Biosphere
Biosphere: the place on Earth’s surface where life dwells. ~ English geologist Eduard Suess
Eduard Suess’s original 1875 definition of biosphere has expanded. The biosphere is now considered the global summation of the Earth’s ecosystems.
Evolution is a tightly coupled dance, with life and the material environment as partners. From the dance emerges the entity Gaia. ~ James Lovelock
From the early 1970s, English naturalist James Lovelock called Earth’s ecosystems the “organs of Gaia.” Lovelock’s conception was that Earth is analogous to a self-regulating organism, which he termed Gaia after the ancient Greek goddess of Earth. From a historical perspective, Lovelock merely revived the idea of James Hutton, who argued in 1875 that Earth was a superorganism.
Earth is not just a machine, but also an organised body, as it has a regenerative power. ~ Scottish geologist James Hutton
Despite withering scientific scorn, the Gaia theory resonated in the public consciousness. Lovelock may have rhapsodized too poetically for scientific minds, but to anyone attuned to Nature the idea that Earth behaves as an entangled gyre makes perfect sense. Further, subsequent science proved the Gaia theory true.
Organisms can influence the physical formation of habitats (ecosystem engineering), fluxes of elements in biogeochemical cycles (for example, ecological stoichiometry), and the productivity of ecosystems (for example, via trophic cascades and keystone species). ~ American ecologist Bradley Cardinale et al
“The history of life on Earth is closely intertwined with the physical and chemical mechanisms of our planet. It is clear that life had a profound role in creating the world, and the planet has similarly affected the trajectory of life.” ~ English Earth scientist Timothy Lenton
Climate
“The ultimate source for all life’s energy, growth, and behavior is the Sun.” ~ Lynn Margulis
Global climate is a confluence of entangled factors involving air, sea, and land. The oceans act as the primary planetary thermostat. They do so by conveying absorbed heat from the tropics toward the polar regions, as warm equatorial waters are carried to higher latitudes by prevailing winds.
Approaching the high latitudes, surface waters surrender their warmth. In losing heat, water becomes dense and descends to the depths, where it contributes to the cold-water currents flowing toward the equator.
The other aspect of oceanic thermal regulation is the removal and storage of carbon dioxide from the atmosphere: the carbon cycle. The atmosphere is naturally more a conduit and climatic expression than regulator. The exhausts of life on land greatly affect the atmosphere’s influence on climate.
Plants inhale atmospheric CO2 and respire O2. Further, greenery has a relatively low albedo. Thus, vegetation tends to keep the planet cool.
To the converse, the accumulative impact of humans has dramatically altered global climate, as industrially fueled atmospheric release of greenhouse gases and other pollutants tilts the planet toward hothouse. Humans are wrenching Earth’s thermostat into a severe mass extinction.
Volcanism
The intensity of mantle plumes occurs coincidentally with cyclic changes on the surface. As these plumes push up to form diapirs (intrusions) in the crust, water shifts toward continents, producing sea-level rise which precipitates volcanic activity which releases greenhouse gases that warm the climate.
Volcanism can also create massive dust veils that promote global cooling for 10–100 years. Countervailing tendencies play out their intensities for different durations.
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Earth acts as an integrated gyre, with an interplay of intricate feedback loops among the biological, climatic, and geological realms. This planetary system has self-organized criticality: supporting or disfavoring life at times, depending upon a confluence of environmental conditions. Past mass extinction events most dramatically demonstrated biotic balance disrupted and restored over the course of millions of years.
Biomes
A biome is a region where organisms live with similar conditions, both geographically and climatically. Biomes bifurcate between aquatic (marine and freshwater) and terrestrial, though land and freshwater are typically classified together because of their proximate geography. Beyond that, land-based biomes are more finely defined by climate, with latitude, elevation, and humidity being significant factors.
Marine biomes are defined by depth, latitude, and water flow. Upwelling cold water that brings nutrients from the deep greatly affects marine life, and so figures as a major factor in defining a marine biome.
Classification
There is the typical cacophony of vocabulary in identifying biomes, which traditionally have local names. Temperate grassland, shrubland, prairie (North America), savanna (Australia), steppe (central Asia), pampas (South America) and veld (South Africa) are all the same biome under a different term.
Adding to the nomenclature noise are numerous biome classification schemes. Almost all are exclusively terrestrial biomes. All start with climate and diverge from there.
American botanist and climatologist Leslie Holdridge came up with the concept of life zones in 1947 which emphasized temperature and precipitation. Holdridge updated his design in 1967, complicating it with humidity provinces and regions of altitude and latitude. The result was 38 different life zones which emphasized soil type and climax vegetation (dominant plants).
Holdridge’s scheme does not work well in predicting soil pattern, and especially breaks down when moisture becomes a determining factor; especially in cold climates, whether oceanic or arid. Nonetheless, it has been used in assessing changes in vegetation patterns due to global warming.
American plant ecologist Robert Whittaker developed his terrestrial biome scheme in the late 1950s, focusing on gradients of temperature and precipitation. Whittaker’s approach was a simplification of Holdridge’s, with workable concepts about different communities of plant and animal life. Its simplicity made it popular.
A terrestrial biome scheme by German ecologist Heinrich Walter was published in 1976 with 9 basic biomes, from equatorial to polar. Like Whittaker, Walter’s approach was based on temperature, moisture, and vegetation types. Walter also accounted for seasons.
In 2001 came a team effort by the Worldwide Fund for Nature (WWF), defining 8 terrestrial and freshwater ecozones, along with 13 marine ecozones; 14 terrestrial biomes with 867 terrestrial ecoregions; 13 freshwater biomes; and 11 marine habitat types.
The WWF system is rigged to hierarchical classification: ecozone, biome, ecoregion, ecosystem, biotype (typically plant or animal), and species. It is thus strongly taxonomic and not well-suited to describing biospheric dynamics.
Bizarrely, missing from all extant biome schemes is the endolithic biome: the microscopic life in rock crevices and underneath the surface, where life originated. ~70% of Earth’s bacteria and archaea live in the planet’s crust, not on it.
