Biogeography: Species Distribution

Biogeography is a branch of geography that studies the past and present distribution of the world's many animal and plant species and is usually considered to be a part of physical geography as it often relates to the examination of the physical environment and how it affected species and shaped their distribution across the world.

As such, biogeography also includes the study of the world's biomes and taxonomy—the naming of species—and has strong ties to biology, ecology, evolution studies, climatology, and soil science as they relate to animal populations and the factors that allow them to flourish in particular regions of the globe.

The field of biogeography can further be broken down into specific studies related to animal populations include historical, ecological, and conservation biogeography and include both phytogeography (the past and present distribution of plants) and zoogeography (the past and present distribution of animal species).

History of Biogeography

The study of biogeography gained popularity with the work of Alfred Russel Wallace in the mid-to-late 19th Century. Wallace, originally from England, was a naturalist, explorer, geographer, anthropologist, and biologist who first extensively studied the Amazon River and then the Malay Archipelago (the islands located between the mainland of Southeast Asia and Australia).

During his time in the Malay Archipelago, Wallace examined the flora and fauna and came up with the Wallace Line—a line that divides the distribution of animals in Indonesia into different regions according to the climates and conditions of those regions and their inhabitants' proximity to Asian and Australian wildlife. Those closer to Asia were said to be more related to Asian animals while those close to Australia were more related to the Australian animals. Because of his extensive early research, Wallace is often called the "Father of Biogeography."

Following Wallace were a number of other biogeographers who also studied the distribution of species, and most of those researchers looked at history for explanations, thus making it a descriptive field. In 1967 though, Robert MacArthur and E.O. Wilson published "The Theory of Island Biogeography." Their book changed the way biogeographers looked at species and made the study of the environmental features of that time important to understanding their spatial patterns.

As a result, island biogeography and the fragmentation of habitats caused by islands became popular fields of study as it was easier to explain plant and animal patterns on the microcosms developed on isolated islands. The study of habitat fragmentation in biogeography then led to the development of conservation biology and landscape ecology.

Historical Biography

Today, biogeography is broken into three main fields of study: historical biogeography, ecological biogeography, and conservation biogeography. Each field, however, looks at phytogeography (the past and present distribution of plants) and zoogeography (the past and present distribution of animals).

Historical biogeography is called paleobiogeography and studies the past distributions of species. It looks at their evolutionary history and things like past climate change to determine why a certain species may have developed in a particular area. For example, the historical approach would say there are more species in the tropics than at high latitudes because the tropics experienced less severe climate change during glacial periods which led to fewer extinctions and more stable populations over time.

The branch of historical biogeography is called paleobiogeography because it often includes paleogeographic ideas—most notably plate tectonics. This type of research uses fossils to show the movement of species across space via moving continental plates. Paleobiogeography also takes varying climate as a result of the physical land being in different places into account for the presence of different plants and animals.

Ecological Biogeography

Ecological biogeography looks at the current factors responsible for the distribution of plants and animals, and the most common fields of research within ecological biogeography are climatic equability, primary productivity, and habitat heterogeneity.

Climatic equability looks at the variation between daily and annual temperatures as it is harder to survive in areas with high variation between day and night and seasonal temperatures. Because of this, there are fewer species at high latitudes because more adaptations are needed to be able to survive there. In contrast, the tropics have a steadier climate with fewer variations in temperature. This means plants do not need to spend their energy on being dormant and then regenerating their leaves or flowers, they don’t need a flowering season, and they do not need to adapt to extreme hot or cold conditions.

Primary productivity looks at the evapotranspiration rates of plants. Where evapotranspiration is high and so is plant growth. Therefore, areas like the tropics that are warm and moist foster plant transpiration allowing more plants to grow there. In high latitudes, it is simply too cold for the atmosphere to hold enough water vapor to produce high rates of evapotranspiration and there are fewer plants present.

Conservation Biogeography

In recent years, scientists and nature enthusiasts alike have further expanded the field of biogeography to include conservation biogeography—the protection or restoration of nature and its flora and fauna, whose devastation is often caused by human interference in the natural cycle.

Scientists in the field of conservation biogeography study ways in which humans can help restore the natural order of plant and animal life in a region. Often times this includes reintegration of species into areas zoned for commercial and residential use by establishing public parks and nature preserves at the edges of cities.

Biogeography is important as a branch of geography that sheds light on the natural habitats around the world. It is also essential in understanding why species are in their present locations and in developing protecting the world's natural habitats.