Vacuum permeability

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Vacuum_permeability

 

Value of μ0
1.25663706127(20)×10−6 N⋅A−2

The vacuum magnetic permeability (variously vacuum permeability, permeability of free space, permeability of vacuum, magnetic constant) is the magnetic permeability in a classical vacuum. It is a physical constant, conventionally written as μ₀ (pronounced "mu nought" or "mu zero"), approximately equal to 4π × 10⁻⁷ H/m (by the former definition of the ampere). It quantifies the strength of the magnetic field induced by an electric current. Expressed in terms of SI base units, it has the unit kg⋅m⋅s⁻²⋅A⁻². It can be also expressed in terms of SI derived units, N⋅A⁻², H·m⁻¹, or T·m·A⁻¹, which are all equivalent.

Since the revision of the SI in 2019 (when the values of e and h were fixed as defined quantities), μ₀ is an experimentally determined constant, its value being proportional to the dimensionless fine-structure constant, which is known to a relative uncertainty of 1.6×10⁻¹⁰, with no other dependencies with experimental uncertainty. Its value in SI units as recommended by CODATA is:

μ₀ = 1.25663706127(20)×10⁻⁶ N⋅A⁻²

This is equal to 4π × [1 − (1.3 ± 1.6) × 10⁻¹⁰] × 10⁻⁷ N/A², with a relative deviation (of order 10⁻¹⁰, i.e. less than a part per billion) from the former defined value that is within its uncertainty.

The terminology of permeability and susceptibility was introduced by William Thomson, 1st Baron Kelvin in 1872. The modern notation of permeability as μ and permittivity as ε has been in use since the 1950s.

Ampere-defined vacuum permeability

Two thin, straight, stationary, parallel wires, a distance r apart in free space, each carrying a current I, will exert a force on each other. Ampère's force law states that the magnetic force F_m per length L is given by $${\displaystyle \frac{|{\mathbf{F}}_{\text{m}}|}{L}=\frac{{\mu }_0}{2\pi }\frac{I^2}{|\mathit{r}|}.}$$From 1948 until 2019, the ampere was defined as "that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10⁻⁷ newton per metre of length". The current in this definition needed to be measured with a known weight and known separation of the wires, defined in terms of the international standards of mass, length, and time in order to produce a standard for the ampere (and this is what the Kibble balance was designed for). Applying Ampère's force law: $${\displaystyle \frac{{\mathbf{F}}_{\text{m}}}{L}=\frac{{\mu }_0}{2\pi }\frac{(1\mathrm{A}{)}^2}{1\mathrm{m}}}$$ $${\displaystyle 2\times {10}^{-7}\mathrm{N}/\mathrm{m}=\frac{{\mu }_0}{2\pi }\frac{(1\mathrm{A}{)}^2}{1\mathrm{m}}}$$ $${\displaystyle {\mu }_0=4\pi \times {10}^{-7}{\text{ N/A}}^2}$$ Thus, during that period, μ₀ had a defined value when expressed in henries per metre (H/m, equivalent to N/A²):

μ₀ = 4π×10⁻⁷ H/m = 1.25663706143...×10⁻⁶ N/A²

In the 2019 revision of the SI, the ampere is defined exactly in terms of the elementary charge and the second, and the value of μ₀ is now determined experimentally (based on the measured value of the fine-structure constant), and the Kibble balance has become an instrument for measuring weight from a known current, rather than measuring current from a known weight.

The 2022 CODATA value for μ₀ in the new system is 4π × 0.99999999987(16)×10⁻⁷ H/m. The relative deviation of the recommended measured value (1.3×10⁻¹⁰ or 0.13 parts per billion) from the former defined value is within its uncertainty (1.6×10⁻¹⁰, in relative terms, or 0.16 parts per billion).

Terminology

NIST/CODATA refers to μ₀ as the vacuum magnetic permeability. Prior to the 2019 revision, it was referred to as the magnetic constant. Historically, the constant μ₀ has had different names. In the 1987 IUPAP Red book, for example, this constant was called the permeability of vacuum. Another, now rather rare and obsolete, term is "magnetic permittivity of vacuum". See, for example, Servant et al. Variations thereof, such as "permeability of free space", remain widespread.

The name "magnetic constant" was briefly used by standards organizations in order to avoid use of the terms "permeability" and "vacuum", which have physical meanings. The change of name had been made because μ₀ was a defined value, and was not the result of experimental measurement (see below). In the new SI system, the permeability of vacuum no longer has a defined value, but is a measured quantity, with an uncertainty related to that of the (measured) dimensionless fine structure constant.

Systems of units and historical origin of value of μ₀

In principle, there are several equation systems that could be used to set up a system of electrical quantities and units. Since the late 19th century, the fundamental definitions of current units have been related to the definitions of mass, length, and time units, using Ampère's force law. However, the precise way in which this has "officially" been done has changed many times, as measurement techniques and thinking on the topic developed. The overall history of the unit of electric current, and of the related question of how to define a set of equations for describing electromagnetic phenomena, is very complicated. Briefly, the basic reason why μ₀ has the value it does is as follows.

Ampère's force law describes the experimentally-derived fact that, for two thin, straight, stationary, parallel wires, a distance r apart, in each of which a current I flows, the force per unit length, F_m/L, that one wire exerts upon the other in the vacuum of free space would be given by $${\displaystyle \frac{F_{\mathrm{m}}}{L}\propto \frac{I^2}{r}.}$$ Writing the constant of proportionality as k_m gives $${\displaystyle \frac{F_{\mathrm{m}}}{L}=k_{\mathrm{m}}\frac{I^2}{r}.}$$ The form of k_m needs to be chosen in order to set up a system of equations, and a value then needs to be allocated in order to define the unit of current.

In the old "electromagnetic (emu)" system of units, defined in the late 19th century, k_m was chosen to be a pure number equal to 2, distance was measured in centimetres, force was measured in the cgs unit dyne, and the currents defined by this equation were measured in the "electromagnetic unit (emu) of current", the "abampere". A practical unit to be used by electricians and engineers, the ampere, was then defined as equal to one tenth of the electromagnetic unit of current.

In another system, the "rationalized metre–kilogram–second (rmks) system" (or alternatively the "metre–kilogram–second–ampere (mksa) system"), k_m is written as μ₀/2π, where μ₀ is a measurement-system constant called the "magnetic constant". The value of μ₀ was chosen such that the rmks unit of current is equal in size to the ampere in the emu system: μ₀ was defined to be 4π × 10⁻⁷ H/m.

Historically, several different systems (including the two described above) were in use simultaneously. In particular, physicists and engineers used different systems, and physicists used three different systems for different parts of physics theory and a fourth different system (the engineers' system) for laboratory experiments. In 1948, international decisions were made by standards organizations to adopt the rmks system, and its related set of electrical quantities and units, as the single main international system for describing electromagnetic phenomena in the International System of Units.

Significance in electromagnetism

The magnetic constant μ₀ appears in Maxwell's equations, which describe the properties of electric and magnetic fields and electromagnetic radiation, and relate them to their sources. In particular, it appears in relationship to quantities such as permeability and magnetization density, such as the relationship that defines the magnetic H-field in terms of the magnetic B-field. In real media, this relationship has the form: $${\displaystyle \mathbf{H}=\frac{\mathbf{B}}{{\mu }_0}-\mathbf{M},}$$ where M is the magnetization density. In vacuum, M = 0.

In the International System of Quantities (ISQ), the speed of light in vacuum, c, is related to the magnetic constant and the electric constant (vacuum permittivity), ε₀, by the equation: $${\displaystyle c^2=\frac{1}{{\mu }_0{\epsilon }_0}.}$$ This relation can be derived using Maxwell's equations of classical electromagnetism in the medium of classical vacuum. Between 1948 and 2018, this relation was used by BIPM (International Bureau of Weights and Measures) and NIST (National Institute of Standards and Technology) as a definition of ε₀ in terms of the defined numerical value for c and, prior to 2018, the defined numerical value for μ₀. During this period of standards definitions, it was not presented as a derived result contingent upon the validity of Maxwell's equations.

Conversely, as the permittivity is related to the fine-structure constant (α), the permeability can be derived from the latter (using the Planck constant, h, and the elementary charge, e): $${\displaystyle {\mu }_0=\frac{2\alpha h}{e^{2}c}=4\pi \times \frac{\alpha \hslash }{e^{2}c}.}$$

In the new SI units, only the fine structure constant is a measured value in SI units in the expression on the right, since the remaining constants have defined values in SI units.

Evolution of birds

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Evolution_of_birds 

 

Archaeopteryx, a basal member of Avialae

 

Ludiortyx, a fossil bird genus of the Cenozoic

The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird. Modern phylogenies place birds in the dinosaur clade Theropoda. According to the current consensus, Aves and a sister group, the order Crocodilia, together are the sole living members of an unranked reptile clade, the Archosauria. Four distinct lineages of bird survived the Cretaceous–Paleogene extinction event 66 million years ago, giving rise to ostriches and relatives (Palaeognathae), waterfowl (Anseriformes), ground-living fowl (Galliformes), and "modern birds" (Neoaves).

Phylogenetically, Aves is usually defined as all descendants of the most recent common ancestor of a specific modern bird species (such as the house sparrow, Passer domesticus), and either Archaeopteryx, or some prehistoric species closer to Neornithes (to avoid the problems caused by the unclear relationships of Archaeopteryx to other theropods). If the latter classification is used then the larger group is termed Avialae. Currently, the relationship between non-avian dinosaurs, Archaeopteryx, and modern birds is still under debate.

Origins

Main article: Origin of birds

See also: Feathered dinosaur, Paraves, Avemetatarsalia, and Dromaeosauridae § Alternative theories and flightlessness

There is significant evidence that birds emerged within theropod dinosaurs, specifically, that birds are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others. As more non-avian theropods that are closely related to birds are discovered, the formerly clear distinction between non-birds and birds becomes less so. This was noted in the 19th century, with Thomas Huxley writing:

We have had to stretch the definition of the class of birds so as to include birds with teeth and birds with paw-like fore limbs and long tails. There is no evidence that Compsognathus possessed feathers; but, if it did, it would be hard indeed to say whether it should be called a reptilian bird or an avian reptile.

The mounted skeleton of a Velociraptor, showing the very bird-like quality of the smaller theropod dinosaurs

Discoveries in northeast China (Liaoning Province) demonstrate that many small theropod dinosaurs did indeed have feathers, among them the compsognathid Sinosauropteryx and the microraptorian dromaeosaurid Sinornithosaurus. This has contributed to this ambiguity of where to draw the line between birds and reptiles. Cryptovolans, a dromaeosaurid found in 2002 (which may be a junior synonym of Microraptor) was capable of powered flight, possessing a sternal keel and ribs with uncinate processes. Cryptovolans seems to make a better "bird" than Archaeopteryx which lacks some of these modern bird features. Because some basal members of Dromaeosauridae, including Microraptor, were capable of powered flight, some paleontologists have suggested that dromaeosaurids are actually derived from a flying ancestor, and that the larger members became secondarily flightless, mirroring the loss of flight in modern paleognaths like the ostrich. The discoveries of further basal dromaeosaurids potentially capable of powered flight, such as Xiaotingia, has provided more evidence for the theory that flight was first developed in the bird line by early dromaeosaurids rather than later by Aves as was previously supposed.

Although ornithischian (bird-hipped) dinosaurs share the same hip structure as birds, birds actually originated from the saurischian (lizard-hipped) dinosaurs if the dinosaurian origin theory is correct. They thus arrived at their hip structure condition independently. In fact, a bird-like hip structure also developed a third time among a peculiar group of theropods, the Therizinosauridae.

An alternate theory to the dinosaurian origin of birds, espoused by a few scientists, notably Larry Martin and Alan Feduccia, states that birds (including maniraptoran "dinosaurs") evolved from early archosaurs like Longisquama. This theory is contested by most other paleontologists and experts in feather development and evolution.

Mesozoic birds

See also: Avialae

The basal bird Archaeopteryx, from the Jurassic, is well known as one of the first "missing links" to be found in support of evolution in the late 19th century. Though it is not considered a direct ancestor of modern birds, it gives a fair representation of how flight evolved and how the very first bird might have looked. It may be predated by Protoavis texensis, though the fragmentary nature of this fossil leaves it open to considerable doubt whether this was a bird ancestor. The skeleton of all early bird candidates is basically that of a small theropod dinosaur with long, clawed hands, though the exquisite preservation of the Solnhofen Plattenkalk shows Archaeopteryx was covered in feathers and had wings. While Archaeopteryx and its relatives may not have been very good fliers, they would at least have been competent gliders, setting the stage for the evolution of life on the wing.

Reconstruction of Iberomesornis romerali, a toothed enantiornithine

The evolutionary trend among birds has been the reduction of anatomical elements to save weight. The first element to disappear was the bony tail, being reduced to a pygostyle and the tail function taken over by feathers. Confuciusornis is an example of their trend. While keeping the clawed fingers, perhaps for climbing, it had a pygostyle tail, though longer than in modern birds. A large group of birds, the Enantiornithes, evolved into ecological niches similar to those of modern birds and flourished throughout the Mesozoic. Though their wings resembled those of many modern bird groups, they retained the clawed wings and a snout with teeth rather than a beak in most forms. The loss of a long tail was followed by a rapid evolution of their legs which evolved to become highly versatile and adaptable tools that opened up new ecological niches.

The Cretaceous saw the rise of more modern birds with a more rigid ribcage with a carina and shoulders able to allow for a powerful upstroke, essential to sustained powered flight. Another improvement was the appearance of an alula, used to achieve better control of landing or flight at low speeds. They also had a more derived pygostyle, with a ploughshare-shaped end. An early example is Yanornis. Many were coastal birds, strikingly resembling modern shorebirds, like Ichthyornis, or ducks, like Gansus. Some evolved as swimming hunters, like the Hesperornithiformes – a group of flightless divers resembling grebes and loons. While modern in most respects, most of these birds retained typical reptilian-like teeth and sharp claws on the manus.

The modern toothless birds evolved from the toothed ancestors in the Cretaceous. Meanwhile, the earlier primitive birds, particularly the Enantiornithes, continued to thrive and diversify alongside the pterosaurs through this geologic period until they became extinct due to the K–T extinction event. All but a few groups of the toothless Neornithes were also cut short. The surviving lineages of birds were the comparatively primitive Palaeognathae (ostrich and its allies), the aquatic duck lineage, the terrestrial fowl, and the highly volant Neoaves.

Radiation of modern birds

See also: Mesozoic–Cenozoic radiation

Modern birds probably originated at the end of Early Cretaceous or at the beginning of the Late Cretaceous. They are split into the paleognaths and neognaths. The paleognaths include the tinamous (grouse-like birds, found only in Central and South America) and the ratites, which nowadays are found almost exclusively in the Southern Hemisphere. The ratites are large flightless birds, and include ostriches, rheas, cassowaries, kiwis and emus. The ratites are a paraphyletic (artificial) grouping because tinamous are part of their evolutionary clade and they have likely lost the ability to fly independently, becoming an example of convergent evolution. However, the evidence about their evolution is still ambiguous, partly because there are no uncontroversial fossils from the Mesozoic and partly because their phylogenetic relationships are still uncertain.

Haast's eagle and moa in New Zealand; the eagle is a neognath, the moa are paleognaths.

The basal divergence within Neognathes is between Galloanserae and Neoaves.

The timing of divergence of these major groups are a matter of debate. It is agreed that modern birds originated in the Cretaceous and that the split between Galloanserae and Neoaves occurred before the Cretaceous–Paleogene extinction event, but there are different opinions about whether the radiation of the remaining neognaths occurred before or after the extinction event. This disagreement is in part caused by a divergence in the evidence, with molecular dating suggesting a Cretaceous radiation and the fossil record suggesting a Paleogene radiation. The latest attempts to reconcile the molecular and fossil evidence estimated the most recent common ancestor of modern birds at 95 million years ago and the split between Galloanseres and Neoaves at 85 million years ago. Notably, these studies show that the rapid proliferation of lineages in Neoaves seems to coincide with the Cretaceous–Paleogene extinction event, suggesting a role for ecological opportunity stimulating diversification in the aftermath of the mass extinction.

In contrast, another recent genomic study suggests that the Galloanserae and Neoaves diverged around the Early-Late Cretaceous boundary (100.5 million years ago), with the paleognaths and neognaths diverging even earlier (around 130 million years ago), and that most terrestrial neoavian orders gradually diverged from one another throughout the Late Cretaceous, roughly in sync with the concurrent radiation of flowering plants. This would suggest that a majority of all terrestrial avian orders coexisted with the non-avian dinosaurs and are K-Pg extinction survivors. In contrast, most major radiations of seabirds and shorebirds (as well as in paleognaths, despite their ancient origins) were found to have only occurred after the K-Pg extinction event, and primarily after the Paleocene–Eocene Thermal Maximum. This clashes with previous studies that found a very rapid radiation of avian orders only after the K-Pg extinction.The results of this study have been disputed by other researchers, due to a lack of fossil evidence to support its conclusions.

The birds that survived the end-of-Cretaceous extinction were likely ground-dwelling (not arboreal) and thus persisted despite the worldwide destruction of forests.

An analysis of the variation of diversification rates through time further revealed a potential effect of climate on the evolution diversification rates in birds in which the generation of new lineages accelerates during periods of global cooling. This can be the result of climate cooling fragmenting tropical biomes and producing widespread allopatric speciation plus an effect of some lineages diversifying in the expanding arid and cool biomes.

Bird skull evolution decelerated compared with the evolution of their dinosaur predecessors after the Cretaceous–Paleogene extinction event, rather than accelerating as often believed to have caused the cranial shape diversity of modern birds.

Classification of modern species

The diversity of modern birds

See also: Sibley–Ahlquist taxonomy of birds and dinosaur classification

The phylogenetic classification of birds is a contentious issue. Sibley & Ahlquist's Phylogeny and Classification of Birds (1990) is a landmark work on the classification of birds (although frequently debated and constantly revised). A preponderance of evidence suggests that most modern bird orders constitute good clades. However, scientists are not in agreement as to the precise relationships between the main clades. Evidence from modern bird anatomy, fossils and DNA have all been brought to bear on the problem but no strong consensus has emerged.

Structural characteristics and fossil records have historically provided enough data for systematists to form hypotheses regarding the phylogenetic relationships between birds. Imprecisions within these methods is the main factor for why a lack of exact knowledge with regards to the orders and families of birds exists. Expansions in the study of computer-generated DNA sequencing and computer generated phylogenetics has provided a more accurate method for classifying bird species - although DNA data studying can only go so far, and questions are still unanswered.

Current evolutionary trends in birds

See also: Bird conservation and Sexual selection in birds

Evolution generally occurs at a scale far too slow to be witnessed by humans. However, bird species are currently going extinct at a far greater rate than any possible speciation or other generation of new species. The disappearance of a population, subspecies, or species represents the permanent loss of a range of genes.

Another concern with evolutionary implications is a suspected increase in hybridization. This may arise from human alteration of habitats enabling related allopatric species to overlap. Forest fragmentation can create extensive open areas, connecting previously isolated patches of open habitat. Populations that were isolated for sufficient time to diverge significantly, but not sufficient to be incapable of producing fertile offspring may now be interbreeding so broadly that the integrity of the original species may be compromised. For example, the many hybrid hummingbirds found in northwest South America may represent a threat to the conservation of the distinct species involved.

Several species of birds have been bred in captivity to create variations on wild species. In some birds this is limited to color variations, while others are bred for larger egg or meat production, for flightlessness or other characteristics.

In December 2019 the results of a joint study by Chicago's Field Museum and the University of Michigan into changes in the morphology of birds were published in Ecology Letters. The study uses bodies of birds which died as a result of colliding with buildings in Chicago, Illinois, since 1978. The sample is made up of over 70,000 specimens from 52 species and spans the period from 1978 to 2016. The study shows that the length of birds' lower leg bones (an indicator of body sizes) shortened by an average of 2.4% and their wings lengthened by 1.3%. The findings of the study suggest the morphological changes are the result of climate change, demonstrating an example of evolutionary change following Bergmann's rule.

The Nature Conservancy

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/The_Nature_Conservancy 

Headquarters in Arlington, Virginia (2022)
Founded	1951 (74 years ago)
Type	501(c)(3) non-profit
Focus	Environmental conservation
Headquarters	Arlington, Virginia, US
Area served	Global
Method	Conservation by design
Members	1+ million
Chief Executive Officer	Jennifer Morris
Key people	Bill Frist, Global Board Chair
Revenue	US$1.29 billion (2018)
Website	www.nature.org

The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia, United States. As of 2021, it works via affiliates or branches in 79 countries and territories, as well as across every state in the US.

Founded in 1951, The Nature Conservancy has over one million members globally as of 2021 and has protected more than 119 million acres (48 million ha) of land in its history. As of 2014, it is the largest environmental non-profit organization by assets and revenue in the Americas.

History

A meeting at the Alabama Nature Conservancy to organize a glass recycling effort in Birmingham, 1972

The Nature Conservancy developed out of a scholarly organization initially known as the Ecological Society of America (ESA). The ESA was founded in 1915, and later formed a Committee on Preservation of Natural Areas for Ecological Study, headed by Victor Shelford. The primary aim of Shelford was to find areas of land that would be beneficial for long-term research. By the 1930s, Shelford and his colleagues such as Aldo Leopold increasingly sought to advocate for conservation.^[6] The divide in viewpoints regarding scholarship or advocacy led the Society to dissolve the committee and in 1946, Shelford and his colleagues formed the Ecologists' Union.^[6][7] The latter group eventually took the name "The Nature Conservancy", in emulation of the British agency of that name, which pursued a mission of conserving open space and wildlife preserves. The Nature Conservancy was incorporated in the United States as a non-profit organization on October 22, 1951.^[7]

As the organization grew, the organization focused largely on buying as much land as possible in the name of conservation with little scientific research conducted on land before being purchased. Patrick Noonan served as president from 1973 to 1980 and spearheaded major land acquisitions, fundraising and decentralized growth of state programs. In 1970 the organization hired its first staff scientist, Robert E. Jenkins Jr., who helped the organization refocus its mission to conserving natural diversity. With Noonan's support, in 1974 Jenkins began to partner with state governments to develop state-by-state inventories which assembled and stored data on the "elements" of nature (e.g. rare species and natural communities) and on "element occurrences" (the specific locations where they occur), which later morphed into the Natural Heritage Network, a network of state natural heritage programs.

Project sites

Nature Conservancy of Tennessee's William B. Clark Sr. Nature Preserve on the Wolf River at Rossville, Tennessee

Clymer Meadow Preserve managed by the conservancy is considered to be one of the few and best preserved examples of Texas Blackland Prairie (eco-region) remaining.

The Nature Conservancy's efforts include conservation in North America, Central America, and South America, Africa, the Pacific Rim, the Caribbean, and Asia.

North America: selected projects

The Nature Conservancy and its conservation partner, Pronatura Peninsula Yucatán, to halt deforestation on private lands in and around the 1.8 million acre (7,300 km²) Calakmul Biosphere Reserve, along the Guatemala–Mexico border. They brokered the protection of 370,000 acres (1,500 km²) of tropical forest in Calakmul. In another program, TNC is working to protect wildlife habitat in the Greater Yellowstone Ecosystem.

In 2007, the Nature Conservancy made a 161,000-acre (650 km²) purchase of New York forestland from Finch Paper Holdings LLC for $110 million, its largest purchase ever in that state. In June 2008, The Nature Conservancy and The Trust for Public Land announced they reached an agreement to purchase approximately 320,000 acres (1,300 km²) of western Montana forestland from Plum Creek Timber Company for $510 million. The purchase, known as the Montana Legacy Project, is part of an effort to keep these forests in productive timber management and protect the area's clean water and abundant fish and wildlife habitat, while promoting continued public access to these lands for fishing, hiking, hunting and other recreational pursuits. As a follow-on, in 2015 The Nature Conservancy made a $134 million transaction to purchase 165,073 acres (668.03 km²) – of forests, rivers and wildlife habitat in the Cascade Mountain Range of Washington and in the Blackfoot River Valley in Montana. The Conservancy also acquired this land from Plum Creek, including 47,921 acres (193.93 km²) in the Yakima River Headwaters in Washington and 117,152 acres (474.10 km²) in the Lower Blackfoot River Watershed in Montana.

Nature United is the Canadian affiliate of The Nature Conservancy. Nature United was founded as a Canadian charity in 2014, building on decades of conservation in Canada. Headquartered in Toronto, the organization has field staff located across the country. Nature United supports Indigenous leadership, sustainable economic development, and large-scale conservation, primarily in the Great Bear Rainforest, Clayoquot Sound, the Northwest Territories, and northern Manitoba.

Africa

In December 2015, The Nature Conservancy announced the finalization of the first ever debt swap in Seychelles aimed at ocean conservation. The new protected area increases the country's marine protected waters from less than 1 percent to more than 30 percent including support for the creation of the second largest Marine Protected Area in the Western Indian Ocean. The debt swap deal was made possible through a partnership with the Seychelles Ministry of Finance, support of debt-holding nations including France, and grants from private organizations led by the Leonardo DiCaprio Foundation.

Financing for this effort was organized by The Nature Conservancy's impact investing unit called NatureVest. NatureVest was created in 2014 with founding sponsorship from JPMorgan Chase with the stated goal of sourcing and putting to work at least $1 billion of impact investment capital for measurable conservation outcomes over three years. For their work on the Seychelles debt restructuring, The Nature Conservancy and JPMorgan Chase were given the FT/ITC Transformational Business Award for Achievement in Transformational Finance. The award is given by the Financial Times and the World Bank's International Finance Corporation (IFC) for ground-breaking, commercially viable solutions to development challenges.

Plant a Billion Trees campaign

The Nature Conservancy's "Plant a Billion Trees" campaign is an effort to plant one billion trees across the globe in forests with the greatest need and has been operating since 2008 to plant trees in Brazil, China, Colombia, Guatemala, Kenya, Tanzania, Mexico, and the United States. As part of the overall campaign, The Nature Conservancy pledged to plant 25 million trees as part of the launch of the United Nations Environment Program (UNEP)'s Billion Tree Campaign. This campaign encourages individuals and organizations to plant their own trees around the world and record this action on the website as a tally. Its "Plant a Billion Trees" campaign in Brazil aims to restore Brazil's Atlantic Forest by planting native trees on 2.5 million acres (10,000 km²) that have been deforested.

Environmental benefits

The Plant a Billion Trees campaign has also been identified as a tool to help slow climate change with forest restoration being an effective way to help regulate emissions in the atmosphere and stabilize global climate.

Operations

In 2012, former president Brian McPeek in his then role as Chief Operating Officer, signs over the deed to 10 acres (4 ha) of land for the initial donation to establish the Everglades Headwaters National Wildlife Refuge in Florida.

Christie Boser from The Nature Conservancy with a specimen of Urocyon littoralis, a small fox endemic to California's Channel Islands

The Nature Conservancy has over one million members across the world as of 2021. As of 2014, it was the largest environmental non-profit organization by assets and revenue in the Americas.

Big business ties

The Nature Conservancy has ties to many large companies, including those in the oil, gas, mining, chemical and agricultural industries. As of 2016, its board of directors included the retired chairman of Duke Energy, and executives from Merck, HP, Google and several financial industry groups. It also has a Business Council which it describes as a consultative forum that includes Bank of America, BP America, Chevron, Coca-Cola, Dow Chemical, Duke Energy, General Mills, Royal Dutch Shell, and Starbucks. The organization faced criticism in 2010 from supporters for its refusal to cut ties with BP after the Gulf oil spill.

Writer and activist Naomi Klein has strongly criticized The Nature Conservancy for earning money from an oil well on land it controls in Texas and for its continued engagement with fossil fuel companies. The Nature Conservancy responded by arguing that it had no choice, under the terms of a lease it signed years prior with an oil and gas company and later came to regret.

In 2020, Bloomberg published an article claiming that some of the companies (such as JPMorgan Chase, Disney, and BlackRock) that purchase carbon credits from The Nature Conservancy were purchasing carbon credits for forests that did not need protection.

In 2021, The Nature Conservancy partnered with Amazon to compensate local farmers for restoring and protecting rainforests in Para, Brazil.

In 2022, a group of 158 conservation, environmental, and social justice non-profit organizations signed an open letter to the Conservancy's CEO, Jennifer Morris, charging that The Nature Conservancy was overly supportive of logging interests and the use of wood products as a natural climate solution. TNC is a member of the Forest Climate Working Group alongside wood product companies like Weyerhaeuser and Enviva, and other conservation organizations like the Trust for Public Land and American Forests.

Efficiency and accountability

The Charity Navigator gave The Nature Conservancy a 4-star rating, with a score of 96%, for the 2022 fiscal year.

Hunting

Like many large environmental groups such as the Sierra Club and the World Wildlife Fund, the Conservancy includes allowances for hunting and fishing within its management policies. The organization does not totally ban hunting or fishing but defers to state hunting and fishing regulations.

Publication

The organization publishes The Nature Conservancy magazine (ISSN 1540-2428; six issues per year).

Gallery

• 
  Award from the Department of Interior
   
• 
  The Table Rocks Environmental Education Program
   
• 
  Lotus Vermeer working with an animal in the field
   
• 
  Regional Ocean Challenges event in Australia
   
• 
  Fox health check at Santa Cruz Island
   
• 
  Virginia Governor Terry McAuliffe presented with a $500,000 environmental grant

Controversies

Land deals controversy

In 2003 The Washington Post ran an investigative series about the Nature Conservancy with allegations of improper dealing and other improprieties that the Nature Conservancy contested. In part, the Post alleged the Conservancy had, time and again, bought ecologically significant tracts of land, attached some development restrictions and then resold the properties to trustees and supporters at greatly reduced prices. The sales were part of a program that limits intrusive development but generally allows buyers to build homes on the land. The buyers then gave the Conservancy cash that was roughly equivalent to the amount of the discounts. That allowed the new owners to take significant tax deductions for charitable gifts.

The Nature Conservancy suspended a range of practices shortly after the articles ran including these sales, licensing its logo to corporations whose executives sat on the Conservancy's governing board and council, all new logging and other "resource extraction activities" such as oil and gas drilling on its nature preserves, and all new loans to employees. The Conservancy launched an independent review that issued its final report in 2004, calling for sweeping reforms aimed at making the Conservancy a model of ethical standards for nonprofit organizations.

Sexual harassment investigation

After service as The Nature Conservancy's president for one year, Brian McPeek resigned on May 31, 2019, after a report on an internal investigation of sexual harassment was revealed by Politico and two other senior executives were ultimately dismissed based on its findings. On June 7, 2019, Mark Tercek, CEO since 2008, announced his resignation following the resignation of McPeek. On June 10, Luis Solorzano, executive director of The Nature Conservancy's Florida-based Caribbean chapter, became the fifth senior official to depart the organization. On June 11, The Nature Conservancy's board chairman Thomas J. Tierney announced that board member and former US Secretary of the Interior Sally Jewell would serve as interim CEO, effective September 2019.