Most organisms in the biosphere exchange the gases oxygen and carbon dioxide with the atmosphere

The biosphere is made up of the parts of Earth where life exists. The biosphere extends from the deepest root systems of trees, to the dark environment of ocean trenches, to lush rain forests and high mountaintops.

Scientists describe the Earth in terms of spheres. The solid surface layer of the Earth is the lithosphere. The atmosphere is the layer of air that stretches above the lithosphere. The Earth’s water—on the surface, in the ground, and in the air—makes up the hydrosphere.

The biosphere has existed for about 3.5 billion years. The biosphere’s earliest life-forms, called prokaryotes, survived without oxygen. Ancient prokaryotes included single-celled organisms such as bacteria and archaea.

Some prokaryotes developed a unique chemical process. They were able to use sunlight to make simple sugars and oxygen out of water and carbon dioxide, a process called photosynthesis. These photosynthetic organisms were so plentiful that they changed the biosphere. Over a long period of time, the atmosphere developed a mix of oxygen and other gases that could sustain new forms of life.

The addition of oxygen to the biosphere allowed more complex life-forms to evolve. Millions of different plants and other photosynthetic species developed. Animals, which consume plants (and other animals) evolved. Bacteria and other organisms evolved to decompose, or break down, dead animals and plants.

The biosphere benefits from this food web. The remains of dead plants and animals release nutrients into the soil and ocean. These nutrients are re-absorbed by growing plants. This exchange of food and energy makes the biosphere a self-supporting and self-regulating system.

The biosphere is sometimes thought of as one large ecosystem—a complex community of living and nonliving things functioning as a single unit. More often, however, the biosphere is described as having many ecosystems.

People play an important part in maintaining the flow of energy in the biosphere. Sometimes, however, people disrupt the flow. For example, in the atmosphere, oxygen levels decrease and carbon dioxide levels increase when people clear forests or burn fossil fuels such as coal and oil. Oil spills and industrial wastes threaten life in the hydrosphere. The future of the biosphere will depend on how people interact with other living things within the zone of life.

In the early 1970s, the United Nations established a project called Man and the Biosphere Programme (MAB), which promotes sustainable development. A network of biosphere reserves exists to establish a working, balanced relationship between people and the natural world.

Currently, there are 563 biosphere reserves all over the world. The first biosphere reserve was established in Yangambi, Democratic Republic of Congo. Yangambi, in the fertile Congo River Basin, has 32,000 species of trees and such endemic species as forest elephants and red river hogs. The biosphere reserve at Yangambi supports activities such as sustainable agriculture, hunting, and mining.

One of the newest biosphere reserves is in Yayu, Ethiopia. The area is developed for agriculture. Crops such as honey, timber, and fruit are regularly cultivated. However, Yayu’s most profitable and valuable resource is an indigenous species of plant, Coffea arabica. This shrub is the source of coffee. Yayu has the largest source of wild Coffea arabica in the world.

Biogenic gases in the atmosphere play a role in the dynamics of Earth’s planetary radiation budget, the thermodynamics of the planet’s moist atmosphere, and, indirectly, the mechanics of the fluid flows that are Earth’s planetary wind systems. In addition, human cultural and economic activities add a new dimension to the relationship between the biosphere and the atmosphere. While humans are biologically trivial compared with bacteria in the exchange of gases with the atmosphere, chemical compounds produced from human industrial activities and other economic enterprises are changing the gaseous composition of the atmosphere in climatically significant ways. The largest changes involve the harvesting of ancient carbon stores. This organic material has been transformed into fossil fuels (coal, petroleum, natural gas, and others) by geologic processes acting upon the remains of plants and animals over many millions of years. Different forms of carbon may be burned and thus used as energy sources. In so doing, organic carbon is converted into carbon dioxide. Additionally, humans are also burning trees, grasses, and other biomass for cooking purposes and clearing the land for agriculture and other activities. The combination of burning both fossil fuels and biomass is enriching the atmosphere with carbon dioxide and adding to the essential reservoir of greenhouse gases (see global warming).

greenhouse effect on Earth

The greenhouse effect on Earth. Some incoming sunlight is reflected by Earth's atmosphere and surface, but most is absorbed by the surface, which is warmed. Infrared (IR) radiation is then emitted from the surface. Some IR radiation escapes to space, but some is absorbed by the atmosphere's greenhouse gases (especially water vapour, carbon dioxide, and methane) and reradiated in all directions, some to space and some back toward the surface, where it further warms the surface and the lower atmosphere.

Encyclopædia Britannica, Inc.

Earth’s atmosphere is largely transparent to sunlight. Of the sunlight absorbed by the entire Earth-atmosphere system, about one-third is absorbed by the atmosphere and two-thirds by Earth’s surface. Sunlight is absorbed by the molecules of the atmosphere, by cloud droplets, and by dust and debris. Though oxygen and nitrogen make up nearly 99 percent of the atmosphere, these diatomic molecules do not vibrate in a way that permits them to absorb terrestrial radiation. They are largely transparent to outgoing terrestrial radiation as well as to incoming solar radiation.

Over the continents, the surface cover of vegetation is the principal absorbing medium of Earth’s surface, although other surfaces such as bare rock, sand, and water also absorb solar radiation. At night, absorption at the surface (that is, below 1.2 metres [4 feet]) is reradiated, in the form of long-wave infrared radiation, away from Earth’s surface back toward space. Most of this infrared radiation is absorbed by the principal biogenic trace gases of the atmosphere—the so-called greenhouse gases: water vapour, carbon dioxide, and methane. Without these biogenic greenhouse gases, Earth would be 33 °C (59 °F) colder on average than it is. A moderate-emission scenario from the 2007 Intergovernmental Panel on Climate Change (IPCC) report predicts that the continued addition of greenhouse gases from fossil fuels will increase the average global temperature by between 2.3 and 4.3 °C (4.1 and 7.7 °F) over the next century. Other scenarios, predicting greater greenhouse gas emissions, forecast even greater global warming.