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99-416: Much like the last glacial period, the penultimate glacial period was caused by a great orbital eccentricity of Earth. This eccentricity causes greater seasonal impacts than normal because it limits the amount of sunlight that reaches the earth's surface, lowering the temperature. Due to this, northern insolation (the amount of sunlight that reaches the surface) is reduced, meaning that during summer, less heat

198-638: A + r p = r a / r p − 1 r a / r p + 1 = 1 − 2 r a r p + 1 {\displaystyle {\begin{aligned}e&={\frac {r_{\text{a}}-r_{\text{p}}}{r_{\text{a}}+r_{\text{p}}}}\\\,\\&={\frac {r_{\text{a}}/r_{\text{p}}-1}{r_{\text{a}}/r_{\text{p}}+1}}\\\,\\&=1-{\frac {2}{\;{\frac {r_{\text{a}}}{r_{\text{p}}}}+1\;}}\end{aligned}}} where: The semi-major axis, a,

297-529: A genetic bottleneck during the Penultimate Glacial Period which reduced numbers to a low level, but a 2012 analysis of three modern African populations finds no evidence for a bottleneck at this time. The dislocation of vegetation during the PGP was thought to have displaced H. sapiens , although studies have shown that the region which the early humans occupied was very lightly disturbed, and

396-670: A potential evapotranspiration ratio (PET) value of <0.25. However, most lowland tropical forests can be classified as tropical moist or wet forests, which differ in regards to rainfall. Tropical forest ecology- dynamics, composition, and function- are sensitive to changes in climate especially changes in rainfall. Soil types are highly variable in the tropics and are the result of a combination of several variables such as climate, vegetation, topographic position, parent material, and soil age. Most tropical soils are characterized by significant leaching and poor nutrients, however there are some areas that contain fertile soils. Soils throughout

495-401: A bottleneck due to the Penultimate Glacial Period is thus unlikely to have occurred. The Antarctic Zone expanded northwards until encompassing the northern Kerguelen Plateau , as evidenced by the maximum abundance of the radiolarians Dictyophimus bicornis , Pseudodictyophimus gracilipes , and P. platycephalus during this glacial. Orbital eccentricity In astrodynamics ,

594-523: A cyclical periodicity of about 3,500 years, with gradual increases in the SASM's strength being punctuated by sudden decreases. These sudden decreases are thought to be related to Dansgaard-Oeschger events . Oceanic cores, taken from western Africa, show the deserts expanded, pushing the savannah and the tropical rainforests downward, and oak trees occupying the Mediterranean coast, disappeared. This

693-650: A half meters, or 59 inches, on average). Amongst this group are the Efe, Aka, Twa , Baka , and Mbuti people of Central Africa. However, the term pygmy is considered pejorative so many tribes prefer not to be labeled as such. Some notable indigenous peoples of the Americas , or Amerindians, include the Huaorani , Ya̧nomamö , and Kayapo people of the Amazon . The traditional agricultural system practiced by tribes in

792-444: A hyperbola, when e equals 1, is parabola. Radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one. Keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1 (or in

891-431: A mean eccentricity of 0.008 59 . Orbital mechanics require that the duration of the seasons be proportional to the area of Earth's orbit swept between the solstices and equinoxes , so when the orbital eccentricity is extreme, the seasons that occur on the far side of the orbit ( aphelion ) can be substantially longer in duration. Northern hemisphere autumn and winter occur at closest approach ( perihelion ), when Earth

990-401: A new niche. Direct competition will often lead to one species dominating another by some advantage, ultimately driving it to extinction. Niche partitioning is the other option for a species. This is the separation and rationing of necessary resources by utilizing different habitats, food sources, cover or general behavioral differences. A species with similar food items but different feeding times

1089-465: A roof over the two remaining layers. It contains the majority of the largest trees, typically 30–45 m in height. Tall, broad-leaved evergreen trees are the dominant plants. The densest areas of biodiversity are found in the forest canopy, as it often supports a rich flora of epiphytes , including orchids, bromeliads, mosses and lichens. These epiphytic plants attach to trunks and branches and obtain water and minerals from rain and debris that collects on

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1188-614: A seasonal basis but dwelt primarily in adjacent savanna and open forest environments where food is much more abundant. Other people described as rainforest dwellers are hunter-gatherers who subsist in large part by trading high value forest products such as hides, feathers, and honey with agricultural people living outside the forest. Many indigenous peoples around the world live within rainforests as hunter-gatherers, or subsist as part-time small scale farmers supplemented in large part by trading high-value forest products such as hides, feathers, and honey with agricultural people living outside

1287-579: A study published in 2020 in the journal Nature. In 2019 they took up a third less carbon than they did in the 1990s, due to higher temperatures, droughts and deforestation. The typical tropical forest may become a carbon source by the 2060s. Despite the negative effects of tourism in the tropical rainforests, there are also several important positive effects. Deposits of precious metals ( gold , silver , coltan ) and fossil fuels ( oil and natural gas ) occur underneath rainforests globally. These resources are important to developing nations and their extraction

1386-725: A trend towards declining populations in rainforests, for example, reptiles that feed on amphibians and reptiles. This trend requires close monitoring. The seasonality of rainforests affects the reproductive patterns of amphibians, and this in turn can directly affect the species of reptiles that feed on these groups, particularly species with specialized feeding, since these are less likely to use alternative resources. Efforts to protect and conserve tropical rainforest habitats are diverse and widespread. Tropical rainforest conservation ranges from strict preservation of habitat to finding sustainable management techniques for people living in tropical rainforests. International policy has also introduced

1485-604: A tropical rainforest is stratified into layers, each hosting unique ecosystems . These include the emergent layer with towering trees, the densely populated canopy layer, the understory layer rich in wildlife, and the forest floor , which is sparse due to low light penetration. The soil is characteristically nutrient-poor and acidic. Tropical rainforests have a long history of ecological succession , influenced by natural events and human activities. They are crucial for global ecological functions, including carbon sequestration and climate regulation. Many indigenous peoples around

1584-424: A value of 0.967. Non-periodic comets follow near- parabolic orbits and thus have eccentricities even closer to 1. Examples include Comet Hale–Bopp with a value of 0.995 1 , Comet Ikeya-Seki with a value of 0.999 9 and Comet McNaught (C/2006 P1) with a value of 1.000 019 . As first two's values are less than 1, their orbit are elliptical and they will return. McNaught has a hyperbolic orbit but within

1683-440: A vast diversity in plant and animal species. The root for this remarkable speciation has been a query of scientists and ecologists for years. A number of theories have been developed for why and how the tropics can be so diverse. Interspecific competition results from a high density of species with similar niches in the tropics and limited resources available. Species which "lose" the competition may either become extinct or find

1782-415: A widespread root network at the surface for more efficient uptake of nutrients in a very nutrient poor and competitive environment. Most of the nutrients within the soil of a tropical rainforest occur near the surface because of the rapid turnover time and decomposition of organisms and leaves. Because of this, the buttress roots occur at the surface so the trees can maximize uptake and actively compete with

1881-465: Is a conic section. It is normally used for the isolated two-body problem , but extensions exist for objects following a rosette orbit through the Galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit . The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: The eccentricity e

1980-643: Is also the path-averaged distance to the centre of mass, while the time-averaged distance is a(1 + e e / 2). [1] The eccentricity of an elliptical orbit can be used to obtain the ratio of the apoapsis radius to the periapsis radius: r a r p = a ( 1 + e ) a ( 1 − e ) = 1 + e 1 − e {\displaystyle {\frac {r_{\text{a}}}{r_{\text{p}}}}={\frac {\,a\,(1+e)\,}{\,a\,(1-e)\,}}={\frac {1+e}{1-e}}} For Earth, orbital eccentricity e ≈ 0.016 71 , apoapsis

2079-458: Is an example of niche partitioning. The theory of Pleistocene refugia was developed by Jürgen Haffer in 1969 with his article Speciation of Amazonian Forest Birds . Haffer proposed the explanation for speciation was the product of rainforest patches being separated by stretches of non-forest vegetation during the last glacial period. He called these patches of rainforest areas refuges and within these patches allopatric speciation occurred. With

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2178-505: Is aphelion and periapsis is perihelion, relative to the Sun. For Earth's annual orbit path, the ratio of longest radius ( r a ) / shortest radius ( r p ) is r a r p = 1 + e 1 − e  ≈ 1.03399 . {\displaystyle {\frac {\,r_{\text{a}}\,}{r_{\text{p}}}}={\frac {\,1+e\,}{1-e}}{\text{ ≈ 1.03399 .}}} The table lists

2277-578: Is balanced by warming in the other, and any overall change will be counteracted by the fact that the eccentricity of Earth's orbit will be almost halved. This will reduce the mean orbital radius and raise temperatures in both hemispheres closer to the mid-interglacial peak. Of the many exoplanets discovered, most have a higher orbital eccentricity than planets in the Solar System. Exoplanets found with low orbital eccentricity (near-circular orbits) are very close to their star and are tidally-locked to

2376-464: Is currently about 0.016 7 ; its orbit is nearly circular. Neptune's and Venus's have even lower eccentricities of 0.008 6 and 0.006 8 respectively, the latter being the least orbital eccentricity of any planet in the Solar System. Over hundreds of thousands of years, the eccentricity of the Earth's orbit varies from nearly 0.003 4 to almost 0.058 as a result of gravitational attractions among

2475-406: Is exposed to the snows of the winter, which don't completely melt. This buildup of ice and snow over thousands of years eventually leads to residual ice sheets, which would also reflect light away from the earth , further cooling the earth. A decrease in greenhouse gas concentrations such as CO 2 , are a result of the expanded ice sheets. This is because as the Earth cooled, and ice sheets expanded,

2574-603: Is generally between 1500 and 2500 m while the upper limit is usually from 2400 to 3300 m. Tropical freshwater swamp forests , or "flooded forests", are found in Amazon basin (the Várzea ) and elsewhere. Rainforests are divided into different strata, or layers, with vegetation organized into a vertical pattern from the top of the soil to the canopy. Each layer is a unique biotic community containing different plants and animals adapted for life in that particular strata. Only

2673-404: Is given by e = 1 + 2 E L 2 m red α 2 {\displaystyle e={\sqrt {1+{\frac {2EL^{2}}{m_{\text{red}}\,\alpha ^{2}}}}}} where E is the total orbital energy , L is the angular momentum , m red is the reduced mass , and α {\displaystyle \alpha }

2772-466: Is moving at its maximum velocity—while the opposite occurs in the southern hemisphere. As a result, in the northern hemisphere, autumn and winter are slightly shorter than spring and summer—but in global terms this is balanced with them being longer below the equator. In 2006, the northern hemisphere summer was 4.66 days longer than winter, and spring was 2.9 days longer than autumn due to orbital eccentricity. Apsidal precession also slowly changes

2871-620: Is no geological evidence to support a similarly sized ice sheet in North America. Ice-rafted debris from the Hudson area indicates that during MIS6, there were far fewer icebergs in the North Atlantic than in the last glacial period. Simulations testing the extent of an ice sheet in North America have shown that a smaller ice sheet is probable, as the simulation produced weather data that is consistent with hypothesized temperatures at

2970-521: Is often given priority to encourage economic growth. Mining and drilling can require large amounts of land development , directly causing deforestation . In Ghana , a West African nation, deforestation from decades of mining activity left about 12% of the country's original rainforest intact. With the invention of agriculture , humans were able to clear sections of rainforest to produce crops, converting it to open farmland . Such people, however, obtain their food primarily from farm plots cleared from

3069-450: Is the result of heavy heat and moisture forming oxides of iron and aluminium, which are insoluble in water and not taken up readily by plants. Soil chemical and physical characteristics are strongly related to above ground productivity and forest structure and dynamics. The physical properties of soil control the tree turnover rates whereas chemical properties such as available nitrogen and phosphorus control forest growth rates. The soils of

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3168-534: Is the result of phosphorus levels in the soils, precipitation, high temperatures and the extensive microorganism communities. In addition to the bacteria and other microorganisms, there are an abundance of other decomposers such as fungi and termites that aid in the process as well. Nutrient recycling is important because below ground resource availability controls the above ground biomass and community structure of tropical rainforests. These soils are typically phosphorus limited, which inhibits net primary productivity or

3267-653: Is thought to have occurred due to southward migration of the subtropical, and high pressure zone of the Mediterranean. The time interval during which the PGP took place coincided with numerous important phases of hominin evolution in Africa, including the evolution of Homo sapiens , the transition from the Acheulean to the Middle Palaeolithic , and other critical cultural and behavioural innovations. Several studies have suggested that H. sapiens went through

3366-492: The Amazon rainforest ) are called carbon sinks . As major carbon reducers and carbon and soil methane storages, their destruction contributes to increasing global energy trapping , atmospheric gases. Climate change has been significantly contributed to by the destruction of the rainforests. A simulation was performed in which all rainforest in Africa were removed. The simulation showed an increase in atmospheric temperature by 2.5 to 5 degrees Celsius. Some species of fauna show

3465-841: The Indigenous peoples of the Americas , the Congo Pygmies in Central Africa, and several tribes in Southeast Asia, like the Dayak people and the Penan people in Borneo . Food resources within the forest are extremely dispersed due to the high biological diversity and what food does exist is largely restricted to the canopy and requires considerable energy to obtain. Some groups of hunter-gatherers have exploited rainforest on

3564-522: The Mesozoic era supercontinent of Gondwana . The separation of the landmass resulted in a great loss of amphibian diversity while at the same time the drier climate spurred the diversification of reptiles. The division left tropical rainforests located in five major regions of the world: tropical America, Africa, Southeast Asia, Madagascar, and New Guinea, with smaller outliers in Australia. However,

3663-509: The Tropic of Cancer and Tropic of Capricorn ). Tropical rainforests are a type of tropical moist broadleaf forest , that includes the more extensive seasonal tropical forests . True rainforests usually occur in tropical rainforest climates where no dry season occurs; all months have an average precipitation of at least 60 mm (2.4 in). Seasonal tropical forests with tropical monsoon or savanna climates are sometimes included in

3762-749: The genetic variation used in evading the damage caused by new pests is still derived from resistant wild stock. Tropical forests have supplied 250 cultivated kinds of fruit , compared to only 20 for temperate forests . Forests in New Guinea alone contain 251 tree species with edible fruits, of which only 43 had been established as cultivated crops by 1985. In addition to extractive human uses, rain forests also have non-extractive uses that are frequently summarized as ecosystem services . Rain forests play an important role in maintaining biological diversity , sequestering and storing carbon , global climate regulation, disease control, and pollination . Half of

3861-519: The inverse sine to find the projection angle of 11.86 degrees. Then, tilting any circular object by that angle, the apparent ellipse of that object projected to the viewer's eye will be of the same eccentricity. The word "eccentricity" comes from Medieval Latin eccentricus , derived from Greek ἔκκεντρος ekkentros "out of the center", from ἐκ- ek- , "out of" + κέντρον kentron "center". "Eccentric" first appeared in English in 1551, with

3960-453: The orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle . A value of 0 is a circular orbit , values between 0 and 1 form an elliptic orbit , 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola . The term derives its name from the parameters of conic sections , as every Kepler orbit

4059-441: The periapsis and apoapsis since r p = a ( 1 − e ) {\displaystyle r_{\text{p}}=a\,(1-e)} and r a = a ( 1 + e ) , {\displaystyle r_{\text{a}}=a\,(1+e)\,,} where a is the length of the semi-major axis . e = r a − r p r

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4158-492: The specific relative angular momentum ( angular momentum divided by the reduced mass). For values of e from 0 to 1 the orbit's shape is an increasingly elongated (or flatter) ellipse; for values of e from 1 to infinity the orbit is a hyperbola branch making a total turn of 2 arccsc ( e ) , decreasing from 180 to 0 degrees. Here, the total turn is analogous to turning number , but for open curves (an angle covered by velocity vector). The limit case between an ellipse and

4257-671: The spider monkey ( Ateles sp.), African giant swallowtail ( Papilio antimachus ), three-toed sloth ( Bradypus tridactylus ), kinkajou ( Potos flavus ), and tamandua ( Tamandua tetradactyla ). The emergent layer contains a small number of very large trees , called emergents , which grow above the general canopy , reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. Some examples of emergents include: Hydrochorea elegans , Dipteryx panamensis , Hieronyma alchorneoides , Hymenolobium mesoamericanum , Lecythis ampla and Terminalia oblonga . These trees need to be able to withstand

4356-498: The " world's largest pharmacy ", because over one quarter of natural medicines have been discovered within them. It is likely that there may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation as a result of human activity. Habitat fragmentation caused by geological processes such as volcanism and climate change occurred in

4455-405: The Amazon is based on swidden cultivation (also known as slash-and-burn or shifting cultivation) and is considered a relatively benign disturbance. In fact, when looking at the level of individual swidden plots a number of traditional farming practices are considered beneficial. For example, the use of shade trees and fallowing all help preserve soil organic matter , which is a critical factor in

4554-612: The Andean foothills, and volcanic areas of Southeast Asia, Africa, and Central America. Oxisols, infertile, deeply weathered and severely leached, have developed on the ancient Gondwanan shields . Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red color and sometimes produces minable deposits (e.g., bauxite ). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile. This high rate of decomposition

4653-667: The Iban "kenyalang" and the Kenyah "mamat". Pygmies who live in Southeast Asia are, amongst others, referred to as " Negrito ". Yam , coffee , chocolate , banana , mango , papaya , macadamia , avocado , and sugarcane all originally came from tropical rainforest and are still mostly grown on plantations in regions that were formerly primary forest. In the mid-1980s and 1990s, 40 million tons of bananas were consumed worldwide each year, along with 13 million tons of mango. Central American coffee exports were worth US$ 3 billion in 1970. Much of

4752-453: The Solar System also helps understand its near-circular orbits and other unique features. Tropical rainforest Tropical rainforests are dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator . They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zone between

4851-471: The Solar System's asteroids have orbital eccentricities between 0 and 0.35 with an average value of 0.17. Their comparatively high eccentricities are probably due to under influence of Jupiter and to past collisions. Comets have very different values of eccentricities. Periodic comets have eccentricities mostly between 0.2 and 0.7, but some of them have highly eccentric elliptical orbits with eccentricities just below 1; for example, Halley's Comet has

4950-574: The Solar System. The Solar System has unique planetesimal systems, which led the planets to have near-circular orbits. Solar planetesimal systems include the asteroid belt , Hilda family , Kuiper belt , Hills cloud , and the Oort cloud . The exoplanet systems discovered have either no planetesimal systems or a very large one. Low eccentricity is needed for habitability, especially advanced life. High multiplicity planet systems are much more likely to have habitable exoplanets. The grand tack hypothesis of

5049-454: The Sun. It was discovered 0.2 AU ( 30 000 000  km; 19 000 000  mi) from Earth and is roughly 200 meters in diameter. It has an interstellar speed (velocity at infinity) of 26.33 km/s ( 58 900  mph). The mean eccentricity of an object is the average eccentricity as a result of perturbations over a given time period. Neptune currently has an instant (current epoch ) eccentricity of 0.011 3 , but from 1800 to 2050 has

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5148-476: The abundance of rainfall changes throughout the year creating distinct moist and dry seasons. Tropical forests are classified by the amount of rainfall received each year, which has allowed ecologists to define differences in these forests that look so similar in structure. According to Holdridge's classification of tropical ecosystems, true tropical rainforests have an annual rainfall greater than 2 m and annual temperature greater than 24 degrees Celsius, with

5247-523: The animal and plant waste. The understory layer lies between the canopy and the forest floor. The understory is home to a number of birds, small mammals, insects, reptiles, and predators. Examples include leopard ( Panthera pardus ), poison dart frogs ( Dendrobates sp.), ring-tailed coati ( Nasua nasua ), boa constrictor ( Boa constrictor ), and many species of Coleoptera . The vegetation at this layer generally consists of shade-tolerant shrubs, herbs, small trees, and large woody vines which climb into

5346-463: The broader definition. Tropical rainforests ecosystems are distinguished by their consistent, high temperatures, exceeding 18 °C (64 °F) monthly, and substantial annual rainfall. The abundant rainfall results in nutrient-poor, leached soils, which profoundly affect the flora and fauna adapted to these conditions. These rainforests are renowned for their significant biodiversity . They are home to 40–75% of all species globally, including half of

5445-398: The case of a gravitational force: e = 1 + 2 ε h 2 μ 2 {\displaystyle e={\sqrt {1+{\frac {2\varepsilon h^{2}}{\mu ^{2}}}}}} where ε is the specific orbital energy (total energy divided by the reduced mass), μ the standard gravitational parameter based on the total mass, and h

5544-529: The climate also resulted in increased storms in the North Atlantic , affecting Europe as well as North America . Isotope dating was conducted in Hulu Cave, eastern China , and found that the penultimate glacial period's presence was felt in central China. The dating showed an increased presence of oxygen-18, an isotope that reflects the meteoric water and cave temperature, as well as precipitation of

5643-471: The coefficient of the inverse-square law central force such as in the theory of gravity or electrostatics in classical physics : F = α r 2 {\displaystyle F={\frac {\alpha }{r^{2}}}} ( α {\displaystyle \alpha } is negative for an attractive force, positive for a repulsive one; related to the Kepler problem ) or in

5742-764: The community. The initial disturbance is often a natural phenomenon or human caused event. Natural disturbances include hurricanes, volcanic eruptions, river movements or an event as small as a fallen tree that creates gaps in the forest. In tropical rainforests, these same natural disturbances have been well documented in the fossil record, and are credited with encouraging speciation and endemism. Human land use practices have led to large-scale deforestation. In many tropical countries such as Costa Rica these deforested lands have been abandoned and forests have been allowed to regenerate through ecological succession. These regenerating young successional forests are called secondary forests or second-growth forests. Tropical rainforests exhibit

5841-452: The definition "...a circle in which the earth, sun. etc. deviates from its center". In 1556, five years later, an adjectival form of the word had developed. The eccentricity of an orbit can be calculated from the orbital state vectors as the magnitude of the eccentricity vector : e = | e | {\displaystyle e=\left|\mathbf {e} \right|} where: For elliptical orbits it can also be calculated from

5940-442: The driving force moving the decomposable carbon from the litter to the soil. Respiration rates are highest early in the wet season because the recent dry season results in a large percentage of leaf litter and thus a higher percentage of organic matter being leached into the soil. A common feature of many tropical rainforests is the distinct buttress roots of trees. Instead of penetrating to deeper soil layers, buttress roots create

6039-755: The eastern and central Amazon as well as the Southeast Asian Rainforest are old and mineral poor whereas the soils of the western Amazon (Ecuador and Peru) and volcanic areas of Costa Rica are young and mineral rich. Primary productivity or wood production is highest in western Amazon and lowest in eastern Amazon which contains heavily weathered soils classified as oxisols. Additionally, Amazonian soils are greatly weathered, making them devoid of minerals like phosphorus, potassium, calcium, and magnesium, which come from rock sources. However, not all tropical rainforests occur on nutrient poor soils, but on nutrient rich floodplains and volcanic soils located in

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6138-492: The easy movement of larger animals such as: ungulates like the okapi ( Okapia johnstoni ), tapir ( Tapirus sp.), Sumatran rhinoceros ( Dicerorhinus sumatrensis ), and apes like the western lowland gorilla ( Gorilla gorilla ), as well as many species of reptiles, amphibians, and insects. The forest floor also contains decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay

6237-454: The emergent layer is unique to tropical rainforests, while the others are also found in temperate rainforests . The forest floor , the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks, swamps and clearings, where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. This more open quality permits

6336-615: The end of the glacial period and increase in atmospheric humidity, rainforest began to expand and the refuges reconnected. This theory has been the subject of debate. Scientists are still skeptical of whether or not this theory is legitimate. Genetic evidence suggests speciation had occurred in certain taxa 1–2 million years ago, preceding the Pleistocene . Tropical rainforests have harboured human life for many millennia, with many Indigenous people in South and Central America, who belong to

6435-437: The forest and hunt and forage within the forest to supplement this. The issue arising is between the independent farmer providing for his family and the needs and wants of the globe as a whole. This issue has seen little improvement because no plan has been established for all parties to be aided. Agriculture on formerly forested land is not without difficulties. Rainforest soils are often thin and leached of many minerals, and

6534-745: The forest canopy are widely recognized as important for the establishment and growth of rainforest trees. It is estimated that perhaps 75% of the tree species at La Selva Biological Station, Costa Rica are dependent on canopy opening for seed germination or for growth beyond sapling size, for example. Tropical rainforests are located around and near the equator, therefore having what is called an equatorial climate characterized by three major climatic parameters: temperature, rainfall, and dry season intensity. Other parameters that affect tropical rainforests are carbon dioxide concentrations, solar radiation, and nitrogen availability. In general, climatic patterns consist of warm temperatures and high annual rainfall. However,

6633-555: The forests. Peoples have inhabited the rainforests for tens of thousands of years and have remained so elusive that only recently have some tribes been discovered. These indigenous peoples are greatly threatened by loggers in search for old-growth tropical hardwoods like Ipe, Cumaru and Wenge, and by farmers who are looking to expand their land, for cattle(meat), and soybeans, which are used to feed cattle in Europe and China. On 18 January 2007, FUNAI reported also that it had confirmed

6732-557: The glacial period, extreme conditions were followed by a mainly treeless landscape all across Europe. This rendered Europe a polar desert just south of the now expanded ice sheets, and the rest of Europe was left with a sporadic herb based plant cover. Europe north of the Alps was a tundra-steppe of predominantly grasses, sedges, and chenopods, while land south of the Alps featured discontinuous steppe vegetation patterns. There were some refugia in

6831-489: The ground. Tropical rainforests exhibit high levels of biodiversity. Around 40% to 75% of all biotic species are indigenous to the rainforests. Rainforests are home to half of all the living animal and plant species on the planet. Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called

6930-472: The heavy rainfall can quickly leach nutrients from area cleared for cultivation. People such as the Yanomamo of the Amazon , utilize slash-and-burn agriculture to overcome these limitations and enable them to push deep into what were previously rainforest environments. However, these are not rainforest dwellers, rather they are dwellers in cleared farmland that make forays into the rainforest. Up to 90% of

7029-487: The hot temperatures and strong winds that occur above the canopy in some areas. Several unique faunal species inhabit this layer such as the crowned eagle ( Stephanoaetus coronatus ), the king colobus ( Colobus polykomos ), and the large flying fox ( Pteropus vampyrus ). However, stratification is not always clear. Rainforests are dynamic and many changes affect the structure of the forest. Emergent or canopy trees collapse, for example, causing gaps to form. Openings in

7128-462: The influence of the planets, is still bound to the Sun with an orbital period of about 10 years. Comet C/1980 E1 has the largest eccentricity of any known hyperbolic comet of solar origin with an eccentricity of 1.057, and will eventually leave the Solar System. ʻOumuamua is the first interstellar object to be found passing through the Solar System. Its orbital eccentricity of 1.20 indicates that ʻOumuamua has never been gravitationally bound to

7227-445: The large surface areas these roots create provide support and stability to rainforests trees, which commonly grow to significant heights. This added stability allows these trees to withstand the impacts of severe storms, thus reducing the occurrence of fallen trees. Succession is an ecological process that changes the biotic community structure over time towards a more stable, diverse community structure after an initial disturbance to

7326-419: The last 400,000 years covered the northern region in a thick ice sheet, which caused a drastic reduction of vegetation. In the Mediterranean, polar winds from the now extended ice sheets brought cooler and wetter conditions that caused a significant reduction in large vegetation such as trees. Pollen sequences found from MIS 6 indicated that early in the glacial period, tree abundance fluctuated heavily. Later in

7425-582: The maintenance of soil fertility in the deeply weathered and leached soils common in the Amazon. There is a diversity of forest people in Asia, including the Lumad peoples of the Philippines and the Penan and Dayak people of Borneo. The Dayaks are a particularly interesting group as they are noted for their traditional headhunting culture. Fresh human heads were required to perform certain rituals such as

7524-409: The ocean waters became colder, which then could absorb more CO 2 from the atmosphere. These factors all feedback into each other: as the ice sheets extended, more CO 2 was absorbed, and more light was reflected off the ice sheets, furthermore expanding the ice sheets, this self-reinforcing cooling setting the world into a glacial period. In northern Europe , the biggest expansion of glaciation of

7623-515: The ongoing challenge of balancing conservation with human development needs. Tropical rainforests are hot and wet. Mean monthly temperatures exceed 18 °C (64 °F) during all months of the year. Average annual rainfall is no less than 1,680 mm (66 in) and can exceed 10 m (390 in) although it typically lies between 1,750 mm (69 in) and 3,000 mm (120 in). This high level of precipitation often results in poor soils due to leaching of soluble nutrients in

7722-459: The parabolic case, remains 1). For a repulsive force only the hyperbolic trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin ⁡ ( e ) {\displaystyle \arcsin(e)} yields the projection angle of a perfect circle to an ellipse of eccentricity e . For example, to view the eccentricity of the planet Mercury ( e = 0.2056), one must simply calculate

7821-514: The past, and have been identified as important drivers of speciation. However, fast human driven habitat destruction is suspected to be one of the major causes of species extinction. Tropical rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is rapidly shrinking. Tropical rainforests have existed on earth for hundreds of millions of years. Most tropical rainforests today are on fragments of

7920-515: The penultimate glacial period. This data led to the confirmation of intense monsoons that impacted most of south-east Asia, and up to modern day Xi'an China. The increase in the intensity of monsoons was due to the orbital shifting of the planet, but was amplified by the ice sheets that formed for the same reason. These factors combined then affected the atmospheric hydrological cycle, creating more intense seasonal winds that led to increased precipitation over south-east Asia. In contrast to Europe, there

8019-479: The place in Earth's orbit where the solstices and equinoxes occur. This is a slow change in the orbit of Earth, not the axis of rotation, which is referred to as axial precession . The climatic effects of this change are part of the Milankovitch cycles . Over the next 10 000 years, the northern hemisphere winters will become gradually longer and summers will become shorter. Any cooling effect in one hemisphere

8118-597: The planets. Luna 's value is 0.054 9 , the most eccentric of the large moons in the Solar System. The four Galilean moons ( Io , Europa , Ganymede and Callisto ) have their eccentricities of less than 0.01. Neptune 's largest moon Triton has an eccentricity of 1.6 × 10 ( 0.000 016 ), the smallest eccentricity of any known moon in the Solar System; its orbit is as close to a perfect circle as can be currently measured. Smaller moons, particularly irregular moons , can have significant eccentricities, such as Neptune's third largest moon, Nereid , of 0.75 . Most of

8217-529: The presence of 67 different uncontacted tribes in Brazil, up from 40 in 2005. With this addition, Brazil has now overtaken the island of New Guinea as the country having the largest number of uncontacted tribes. The province of Irian Jaya or West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups. The pygmy peoples are hunter-gatherer groups living in equatorial rainforests characterized by their short height (below one and

8316-524: The rainfall in the Amazon area is produced by the forests. The moisture from the forests is important to the rainfall in Brazil , Paraguay , Argentina Deforestation in the Amazon rainforest region was one of the main reason that cause the severe Drought of 2014–2015 in Brazil For the last three decades, the amount of carbon absorbed by the world's intact tropical forests has fallen, according to

8415-403: The rapid uptake of other trees. These roots also aid in water uptake and storage, increase surface area for gas exchange, and collect leaf litter for added nutrition. Additionally, these roots reduce soil erosion and maximize nutrient acquisition during heavy rains by diverting nutrient rich water flowing down the trunk into several smaller flows while also acting as a barrier to ground flow. Also,

8514-455: The sheltered areas of the mountainous Alps and the western Balkans where tree populations survived. This was due to temperature variations not being extreme in these locations, as well as precipitation still being sufficient. This is unlike the rest of Europe, such as in France where pollen samples revealed a precipitation decrease of almost 60% compared to the modern day. The drastic changes in

8613-466: The specifics of the origin of rainforests remain uncertain due to an incomplete fossil record. Several biomes may appear similar-to, or merge via ecotones with, tropical rainforest: Moist seasonal tropical forests receive high overall rainfall with a warm summer wet season and a cooler winter dry season. These forests usually fall under tropical monsoon or tropical savanna climates. Some trees in these forests drop some or all of their leaves during

8712-417: The star. All eight planets in the Solar System have near-circular orbits. The exoplanets discovered show that the Solar System, with its unusually-low eccentricity, is rare and unique. One theory attributes this low eccentricity to the high number of planets in the Solar System; another suggests it arose because of its unique asteroid belts. A few other multiplanetary systems have been found, but none resemble

8811-534: The supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. It is suggested that the total arthropod species richness of the tropical canopy might be as high as 20 million. Other species inhabiting this layer include many avian species such as the yellow-casqued wattled hornbill ( Ceratogymna elata ), collared sunbird ( Anthreptes collaris ), grey parrot ( Psitacus erithacus ), keel-billed toucan ( Ramphastos sulfuratus ), scarlet macaw ( Ara macao ) as well as other animals like

8910-589: The time. This simulation showed the precipitation rates over North America doubled during MIS6, which would have been a result of the icy winds expanding southward further into the continent, as well as the increased storms. A 2019 study suggested that the Penultimate Glacial Period was warmer in North America than the Last Glacial Period. In South America, the intensity of the South American Summer Monsoon (SASM) varied with

9009-404: The trees to capture sunlight. Only about 5% of sunlight breaches the canopy to arrive at the understory causing true understory plants to seldom grow to 3 m (10 feet). As an adaptation to these low light levels, understory plants have often evolved much larger leaves. Many seedlings that will grow to the canopy level are in the understory. The canopy is the primary layer of the forest, forming

9108-482: The tropical rainforests fall into two classifications which include the ultisols and oxisols . Ultisols are known as well weathered, acidic red clay soils, deficient in major nutrients such as calcium and potassium. Similarly, oxisols are acidic, old, typically reddish, highly weathered and leached, however are well drained compared to ultisols. The clay content of ultisols is high, making it difficult for water to penetrate and flow through. The reddish color of both soils

9207-426: The typical Yanamomo diet comes from farmed plants. Some action has been taken by suggesting fallow periods of the land allowing secondary forest to grow and replenish the soil. Beneficial practices like soil restoration and conservation can benefit the small farmer and allow better production on smaller parcels of land. The tropics take a major role in reducing atmospheric carbon dioxide . The tropics (most notably

9306-728: The uptake of carbon. The soil contains microbial organisms such as bacteria, which break down leaf litter and other organic matter into inorganic forms of carbon usable by plants through a process called decomposition. During the decomposition process the microbial community is respiring, taking up oxygen and releasing carbon dioxide. The decomposition rate can be evaluated by measuring the uptake of oxygen. High temperatures and precipitation increase decomposition rate, which allows plant litter to rapidly decay in tropical regions, releasing nutrients that are immediately taken up by plants through surface or ground waters. The seasonal patterns in respiration are controlled by leaf litter fall and precipitation,

9405-466: The values for all planets and dwarf planets, and selected asteroids, comets, and moons. Mercury has the greatest orbital eccentricity of any planet in the Solar System ( e = 0.2056 ), followed by Mars of 0.093 4 . Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion. Before its demotion from planet status in 2006, Pluto

9504-627: The winter dry season, thus they are sometimes called "tropical mixed forest". They are found in parts of South America, in Central America and around the Caribbean , in coastal West Africa , parts of the Indian subcontinent , and across much of Indochina . These are found in cooler-climate mountainous areas, becoming known as cloud forests at higher elevations. Depending on latitude, the lower limit of montane rainforests on large mountains

9603-626: The world have inhabited rainforests for millennia, relying on them for sustenance and shelter, but face challenges from modern economic activities. Conservation efforts are diverse, focusing on both preservation and sustainable management. International policies, such as the Reducing Emissions from Deforestation and Forest Degradation ( REDD and REDD+ ) programs, aim to curb deforestation and forest degradation. Despite these efforts, tropical rainforests continue to face significant threats from deforestation and climate change , highlighting

9702-457: The world's animal and plant species, and two-thirds of all flowering plant species. Their dense insect population and variety of trees and higher plants are notable. Described as the "world's largest pharmacy", over a quarter of natural medicines have been discovered in them. However, tropical rainforests are threatened by human activities, such as logging and agricultural expansion, leading to habitat fragmentation and loss . The structure of

9801-420: Was considered to be the planet with the most eccentric orbit ( e = 0.248 ). Other Trans-Neptunian objects have significant eccentricity, notably the dwarf planet Eris (0.44). Even further out, Sedna has an extremely-high eccentricity of 0.855 due to its estimated aphelion of 937 AU and perihelion of about 76 AU, possibly under influence of unknown object(s) . The eccentricity of Earth's orbit

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