The term "Biosphere" was coined by Russian scientist Vladimir Vernadsky in the 1929.
The biosphere is the life zone of the Earth and includes all living organisms, including man, and all organic matter that has not yet decomposed.
Life evolved on earth during its early history between 4.5 and 3.8 billion years ago and the biosphere readily distinguishes our planet from all others in the solar system.
The chemical reactions of life (e.g., photosynthesis-respiration, carbonate precipitation, etc.) have also imparted a strong signal on the chemical composition of the atmosphere, transforming the atmosphere from reducing conditions to and oxidizing environment with free oxygen
Coral reef in Papua New Guinea. Coral reefs are sometimes referred to as the rainforest of the ocean because of the superabundance of life contained within them. All told, 90,000 unique species of marine plants and animals have been identified in coral reefs.
Rainforest in Blue Mountains, Australia. Much of the world’s biodiversity is found in the rainforests scattered about the globe. Despite the vital importance of rainforests to human life and the Earth system as a whole, they are under constant threat from humans who take over these life-saturated forests for farming and other uses.
The Florida Keys connected by Highway One. The landscapes we enjoy today were once quite different. For example, 125,000 years ago, the Florida Keys were an underwater coral reef. Then, as the Earth settled into an ice age, sea levels fell, leaving the islands up to 120 m above sea level. Today, the low-lying islands are now at risk of re-submergence due to sea level rise that is the result of human-caused global warming.
The biosphere is the life zone of the Earth and includes all living organisms, including man, and all organic matter that has not yet decomposed.
Life evolved on earth during its early history between 4.5 and 3.8 billion years ago and the biosphere readily distinguishes our planet from all others in the solar system.
The chemical reactions of life (e.g., photosynthesis-respiration, carbonate precipitation, etc.) have also imparted a strong signal on the chemical composition of the atmosphere, transforming the atmosphere from reducing conditions to and oxidizing environment with free oxygen
What is the biosphere?
The biosphere – the sphere of life – was named by Eduard Suess in 1875 but not fully described as a concept until the work of Vladimir Vernadsky in the 1920s. The biosphere is made up of biomes, or biophysical zones, filled with many ecosystems. Each ecosystem is composed of an intricate set of species adapted to prevailing conditions, from below ocean floors, to the land surface, to above the highest mountains. It includes life forms ranging in size from microscopic bacteria to the gargantuan blue whale. While persistent for billions of years, the biosphere has been hit by five mass extinctions in the geologic past and now faces existential threats to species diversity from human activity.
How does the biosphere work?
Throughout the evolution of life on Earth, from primitive organisms to the present set, all life forms have found ways to obtain energy, acquire nutrients to build organic molecules, and reproduce. Energy from the sun is captured by photosynthesizing organisms called autotrophs, or producers, that can harness solar energy to convert inorganic molecules into organic molecules -- the building blocks of life. These organic molecules store energy and are consumed by other non-photosynthetic organisms called heterotrophs, or consumers. This seemingly simple process -- grass being eaten by deer, for example -- took billions of years to develop. Through the process of evolution, species diversify to fill the available opportunities for existence, creating an ever changing set of plants and animals found in the Earth’s biomes from tundra to rainforests.
Diversity of Life
Coral reef in Papua New Guinea. Coral reefs are sometimes referred to as the rainforest of the ocean because of the superabundance of life contained within them. All told, 90,000 unique species of marine plants and animals have been identified in coral reefs.
Life is ubiquitous on Earth, yet biological productivity varies greatly from deserts to rainforests. Some 1.9 million species have been named, but there are an estimated five to thirty million or more species making up the biodiversity of Earth. Many of the unidentified species are in particularly hard to get to places, such as Antarctic ocean environments, or extremophiles living where it is intensely hot or cold or acidic. Below foot and beneath the sea, thousands if not millions of different organisms are teeming, many are unidentified as there just hasn’t been enough time and attention to sort out all these small life forms.
Phytomass, or the mass of plants, is estimated to be about 500 to 800 GtC (billion tons of carbon). Estimates of the mass of heterotrophs are dominated by large uncertainties regarding the mass of organisms living in the soil, deep below the soil, and in ocean sediments. Prokaryotes, simple organisms without a nucleus (bacteria and archaea), alone may be equal in mass to that of plants. Land and ocean heterotrophs other than prokaryotes make up a relatively small contribution to the total mass. Estimates of the total mass of the biosphere are more than 1 TtC (trillion tons of C) and perhaps as much as 4 TtC.
Rainforest in Blue Mountains, Australia. Much of the world’s biodiversity is found in the rainforests scattered about the globe. Despite the vital importance of rainforests to human life and the Earth system as a whole, they are under constant threat from humans who take over these life-saturated forests for farming and other uses.
How is the biosphere changing?
The suite of species on Earth at any given time is continually changing through the process of evolution. Over geologic time, more species have gone extinct than exist today. A dramatic example of this change is past extinction events. Paleobiologists and geologists have pieced together evidence in the geologic record of five mass extinction events reducing the Earth’s biodiversity to a portion of its full potential. A notable example is the mass extinction 65 million years ago that coincided with the end of the age of dinosaurs.
Abrupt change in the physical and chemical factors fundamental to life are key in mass extinctions. After each mass extinction the diversity of life slowly recovers to fill the ecospace available in the Earth’s environment. This process can take millions of years of evolution.
Potential causes for mass extinctions in the past include massive and sustained volcanic eruptions and impacts from comets and/or asteroids – both causing consequent alteration of the atmosphere from the lofted debris that blocks incoming sunlight. Sustained or very rapid climate change and sea-level change are also possible explanations of past mass extinctions.
Since the last ice age, human activity changing land use has been a dramatic factor in the disruption of species habitat. For example, about 35% of ice-free land is devoted to human agriculture, and as a consequence of this expansion, species are forced into environments in which they are ill suited to survive. Since the industrial revolution, human activity has altered air and water quality and is forcing a change in climate. These factors, in addition to land use change, interact in complex ways to affect biodiversity. Many scientists consider our present age a 6th mass extinction. An estimate of extinction from future climate change (projected in the range of 3.6 to 5.4 deg F) when compounded by other human impacts to biodiversity, finds that 20 to 30 percent of the identified species known today could be lost along with the ecosystem services they provide.
What is the hydrosphere?
The hydrosphere is the sum of all water on Earth and the water cycle that distributes it around the planet. Earth is unique in the solar system for its abundant surface waters. Our orbital distance from the sun, in addition to our unique atmosphere, gives Earth the right temperature in our middle-aged solar system to have water as a liquid, and lots of it. Venus is too hot, Mars is too cold. Earth is just right. Noted astronomer Carl Sagan described Earth as seen from distant space as a "pale blue dot," signaling our planet as an outpost of life. It's because of the hydrosphere that life flourishes on Earth.
Just as important as the existence of water is the hydrologic cycle that moves water around the globe. Driven by solar energy, surface waters evaporate into the atmosphere, condense, and fall back to the surface as precipitation, shaping continents, creating rivers, and filling lakes. This process has eroded billions of tons of surface material from the continents to the oceans, forming the major river deltas. By far, most of the hydrosphere is salt water - around 97 percent - but the 3 percent that is fresh is critical for terrestrial and fresh water species.
Water Distribution Water on Earth. Most of the water on Earth is either salty or inaccessible to humans. Only 3% is fresh, and of that only about 32% is unfrozen.
The variable hydrosphere
Precipitation around the globe is highly variable – from deserts (0 to 50 cm per year) to wet rainforests (125-660 cm per year). This variability is a key attribute of productive terrestrial ecosystems. While most precipitation evaporates from and falls onto the oceans, precipitation on land dominates as a key determinant of terrestrial biological zones of the Earth. While some organisms called extremophiles have found ways to adapt to very dry, hot, frozen, or low or high pH environments, the most abundant ecosystems on Earth exist where temperatures are tropical to temperate, nutrients are plentiful, and water is available.
Global Precipitation This animationillustrates the variability of precipitation around the globe. Tropical areas in South America and Africa, for instance, may receive up to 15 mm of rain each day, while arid regions like the Sahara receive little to none at all.(Source: NASA)
How is the hydrosphere changing?
Human contributions to greenhouse gases in the atmosphere are warming the earth's surface - a process which is projected to increase evaporation of surface water and accelerate the hydrologic cycle. In turn, a warmer atmosphere can hold more water vapor. Some evidence suggests global warming is already responsible for more extreme precipitation events. Precipitation in a warming world is also projected to lead to departures from current timing and patterns of rainfall distribution.
The Florida Keys connected by Highway One. The landscapes we enjoy today were once quite different. For example, 125,000 years ago, the Florida Keys were an underwater coral reef. Then, as the Earth settled into an ice age, sea levels fell, leaving the islands up to 120 m above sea level. Today, the low-lying islands are now at risk of re-submergence due to sea level rise that is the result of human-caused global warming.
While the exact changes are difficult to project, it is highly likely that some places will get drier while other places get wetter over the course of the 21st century as a result of global warming. For example, current climate models indicate that with global warming, high latitudes in the Northern Hemisphere are likely to see more precipitation.
Changes in types of precipitation may occur as well. Some precipitation may shift to rain rather than snow. This would decrease mountain snowpack and affect the timing and quantity of seasonal runoff. Changes in the patterns of spring runoff from major snow-fed river systems, such as those that flow from the Himalayas, will impact the lives and livelihoods of upwards of a billion people who depend upon snowmelt-fed rivers for domestic, agricultural, and industrial use.
As the Earth warms, so too will the ocean. As water warms, it expands. Expansion of warming water makes up about half of the present rise in sea level. The rest of the sea level rise we are currently witnessing is the result of land-based snow and ice melting into the ocean. The melt water component of sea level is expected to make up a more significant component of sea level rise as this century unfolds. The 2013 Intergovernmental Panel on Climate Change report found a 0.19 m rise in sea level between 1901 and 2010 and projected an additional 0.52-0.98 m of sea level rise over this century. However, recent research suggests that the amount of glacier melt could be significantly greater, raising sea level a meter or more. Island nations with little elevation above sea level are in peril, as are many countries with large coastal populations, such as the United States. Lowland settlements will be faced with a choice: whether to hold the line with engineered structures or retreat to higher ground.
