Ecozones and biogeographic realms and the management of natural resources
Ecozones and biogeographic realms are essential concepts in biogeography, which examines the distribution of living organisms across the globe. Ecozones are large regions characterized by unique physical attributes—such as climate, soil, and geology—that support particular plant and animal communities. These regions reflect both current environmental conditions and historical ecological developments. Biogeographic realms, on the other hand, are broader areas that encompass several ecozones and are identified based on shared geographical and biological features. They can be subdivided into provinces and districts to capture local variations in species types.
Understanding ecozones and biogeographic realms is crucial for managing natural resources effectively, as they provide insights into the relationships between climate, vegetation, and biodiversity. Human activities, including agriculture, logging, and urban expansion, significantly impact these regions, often leading to the degradation of original ecosystems. Therefore, recognizing and classifying these areas helps inform conservation efforts and the sustainable use of resources. The study of these realms and ecozones also extends to marine environments, where coastal zones are particularly influenced by human activity, making their classification vital for ecological preservation and resource management.
Ecozones and biogeographic realms and the management of natural resources
Ecozones and biogeographic realms are large-scale classifications that help scientists assess population sizes, histories, and locations of plant and animal species worldwide. The information aids the management and conservation of biological resources and is used to guide the choices of natural United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage sites. It also provides clues to how species evolved.
Background
Biogeography is the study of the distribution of living organisms in the world, past and present. “Ecozone” (short for “ecological zone”), “biogeographic realm,” “life zone,” and “biogeographic zone” are broadly synonymous terms for the major physical demarcations in this distribution. These terms are similar to the concept of the biome. However, whereas a biome is generally held to be a major community defined by principal vegetation and animal groups adapted to a particular environment, the ecozone takes into account the geological and evolutionary history of a region.
The idea for dividing the into distinct regions based on biological criteria dates to scientist-explorers of the eighteenth and early nineteenth centuries. In 1778, after sailing around the world with Captain James Cook, the English scientist J. R. Forster claimed that the world was composed of belts of similar vegetation, each fostered by a distinct climate. In 1804, German scientist Alexander von Humboldt, considered by many to be the father of biogeography, built upon Forster’s conclusions to demonstrate that vegetation varied regularly in accordance with altitude just as it did with distance from the equator.
Biogeographic Realms
Miklos D. F. Udvardy proposed the modern biogeographic realm schema in a 1975 paper, “A Classification of the Biogeographic Provinces of the World.” He defined a biogeographic realm as a continental or subcontinent region with unifying features of geography and plant and animal life. Each realm could be further divided into subrealms, or biogeographic provinces, and these into subprovinces, districts, and subdistricts, in order to define more precisely local variations in species types and distribution.
Udvardy recognized eight major biogeographic realms. Each represents a region in which life-forms have adapted as a community to climatic conditions. The realms draw upon the established five classes of biomes to identify vegetation-climate interrelations: tropical humid rain forests, subtropical and temperate rain forests, temperate needle-leaf forests, tropical dry or deciduous forests, and temperate broad-leaf forests and subpolar deciduous thickets. The Nearctic Realm, comprising 22.9 million square kilometers of the Earth’s surface, includes most of North America. The Palearctic Realm, comprising 54.1 million square kilometers, covers most of Eurasia and North Africa. The Afrotropical Realm, comprising 22.1 million square kilometers, contains sub-Saharan Africa. The Indomalayan Realm, comprising 7.5 million square kilometers, includes Afghanistan-Pakistan, South Asia, and Southeast Asia. The Oceanic Realm, comprising 1 million square kilometers, groups together Polynesia, Fiji, and Micronesia. The Australian Realm, which is 7.7 million square kilometers, similarly groups together Australia, New Guinea, and associated islands. The Antarctic Realm, 0.3 million square kilometers, comprises the continent of Antarctica. Finally, the Neotropical Realm, 19 million square kilometers, includes South America and the Caribbean.
Ecozones
Although the terms “ecozone” and “ecological zone” are used with varying meanings by others, Jürgen Schultz supplied the definitive treatment of the concept. In The Ecozones of the World (2005), he defines an ecozone as a large region of land where physical characteristics, such as climate, soil type, landscape, and geology, create a distinctive environment that supports a mixture of plant life that in turn supports a mixture of animal species. As do other classification schemes, Schultz’s recognizes that vegetation is the salient feature of a region, and he organizes the ecozones spatially by relating vegetation to and (as some classification schemes do not) seasonal variations in climate. Schultz emphasizes that no strict borders separate the ecozones; rather, they are concentrations of highly uniform life and landscape.
Shultz recognizes nine ecozones. The polar subpolar zone includes the areas between the North and South Poles and their respective polar tree lines, 22 million square kilometers. All of it lies within the area of permafrost; some parts are ice-covered (polar deserts), and some are tundra or bare rock. It is quite barren, characterized by very low average temperature, precipitation, and biological production; a short growing season; and low total biomass.
Theboreal zone, found only in the Northern Hemisphere, covers 20 million square kilometers and generally extends from the polar tree line to the central steppes (grassy plains). It is best known as a region of coniferous forests.
Most of the temperate midlatitudes zone also is located in the Northern Hemisphere—in eastern and western Eurasia and North America—although there are small areas of it in South America, Australia, and New Zealand. It includes 14.5 million square kilometers in narrow corridors between boreal evergreen forests and steppes. It is moderate in most of its characteristics, such as average temperature, precipitation, growing season, and total biomass.
The dry midlatitudes zone occupies small areas of North America, large swaths of east-central Eurasia, the eastern part of Patagonia in South America, and part of New Zealand, for a total area of 16.5 million square kilometers. Although this zone has various subdivisions, it is arid, with at most five months of plant growth and widely dispersed plants, such as cactus, adapted to dry, salty soils.
The subtropics with winter rain zone includes 2.5 million square kilometers, most of it along the Mediterranean coasts of Europe and western North Africa, but it also includes areas in southern Australia. Because the Euro-African and the Australia areas are so far apart, their plant and animal life vary considerably.
The subtropics with year-round rain zone includes 6 million square kilometers total; parts of it occur in the south of the United States, southern China, southeastern South America, eastern South Africa, and eastern Australia. The zone sees high average temperature and precipitation, a long growing season, and very large biomass.
The dry tropics and subtropics zone is the largest: 31 million square kilometers, which is nearly 21 percent of the entire world landmass. Deserts, semideserts, thorn savanna, and thorn steppe lie within it.
The tropics with summer rain zone constitutes, approximately, bands of moist and dry savannas north and south of the equator, 25 million square kilometers, in northern and eastern South America, central and Southern Africa, India, Southeast Asia, and northern Australia and nearby islands. Areas of it lie in Central America as well.
The last zone, tropics with year-round rain, is primarily equatorial: northern South America, Central Africa, Indonesia, and Malaysia. This zone comprises tropical rain forests in its 12.5 million square kilometers and has highest values in all categories of ecozone messurement—for example, the highest average temperature, precipitation, length of growing season, and biomass.
Human Impact
In comparison with Earth’s landmass, the planet’s oceans are not yet thoroughly studied for classification into biological regions. The difficulty of exploration and the flowing, changing nature of oceans make it difficult to distinguish boundaries underwater. However, in order to identify and protect at-risk ecosystems and to estimate exploitable resources, scientists have proposed various marine ecozones for coastal areas, which are the best understood. They also have the greatest human presence and use, including fishing, waste disposal, recreation, and transportation. These zones include beaches, coral reefs, kelp forests, human-made structures such as docks and pilings, mangrove swamps, mudflats, rocky shores, and salt marshes. (Deep-sea ecosystems may eventually be construed to compose ecozones, such as the ecosystems around underwater volcanic vents.)
On land, logging, farming, grazing domestic animals, and construction of cities account for the greatest modifications to ecozones. Because of these, the original vegetation cover in many temperate and tropical zones has been removed, wholly or partly. Schultz contends that agriculture and grazing represent the optimal expression of biological production within the physical environment of an ecozone.
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