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History of Ecological Sciences, Part 63: Biosphere Ecology

2019; Ecological Society of America; Volume: 100; Issue: 3 Linguagem: Inglês

10.1002/bes2.1568

2327-6096

Frank N. Egerton,

Space Science and Extraterrestrial Life

This is a new, ecological age, and its universal religion will probably become like [Gerd Heinrich's], that of nature on a global scale. Our moral choices will be informed by that vision of the whole, which is greater than all of us humans combined. Individually, we are like cells of a giant organism, the earth's biosphere. —Bernd Heinrich (2007) Biogeochemistry, Gaia, and Earth system science are versions of biosphere ecology. Global warming might be considered a biosphere pathology. Part 63 of this series begins with very early studies into what we would now call biosphere ecology. Photosynthesis is a very important component of this history. During the 400s C.E., Rufinus of Aquileia translated from Greek into Latin pseudo-Clement's Recognitions, a conversation between a skeptical father and his Christian sons. One question raised was "Does not the rebirth of seed from earth and water and its growth into plants for the use of man sufficiently demonstrate the workings of the providence of God?" (translated in Howe 1965:409). One son responded: "When they are sown, the earth, by the divine will, pours out upon these seeds the water it has received…" (in Howe 1965:410; Egerton 2014a,b:208). The son then proposed seeds be planted in a known weight of dirt, with nothing added but water. After the plants have grown, they can be weighed and the dirt again weighed. The dirt will be seen to have lost no weight, and so the plants' substance clearly came only from water. German scholar-diplomat Nikolaus (or Nicholas) von Cusa (ca.1401–64) in 1450 wrote Idiota de staticis experimentis, which included an account of pseudo-Clement's experiment (Hoff 1964, Howe 1965, Hofmann 1971). To the previous account, Nikolaus added "by the operation of the Sunne" (translation in Hoff 1964:108). He also suggested weighing the seeds or seedlings before the experiment and afterward to burn the plants to determine their dry weight. These first two accounts are presented as hypothetical, though at least the first account would have to have had a real experiment as its basis in order to be confident of the results. Leonard K. Nash compiled a case history of experimental science, Plants and the Atmosphere (1957), in which Belgian physician Johann Baptista van Helmont (1577–1644), who coined the word "gas" (Partington 1962:index, Pagel 1972, Hill 2013:xv–xvi) and English aristocrat Robert Boyle (1627–91), active member of the Royal Society of London (Partington 1962:index, Hall 1967, 1970, Hunter 2015), conducted actual experiments (van Helmont using a willow tree), which seemed to indicate that plants grew from water alone, since their experimental plants used an insignificant amount of dirt, as weighed before and after their experiments (Nash 1957:328–335). Boyle, a "skeptical chemist," used distilled water, but even so, he wondered whether the glass container might have lost any substance into the water and then into the plant (1661). Their conclusion was soon undermined by studies on plant anatomy by Italian medical professor Marcello Malpighi (1628–94) (Adelmann 1966, Belloni 1974) and English physician Nehemiah Grew (1641–1712; Metcalf 1972). Malpighi's study was conducted in 1675 and published in 1686, and Grew conducted his in 1676, yet published in 1682 (Nash 1957:435). They discovered that plant leaves have pores (stomata) that allowed air to move in or out (Nash 1957:335–336). Another Englishman of that period, John Evelyn (1620–1706), who was a member of the Royal Society of London, as were Boyle, Grew, and Woodward, focused upon practical issues (Avignon 1971). One of Evelyn's books was Fumifugium, or, the Inconveniences of the Aer, and the Smoak of London Dissipated (1661). In it, he "proposed removing certain trades and planting a green belt of fragrant trees and shrubs around the city" (Avignon 1971:495). These sensible recommendations would have ameliorated the problem to the extent the city implemented them. But Londoners were used to the smoke, and they only got around to doing something about it after the Great Smog of 1952, which killed 12,000 (Flannery 2005:38). In Sylva, or, a Discourse of Forest Trees, and the Propagation of Timber in His Majesty's Dominions (Evelyn 1664), "Evelyn argued that the excessive humidity of Ireland and North America was due to excessive rain and mists attracted by their dense forests" (Fleming 1998:27). In this case, he suggested that cutting the forests would cause better climate, benefitting human health (and be useful to the British Navy). English naturalist John Woodward, M.D. (1665–1728), had an early interest in botany that later faded while his interest in paleontology grew (Eyles 1971, 1976, Levine 1977). He carried out in 1691–92 "Some Thoughts and Experiments concerning Vegetation" (1699). He conducted a controlled experiment, in which he grew common spearmint of the same size in three containers, containing spring water, rainwater, and Thames River water. He concluded that impurities provided important nutrients. He discovered, but did not name, transpiration (1699:208): "The much greatest part of the Fluid Mass that is drawn off and convey'd into the Plants, does not settle or abide there, but passes through the Pores of them, and exhales up into the Atmosphere." However, that discovery led him to mistakenly conclude (1699:221): "Water serves only for a Vehicle to the terrestrial Matter which forms Vegetables; and does not in itself make any addition unto them." Woodward also reported (1699:209) that in America, the early settlers were annoyed by the humidity, but after they cut down the forests, "the Air mended and cleared up apace: changing into a Temper much more dry and serene than before." John Evelyn was undoubtedly pleased when he read that. The 1600s was also when meteorology received a significant boost by the invention of meteorological instruments, led by Italian investigators. Galileo let the way by developing the telescope and assisting with development of microscopes. Rain gauges and wind (weather) vanes predate the 1600s, but it was the barometer and thermometer that developed in Italy were key instruments for the origins of meteorology (Middleton 1969:3–80). At this point in our history, more recent sources supplement Nash's account. I know of no other science that has as many historical resources as specialists who study photosynthesis. Advances in Photosynthesis and Respiration is the name of a collection of 22 monographs published by Springer, 1994–2006, with presumably more to come. Especially noteworthy is Volume 20: Discoveries in Photosynthesis (2005), edited by Govindjee, J.T. Beatty, H. Gest, and J.F. Allen. For our purposes, the most important of its papers is by Govindjee and David Krogmann, "Discoveries in Oxygenic Photosynthesis" (1727–2003) (2005). Other papers will also be cited. A later English clergyman Stephen Hales (1677–1761) conducted more sophisticated plant physiology experiments than ever before, published in his Vegetable Staticks (1727) (Partington 1962:112–123, Guerlac 1972, Allan and Schofield 1980, Govindjee and Krogmann 2005:64–66). Hales was at Cambridge University during the time of Newton, and he absorbed the importance of measurement in science. He conducted experiments on blood pressure, using two horses and a deer, before he turned to plant physiology. Van Helmont and Boyle were first to conduct quantitative studies on plant physiology, but at a simple level. Hales was influenced by his previous studies on animal physiology, and he went far beyond those predecessors. He studied what is now called transpiration, and he invented the pneumatic trough for his studies (Parascandola and Ihde 1969:353–357). He also observed that the pores in leaves let air in and moisture out. Nash (1957:340–342) quoted Hales' 122nd experiment, which was a controlled experiment. He believed he had demonstrated that air is important for plant growth. However, he could not distinguish one kind of air from another. He also concluded that water is important for plant growth. As science gathered momentum during mid-1700s in western Europe, old verities, such as air and water as elements, were no longer assumed to be true. Parisian Antoine-Laurent Lavoisier (1743–94) was son of a solicitor who acquired wealth through inheritance and then through marriage (McKie 1962, Guerlac 1973:67, 1975, Hill 2013:xvii–xviii). He received an excellent science education and became the leading chemist in Europe (Partington 1962:363–494), until his life was cut short by a guillotine during the French Revolution. His interests, however, were quite broad and also included physiology, geology, economics, and social reform. He was both a skeptic and a careful experimenter, both of which traits were displayed in his 1770 memoir (published 1773) on the nature of water and experiments that proved the impossibility of changing it into earth. Lavoisier also showed that he had mastered all the relevant literature and built upon achievements by Hales and others. Nash (1957:344–350) discussed this memoire and rendered passages into English. Lavoisier's many chemical inquiries culminated in his revolutionary Traité élémentaire de Chimie (1789, English 1952). He established a definition of an element as a substance that persists through chemical reactions and cannot be reduced to more fundamental substances. Englishman Joseph Priestley (1733–1804) was son of a small-town cloth dresser or finisher and was a studious boy (Partington 1962:237–296, Schofield 1963, 1975, 1997). He studied to become a minister, and did, but in the Unitarian Church, not the Church of England. He also opened a school, and he had broad intellectual interests, perhaps as broad as Lavoisier's, though not in all the same subjects. He began scientific research on electricity and optics. Only in 1769, when a fourth edition of Hales' Vegetable Staticks appeared did he become interested in air and began reading chemical works. His first publication in this new direction was lengthy: "Observations on Different Kinds of Air" (1772). He collected air from an enclosed mouse and enclosed plant and tested the airs (Nash 1957:350–358, Gorham 1991:203). When only a mouse was enclosed, the air became poisonous, killing the mouse and extinguishing a candle. However, when a plant was enclosed with the mouse, the mouse survived and the candle remained lit. The plant also did well in air that had killed a mouse. He showed his experiment to a visiting American friend, Benjamin Franklin, who commented that animals eat plants, and in turn, animal wastes provide fertilizer for plants (Nash 1957:355, Drouin 2010:7–8). Priestley was busy with various endeavors and did not resume work on this research until 1774, when he announced a new discovery: he heated what we call mercuric oxide and released a new gas which he called "dephlogisticated air" (oxygen) within the context of an older theory of combustion (Partington 1962:256–263, Hill 2013:xvii–xviii). In it, a candle burned more brightly than in ordinary air. In October 1774, he visited a group of French scientists, including Lavoisier, and told about his discovery. Later, Lavoisier repeated Priestley's experiment and obtained the same results, but with a different explanation (Guerlac 1973:75). It became one of the stepping stones to Lavoisier's scientific revolution. Ironically, Priestley was radical in his religion and politics, which drove him to American for his last years (Jackson 2005:254–321), but scientifically, he was too conservative to accept Lavoisier's new chemistry. Even so, one science historian has argued that Priestley's understanding differed from traditional phlogiston theory (Holmes 2000). In spring 1778, Swedish apothecary Carl Wilhelm Scheele (1742–86) published observations that challenged some of Priestley's early discoveries (Nash 1957:358, Boklund 1975). Priestley then repeated those experiments and could not obtain some results previously published (Nash 1957:358–369). Dutch physician Jan IngenHousz (1730–99) had graduated from the University of Louvain in 1753, then spent four years at universities of Leyden, Paris, and Edinburgh (Nash 1957:369–384, 409–419, Partington 1962:278–280, Van der Pas 1973, Magiels 2010, Hill 2013:xxi). Afterward, he returned to his hometown, Breda, on the coast. At other times, he would live in England and in Vienna. He investigated this puzzle of plants and gases in summer 1779, conducting over 500 experiments (IngenHousz 1779). He discovered that green plants only purify air in sunlight, and that at night they render air noxious, as animals do. It was the first of his 19 publications on plants and the atmosphere, 1779–1798 (listed in Magiels 2010:390–391). Ingenhousz's biographer concluded that he deserved credit for discovery of photosynthesis (Magiels 2010:359). A Swiss pastor (until 1769) and librarian (after 1769) and naturalist, Jean Senebier (1742–1808) took the next step (Nash 1957:385–388, Partington 1962:280–283, Pilet 1975b, Hill 2013:xix–xxi). His early interest was animal physiology and later plant physiology. Nash found that in 1783–88 Senebier published over 2100 pages on plants and the atmosphere. In 1782, he denied that plants rendered air noxious at night, but by 1788, he changed his mind. He showed that [using modern names] carbon dioxide is absorbed by plants that are producing oxygen and that the amount of oxygen produced is about equivalent to the amount of carbon dioxide absorbed. Other British scientists also conducted chemical experiments. In 1783, two of them, Henry Cavendish (1731–1810) and James Watt (1736–1819), conducted an experiment that indicated that water is composed of two different substances (Partington 1962:344–348, McCormmach 1971, Dorn 1976), a timely discovery: "It was two discoveries, of oxygen and the composition of water, that formed the experimental basis of Lavoisier's new oxidation chemistry…" Lavoisier initiated his chemical revolution in 1785 (Partington 1962:440–452). that water is incorporated into the dry matter of plants; that plant carbon is derived from the carbon dioxide of the air, not from humus or soil; that the minerals in plants are absorbed from the soil, not created by a vital force; and that minerals are essential to plant growth. Hill also summarized his nine chapters (2013:155–159). Scotsman James Hutton (1726–97) was son of prosperous Edinburgh merchant who died when James was three (Eyles 1972). The family, however, remained well-off and James attended the University of Edinburgh, where he seemed most interested in chemistry and other physical sciences. He then studied medicine and earned an M.D. in 1749, with a thesis entitled De sanguine et circulation microcosmi. He never practiced medicine. He had inherited a farm and decided to become a farmer. However, Scottish farming was not very productive, so he toured English farms for about a year in 1752–53, followed by similar tours in Holland, Belgium, and northern France, during several months in 1754. He farmed for 14 years before renting out his farm and returning to Edinburgh in 1767. He associated with leading intellectuals in Scotland and England, including Joseph Black, Adam Smith, and James Watt. When the Royal Society of Edinburgh was founded in 1783, he was one of its first members and was quite active in its affairs. He had been thinking about a theory of earth history for a number of years and in 1785 presented a 28-page "Abstract of a Dissertation… concerning the System of the Earth, Its Duration, and Stability." It was about processes at work, with no data to illustrate them (Hutton 1987). He then spent a decade expanding it into his two-volume Theory of the Earth (1795). Joseph Black claimed that Hutton had developed his main ideas twenty years earlier (Eyles 1972:579). In 1795, Hutton developed and used his uniformitarian principle, that the geological processes at work now are key to understanding past geological activity. No more starting history of the world with the Biblical Genesis (though he did not say so). Hutton was perhaps first to think in terms of an earth system (1795:II, 540): "The system of this earth appears to comprehend many different operations; and it exhibits various powers co-operating for the production of those effects which we perceive." He began his argument with a fact he stated was widely known: Land was formerly under water. The system which he built upon this fact was that the earth undergoes constant change. The final 27-page chapter of Volume 2 summarized the arguments in his treatise. He finally asked what forces could effect these changes, and on that, he had no answer. Hutton's treatise was understandable, but not reader-friendly. He became friendly with a younger man, John Playfair (1748–1819), who was a professor of mathematics at the University of Edinburgh (Challinor 1975, Dean 2004). Playfair had become interested in Hutton's work, and after Hutton died, Playfair wrote Illustrations of the Huttonian Theory of the Earth (1802). Playfair had published capable contributions to mathematics, but he is most remembered for his Illustrations of the Huttonian Theory of the Earth, the first part of which (pages 4–140) summarized Hutton's treatise. The second part (pages 141–528) consists of his own contributions, guided by Hutton's teachings. Parisian biologist Jean Baptiste de Lamarck (1744–1829) is remembered primarily for his theory of evolution, published in 1801 and 1809 (Landrieu 1909, Burlingame 1973:589–590). However, he had broad interests, one of which was discussed in Hydrogélogie (1802, English, 1964). It was part of his larger concept of terrestrial physics, which included meteorology, geology, and biology, which, however, he never completed. Like Hutton, he was a uniformitarian, but came to that perspective independently of Hutton, whose work he never studied. In Hydrologie, Lamarck sought to answer four major questions. The first three were geological, but the fourth was: "What are the general effects of living organisms on the mineral substances which form the earth's crust and external surface?" (1964:16, 78). His discussion began with his understanding of chemistry, which does not resemble modern understanding, nor would contemporary chemists have found it mainstream (Lamarck 1964:78–85). It is unlikely that Lamarck had absorbed much knowledge of Lavoisier's chemical revolution. Next, Lamarck stated: "The organic action of living organisms continuously creates combinations of substances which would never have existed otherwise." This sweeping claim is too broad, since living organisms produce carbon dioxide, as do inanimate processes, such as fire. Nevertheless, he was calling attention to a subject worthy of investigation. However, contemporaries who tried to read his book would likely not have continued to read as far as page 78, where this statement is. … Insects which prey upon others are not without some others of lesser Rank to feed upon them likewise, and so to Infinity; for that there are Beings subsisting, which are not commonly visible may be easily demonstrated…in a microscope. So, Nat'ralists observe, a Flea Hath smaller Fleas that on him prey. And these have smaller yet to bite 'em. And so proceed ad infinitum. …the tree-louse lives upon plants. The fly called musca aphidivora lives upon the tree-louse. The hornet and wasp fly upon the Musca aphidivora. The dragon fly upon the hornet and wasp fly. The spider on the dragon fly. The small birds on the spider. And lastly, the hawk kind on the small birds. In like manner the monoculus delights in putrid waters, the knat eats the monoculus, the frog eats the knat, the pike eats the frog, the sea calf eats the pike. Linnaeus believed God designed nature, and that such food chains ensured that no species became too numerous to be supported by its food species. The economy of nature was Linnaeus' name for the balance of nature (Egerton 1973:335–337). By the side of many of these nests a small flying fish was placed: which, I suppose, had been brought by the male bird for its partner…quickly a large and active crab (Graspus), which inhabits the crevices of the rock, stole the fish from the side of the nest, as soon as we had disturbed the birds. Not a single plant, not even a lichen, grows on this island; yet it is inhabited by several insects and spiders. The following list completes, I believe, the terrestrial fauna: a species of Feronia and an acarus, which must have come here as parasites on the birds; a small brown moth, belonging to a genus that feeds on feathers; a staphlinus (Quedius) and a woodlouse from beneath the dung; and lastly, numerous spiders, which I suppose prey on these small attendants on, and scavengers of the waterfowl. Rear-Admiral William Symonds read this and told Darwin he had seen St. Paul crabs drag young birds from nests and eat them. Darwin added his information in the second edition of his Journal (1845) (Edwards 1985:34). In The Origin of Species (1859:73–74), Darwin told a well-known account of a food chain involving red clover pollinated by humble bees, with field mice eating bees, and domestic cats eating the mice (Egerton 2007a,b,c:51–52). He drew upon H.W. Newman's "On the Habits of the Bombinatrices" (1850–51). Darwin thought mice might decimate the bees, leaving clover unpollinated, if cats did not limit the mouse population. His food chain was later found to be too simple, since honey bees also pollinate red clover (McAtee 1947). A remarkable German zoologist, Karl Semper (1832–93), delivered 12 lectures in Boston (1877), which he published in German and English editions, Animal Life as Affected by the National Conditions of Existence (1881). It was the first detailed synthesis of animal ecology, and it included a quantitative, narrative model of a food chain (1881:51–52). He had studied engineering and later physiology (Mayr 1975), so he was accustomed to thinking quantitatively, when few other biologists were. He explained that when herbivores eat vegetation, due to oxidation there is a loss of organic material; he estimated that 1,000 units of vegetation could produce 100 units of herbivore, and that this ratio was also true when a predator eats 100 units of herbivore, it produces 10 units of a predator. His ratio was also adopted by a more recent zoologist (Pequegnat 1958), who likely was unfamiliar with Semper's estimate. A year after Semper gave his Boston lectures, a French professor of sociology at the Lycée de Dijon, Alfred V. Espinas (1844–1922), published Des Sociétés Animales (1878). It was not on food chains or webs, but since social species are involved in food chains and webs, it seems useful to mention it. Italian zoologist Lorenzo Camerano (1856–1917) grew up in Torino, attended its university, and later taught there (Cohen 1994). The earliest known diagrams of food webs were two he published (Camerano 1880). He was primarily an entomologist, and many of his publications were descriptive. His article on food webs was atypical of his publications. J.E. Cohen (1994:353) suggested that paper shows influence of Darwin's Origen of Species (1859). Cohen had Camerano's food web article translated into English (Camerano 1994). Camerano's two food web diagrams are like none published later (Egerton 2014a,b:62–63), indicating that they had little influence. They nevertheless indicate progress in the study of food webs. Illinoian zoologist Stephen A. Forbes (1844–1930) served in the Union Army during the Civil War and afterward attended the Rush Medical College, Chicago, and later Illinois State Normal University, near Bloomington, Indiana (Croker 2001:7–59). He worked for the state in several positions, mainly as a professor and state entomologist, and his writings were a source for American animal ecology (Croker 2001:109–125, Egerton 2014a,b:64–65). Forbes is most remembered for "The Lake as a Microcosm" (1887, 1925, 1977, 1991). Many of his other publications, 1878–88, were on food of fish and of insects (Forbes 1977), which can be considered studies in short food chains. The next earliest web diagram I know was by entomologists W. Dwight Pierce, Robert Asa Cushman, and C.E. Hood, in their study of The Insect Enemies of the Cotton Boll Weevil (1912). I am unaware of any later web diagramer having followed their ingenious example (reproduced in Egerton 2007b:54). However, since it was in a bulletin of the U.S. Department of Agriculture, it likely was read by other entomologists. Only a year later, animal ecologist Victor E. Shelford (1877–1968) published Animal Communities in Temperate America, as Illustrated in the Chicago Region (1913), with diagrams of both land and aquatic food webs, having original designs of his diagrams (both reproduced in Egerton 2007b:54–55). Although he grew up on a New York state farm, his two degrees were from the University of Chicago (B.S., 1903, Ph.D., 1907). He was on the Chicago faculty that year; in 1914, he permanently moved to the University of Illinois and became one of the leaders of American ecology (Croker 1991). Although Shelford later studied marine life, the aquatic food chain in his Animal Communities (1913) was in freshwater. The earliest known food web diagram for a marine community was by Danish fishery biologist Johannes Petersen (1860–1928), in "A Preliminary Result in the Investigations on the Valuation of the Sea" (1915). He had studied the Kattegat, a shallow bay between Denmark and Sweden about 150 miles long and about 90 miles wide (Schlee 1973:216–219). He attempted to establish its annual productivity, and his diagram resembled no others known to me (reproduced in Egerton 2007b:56). However, his colleague, Harold H. Blegvad (1886–1951) conducted a somewhat similar study, "Food of Fish and Principal Animals in Nyborg Fjord" (1916), and drew a food web diagram similar to Petersen's. English ecologists Charles Elton (Summerhayes and Elton 1923, Elton 1927) and Alister Harding (1924), both of whom we met earlier (Egerton 2014a:73–75, 2014b:407–411) were soon studying food webs (Dunne 2006:29). Food webs were included in the first detailed ecology synthesis, by Allee et al. (1949:511–519). Stuart Pimm published an important later synthesis, Food Webs (1982). This is not a context for a full history of food chains and webs, which I and others have previously published. Mine goes from Richard Bradley to Rachel Carson (Egerton 2007b). These recent studies indicate the continuing and diverse studies on food webs: Joel Cohen et al., Community Food Webs (1990); Jennifer Dunne (2006) has surveyed the history of food web studies from Elton to 2005, though she only focused upon theoretical ideas; and Craig A. Layman and ten colleagues published A Primer on the History of Food Web Ecology: Fundamental Contributions of Fourteen Researchers (2015). More recently, Thomas Ings and Joseph Howes "The History of Ecological Networks" (2018) emphasized food networks. The journal Food Webs began in 2014. This is a heading of convenience, not of logic, to encompass two very different phenomena being discovered at the same time: repeating irregularities in earth orbits by Milutin Milankovich (1879–1958), now known as Milankovich cycles; and continental drift, by Alfred Wegener (1880–1930). Milankovich was Serbian, and born in the Austro-Hungarian Empire (Weart 2003:17–18, 47–50, Flannery 2005:41–42). He attended the Vienna University of Technology, 1896–1902, and earned a degree in civil engineering, and a Ph.D. in December 1904. Later, he became interested in causes of ice ages and read literature on it. He was neither first nor last to study cycles of the earth's movements daily and annually, but he suggested that three long-term recurring Earth cycles affect earth's climate: (1) variation in elliptical orbit of earth around the sun, completed every 100,000 years; (2) axial tilt of Earth spin, completed every 42,000 years; and (3) axial precession (wobble) of Earth, every 22,000 years. The cause of these irregularities was the gravitational pull of other planets as they orbit daily and annually around the sun. These varying pathways were thought to explain ice ages, which does happen when continental drift leaves large land masses near the poles. He published his Canon of Insolation of the Ice-Age Problem in Serbian in 1941, with English translation not published until 1969. Wegener was from Berlin and studied astronomy at Heidelberg, Innsbruck universities, and earned his Ph.D. at Berlin (Bullen 1976, Schwarzbach 1986) He then became interested in meteorology and geology. He announced his theory of continental drift in 1911 and later published Die Entstehung der Kontinente und Ozeane (1915). It became a controversial theory that was only widely accepted during the 1960s. In 1930, he was in Greenland, and on his birthday undertook a journey to the coast and was never seen again. Continental drift, or now, an aspect of plate tectonics, shifts continental climates from its pattern before movement to a different climate after movement. It is caused by internal dynamics of the fluid molten matter in the center of the earth. Ecosystems are discussed in part 59 of this history (Egerton 2017), with earlier, more detailed treatments, being by Hagen (1992), Golley (1993), and Coleman (2010). This part 63 summary places the theory into a sequence of concepts leading to biosphere ecology. An ecosystem is a subset of global ecology in the sense of being a distinct portion that contributes to the whole, while also being influenced by the whole. A forest is an example of an ecosystem; if on fire it contributes, however slightly, to global warming, and a forest not on fire is a CO2 sink. Collectively, ecologists are world travelers, and only some small ecosystems are by now still undescribed. Some ecosystems are rather isolated, such as an