15.2 Factors Influencing Biodiversity

Biodiversity, the variety of life on Earth, is shaped by complex interactions between living and non-living factors. Climate, topography, and soil play crucial roles in determining where species thrive. Human activities, like habitat destruction and pollution, significantly impact biodiversity.

The distribution of species across the planet follows patterns, with more diversity generally found near the equator. Understanding these patterns and the factors influencing them is key to protecting Earth's incredible array of life forms and ecosystems.

Biodiversity Drivers

Abiotic and Biotic Factors

• Biodiversity is influenced by a complex interaction of abiotic and biotic factors
• Abiotic factors include climate, topography, soil, and latitude
• Biotic factors include interactions between species (competition, predation, mutualism)

Anthropogenic Influences

• Human activities can have significant negative impacts on biodiversity
• Habitat destruction, overexploitation, pollution, and climate change are major threats
• Introduction of invasive species through human trade and transportation disrupts ecosystems
• Evaluating human impacts is essential for developing effective conservation strategies (habitat protection, sustainable resource management, reducing greenhouse gas emissions)

Climate, Topography, and Soil Influences

Climate Effects on Species Distribution

• Climate influences biodiversity through temperature and precipitation patterns
• Temperature affects metabolic rates, growth, and reproduction of organisms
• Warmer climates generally support higher biodiversity
• Precipitation patterns influence water availability, a critical resource for all life
• Precipitation determines the distribution of vegetation types (forests, grasslands, deserts)

Topographic Diversity of Microhabitats

• Topography creates diverse microhabitats with varying environmental conditions
• Microhabitats vary in temperature, moisture, and exposure to sunlight
• Elevation gradients lead to changes in temperature and precipitation
• Distinct vegetation zones and associated fauna occur along elevation gradients
• Aspect (direction a slope faces) influences solar radiation received, affecting temperature and moisture
• Landforms (mountains, valleys, plateaus) create physical barriers and corridors influencing species distribution and gene flow

Soil Characteristics and Plant Diversity

• Soil characteristics play a crucial role in determining plant diversity and, consequently, animal diversity
• Nutrient availability, pH, and moisture content are key soil factors
• Nutrient-rich soils support a higher diversity of plant species
• Diverse plant communities provide varied food sources and habitats for animals
• Soil pH affects nutrient availability and presence of microorganisms
• Soil pH influences plant species composition
• Soil moisture content determines the distribution of plant species adapted to different water availability levels (deserts to wetlands)

Latitude and Species Richness

Latitudinal Biodiversity Gradient

• Species richness generally increases from the poles towards the equator
• Pattern known as the latitudinal biodiversity gradient
• Observed across multiple taxonomic groups (plants, animals, microorganisms)
• Observed across different ecosystems (terrestrial, freshwater, marine habitats)

Hypotheses Explaining the Gradient

• Energy hypothesis: higher solar energy input and productivity in the tropics support more species
• Evolutionary time hypothesis: tropics have had more time for species to evolve and accumulate due to longer geological stability
• Area hypothesis: larger land area in the tropics provides more space for species to coexist
• Relationship between latitude and species richness is not always linear
• Other factors (climate, topography, historical events) can influence regional biodiversity patterns

Implications for Conservation

• Understanding the latitudinal biodiversity gradient is crucial for predicting impacts of climate change on species distribution
• Gradient guides conservation efforts by identifying regions of high biodiversity
• Prioritizing protection of tropical ecosystems is essential for maintaining global biodiversity

Human Impact on Biodiversity

Habitat Alteration

• Habitat destruction, fragmentation, and degradation are major threats to biodiversity
• Land-use changes (deforestation, urbanization, agricultural expansion) reduce available space for species
• Habitat loss leads to population declines and local extinctions
• Fragmentation isolates populations, reduces gene flow, increases risk of inbreeding and genetic drift

Overexploitation of Species

• Overfishing, overhunting, and overharvesting of plants and animals deplete populations
• Overexploitation can lead to extinction in extreme cases
• Examples include overfishing of cod, overhunting of passenger pigeons, overharvesting of medicinal plants

Pollution and Environmental Degradation

• Chemical contamination, plastic waste, and nutrient runoff have detrimental effects on biodiversity
• Pollution alters habitats, reduces water quality, and causes direct mortality of organisms
• Examples include oil spills affecting marine life, pesticide accumulation in food chains, eutrophication of water bodies

Climate Change Impacts

• Climate change, largely driven by human activities, increasingly affects biodiversity
• Alters temperature and precipitation patterns, leading to shifts in species distribution
• Causes phenology mismatches between interacting species (plants and pollinators, predators and prey)
• Increases the risk of extinction for vulnerable species unable to adapt or migrate