What Is The Biosphere?

We explain the ecological structure and content of “the living Earth" - its biogeographical realms, bioregions and ecoregions, along with its communities of species, populations and individual organisms. We also ask: how is the biosphere affected by climate change?
Tiger in the wild
Image: Moni Sertel/CC BY-SA 2.0

The term “biosphere” describes the layer of Planet Earth where life exists. A synonym might be “the living Earth“. It’s the global ecological environment (or ecosphere), with its interactive network of living beings, including their relationship with the air above them (the atmosphere), the ground beneath their feet (the lithosphere), the rivers, lakes and oceans (the hydrosphere), and the polar and other frozen zones (the cryosphere).

It extends to wherever life is on Earth. So, it extends from as deep as 10,000 metres (6 mi) below the floor of the Pacific Ocean (where traces of microbes have been found), up to 37,000 feet where birds have been seen to fly. 1 2 It’s the home of Earth’s amazing biodiversity – its rich variety of plant and animal species.

Because it is composed of living things, the biosphere is particularly affected by rising temperatures and all the other distressing effects of global warming, including floods and sea-level rise. In fact, climate change is probably the single most important challenge the biosphere has faced, since the Cretaceous–Paleogene mass extinction 66 million years ago, when it suffered a catastrophic loss of biodiversity as the dinosaurs perished, along with three-quarters of all plants and animal species.

The word “biosphere” actually refers to any closed, self-regulating space which contains biological communities of interacting organisms. For example, it includes biospheres anywhere in the Universe, as well as artificially created ones here on Earth, such as Biosphere 2 – the Earth system science facility in Oracle, Arizona – and BIOS-3 – the underground biophysics research facility at Krasnoyarsk in Russia. 3

When Was the Term “Biosphere” first Used?

The term “biosphere” was first employed by the Austrian geologist Eduard Suess (1831-1914) in 1875. 4 But it was given an ecological context by the Russian geochemist Vladimir I. Vernadsky (1863-1945), who defined ecology as “the science of the biosphere”. The term “ecosystem” was first coined in 1935 by the English botanist Sir Arthur Tansley (1871-1955).

When Did The Biosphere Start To Evolve?

The Earth’s earliest life-forms are believed to be fossilized microorganisms, unearthed in sediments discharged from splits in the ocean floor. Geoscientists estimate they may have originated as early as 4.28 billion years ago, roughly 130 million years after the oceans appeared, and only 260 million years after Earth itself was formed 4.54 billion years ago. 5 However the earliest confirmed life forms are Australian microorganisms dating to 3.5 billion years ago. 6

Interdisciplinary research by experts in paleontology, astrobiology, geophysics and biochemistry points to life having evolved in the sea, as the only source of the necessary chemicals. During this evolutionary process, molecules of simple organic compounds gradually clustered, then reclustered, forming ever more efficient pathways for energy transformation, until they became capable of reproduction. 7 8 9

What Are The Vital Resources Of The Biosphere?

The biosphere (life on Earth) depends on sunlight for its energy. Sunlight, is captured by plants, and turned into energy through the mechanism of photosynthesis. Since nearly all life depends ultimately upon green plants, almost all species of animals, fungi, parasitic plants and many bacteria rely directly or indirectly upon photosynthesis. But see: 7 Effects of Climate Change on Plants.

In addition to sunlight, the biosphere is also dependent upon the continuous cycling of critical matter, through the so-called biogeochemical cycles of essential chemicals. These pathways, like the carbon cycle, the nitrogen cycle, the sulfur cycle, the phosphorus cycle, the water cycle and others, provide a regular supply of raw materials which – when combined to form proteins, lipids, carbohydrates, and nucleic acids – provide the building blocks for the creation of life.

Classification Of The Biosphere

Biogeographical Realms, Bioregions & Ecoregions

The biosphere is commonly divided into a hierarchy of rather vaguely defined geographical units, according to size. (A) The largest units are “biogeographical realms“. These are large spatial areas of the Earth’s land surface that share similar biological evolutionary history and patterns of terrestrial organisms. (B) These realms are then divided into “bioregions.” These are areas whose limits are naturally defined by topographic and biological features (such as mountain ranges and biota), rather than political boundaries. (C) Bioregions are divided into “ecoregions“. An ecoregion is a relatively extensive area of land or water defined by its climate, landforms, soil characteristics, species and environmental conditions. (D) Finally, we arrive at the most important and most commonly used ecological unit – the biome. It’s the only unit that is small enough to be distinct, but large enough to matter.

What Are Biomes?

Biomes are biological communities of plants and animals that have formed because they share the same climate, typically one with the same temperature, amount of rainfall and humidity. 10 A biome covers a wider physical area than an ecosystem or habitat: a biome may consist of hundreds, if not thousands, of ecosystems, and a great many habitats.

The American plant ecologist Robert Whittaker (1920-80) proposed the following biome types (edited), which he based largely on precipitation and temperature: Tropical rainforest – Montane rainforest – Temperate forest – Taiga – Thorn scrub – Temperate woodland – Temperate shrublands – Savanna – Temperate grassland – Tundra – Desert – Bog – Fresh-water swamp – Mangrove swamps – Salt marsh – and Wetland. 11

What Is Biota?

The term ‘biota’ refers to the entire collection of organisms of a geographic region (like a biome) or a time period. For example, one might talk about the role of the wildebeest in the biota of the Maasai Mara grasslands of south-western Kenya, or the symbiotic role of polar bears and seals in the biota of the Arctic ice. The Earth’s biotas make up the biosphere.

What Are Ecosystems?

An ecosystem is the second level of ecological community, after biome. If biomes are smaller biospheres, then ecosystems are smaller scale biomes. A lake, for example, is not just an expanse of water – it’s a whole ecosystem of aquatic life, wetland creatures, insects, grasses, nutrients, climate, and all of the biological life contained within it. Likewise, a forest is not simply a series of trees but rather a complex interlocking system of soil, air, and water, of insects, bacteria, viruses, fungi, grasses, herbs, birds, mammals and foliage.

Ecosystems typically are home to three general categories of organisms, separated by their methods of obtaining energy. These organisms are: (1) the primary producers, largely green plants who store energy made from sunlight; (2) the consumers, a category which incorporates all the animals; and (3) the decomposers, that is all the tiny microorganisms that break down the remains of dead plants and animals into simpler components and nutrients for recycling across the ecosystem and biosphere. For more, see: Food Web on Land: Who Eats Who?

What Are Communities Of Species?

The third level of the biosphere, one step down from ecosystems, consists of smaller biotic units called communities of species, who share a particular habitat. Examples of communities include the organisms around a pond, in a cave, along a stream, on a beach or underneath an urban motorway. The communities in a particular location are those that can survive the local abiotic factors such as temperature, pH and nutrients, as well as the localized biotic factors such as predators and food sources.


One step down from the community of species is a population. A population, the fourth level of the biosphere, consists of members of a single species living in a particular habitat. A population can include thousands of members or just only a few hundred. The addition or loss of a population can adversely affect an entire community or small ecosystem. In a stretch of meadowland, for instance, there may be many species of insects, of birds, of small mammals, each one representing a separate breeding unit, but each reliant on the others for its continued existence.


At the base of the biosphere are organisms, the final level of the biosphere. Organisms are commonly classified by their cellular structure or by the way they obtain energy. Cellular structure subdivides organisms into prokaryotes, (who have free-floating DNA inside cells without a nuclei), and eukaryotes (whose DNA is located within a cell’s nucleus). Organisms are considered either autotrophs, such as plants, which obtain energy from light or inorganic chemical reactions; and heterotrophs, such as animals, which must consume other organisms to obtain energy. Organisms include the biosphere’s decomposers, microorganisms that break down dead or decaying organisms into simpler substances and nutrients which they then recycle.

What Is Biodiversity?

Biodiversity refers to the variety of species on Earth. Biodiversity essentially measures variety at the genetic, species, and ecosystem level. It is typically greater in equatorial regions, due to the warm climate and the high absorption of solar energy. 

The biosphere plays host to between 3 and 30 million species of plants, animals, fungi, single-celled organisms such as bacteria, and single-celled eukaryotes like protozoans. Of this total, no more than 1.4 million species have been identified to date, and less than 1 percent have been studied for their ecological role.

Just over half the named species are insects, which dominate terrestrial and freshwater communities worldwide; the specimen cases and laboratories of entomologists are filled with insects yet to be named and described. Hence, the relationships of organisms to their environments and the roles that species play in the biosphere are only beginning to be understood.

The Earth is filled with so many types of creature and so many different types of biological communities because species have been able to adapt to almost any kind of environment through natural selection. Life-forms have evolved that are able to survive in the darkest ocean depths, the frozen conditions of Antarctica, and the near-boiling temperatures of geothermal springs. The enormous richness and diversity of abilities found among different species of living organisms is the Earth’s greatest and most irreplaceable resource.

Read our article: How To Reduce Your Carbon Footprint.

Loss of Biodiversity in the Biosphere

The biggest threats to animal biodiversity are commercial development, deforestation and climate change – all caused by human activities. For details, see: List of Endangered Species. For profiles of certain animals and birds, see the following articles:

10 Endangered Animals
10 Endangered Birds of Prey
10 Iconic Birds Threatened by Climate Change

How Is The Biosphere Affected By Global Warming?

Global warming poses an existential threat to a number of Earth’s biomes, and to thousands, perhaps millions, of different ecosystems. The effects of climate change on animals are already intensifying. Indeed, if global warming is not brought under control, virtually every ecosystem on Earth is likely to change dramatically, to the point of becoming an entirely new biome, according to a new study conducted by 42 scientists from around the world. 12

Global warming is already beginning to cause obvious and visible damage to the climate system in both hemispheres. The last five full years (2014-18) have been the hottest ever, with record-breaking heatwaves in Australia, Europe and the Indian sub-continent. 13 Longer and more intense droughts were also seen recently in Australia and China. Yet the world continues to consume the same amount of fossil fuels, energy consumption is up and so are CO2 emissions.

The Polar Biome

This biome – which includes the Greenland ice sheet and the Antarctic ice sheet – plays a critical role in Earth’s climate system, because snow and ice reflect solar energy from the sun back into space, through a mechanism known as the “albedo effect“. Conversely, the warmer it gets and the more ice that melts, the less reflection and the more solar energy that reaches Earth, which leads to more ice melt and so on. Of course, if land-based ice melts, it leads directly to a rise in sea levels. Recently, Greenland’s ice sheet has been melting at record rates in heatwave weather.

The ice sheets of West and East Antarctica are also shedding mass. Its two biggest glaciers look alarmingly unstable. Recent studies into the ice of Antarctica by Robert DeConto and David Pollard suggest that – instead of a 1-4 feet increase in ocean levels by the end of the century, as the IPCC outlines – a rise of six feet is more likely. 14

If carbon emissions continue to rise, then under certain conditions the total 11 feet of ice locked up in West Antarctica might be released. 15 16


This biome, located between the North Pole and the boreal forests of the taiga, covers about 11.5 million sq km of the earth’s surface, mainly in Russia, Greenland and Alaska. It has little biodiversity, no rain to speak of, and no trees because the ground is frozen. What it does have is millions of tonnes of frozen carbon locked up in its permafrost (permanently frozen soil). Except that the soil is gradually thawing because of rising temperatures, releasing more and more of its carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). These emissions are already occurring and cannot be effectively controlled by human intervention. And once the thaw starts in earnest it might trigger an irreversible, runaway process of global warming. 17


A little warmer and wetter than tundra, the boreal taiga forests of Canada, Alaska and Russia constitute the world’s largest biome, covering some 17 million sq km of the earth’s surface. These forests sit on top of their own carbon-rich permafrost, which is also thawing. Scientists estimate that the world’s permafrost (mostly under the tundra or taiga) stores about 1,500 billion tons of carbon – a significant proportion of which could end up in the atmosphere if temperatures continue to rise.

In 2019, which was not the hottest year on record, wildfires sparked by unseasonably high temperatures engulfed large areas of Siberia destroying 43,000 square km of boreal forest and creating smoke clouds covering more than 5 million square kilometers, larger than the size of the European Union. 18 In Canada, 18,000 square km were burned out, while in Alaska 670 square km were destroyed. These fires not only led to greater thawing of the permafrost, but also caused a huge spike in global CO2 emissions from the burning trees.


The Amazon Rainforest, more than half as big as the United States (including Alaska and Hawaii), accounts for about 55 percent of the planet’s surviving rainforest, and is home to 1 in 10 of the world’s species or 10 percent of the world’s store of genetic blueprints. 19 This unique tropical biome contains many of the secrets of life on planet earth, such as the origins and causes of many diseases, as well as their antidotes. If it goes up in smoke it will be an unimaginable catastrophe. For more on this unique biome, see: Deforestation in The Amazon Rainforest.

For details of the climate and wildlife of the world’s second largest tropical forest, see: Congo Rainforest May disappear by 2100.

For an insight into the land problems of the world’s third largest area of tropical rainforest, see: Deforestation in Southeast Asia.

Unfortunately, continuing global warming – as well as human farming methods – is drying out the rainforest and causing fires, which releases large quantities of CO2 into the atmosphere, which further dries out the forest causing more fires, and so on.

This spiral and its warming effect on the temperature, humidity and transpiration of the rainforest has led to warnings that the Amazon water cycle may soon become irreversibly broken, locking in a trend of declining rainfall and longer dry seasons. An irreversible tipping point, say some scientists, will be when deforestation reaches between 20 and 25 percent (the current level is 17 percent). At that point, they predict that half the shrinking forest will turn to savanna. 20 21

The Australian bushfires 2019/2020 devastated over 186,000 sq km of forests and land, including parts of the country’s primary rainforests, that had never been burned before.


The largest separate environment in the biosphere, the ocean biome (actually several biomes) plays a key role in Earth’s increasingly fragile climate system. ( See also: How Do Oceans Influence Climate.) As well as acting as a buffer absorbing excess heat and carbon dioxide from the air, thus helping to limit global warming, oceans are home to the world’s largest single collection of living creatures. Unfortunately, rising temperatures are increasing the acidity level of the oceans which is proving fatal to many marine ecosystems. (See also: Effects of Global Warming on the Oceans.)

According to the IPCC’s Special Report on Global Warming, up to 90 percent of coral reefs are likely to die if the temperature increase reaches 1.5°C. If it reaches 2°C, 99 percent will disappear. Known as the “rainforests of the sea”, coral reefs form the most diverse habitat and marine ecosystem in the ocean, supporting 1 in 4 of all marine species. Their survival is also vital to the survival of thousands of other marine species – many of which we rely upon for food. Reefs also provide a livelihood for as many as 500 million people around the globe.


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