing sustainability and guiding policy decisions.

Addressing Human-Caused Issues

• Some environmental problems, like natural disasters, can't be solved but require adaptation strategies.
• Human activities like driving and agriculture create environmental challenges that can be addressed through sustainable practices.
• Solutions must be scientifically informed, economically viable, and socially equitable to be effective.

Socioeconomic Considerations

• Implementing sustainable solutions involves navigating economic and political landscapes, as scientific solutions alone may not be feasible.
• For example, stopping fossil fuel use is scientifically sound but poses economic challenges.
• Sustainable solutions must balance environmental integrity with economic and social realities.

The Role of Policy and Governance

• Environmental problems are often addressed through government action, starting with public awareness and scientific assessment.
• Agencies like the EPA evaluate the potential impacts of environmental issues and the costs of action versus inaction using risk analysis.
• Policymakers develop laws and regulations based on scientific data to ensure sustainable practices are enforced.

The Tragedy of the Commons

• Illustrates how shared resources can be overused and depleted without regulation.
• Individuals benefit from exploiting common resources, leading to collective loss.
• Legal frameworks are needed to protect these resources.
• Environmental laws serve as a check against this phenomenon, ensuring sustainable use of air, water, and other natural resources.

Historical Context of Environmental Legislation

• The National Environmental Policy Act (NEPA) of 1969 established a framework for environmental protection in the U.S.
• NEPA led to the creation of the Environmental Protection Agency (EPA), which oversees environmental regulations and policies.
• The Clean Air Act of 1970 is a significant example of legislation aimed at improving air quality and promoting sustainability.

Case Study: Lake Washington Eutrophication

• Eutrophication was caused by the diversion of treated sewage containing nitrates and phosphates, leading to algal blooms.
• The decomposition of dead algae depleted oxygen levels in the water, creating a dead zone.
• This case highlights the importance of understanding nutrient cycles and the impact of human activities on aquatic ecosystems.

Understanding Producers

• Producers are organisms that capture sunlight and convert it into chemical energy through photosynthesis, typically plants.
• They are the base of the food chain, providing energy for consumers and decomposers.
• Examples include various plants, algae, and some bacteria that perform photosynthesis.

Net Primary Productivity (NPP)

• Measure of the amount of sugar (energy) stored by producers in an ecosystem after accounting for their own respiration.
• It's crucial for understanding the energy available to consumers and decomposers in the ecosystem.
• High NPP correlates with greater biological diversity, as seen in tropical rainforests, which have abundant sunlight and rainfall.

Factors Influencing NPP

• Abiotic factors such as sunlight, water availability, and nutrient levels significantly affect NPP.
• Ecosystems with optimal conditions for these factors tend to have higher NPP, supporting more diverse life forms.
• Increased rainfall can enhance plant growth, leading to higher NPP.

Importance of Measuring NPP

• Ecologists measure NPP to assess ecosystem health and productivity.
• Understanding NPP helps in conservation efforts and managing natural resources effectively.
• It provides insights into how energy flows through ecosystems and the impacts of human activities.

The Photosynthesis Equation

• Photosynthesis chemical equation: Sunlight + H2O + CO2 >>> C6H12O6 + O2.
• It involves capturing sunlight and converting it into glucose (sugar), with oxygen released as a by-product.
• It highlights the transformation of solar energy into chemical energy stored in sugar molecules.

Role of Photosynthesis in Ecosystems

• Photosynthesis is essential for producing the energy that sustains life in ecosystems.
• Plants use the sugar produced for their own metabolic processes, primarily to create ATP for energy.
• The sugar not immediately used contributes to the NPP, which is available to consumers.

Understanding Aerobic Respiration

• Aerobic respiration equation: C6H12O6 + O2 >>> Energy (ATP) + H2O + CO2.
• Releases the energy stored in sugar, allowing cells to perform necessary functions.
• Water and carbon dioxide are by-products of this metabolic process.

Importance of Metabolism in Ecosystems

• All living organisms, including producers, consumers, and decomposers, metabolize sugar to obtain energy.
• Metabolism is crucial for growth, reproduction, and maintaining homeostasis in organisms.
• Understanding metabolism helps explain energy flow and nutrient cycling in ecosystems.

Lab Activity Overview

• Measure the NPP and metabolic rate of a producer (plant) using a controlled experiment.
• Materials include glass bottles, CO2 test kits, and a light source to create different conditions (light vs. dark).

Methodology

• Label two bottles as LIGHT and DARK, fill with water, and add equal amounts of Elodea (a water plant).
• Place the LIGHT bottle under a light source and the DARK bottle in a dark space for 48 hours.
• Measure initial and final CO2 concentrations to determine changes.

Key Concepts of Thermodynamics

• Energy is defined as the ability to do work, essential for all living systems.

• First law of thermodynamics: Energy cannot be created or destroyed, only transformed in a closed system.

• Second law of thermodynamics: Energy transformations are inefficient, leading to energy loss as heat.

• These laws provide a framework for understanding energy dynamics in ecological studies.

• Thermodynamics highlight the importance of energy efficiency in ecosystems and human impacts on these systems

• Understanding thermodynamics is essential for addressing environmental issues.

• Energy flows in one direction through ecosystems, from producers to consumers.

• Energy is not recycled; it must be continuously supplied (e.g., sunlight).

Understanding Primary Productivity

• Primary productivity (NPP) is the rate at which energy is converted to organic substances by producers.
• Sunlight is the primary energy source for ecosystems, captured by plants during photosynthesis.
• NPP is crucial for supporting diverse animal populations, as it determines energy availability.
• Higher NPP correlates with greater biodiversity in ecosystems, as more energy supports more life forms.

Producers and Consumers

• Producers (autotrophs) convert sunlight into energy-rich compounds, mainly glucose.
• Consumers (heterotrophs) rely on producers for energy, either directly or indirectly.
• Trophic levels include: primary consumers that eat producers, secondary consumers that eat primary consumers, and tertiary consumers that are apex predators.
• Decomposers recycle nutrients back into the ecosystem, playing a critical role in energy flow.

The 10% Rule

• Illustrates energy loss at each trophic level, impacting population dynamics.
• Only about 10% of energy is passed from one trophic level to the next, with 90% lost as heat.
• This principle explains why ecosystems have fewer top predators than primary consumers.
• The implications of the 10% rule are significant for conservation and management of wildlife populations.

Biogeochemical Cycles Overview

• Matter is conserved in ecosystems and is recycled between abiotic and biotic components.
• Matter differs from energy, which flows through and is lost.
• Organisms obtain matter from the environment to build their bodies, which is returned upon death.
• Key cycles include the carbon, nitrogen, phosphorus, and hydrological cycles.

The Carbon Cycle

• Carbon is the backbone of organic molecules
• Plants absorb CO2 during photosynthesis, converting it into glucose, which is then metabolized.
• When organisms die, carbon is returned to the atmosphere or can become fossilized.
• This cycle illustrates the interconnectedness of life and the environment.
• Human activities, like fossil fuel combustion, disrupt the carbon cycle, leading to climate change.

Carbon Cycle and Its Implications

• Plants absorb atmospheric CO2 during photosynthesis, converting it into sugars for energy storage.
• Sugars can be metabolized by plants or consumed by animals, returning CO2 to the atmosphere.
• If sugars are not metabolized, they can fossilize into fossil fuels or marine sediments (limestone).
• Fossil fuels and limestone act as carbon sinks, reducing atmospheric CO2 levels.

Fossil Fuels and Environmental Impact

• The combustion of fossil fuels for energy releases significant amounts of CO2, exacerbating global warming.
• The increase in atmospheric CO2 leads to environmental issues like rising sea levels and extreme weather patterns.
• Marine ecosystems are particularly affected by ocean acidification, impacting coral reefs and marine life.
• Sustainable energy alternatives are essential to mitigate these impacts and reduce reliance on fossil fuels.

Importance of Nitrogen in Ecosystems

• Nitrogen, a key component of amino acids and nucleic acids, can't be used directly by most organisms.
• The atmosphere is composed of 79% N2, but it is inert and cannot be used directly by most organisms.
• Nitrogen fixation is the process by which specialized bacteria convert N2 into usable forms (e.g., NO3-).
• Plants assimilate fixed nitrogen, which is then transferred to animals through the food chain.
• Denitrification processes convert nitrates back to N2, completing the nitrogen cycle.

Human Impact on the Nitrogen Cycle

• Excessive use of nitrogen fertilizers can lead to nutrient runoff, causing algal blooms in aquatic systems.
• Algal blooms deplete oxygen in water, leading to dead zones where aquatic life cannot survive.
• Sustainable agricultural practices are necessary to minimize nitrogen pollution and maintain ecosystem health.

Phosphorus Sources and Cycling

• Phosphorus is essential for DNA, RNA, and ATP, making it crucial for energy transfer in living organisms.
• Unlike nitrogen, phosphorus does not exist in the atmosphere; it is derived from rocks, particularly potash.
• Erosion of phosphate-rich rocks releases phosphates into soil and water, where they are absorbed by plants.
• Sedimentation can remove phosphates from the ecosystem, trapping them in rocks again.

Human Influence on the Phosphorus Cycle

• Overuse of phosphorus fertilizers can lead to runoff, contributing to water pollution and eutrophication.
• Sustainable farming practices are essential to manage phosphorus levels and prevent environmental degradation.
• The demand for phosphorus in agriculture is increasing, raising concerns about resource depletion.
• The balance of phosphorus is vital for ecosystem sustainability.

Water Movement in Ecosystems

• The hydrological cycle describes the continuous movement of water through the environment, essential for life.
• Water vapor accumulates in the atmosphere, forming clouds and eventually falling as precipitation.
• Precipitation can infiltrate the soil, run off into bodies of water, or evaporate back into the atmosphere.
• Variations in precipitation and evaporation rates impact ecosystem productivity and biodiversity.

Impact of Water Availability on Ecosystems

• Rainforests have high precipitation, leading to rich biodiversity and rapid plant growth.
• Deserts, with low precipitation, support fewer species and lower biodiversity.
• Climate change is altering precipitation patterns, impacting ecosystems globally.
• Sustainable water management practices are necessary to ensure ecosystem health.

Understanding Biomes

• Biomes are large areas characterized by similar abiotic conditions, supporting specific plant and animal communities.
• Major terrestrial biomes include tundra, tropical rainforests, and taiga, each with unique adaptations.
• Aquatic biomes, such as coral reefs and estuaries, also exhibit distinct ecological characteristics.
• Students should familiarize themselves with the key features and locations of major biomes.

Ecosystem Services and Human Interaction

• Ecosystem services are benefits provided by natural systems, essential for human survival and economic activity.
• Examples include oxygen production, water purification, and nutrient cycling, all vital for life.
• The economy relies on these services, yet often undervalues them, leading to environmental degradation.
• The Tragedy of the Commons illustrates the consequences of overexploiting shared resources.
• Understanding ecosystem services is critical for developing sustainable economic policies.