A nutrient cycle (or ecological recycling) is the movement and exchange of
inorganic and organic matter back into the
production
Production may refer to:
Economics and business
* Production (economics)
* Production, the act of manufacturing goods
* Production, in the outline of industrial organization, the act of making products (goods and services)
* Production as a stati ...
of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of
mineral nutrients
In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...
is cyclic. Mineral cycles include the
carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...
,
sulfur cycle,
nitrogen cycle,
water cycle
The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
,
phosphorus cycle
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the moveme ...
,
oxygen cycle
Oxygen cycle refers to the movement of oxygen through the atmosphere (air), biosphere (plants and animals) and the lithosphere (the Earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as wel ...
, among others that continually recycle along with other mineral nutrients into
productive
Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proces ...
ecological nutrition.
Outline
The nutrient cycle is nature's recycling system. All forms of recycling have feedback loops that use energy in the process of putting material resources back into use. Recycling in ecology is regulated to a large extent during the process of
decomposition
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
.
Ecosystems employ
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
in the food webs that recycle natural materials, such as
mineral nutrients
In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...
, which includes
water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
. Recycling in natural systems is one of the many
ecosystem services
Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. ...
that sustain and contribute to the well-being of human societies.
There is much overlap between the terms for the
biogeochemical cycle and nutrient cycle. Most textbooks integrate the two and seem to treat them as synonymous terms.
However, the terms often appear independently. Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it. While an ecosystem often has no clear boundary, as a working model it is practical to consider the functional community where the bulk of matter and energy transfer occurs.
Nutrient cycling occurs in ecosystems that participate in the "larger biogeochemical cycles of the earth through a system of inputs and outputs."
Complete and closed loop
![Nutrient cycle](https://upload.wikimedia.org/wikipedia/commons/b/b7/Nutrient_cycle.svg)
Ecosystems are capable of complete recycling. Complete recycling means that 100% of the waste material can be reconstituted indefinitely. This idea was captured by
Howard T. Odum
Howard Thomas Odum (September 1, 1924 – September 11, 2002), usually cited as H. T. Odum, was an American ecologist. He is known for his pioneering work on ecosystem ecology, and for his provocative proposals for additional laws of thermod ...
when he penned that "it is thoroughly demonstrated by ecological systems and geological systems that all the chemical elements and many organic substances can be accumulated by living systems from background crustal or oceanic concentrations without limit as to concentration so long as there is available solar or another source of potential energy"
In 1979
Nicholas Georgescu-Roegen
Nicholas Georgescu-Roegen (born Nicolae Georgescu, 4 February 1906 – 30 October 1994) was a Romanian mathematician, statistician and economist. He is best known today for his 1971 ''The Entropy Law and the Economic Process'', in which he argu ...
proposed the
fourth law of entropy stating that complete recycling is impossible. Despite Georgescu-Roegen's extensive intellectual contributions to the science of
ecological economics, the fourth law has been rejected in line with observations of ecological recycling.
However, some authors state that complete recycling is impossible for technological waste.
Ecosystems execute closed loop recycling where demand for the nutrients that adds to the growth of
biomass exceeds supply within that system. There are regional and spatial differences in the rates of growth and exchange of materials, where some ecosystems may be in nutrient debt (sinks) where others will have extra supply (sources). These differences relate to climate, topography, and geological history leaving behind different sources of parent material.
In terms of a food web, a cycle or loop is defined as "a directed sequence of one or more links starting from, and ending at, the same species."
An example of this is the microbial food web in the ocean, where "bacteria are exploited, and controlled, by protozoa, including
heterotrophic
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
microflagellates which are in turn exploited by ciliates. This grazing activity is accompanied by excretion of substances which are in turn used by the bacteria so that the system more or less operates in a closed circuit."
Ecological recycling
![FoodWebSimple](https://upload.wikimedia.org/wikipedia/commons/6/65/FoodWebSimple.svg)
An example of ecological recycling occurs in the
enzymatic
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...
digestion
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...
of
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
. "Cellulose, one of the most abundant organic compounds on Earth, is the major
polysaccharide in plants where it is part of the cell walls. Cellulose-degrading enzymes participate in the natural, ''ecological recycling'' of plant material."
Different ecosystems can vary in their recycling rates of litter, which creates a complex feedback on factors such as the competitive dominance of certain plant species. Different rates and patterns of ecological recycling leaves a legacy of environmental effects with implications for the future evolution of ecosystems.
Ecological recycling is common in organic farming, where nutrient management is ''fundamentally different'' compared to agri-business styles of
soil management
Soil management is the application of operations, practices, and treatments to protect soil and enhance its performance (such as soil fertility or soil mechanics). It includes soil conservation, soil amendment, and optimal soil health. In agricu ...
. Organic farms that employ ecosystem recycling to a greater extent support more species (increased levels of biodiversity) and have a different
food web
A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one o ...
structure.
Organic agricultural ecosystems rely on the services of biodiversity for the recycling of nutrients through soils instead of relying on the supplementation of
synthetic fertilizers.
The model for ecological recycling agriculture adheres to the following principals:
*Protection of biodiversity.
*Use of renewable energy.
*Recycling of plant nutrients.
Where produce from an organic farm leaves the farm gate for the market the system becomes an open cycle and nutrients may need to be replaced through alternative methods.
Ecosystem engineers
![WhalePump](https://upload.wikimedia.org/wikipedia/commons/b/bb/WhalePump.jpg)
The persistent legacy of environmental feedback that is left behind by or as an extension of the ecological actions of organisms is known as
niche construction
Niche construction is the process by which an organism alters its own (or another species') local environment. These alterations can be a physical change to the organism’s environment or encompass when an organism actively moves from one habita ...
or ecosystem engineering. Many species leave an effect even after their death, such as coral skeletons or the extensive habitat modifications to a wetland by a beaver, whose components are recycled and re-used by descendants and other species living under a different selective regime through the feedback and agency of these legacy effects.
Ecosystem engineers can influence nutrient cycling efficiency rates through their actions.
Earthworms, for example, passively and mechanically alter the nature of soil environments. Bodies of dead worms passively contribute mineral nutrients to the soil. The worms also mechanically modify the physical structure of the soil as they crawl about (
bioturbation), digest on the
mold
A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...
s of organic matter they pull from the
soil litter
Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constitu ...
. These activities transport nutrients into the
mineral layers of soil. Worms discard wastes that create
worm castings
Vermicompost (vermi-compost) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and ...
containing undigested materials where bacteria and other decomposers gain access to the nutrients. The earthworm is employed in this process and the production of the ecosystem depends on their capability to create feedback loops in the recycling process.
Shellfish are also ecosystem engineers because they: 1) Filter suspended particles from the water column; 2) Remove excess nutrients from coastal bays through
denitrification
Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitr ...
; 3) Serve as natural coastal buffers, absorbing wave energy and reducing erosion from boat wakes, sea level rise and storms; 4) Provide nursery habitat for fish that are valuable to coastal economies.
Fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
contribute to
nutrient cycling
A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
and nutritionally rearrange patches of
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
creating
niches for other organisms. In that way
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
in growing
dead wood
''Dead Wood'' is a 2007 British horror film, written, produced and directed by Richard Stiles and David Bryant and starring Emily Juniper, Fergus March, Rebecca Craven, Nina Kwok and John Samuel Worsey with Bryant appearing in a small role. ''D ...
allow
xylophages to grow and develop and
xylophages, in turn, affect dead wood, contributing to wood
decomposition
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
and
nutrient cycling
A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
in the
forest floor
The forest floor, also called detritus, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shed vegetative parts, such as leaves, branches, bark, and stems, existing in various stages ...
.
History
![Berge naturreservat omkullfallet liten tall](https://upload.wikimedia.org/wikipedia/commons/5/53/Berge_naturreservat_omkullfallet_liten_tall.jpg)
Nutrient cycling has a historical foothold in the writings of
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
in reference to the decomposition actions of earthworms. Darwin wrote about "the continued movement of the particles of earth".
Even earlier, in 1749
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
wrote in "the economy of nature we understand the all-wise disposition of the creator in relation to natural things, by which they are fitted to produce general ends, and reciprocal uses" in reference to the balance of nature in his book ''Oeconomia Naturae''.
In this book he captured the notion of ecological recycling: "The 'reciprocal uses' are the key to the whole idea, for 'the death, and destruction of one thing should always be subservient to the restitution of another;' thus mould spurs the decay of dead plants to nourish the soil, and the earth then 'offers again to plants from its bosom, what it has received from them.'"
The basic idea of a balance of nature, however, can be traced back to the Greeks:
Democritus
Democritus (; el, Δημόκριτος, ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greek pre-Socratic philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. No ...
,
Epicurus, and their Roman disciple
Lucretius
Titus Lucretius Carus ( , ; – ) was a Roman poet and philosopher. His only known work is the philosophical poem ''De rerum natura'', a didactic work about the tenets and philosophy of Epicureanism, and which usually is translated into En ...
.
Following the Greeks, the idea of a hydrological cycle (water is considered a nutrient) was validated and quantified by
Halley Halley may refer to:
Science
* Halley's Comet, officially designated 1P/Halley, a comet that becomes visible from Earth every 75-76 years
* Halley (lunar crater), a lunar crater named after Edmond Halley
* Halley (Martian crater), a Martian cra ...
in 1687.
Dumas and Boussingault (1844) provided a key paper that is recognized by some to be the true beginning of biogeochemistry, where they talked about the cycle of organic life in great detail.
From 1836 to 1876,
Jean Baptiste Boussingault
Jean-Baptiste Joseph Dieudonné Boussingault (2 February 1801 – 11 May 1887) was a French chemist who made significant contributions to agricultural science, petroleum science and metallurgy.
Biography
Jean-Baptiste Boussingault – an agric ...
demonstrated the nutritional necessity of minerals and nitrogen for plant growth and development. Prior to this time influential chemists discounted the importance of mineral nutrients in soil.
Ferdinand Cohn is another influential figure. "In 1872, Cohn described the 'cycle of life' as the "entire arrangement of nature" in which the dissolution of dead organic bodies provided the materials necessary for new life. The amount of material that could be molded into living beings was limited, he reasoned, so there must exist an "eternal circulation" (ewigem kreislauf) that constantly converts the same particle of matter from dead bodies into living bodies."
These ideas were synthesized in the Master's research of
Sergei Vinogradskii from 1881-1883.
Variations in terminology
In 1926
Vernadsky coined the term
biogeochemistry
Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the cryosphere, ...
as a sub-discipline of
geochemistry
Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...
.
However, the term nutrient cycle pre-dates biogeochemistry in a pamphlet on silviculture in 1899: "These demands by no means pass over the fact that at places where sufficient quantities of humus are available and where, in case of continuous decomposition of litter, a stable, nutrient humus is present, considerable quantities of nutrients are also available from the biogenic ''nutrient cycle'' for the standing timber.
In 1898 there is a reference to the nitrogen cycle in relation to
nitrogen fixing microorganisms.
Other uses and variations on the terminology relating to the process of nutrient cycling appear throughout history:
*The term mineral cycle appears early in a 1935 in reference to the importance of minerals in
plant physiology: "...ash is probably either built up into its permanent structure, or deposited in some way as waste in the cells, and so may not be free to re-enter the ''mineral cycle''."
*The term nutrient recycling appears in a 1964 paper on the food ecology of the wood stork: "While the periodic drying up and reflooding of the marshes creates special survival problems for organisms in the community, the fluctuating water levels favor rapid ''nutrient recycling'' and subsequent high rates of primary and secondary production"
*The term natural cycling appears in a 1968 paper on the transportation of leaf litter and its chemical elements for consideration in fisheries management: "Fluvial transport of tree litter from drainage basins is a factor in ''natural cycling'' of chemical elements and in degradation of the land."
*The term ecological recycling appears in a 1968 publication on future applications of ecology for the creation of different modules designed for living in extreme environments, such as space or under sea: "For our basic requirement of recycling vital resources, the oceans provide much more frequent ''ecological recycling'' than the land area. Fish and other organic populations have higher growth rates, vegetation has less capricious weather problems for sea harvesting."
*The term bio-recycling appears in a 1976 paper on the recycling of organic carbon in oceans: "Following the actualistic assumption, then, that biological activity is responsible for the source of dissolved organic material in the oceans, but is not important for its activities after death of the organisms and subsequent chemical changes which prevent its ''bio-recycling'', we can see no major difference in the behavior of dissolved organic matter between the prebiotic and post-biotic oceans."
Water is also a nutrient.
In this context, some authors also refer to precipitation recycling, which "is the contribution of evaporation within a region to precipitation in that same region."
These variations on the theme of nutrient cycling continue to be used and all refer to processes that are part of the global biogeochemical cycles. However, authors tend to refer to natural, organic, ecological, or bio-recycling in reference to the work of nature, such as it is used in organic farming or ecological agricultural systems.
Recycling in novel ecosystems
An endless stream of technological waste accumulates in different spatial configurations across the planet and turns into a predator in our soils, our streams, and our oceans.
This idea was similarly expressed in 1954 by ecologist
Paul Sears
Paul Bigelow Sears (December 17, 1891 – April 30, 1990) was an American ecologist and writer. He was born in Bucyrus, Ohio. Sears attended Ohio Wesleyan University (B.Sc. in Zoology, 1913; B.A. in Economics, 1914), the University of Nebraska at ...
: "We do not know whether to cherish the forest as a source of essential raw materials and other benefits or to remove it for the space it occupies. We expect a river to serve as both vein and artery carrying away waste but bringing usable material in the same channel. Nature long ago discarded the nonsense of carrying poisonous wastes and nutrients in the same vessels."
Ecologists use
population ecology
Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment, such as birth and death rates, and by immigration and emigration.
The discipline is import ...
to model contaminants as competitors or predators.
Rachel Carson
Rachel Louise Carson (May 27, 1907 – April 14, 1964) was an American marine biologist, writer, and conservationist whose influential book '' Silent Spring'' (1962) and other writings are credited with advancing the global environmental ...
was an ecological pioneer in this area as her book ''
Silent Spring
''Silent Spring'' is an environmental science book by Rachel Carson. Published on September 27, 1962, the book documented the environmental harm caused by the indiscriminate use of pesticides. Carson accused the chemical industry of spreading d ...
'' inspired research into biomagification and brought to the world's attention the unseen pollutants moving into the food chains of the planet.
In contrast to the planets natural ecosystems, technology (or
technoecosystems) is not reducing its impact on planetary resources. Only 7% of total
plastic waste
Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...
(adding up to millions upon millions of tons) is being recycled by industrial systems; the 93% that never makes it into the industrial recycling stream is presumably ''absorbed'' by natural recycling systems In contrast and over extensive lengths of time (billions of years) ecosystems have maintained a consistent balance with
production
Production may refer to:
Economics and business
* Production (economics)
* Production, the act of manufacturing goods
* Production, in the outline of industrial organization, the act of making products (goods and services)
* Production as a stati ...
roughly equaling
respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gre ...
consumption
Consumption may refer to:
*Resource consumption
*Tuberculosis, an infectious disease, historically
* Consumption (ecology), receipt of energy by consuming other organisms
* Consumption (economics), the purchasing of newly produced goods for curren ...
rates. The balanced recycling efficiency of nature means that production of decaying waste material has exceeded rates of recyclable consumption into food chains equal to the global stocks of
fossilized fuels that escaped the chain of decomposition.
Microplastics
Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...
and
nanosilver materials flowing and cycling through ecosystems from pollution and discarded technology are among a growing list of emerging ecological concerns.
For example, unique assemblages of marine microbes have been found to digest plastic accumulating in the worlds oceans.
Discarded technology is absorbed into soils and creates a new class of soils called
technosols.
Human wastes in the
Anthropocene
The Anthropocene ( ) is a proposed geological epoch dating from the commencement of significant human impact on Earth's geology and ecosystems, including, but not limited to, anthropogenic climate change.
, neither the International Commissio ...
are creating new systems of ecological recycling, novel ecosystems that have to contend with the
mercury cycle and other synthetic materials that are streaming into the
biodegradation
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegrada ...
chain.
Microorganisms have a significant role in the removal of synthetic organic compounds from the environment empowered by recycling mechanisms that have complex biodegradation pathways. The effect of synthetic materials, such as
nanoparticle
A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...
s and microplastics, on ecological recycling systems is listed as one of the major concerns for ecosystem in this century.
Technological recycling
Recycling in human industrial systems (or
technoecosystems) differs from ecological recycling in scale, complexity, and organization. Industrial recycling systems do not focus on the employment of ecological food webs to recycle waste back into different kinds of marketable goods, but primarily employ people and
technodiversity instead. Some researchers have questioned the premise behind these and other kinds of technological solutions under the banner of 'eco-efficiency' are limited in their capability, harmful to ecological processes, and dangerous in their hyped capabilities.
Many technoecosystems are competitive and parasitic toward natural ecosystems.
Food web or biologically based "recycling includes metabolic recycling (nutrient recovery, storage, etc.) and ecosystem recycling (leaching and ''in situ'' organic matter mineralization, either in the water column, in the sediment surface, or within the sediment)."
See also
*
Plastic pollution
Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...
References
External links
Soil and Water Conservation SocietyBaltic Ecological Recycling Agriculture and Society*
Dianna CohenTough truths about plastic pollutionon TED.com
Plastic pollution coalitionNutrient Cycling in Agroecosystems journal*Nova Scotia Agricultural Colleg
{{Recycling
Ecology
Systems ecology
Recycling
Ecological economics