♻️AP Environmental Science Unit 2 – The Living World: Biodiversity

What's Biodiversity?

• Biodiversity encompasses the variety of life on Earth at all levels, from genes to ecosystems
• Includes diversity within species (genetic diversity), between species (species diversity), and of ecosystems (ecosystem diversity)
  • Genetic diversity: variations in genes within a species, providing the basis for adaptation and evolution
  • Species diversity: the number and variety of species within a given area or ecosystem
  • Ecosystem diversity: the variety of habitats, communities, and ecological processes in the biosphere
• Biodiversity is the result of billions of years of evolution, shaped by natural processes and, more recently, human influence
• Estimated that Earth is home to millions of species, but the exact number is unknown due to many undiscovered or undescribed species
  • Scientists have identified and described approximately 1.7 million species so far
• Biodiversity is not evenly distributed across the planet; some regions (biodiversity hotspots) have a higher concentration of species than others
  • Examples of biodiversity hotspots include tropical rainforests (Amazon), coral reefs (Great Barrier Reef), and Mediterranean-type ecosystems (California Floristic Province)

Why Biodiversity Matters

• Biodiversity is essential for the functioning and stability of ecosystems
  • Each species plays a unique role in the ecosystem (niche), contributing to the overall balance and resilience
• Diverse ecosystems are more resilient to disturbances and can recover more quickly from environmental stresses (drought, fire, or disease)
• Biodiversity provides numerous ecosystem services that benefit humans, such as:
  • Provisioning services: food, fuel, fiber, and medicine
  • Regulating services: climate regulation, water purification, and pollination
  • Cultural services: recreational, aesthetic, and spiritual benefits
• Many industries rely on biodiversity, including agriculture, forestry, fisheries, and tourism
  • Diverse genetic resources are crucial for developing new crop varieties and improving agricultural productivity
• Biodiversity has intrinsic value, independent of its utility to humans
  • Many people believe that all species have a right to exist and that we have a moral obligation to protect them

Types of Biodiversity

• Alpha diversity: the diversity within a particular area, community, or ecosystem
  • Measured by the number of species (species richness) and their relative abundances (species evenness)
• Beta diversity: the change in species composition between different areas or along environmental gradients
  • Measures the difference in species identities between two or more sites
• Gamma diversity: the total diversity across a large region or landscape, encompassing multiple ecosystems
  • Represents the overall species diversity of a region, considering both alpha and beta diversity
• Functional diversity: the variety of ecological roles or functions performed by species in an ecosystem
  • Focuses on the traits of organisms (morphological, physiological, or behavioral) and how they influence ecosystem processes
• Phylogenetic diversity: the evolutionary history and relatedness of species in a community or region
  • Considers the evolutionary relationships among species, based on their shared ancestry

Measuring Biodiversity

• Species richness: the number of different species in a given area or community
  • A simple measure of diversity, but does not account for the relative abundances of species
• Species evenness: the relative abundances of different species in a community
  • A community with similar abundances of all species is considered more diverse than one dominated by a few species
• Shannon diversity index (H'): a measure that combines both species richness and evenness
  • Calculated as: $H' = -\sum_{i=1}^{s} p_i \ln p_i$, where $s$ is the number of species and $p_i$ is the proportion of individuals belonging to the $i$-th species
• Simpson diversity index (D): another measure that accounts for both richness and evenness
  • Calculated as: $D = \sum_{i=1}^{s} p_i^2$, where $s$ is the number of species and $p_i$ is the proportion of individuals belonging to the $i$-th species
• Rarefaction curves: a graphical method for comparing species richness between communities with different sample sizes
  • Plots the number of species as a function of the number of individuals sampled, allowing for standardized comparisons
• Remote sensing and geographic information systems (GIS) are increasingly used to map and monitor biodiversity at large scales
  • Satellite imagery can detect changes in land cover, habitat fragmentation, and species distributions

Threats to Biodiversity

• Habitat loss and fragmentation: the primary threat to biodiversity worldwide
  • Caused by human activities such as deforestation, urbanization, and agricultural expansion
  • Reduces the total area of available habitat and isolates populations, leading to decreased genetic diversity and increased extinction risk
• Overexploitation: the unsustainable harvest of species for human use
  • Examples include overfishing, poaching, and the illegal wildlife trade
  • Can lead to population declines, local extinctions, and disruptions to ecosystem functioning
• Invasive species: non-native species that establish and spread in new environments, often outcompeting native species
  • Can be introduced intentionally (ornamental plants) or accidentally (ballast water from ships)
  • Invasive species can alter ecosystem structure and function, leading to biodiversity loss
• Climate change: the long-term alteration of temperature and weather patterns, primarily due to human activities
  • Affects biodiversity by shifting species ranges, altering phenology, and disrupting species interactions
  • Can exacerbate other threats, such as habitat loss and invasive species spread
• Pollution: the introduction of harmful substances into the environment
  • Includes chemical pollutants (pesticides, industrial waste), nutrient pollution (eutrophication), and plastic pollution
  • Can have direct toxic effects on organisms, alter habitat quality, and disrupt ecosystem processes

Conservation Strategies

• Protected areas: designated regions managed for long-term conservation of biodiversity
  • Examples include national parks, wildlife refuges, and marine protected areas
  • Aim to safeguard habitats, species, and ecosystem services by limiting human activities
• Habitat restoration: the process of assisting the recovery of degraded, damaged, or destroyed ecosystems
  • Involves actions such as revegetation, invasive species removal, and reintroduction of native species
  • Goal is to restore ecosystem structure, function, and biodiversity to a more natural state
• Sustainable resource management: practices that balance human use with the long-term maintenance of biodiversity
  • Examples include sustainable forestry, fisheries management, and agroecology
  • Aims to minimize the negative impacts of resource extraction while supporting local livelihoods and economies
• Ex-situ conservation: the conservation of species outside their natural habitats
  • Includes captive breeding programs, seed banks, and gene banks
  • Serves as a backup strategy for species at high risk of extinction in the wild
• Community-based conservation: an approach that engages local communities in conservation efforts
  • Recognizes the importance of traditional ecological knowledge and the role of local people in managing natural resources
  • Aims to balance conservation goals with community needs and values

Case Studies

• Amazon rainforest: the world's largest tropical rainforest, home to unparalleled biodiversity
  • Threatened by deforestation, primarily driven by cattle ranching and soybean production
  • Conservation efforts include establishing protected areas, supporting sustainable land use practices, and promoting international cooperation
• Great Barrier Reef: the world's largest coral reef system, supporting a vast array of marine life
  • Threatened by climate change, ocean acidification, and water quality degradation
  • Conservation strategies include reducing greenhouse gas emissions, improving water quality management, and implementing marine protected areas
• Yellowstone National Park: the world's first national park, known for its geothermal features and iconic wildlife
  • Faced challenges related to overexploitation, habitat fragmentation, and invasive species
  • Conservation successes include the reintroduction of gray wolves and the recovery of grizzly bear populations
• Island biodiversity: islands are hotspots of biodiversity, often with high levels of endemism
  • Particularly vulnerable to threats such as invasive species, habitat loss, and climate change
  • Conservation efforts focus on eradication of invasive species, habitat restoration, and community-based management

Key Takeaways

• Biodiversity is the variety of life on Earth at all levels, from genes to ecosystems, and is essential for the functioning and resilience of the biosphere
• Biodiversity provides numerous benefits to humans, including ecosystem services, genetic resources, and intrinsic value
• Biodiversity can be measured using various metrics, such as species richness, evenness, and diversity indices
• Major threats to biodiversity include habitat loss, overexploitation, invasive species, climate change, and pollution
• Conservation strategies aim to protect and restore biodiversity through approaches such as protected areas, habitat restoration, sustainable resource management, ex-situ conservation, and community-based conservation
• Effective biodiversity conservation requires a multifaceted approach that addresses the root causes of biodiversity loss and engages stakeholders at all levels, from local communities to international policymakers
• Preserving biodiversity is crucial for maintaining the health and resilience of the planet, as well as ensuring the well-being of current and future generations