Biology: How Life Works - The Anthropocene

The Anthropocene

• Refers to the current geological era, emphasizing the significant impact of humans on Earth
• Chapter 48 of "Biology: How Life Works" by Morris et al. covers the Anthropocene

Objectives of Studying the Anthropocene

• Understanding the definition of the Anthropocene
• Examining human impact on the carbon cycle
• Analyzing human impact on the nitrogen and phosphorus cycles
• Investigating human influence on evolution
• Defining and understanding conservation biology

Defining the Anthropocene

• The human population has surpassed 7 billion
• Several revolutions in human history fueled population and consumption growth like argicultural, industrial, medical/sanitation, tech, green, and gene revolutions
• A key question is determining Earth's carrying capacity for humans

Ecological Footprint

• Measures the total land and water needed to provide resources and dispose of waste for a person or population
• About 20% of the global population (in developed nations) consumes 80% of resources
• The other 80% (in developing nations) uses the remaining 20% of resources

Importance of Healthy Ecosystems

• They provide essential services to humans
• They face increased pressure due to population growth in developing countries and high consumption in developed countries

Human Impact: Population Growth

• Increasing demand for resources leads to habitat destruction worldwide, particularly in developing nations.

Human Impact: Increased Consumption

• Rising need for energy sources in industrialized and industrializing countries strains resources further

Examples of Human Influences on the Environment

• Carbon cycle disruption leading to climate change and ocean acidification
• Nitrogen and phosphorus cycle alterations through chemical fertilizers, causing eutrophication
• Loss of biodiversity due to habitat destruction, overharvesting, biocides, and invasive species

Disruptions to the Carbon Cycle

• Humans release CO2 through fossil fuel use, impacting the carbon cycle
• Industrialized nations heavily rely on fossil fuels, with increasing consumption in recent decades
• This usage leads to habitat damage and pollution

Climate Change: Greenhouse Effect

• Earth's surface temperature rises as it absorbs solar radiation and emits infrared radiation
• Greenhouse gases in the atmosphere trap infrared radiation

Factors Contributing to Climate Change

• They include water vapor, ozone, carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons (CFCs)

Climate Change: Global Trends

• Global Climate Change refers to long-term shifts in temperature, precipitation, and storm patterns
• Global warming signifies an increase in average global temperatures
• Rapid climate changes are now attributed to human activities like fossil fuel use, combustion, and deforestation

Climate Change: Impacts Examined Through Models

• Accurate climate models account for both natural and human activities
• Evidence includes flowering times, altered growth patterns, and species migrations

Plant Responses to Climate Change

• Plants flower earlier, alter their growth patterns, and migrate northward

Impact on Plant Communities

• Plant community responses vary globally depending on location and sensitivity to temperature / precipitation changes

Ocean Acidification

• Rising atmospheric CO2 levels lead to acidification of oceans, decreasing pH
• Increased levels in the ocean in recent decades cause pH to drop

Impact on Marine Life

• Organisms with calcium carbonate shells struggle to build and maintain shells
• Coral bleaching and global reef damage are linked to ocean acidification

Probable Solutions for Mitigating Carbon Cycle Disruptions

• Reduced consumption of fossil fuels
• Increased use of energy alternatives like biomass, hydroelectric, and nuclear power
• Switch to reliance on renewable energy sources such as solar, wind, geothermal, tidal, and wave energy

Impact: Use of Chemical Fertilizers

• Increased use of synthetic fertilizers (nitrogen and phosphorus) leads to nutrient pollution
• Use on farms, lawns, and golf courses can cause eutrophication, or nutrient enrichment
• This process has accelerated in the last 50 to 60 years due to human activities

Harmful Algol Blooms Caused by Chemical Fertilizers

• Increased algae and cyanobacteria populations occur in lakes and oceans because of runoff
• Algal and cyanobacterial masses die and sink
• Heterotrophic bacteria decompose them (respiration) and bacteria can deplete O₂ in bottom waters

Consequences of Chemical Run Off

• It can have catastrophic consequences for animal life on the sea or lake floor

Resulting Dead Zones

• Chemical fertilizers contribute to the formation of dead zones
• These areas have low oxygen levels in aquatic ecosystems
• Hundreds of such zones have been identified, expanding yearly

Examples of Chemical Fertilizers

• The Gulf of Mexico dead zone caused by nutrients from the Mississippi River

Demand for Agricultural Land: Consequences

• Results in the massive use of chemicals (e.g. fertilizers/pesticides) and water
• Includes conversion of habitats for agriculture (deforestation)
• Results in poor management of farmland (e.g. erosion/desertification)

Human Influences on Evolution: Deforestation

• Increased deforestation (especially in tropical areas) to gain more agricultural land
• Deforestation causes increased CO2 levels (from burning and reduced vegetation)

Overharvesting Resources Concerns

• Overfishing concerns are about freshwater and oceans that deplete fish populations
• Forests used to be overharvested with agriculture
• Consequences that increase impact on climate change

Biocides

• Chemical biocides are synthetic chemicals (pesticides) designed to kill pests
• Pests develop resistance over time
• Use of natural methods (e.g. natural predators) or plant crops in mixed plant communities

Chemical Biocides - Antibiotics

• Increased use of antibiotics disrupts bacterial communities (e.g. the human microbiome, in ecosystems)
• Leads to increased antibiotic resistance

Invasive Species Overview

• Spread widely and become dominant in a community which will alter the ecosystem and it's function
• They lack natural controls like predation, disease, or competition in invaded areas
• Disrupt networks involving mutualistic interactions (e.g. corals, lichens, pollinators)

Conservation Biology Overview

• Addresses challenge of sustaining biodiversity in a changing world crowded with people
• Biodiversity provides important ecosystem services
• Loss of ecosystem services will affect humans' survival

Focuses of Conservation Biology

• Individual species (e.g. programs to protect elephants, rhinos)
• Conserving many species by protecting and restoring ecosystems (e.g.Yellowstone National Park)
• Reserves that protect habitat, provide land to restore degraded habitats, and provide managed areas (include corridors that provide routes for migration from one reserve to another)

Future Goal for Conservation

• Aim for sustainable development = an important principle for balancing priorities for humans and natural world
• Rate of resource use by humans – must be less than rate that those resources can be replenished

Biodiversity Long Term Outlook

• Future includes fewer species to work with
• Need to feed the world gives good reasons to conserve the biodiversity
• Lost species means lost discovery of novel compounds
• Minished biodiversity also makes communities less productive and less resilient to disturbances