2.1 Ecosystems and biodiversity

Ecosystems are complex networks of living organisms and their environment, working together as a functional unit. From energy flow to nutrient cycling, these systems maintain ecological balance through intricate processes. Understanding ecosystem structure and function is crucial for grasping environmental systems.

Biodiversity, the variety of life on Earth, is influenced by factors like geography, evolution, and human activities. It plays a vital role in ecosystem stability and provides essential services to humans. Exploring biodiversity helps us appreciate the interconnectedness of environmental processes and the importance of conservation efforts.

Ecosystem Structure and Function

Components and Interactions

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• Ecosystems form complex, interconnected systems composed of living organisms and their physical environment, interacting as a functional unit
• Biotic components include producers, consumers, and decomposers, forming intricate food webs and energy flow pathways
  • Producers (plants, algae) convert sunlight into energy through photosynthesis
  • Consumers (herbivores, carnivores, omnivores) obtain energy by feeding on other organisms
  • Decomposers (bacteria, fungi) break down dead organic matter, recycling nutrients
• Abiotic factors significantly influence ecosystem structure and function
  • Climate affects temperature and precipitation patterns
  • Soil composition determines nutrient availability and plant growth
  • Water availability impacts species distribution and ecosystem processes

Ecological Processes and Dynamics

• Ecosystem processes maintain ecological balance
  • Energy flow moves through trophic levels, with energy loss at each transfer (10% rule)
  • Nutrient cycling involves the movement of essential elements (carbon, nitrogen, phosphorus) through biotic and abiotic components
  • Water cycling (hydrologic cycle) includes processes like evaporation, precipitation, and transpiration
• Ecological succession describes gradual change in species composition over time
  • Primary succession occurs on newly exposed surfaces (volcanic islands, retreating glaciers)
  • Secondary succession takes place in disturbed areas with existing soil (forest regrowth after fire)
• Keystone species play disproportionately large roles in maintaining ecosystem structure and function
  • Sea otters in kelp forests control sea urchin populations, preserving kelp habitat
  • Beavers create wetland habitats through dam-building activities, benefiting numerous species

Ecosystem Services and Human Benefits

• Ecosystem services provide vital benefits to human societies and the global environment
  • Provisioning services supply resources (food, water, timber, medicinal plants)
  • Regulating services maintain environmental conditions (climate regulation, flood control, water purification)
  • Supporting services underpin other ecosystem functions (soil formation, nutrient cycling, primary production)
  • Cultural services offer non-material benefits (recreation, aesthetic enjoyment, spiritual fulfillment)

Factors Influencing Biodiversity

Biodiversity Concepts and Patterns

• Biodiversity encompasses genetic, species, and ecosystem diversity
  • Genetic diversity represents the variety of genes within a species
  • Species diversity refers to the number and abundance of different species in an area
  • Ecosystem diversity describes the variety of habitats and ecological processes in a region
• Biogeographical factors influence patterns of biodiversity distribution across the globe
  • Latitude affects species richness, with higher diversity generally found near the equator (tropical rainforests)
  • Altitude impacts species composition, creating distinct zones of vegetation on mountains
  • Isolation leads to unique species adaptations and endemism (Galapagos Islands)

Evolutionary and Ecological Processes

• Evolutionary processes drive the development and maintenance of biodiversity over time
  • Speciation creates new species through mechanisms like allopatric or sympatric speciation
  • Adaptive radiation produces diverse species from a common ancestor (Darwin's finches)
• Intermediate disturbance hypothesis suggests moderate levels of disturbance promote biodiversity
  • Creates opportunities for species coexistence by preventing competitive exclusion
  • Examples include periodic flooding in riparian ecosystems or small-scale forest fires
• Biodiversity enhances ecosystem stability through functional redundancy
  • Multiple species perform similar ecological roles, providing a buffer against environmental changes
  • Pollination services maintained by various insect species ensure plant reproduction even if one pollinator declines

Biodiversity-Ecosystem Functioning Relationships

• Diversity-stability hypothesis posits more diverse ecosystems are generally more stable and resilient
  • Greater species richness increases the likelihood of functional redundancy
  • Diverse ecosystems better withstand and recover from disturbances (climate extremes, disease outbreaks)
• Trophic cascades demonstrate interconnectedness of species within ecosystems
  • Top-down control occurs when predators regulate lower trophic levels (wolf reintroduction in Yellowstone)
  • Bottom-up control happens when resource availability at lower trophic levels affects higher levels (phytoplankton blooms influencing marine food webs)

Human Impacts on Ecosystems

Habitat Alteration and Loss

• Habitat destruction and fragmentation lead to biodiversity loss and ecosystem degradation
  • Deforestation for agriculture and urbanization reduces available habitat (Amazon rainforest)
  • Fragmentation creates isolated patches, impacting species movement and gene flow
• Climate change alters species distributions, phenology, and ecosystem dynamics globally
  • Shifting temperature and precipitation patterns force species to migrate or adapt
  • Phenological mismatches occur when interdependent species' life cycles become desynchronized (plants flowering before pollinators emerge)

Resource Exploitation and Pollution

• Overexploitation of natural resources can lead to population collapses and trophic cascades
  • Overfishing depletes fish stocks and disrupts marine food webs (cod fishery collapse)
  • Unsustainable hunting practices threaten large mammal populations (elephants, rhinos)
• Pollution impacts ecosystem health and biodiversity through various mechanisms
  • Chemical contaminants bioaccumulate in food chains, affecting top predators (DDT and bald eagles)
  • Excess nutrients from agricultural runoff cause eutrophication in aquatic ecosystems
  • Plastic pollution harms marine life through ingestion and entanglement

Invasive Species and Urbanization

• Invasive species disrupt native ecosystems by outcompeting indigenous species and altering processes
  • Introduced predators decimate native fauna unprepared for new threats (cane toads in Australia)
  • Invasive plants modify habitat structure and fire regimes (cheatgrass in North American prairies)
• Urbanization and infrastructure development contribute to habitat loss and fragmentation
  • Urban sprawl reduces available natural areas and creates heat island effects
  • Roads and other linear infrastructure create barriers to species movement, impacting gene flow

Measuring Human Impact

• Ecological footprint quantifies human demand on Earth's ecosystems
  • Measures the biologically productive area needed to support human consumption and waste absorption
  • Highlights unsustainable nature of current consumption patterns in many regions
  • Allows comparison of resource use between countries and individuals

Ecosystem Conservation and Restoration

Protected Areas and Conservation Strategies

• Protected area networks play crucial roles in preserving biodiversity and ecosystem integrity
  • National parks protect large, intact ecosystems (Yellowstone, Serengeti)
  • Marine reserves safeguard critical marine habitats and fish populations (Great Barrier Reef Marine Park)
• Conservation genetics and captive breeding programs maintain genetic diversity in endangered species
  • Genetic rescue introduces new genetic material to inbred populations (Florida panther)
  • Ex-situ conservation preserves species outside their natural habitats (zoos, seed banks)

Ecosystem Restoration and Management

• Ecological restoration techniques aim to return degraded ecosystems to functional states
  • Reforestation projects replant trees in deforested areas (Atlantic Forest Restoration Pact in Brazil)
  • Wetland reconstruction restores hydrological functions and habitat (Everglades restoration)
• Ecosystem-based management integrates scientific knowledge with stakeholder involvement
  • Adaptive management approaches use monitoring and feedback to adjust conservation strategies
  • Community-based conservation involves local populations in resource management decisions

Economic and Policy Approaches

• Payment for ecosystem services (PES) schemes provide economic incentives for conservation
  • Compensate landowners for maintaining ecosystem services (Costa Rica's national PES program)
  • Carbon offset programs reward forest conservation and reforestation efforts
• Biodiversity offsetting aims to achieve no net loss of biodiversity
  • Compensates for unavoidable impacts through habitat creation or restoration elsewhere
  • Requires careful planning and long-term monitoring to ensure effectiveness
• International agreements and policies provide frameworks for global cooperation
  • Convention on Biological Diversity sets targets for biodiversity conservation
  • CITES regulates international trade in endangered species
  • Paris Agreement addresses climate change mitigation and adaptation strategies