The scope of biogeography is extensive, primarily bridging biology and geography to study the biosphere. Given the dynamic nature of the environment, factors such as climate change, natural resource exploitation, and human conflict leave significant impacts on ecosystems and life forms.
Understanding biogeography aids in environmental awareness, contributes to human development, and supports the improvement of living standards over time.
It draws on disciplines like botany, zoology, hydro-geomorphology, climatology, geology, pedology, and anthropology, originally relying on taxonomy and later integrating ecological and analytical approaches.
From the 1960s onward, technological advances, including remote sensing, GPS, and statistical software, have enhanced precision in mapping and understanding organism distribution, especially in inaccessible areas.
Modern biogeography now studies geographic variation from genes to ecosystems, incorporating factors like latitude, elevation, depth, isolation, and area. A biogeographer must thus master phytogeography (plants) and zoogeography (animals), managing vast information across spatial and temporal scales.
In the late 19th century, P.L. Sclater (ornithologist) and A.R. Wallace (naturalist) categorized global fauna into two main realms:
They established six major biogeographic regions: Nearctic, Neotropical, Palaearctic, Ethiopian, Oriental, and Australian, which remain widely used today.
Biogeography is broadly divided into two subfields:
This field investigates the past distribution of species using biotic (e.g., adaptation, predation, competition) and abiotic (e.g., geology, climate, soil, light) factors to understand evolution in particular regions.
Tropical regions contain more species than higher latitudes due to fewer climatic disruptions during glacial periods, resulting in lower extinction rates and stable populations.
The field incorporates paleogeographic concepts such as plate tectonics and utilizes fossil records to track species migration via continental drift.
Focuses on the current distribution of plants and animals, based on environmental conditions and ecosystem dynamics. Its major research areas include:
This explores the effect of diurnal and seasonal temperature variations. Greater fluctuations, common at high latitudes, limit species diversity compared to the stable climates of the tropics. Topography also influences temperature patterns regardless of vegetation cover.
This involves studying evapotranspiration, the process by which plants release water vapor through evaporation and transpiration. In warm and moist regions like the tropics, high evapotranspiration supports lush vegetation. In contrast, cold regions have low evapotranspiration and reduced plant growth.
This concept explains that greater habitat diversity leads to greater species diversity. Diverse landscapes offer multiple ecological niches, increasing biodiversity.
The Earth is the only known planet in the universe that supports life. It sustains diverse organisms including plants, animals, humans, and microorganisms. However, their distribution across the planet is not uniform and is mainly shaped by climatic conditions such as temperature and rainfall.
Organisms inhabit regions where they are well adapted to the prevailing climate. Thus, a biome can be defined as “a distinct ecological community of plants and animals, living together in a particular climate.”
The following are the major biomes of the world based on climatic and ecological characteristics:
The tropical rainforest biome is known for its hot and moist environmental conditions. It is predominantly located along the earth’s equator, with significant presence in South America, Africa, and Southeast Asia.
These biogeographical regions receive consistent annual rainfall between 1500 mm and 4000 mm. The average annual temperature remains around 25° C, while humidity levels vary between 77% and 88%.
The synergy of persistent warmth and high moisture levels makes tropical rainforests an ideal ecosystem for rich biodiversity, hosting the highest number of plant and animal species globally.
Micro-organisms, such as bacteria and fungi, thrive due to the hot and humid climate. These organisms accelerate the decomposition of organic matter, facilitating rapid nutrient absorption by plants.
However, the high volume of rainfall leads to nutrient leaching, rendering the soil infertile and acidic. Despite this, vegetation continues to flourish due to the rapid uptake of available nutrients.
The tropical rainforest receives around 12 hours of sunlight daily, but due to dense foliage, only 2% of sunlight reaches the forest floor. This biome contains the densest plant cover on Earth, generally organized into three strata:
Vegetation is highly diverse, consisting of tall trees (20–35 m) with reinforced trunks and shallow roots. Most trees are evergreen with large, dark green leaves. Plant species include:
The survival of plants depends on their ability to adapt to low light or grow rapidly toward the canopy to access sunlight.
No other biome offers such consistent access to water and food, which supports a vast and diverse animal population. The fauna includes:
Many of these smaller animals spend their lives without ever touching the ground.
Prominent large mammals include tigers, leopards, gorillas, and rhinoceroses. Several species utilize the upper vegetation for both food and shelter.
Noteworthy rainforest species and adaptations include:
Temperate deciduous forest biomes, also known as Mid-Latitude deciduous forest biomes, are geographically located between the polar regions and the tropics. These forests are widespread across the eastern United States and Canada, central Europe, and parts of China and Japan.
These biogeographical zones experience the influence of air masses from both cold polar areas and warm tropical regions, resulting in notable seasonal variations in climate.
Temperature in this biome ranges from -30°C to 30°C, and annual precipitation varies between 750 mm and 1500 mm. A substantial portion of the global human population resides in these regions.
The dominant vegetation in this biome is composed of deciduous trees, named after their ability to shed leaves annually during autumn. These fallen leaves decompose and enrich the soil with nutrients, making the forest soil extremely fertile.
Common tree species include maple, oak, hickory, birch, magnolia, hemlock, spruce, and fir.
Deciduous forests form multiple growth layers:
In spring and summer, deciduous trees produce thin, broad, lightweight leaves that turn green due to warm temperatures and ample sunlight.
However, during cold seasons, these broad leaves increase water loss and are prone to tissue damage. As temperatures drop and sunlight becomes limited, trees begin to shed their leaves.
Deciduous trees enter dormancy during winter and bloom again with the onset of spring.
This biome is home to a wide range of mammals, birds, insects, and reptiles. Common species include:
As seasons change, animals adapt by either hibernating or migrating to warmer regions. Birds are known for long migrations, while many mammals enter hibernation during winter when food is scarce.
In preparation for winter, animals like squirrels, chipmunks, and jays collect and store nuts and seeds inside tree hollows. Cold temperatures slow down decomposition, preserving their food supply until spring returns.
The taiga biome, also known as the Boreal forest or Coniferous forest biome, is the largest biome in the world, located between 50°N and 60°N latitudes in the northern hemisphere. It stretches across the northern regions of North America, Europe, and Asia, with Siberia occupying the maximum area, sometimes referred to as the Siberian desert.
The biome is influenced heavily by cold temperatures due to its proximity to the polar regions. While Moscow (Russia) and Toronto (Canada) are the major population centers in the southern taiga, the northern zones are sparsely populated and often labeled as cold deserts.
Climate in the taiga biome is marked by long, cold winters and short, cool summers. Average summer temperatures range from -40°C to 20°C, with annual precipitation between 300 mm and 900 mm. Snowfall is common during winters, while precipitation in the lower latitudes remains relatively evenly spread throughout the year.
This region was once covered by glaciers millions of years ago, leaving behind gouged and depressed terrains that now form bogs, lakes, and other geomorphic structures. The soil is nutrient-poor, acidic, rocky, and often covered with undecomposed leaf litter. Permafrost patches are also common in certain areas.
Plant diversity is limited due to the harsh and cold conditions. The most common tree types include conifers such as evergreens, spruce, fir, pine, and larch (a deciduous conifer). Other trees like birch and aspen are also present.
Evergreen trees retain their leaves year-round, conserving energy for structural growth rather than producing new leaves annually. Their needle-like leaves and conical shape help reduce snow accumulation and prevent branch breakage.
During winter, frozen soil prevents water uptake by roots, making survival strategies essential for plants in this biome.
The taiga supports a variety of animal life, although many species are not capable of year-round survival due to the extreme cold. Common mammals include moose, deer, bears, bobcats, squirrels, chipmunks, ermine, and moles.
Birds such as the bald eagle, woodpeckers, and warblers are also present. The taiga is considered a key breeding ground for numerous insects, attracting migratory birds that come to nest and feed on the abundant insect population.
Many animals migrate to warmer climates as the cold sets in, while others rely on hibernation. To withstand subzero temperatures, animals develop insulating features such as thick fur or feathers for protection against the cold.
The bogs, lakes, and ponds formed from glacial depressions act as the primary water sources in summer, maintaining biodiversity despite the tough environment.
The tropical grasslands, also known as the Savannah biome, are ecosystems dominated by tall grasses and occasional trees, with regions of chaparral and woodlands included. These areas are widespread across Botswana, Namibia, Kenya, Brazil, India, Australia, and the USA.
This biome experiences a climate with 6 to 8 months of summer and a dry winter season. Rainfall varies significantly, from 250 mm/year to 1250 mm/year, and is often unpredictable and inconsistent.
The limited tree growth is due to a combination of climatic conditions, soil fertility, and agricultural exploitation. Human activities like burning grasslands and tree felling for agriculture have significantly altered these landscapes.
The flora of the Savannah biome is primarily composed of a wide variety of grasses, with some growing as tall as 2 to 3 meters, commonly referred to as 'Elephant Grass'. Scattered trees and tree clusters also occur in some locations.
Prominent tree species include the acacia and baobab, especially in the African Savannahs. In some areas, such as the prairies, trees are nearly absent.
Fire plays a significant ecological role by burning old grass, which in turn promotes regeneration of grasses using underground water reserves and replenishes soil nutrients.
The baobab tree has adapted by producing small leaves during the wet season to limit water loss and storing water in its large trunk to survive drought. Similarly, the acacia tree develops long taproots that access deep water sources.
The African Savannahs support a diverse range of animals including elephants, lions, leopards, cheetahs, rhinoceroses, zebras, hyenas, ostriches, and starlings. These animals rely heavily on rainwater as a key resource.
Birds, insects, and mammals migrate seasonally in search of water, both within and beyond the biome.
Fires are common in dry grasslands. Animals have evolved strategies to survive such events: some, like antelopes, gazelles, and lions, escape by running; birds fly away; and small creatures like rodents and reptiles often hide in burrows until danger passes.
Once the rainy season begins, animals return to their original habitats, resuming life in the now-replenished ecosystem.
The temperate grasslands biome is defined by the dominance of grasses and the absence of trees and shrubs. Unlike tropical grasslands, these occur in regions north and south of the tropics.
Major temperate grasslands around the world include:
Temperature ranges are highly variable, from –40°C in winter to 38°C in summer. The average annual rainfall ranges between 500 mm and 800 mm, which is considered relatively low. The growth of grasses is positively correlated with rainfall.
Drought and fire play essential roles in preventing tree growth, similar to processes seen in tropical grasslands.
Plants found in steppe regions typically grow in dry habitats and reach up to 30 cm in height. Representative grass species include:
A notable plant is 'Sweet' (Adonis Vernalis), which grows in the steppes and is used as a tranquilizer and medicine for heart and kidney conditions.
The temperate grasslands are home to a diverse range of animals including:
The saiga antelope is adapted to extremely cold and dusty environments with its large, inflatable, and movable nose structure.
Human activities such as livestock grazing, wheat cultivation, overgrazing, ploughing, and irrigation are having a significant impact on the integrity of the steppe ecosystems.
The desert biome is typically defined by low annual precipitation, ranging from 100 mm to 370 mm. Rainfall in these regions is seasonal and unpredictable, with occasional dry spells lasting for years, as seen in the Atacama Desert of Chile, where rainfall has not been measured for several years in some areas.
Deserts can be classified into three types: hot, cold, and semi-arid, based on geographic location, atmospheric pressure, and proximity to mountain ranges. Some well-known deserts include:
Deserts can also be coastal, such as the Atacama and Namib deserts, which are located along the west coasts of continents between 20° and 30° latitude. Prevailing easterly winds prevent moisture from reaching the land, contributing to desert conditions. Semi-arid deserts, such as the Gobi Desert and the Great Basin Desert, often lie in rainshadow regions.
Deserts experience large daily temperature variations, with extreme heat during the day and freezing temperatures at night. This temperature fluctuation presents challenges for survival.
Plant life in deserts is sparse and highly adapted to extreme dry conditions. Typical plants include:
Plants in the desert have developed specialized root systems to access water. Some plants, like the mulga tree, have unique root systems that collect water and funnel it down towards their roots. Many desert plants, such as cacti, store water in their roots, stems, or leaves, making them succulent.
Succulent plants can also minimize water loss by having small leaves, a waxy coating, or reduced surface area. These adaptations help them survive in harsh, dry environments.
Despite the challenging conditions, the desert is home to a variety of animals, including reptiles, insects, birds, and small mammals. Notable examples of desert fauna include:
The camel is particularly well-suited for desert life, as it can store large amounts of water in its abdomen sacs and survive without water for several days. Most desert animals are nocturnal, becoming active during the cooler nighttime temperatures. They often seek shelter by burrowing into the ground during the hot daytime hours.
The Arctic tundra is a biogeographical region found in northern Alaska, Canada, and Siberia. The term tundra is derived from the Finnish word meaning "treeless." The climate in this biome is characterized by long, cold winters and short, cool summers.
With an average annual precipitation of about 250 mm, the Arctic tundra experiences dry winds that create conditions similar to those found in deserts. A significant feature of the tundra is the presence of permafrost, a layer of subsoil consisting mostly of gravel and finer materials that remain frozen year-round. The lack of cracks and pores in the permafrost creates obstacles for plant roots and water penetration.
During the summer, the tundra is often covered with surface water. However, because of the permafrost, this water cannot percolate deep into the ground, forming pools of water on the surface. The region receives very little sunlight throughout the year, and though the Sun stays in the sky for 24 hours a day during the summer, it remains close to the horizon, providing only low-intensity sunlight.
Due to the short growing season (lasting only about 50 to 90 days), the flora of the Arctic tundra is adapted to survive under harsh conditions. About 1700 species of plants thrive in this biome. The short growing season and permafrost prevent plants from extending their roots deeply, making plant growth limited to very shallow depths.
Common plants include mosses, lichens, shrubs, and grasses. The small leaf size of many plants is a key adaptation, as it helps retain moisture, allowing the plants to conserve the limited water available.
The fauna of the Arctic tundra consists mostly of animals that either migrate during the winter months or hibernate to survive the extreme cold. Some animals, like the musk-ox, Arctic wolf, and brown bear, are adapted to live in the tundra year-round.
Other examples of tundra fauna include lemmings, voles, caribou, arctic hares, squirrels, arctic foxes, wolves, and polar bears. Numerous migratory birds also frequent the tundra during the summer, such as ravens, snow buntings, falcons, loons, sandpipers, terns, and various species of gulls.
A unique adaptation of animals in the Arctic tundra is hibernation, which allows animals to survive the long winter months. For example, bears store fat beneath their skin during the summer, which is then gradually converted into energy to sustain them through hibernation. Additionally, animals like the musk-ox have thick fur that protects them from cold winds and icy waters, while their large hooves help them break through ice to access water beneath the surface.