Biogeography is the study of where species live and why they are found in those locations. It investigates the geographical distribution of living organisms and the influences shaping these patterns. This field integrates concepts from ecology, evolutionary biology, taxonomy, geology, paleontology, and climatology. It provides insights into both short-term habitat interactions and long-term evolutionary changes that determine global species distribution.
Influences on Species Distribution
Species distribution is determined by a complex interplay of environmental, historical, and biological factors. Abiotic environmental factors, such as temperature, rainfall, elevation, and available resources, influence where species can survive. Topography, soil composition, and water availability also play roles, dictating habitat suitability for plant and animal communities.
Historical factors, spanning vast geological timescales, also mark species distribution. Tectonic plate movement has reshaped landmasses and oceans, leading to species isolation and diversification. Glaciation events, with widespread ice sheets, caused shifts in climate and habitat, leading to range breaks and local extinctions. Past land bridges, like the Bering Land Bridge, allowed species migration between continents. Evolutionary history further influences distribution, as related species may share similar range limits due to shared ancestral traits.
Biological interactions within an ecosystem also affect where species are found. Competition for limited resources can restrict a species’ geographic range. Predation can limit prey populations, influencing their distribution, while symbiotic relationships create dependencies that tie species to specific areas. Disease and parasitism can also impact species survival and reproduction, altering their distribution patterns. Dispersal limitations, or the ability of a species to move, also play a role; for example, coconut palms are found on many tropical islands because their fruits can float across oceans.
Recognizing Distribution Patterns
Scientists observe several large-scale patterns in how species are distributed. Biogeographic realms are broad divisions of Earth’s land surface based on species’ historical and evolutionary distributions. Examples include the Nearctic realm (North America) and the Palearctic realm (Europe, Asia, North Africa). These realms reflect long periods of geographic isolation and shared evolutionary histories.
The latitudinal diversity gradient describes the general increase in species richness from the poles towards the equator. Tropical regions harbor a greater variety of life compared to temperate or polar areas. Higher solar energy and water availability in the tropics, along with a relatively consistent environment, contribute to this pattern.
Endemism refers to species found naturally only within a specific geographic area. Australia, for example, is renowned for its high levels of endemism, with approximately 75% of its living plant and mammal species found nowhere else. The wallaby and echidna are examples of species endemic to Australia.
Disjunct distributions occur when closely related species or populations are found in widely separated geographic areas. This pattern can arise from historical continental drift, where a continuous range was split by landmass separation, or through long-distance dispersal events. Birds, for instance, can cross oceans to colonize new habitats. These separated populations provide clues about past geological and ecological changes.
Tools and Techniques for Study
Scientists employ a range of tools and techniques to study species distribution.
Fieldwork
Fieldwork, including direct surveys and observations, is a foundational method for gathering data on species occurrences. Researchers record sightings and collect specimens to document where species live. This approach provides ground-truth data for understanding local distribution patterns.
Mapping Technologies
Mapping technologies, particularly Geographic Information Systems (GIS), are used to visualize, analyze, and manage spatial data. GIS software integrates environmental data, such as elevation and climate, with species occurrence records. This helps identify environmental correlates of species presence and create detailed distribution maps.
Remote Sensing
Remote sensing uses satellite imagery and airborne sensors to collect information about Earth’s surface. This technology provides large-scale data on land cover, climate patterns, and vegetation health. Satellite data characterize environmental variables across vast areas.
Genetic Analysis
Genetic analysis provides insights into evolutionary relationships, population connectivity, and dispersal patterns. By examining DNA, scientists determine how populations are related and reconstruct historical migration routes. This approach complements ecological and geological data by revealing hidden connections.
Predictive Modeling
Predictive modeling, using species distribution models (SDMs), forecasts how species distributions might change under different environmental scenarios. These models analyze relationships between known species occurrences and environmental variables. This allows researchers to predict future ranges under climate change or identify suitable habitats for conservation.
Relevance for the Planet and People
Understanding species distribution is important for global conservation. Identifying biodiversity hotspots allows biologists to prioritize regions for protection, focusing resources for greatest impact. This knowledge aids in designing effective protected areas and wildlife corridors, facilitating species movement and maintaining genetic diversity.
Species distribution studies help predict and mitigate climate change impacts. As temperatures rise and precipitation shifts, species ranges are expected to change. Models forecast these shifts, allowing proactive conservation strategies to help species adapt.
Managing invasive species is another important application. Invasive species are non-native organisms that outcompete native species, disrupt food chains, and degrade ecosystems. Understanding their distribution and predicting their spread allows for targeted management to control or eradicate them.
Knowledge of species distribution contributes to understanding ecosystem health and services. Ecosystems offer human benefits. Studying where species occur helps scientists assess ecosystem health and identify vulnerabilities. This understanding informs sustainable land management and policies for preserving the intricate web of life.