A várzea forest is a seasonal floodplain forest inundated by whitewater rivers that occurs in the Amazon biome. Until the late 1970s, the definition was less clear and várzea was often used for all periodically flooded Amazonian forests.
Along the Amazon River and many of its tributaries, high annual rainfall that occurs mostly within a rainy season results in extensive seasonal flooding of areas from stream and river discharge. The result is a 10–15 m (33–49 ft) rise in water level, with nutrient rich waters.
The Iquitos várzea ecoregion covers the margins of the upper Amazon and its tributaries. Further down are the Purus várzea in the middle Amazon, the Monte Alegre várzea and Gurupa várzea on the lower Amazon and the Marajó várzea at the mouth of the Amazon. The Marajó várzea is affected by both freshwater and tidal flows.
Várzea forests can be split into two categories: low várzea and high várzea. Low várzea forests can be categorized by lower lying areas where the annual water column has an average height of more than 3 m (10 ft), where the period of flooding is greater than 50 days per year. High várzea forests are categorized as the areas where the average annual water column is less than 3 m (10 ft) high and flooding periods are less than 50 days per year. Amazonian várzea forests are flooded by nutrient rich, high sediment whitewater rivers such as the Solimões-Amazon, the Purus, and Madeira rivers. This makes the várzea areas distinct from igapós, floodplains from nutrient poor blackwater. The water level fluctuations that the várzea experiences result in distinct aquatic and terrestrial phases within the year. Amazonian white water river floodplains cover an area of more than 300,000 km2 (120,000 sq mi), and várzea forests cover approximately 180,000 km2 (69,000 sq mi) of the Amazon basin. 68% of the Amazonian river basin is located in Brazil, with the remaining areas located in Bolivia, Colombia, Ecuador, French Guiana, Peru, Suriname, and Guyana. The várzea extends from this basin upward into the land before reaching slopes into the terra firme forests.
Várzea habitats are generally diverse, consisting of forests, grasslands, lakes, flooded fields, and swamps. Approximately 75% of the várzea areas consist of dense canopy forests, with the other 25% being represented by the remaining habitats. Within the várzea, topographic variation leads to different flooding durations and severity, resulting in vegetation being separated where plants with different tolerances to flooding inhabit different areas.
Due to the renewal of soil nutrients caused by the annual white water flooding, várzea forests are some of the most productive areas of Amazonia and serve as important breeding grounds for fish, birds, mammals, and reptiles. In order to grow and survive in this environment, both plants and animals must have a large range of morphological, anatomical, physiological and ethological adaptations. For example, during the flooding season, fish and other aquatic organisms take advantage of the lower density of predators, which have migrated or are confined to smaller, dryer areas, and use this time to reproduce.
Both Amazonian manatees (Trichechus inunguis) and river dolphins (Inia geoffrensis) spend time in várzea areas during high water periods of the flood season. In addition, black caiman (Melanosuchus niger) are abundant and also play an important ecological role. The charismatic jaguar (Panthera onca) is also found in a variety of várzea habitat types.
In the várzea, tree species richness, distribution and vegetation structure are influenced by a variety of characters such as topography and sedimentation dynamics. Leguminosae and Euphorbiaceae are two of the most important and abundant families within both high and low várzea habitats. Due to the cycles of both sedimentation and erosion, habitat types of different successional stages occur simultaneously within limited areas of the várzea. Most species tend to grow in areas that are subjected to the river flood pulse, but not in areas that are influenced by the sea and tides. This results in waterlogged or flooded conditions for up to seven months of the year, and consequently plant species numbers in the várzea are lower than the non-flooded terra firme forests.
Like many tropical environments, in the várzea there is evidence that nitrogen is a limiting factor for primary production; however, nitrogen reaches the floodplain via flooding as dissolved and particulate matter.
In general, soils of the várzea initially are very fertile from the white water flooding, but after two or three years of cultivation the soil fertility declines. Because of the várzea forests inherent nutrient rich environment and the proximity to rivers, which act as transport routes for local peoples, these areas have historically favored human occupation, resulting in the most densely populated environment of Amazonia. People have been known to plant rice, corn, beans, peppers, and bananas in várzea floodplains bordering rivers. In terms of seed dispersal, local peoples have influenced both the establishment and regeneration of várzea forests by controlling populations of fish, birds, rodents, and other seed dispersers and also by removing natural vegetation to make room for agriculture and cattle. Historically, cattle ranching on natural pasture areas was a principal economic activity in the Amazonian floodplains, an activity that has continued into the present. However, in modern times land is usually cleared for cattle ranching. In some areas, such as the floodplains of Amapá, cattle herds have been traded in favor of water buffalo, which do better in the wetter várzea habitat. Both cattle and water buffalo cause damage to river banks and can lead to extensive soil erosion.
One of the main impacts people have had on the várzea is deforestation for logging and agricultural purposes. Várzea forests show promise for timber production and forest management within Amazonia because they are less species rich than terra firme forests, but still with great amounts of timber. In addition, due to the fertile alluvial soils within várzea forests, trees typically grow more rapidly in the várzea than within terre firme forests and transport of logs is made easy by the use of the river. Most likely a result of the above reasoning, within Amazonia, logging has traditionally been centered in the várzea, and only in recent years has expanded into terra firme areas. In addition to deforestation of the várzea via logging, landowners may also dig channels to widen or connect streams in várzea areas in order to more easily transport logs or move to new, unexploited areas of the forest, which leads to loss of forest and soil degradation within the várzea habitat. It has been found that from 1976 to 1991 the areal extent of mixed species várzea had a net decrease of 25%, while other types of surrounding habitats, such as palm forest or herbaceous cover, increased. The main impacts associated with the loss of várzea areas were logging, heart of palm extraction, and agricultural conversion.
An additional major impact from humans seen in the várzea is the extraction or mass production of the açaí palm (Euterpe oleracea) for the palm or for the well known açaí berry. The juice obtained from açaí is a major part of the diet for some regional populations within the Amazon and in some regions is the most important monetary crop. In açaí agroforests, other species surrounding clumps of the palm are commonly heavily pruned to remove competition.
People have also had a severe impact on animal populations in the varzea. For example, selective hunting within the várzea of the red howler monkey (Alouatta seniculus) and the tufted capuchin monkey (Cebus apella) has had large effects on the regeneration of Fig (Ficus sphenophylla) trees. Both species of monkey are known to be important seed dispersers within the várzea.
A Directory of Important Wetlands in Australia (DIWA) is a list of wetlands of national importance to Australia. Intended to augment the list of wetlands of international importance under the Ramsar Convention, it was formerly published in report form, but is now essentially an online publication. Wetlands that appear in the Directory are commonly referred to as "DIWA wetlands" or "Directory wetlands".Belterra, Pará
Belterra is a municipal seat and rubber plantation site some 40 km (25 mi) south of the city of Santarém, Brazil (in the federal state of Pará) at the edge of the Planalto at 165 m (541 ft) above sea level.Black squirrel monkey
The black squirrel monkey (Saimiri vanzolinii), also known as the blackish squirrel monkey or black-headed squirrel monkey, is a small New World primate, endemic to the central Amazon in Brazil. It largely resembles the female of the far more common Bolivian squirrel monkey, though the latter lacks the black central back.This squirrel monkey has one of the most restricted geographical distributions for a primate, living in várzea forest in the confluence of the Japura and Solimões rivers. Its entire range is within the Mamirauá Sustainable Development Reserve. It resides in the reserve with two other Saimiri species. It is a social primate that travels with other black squirrel monkeys in large troops within its habitat. Its small size makes it an easy target for its predators; however, it may resist predators when it travels in large troops.Its species overall has positive effects on the economy.Campinarana
Campinarana (NT0158, Portuguese pronunciation: [kɐ̃ˌpinɐˈɾɐ̃nɐ]), also called Rio Negro Campinarana or Amazon caatinga, is a neotropical ecoregion in the Amazon biome of the north west of Brazil and the east of Colombia that contains vegetation adapted to extremely poor soil. It includes savannah, scrub and forest, and contains many endemic species of fauna and flora.Collared titi
The collared titi (Cheracebus torquatus) is a species or a closely related complex of species of titi, a type of New World monkey, from South America.Dusky-headed parakeet
The dusky-headed parakeet (Aratinga weddellii), also known as Weddell's conure or dusky conure in aviculture, is a small green Neotropical parrot with dusty grey head found in wooded habitats in the western Amazon basin of South America. Its range extends from southeastern Colombia south through eastern Ecuador, eastern Peru and southwest Amazonian Brazil, to central Bolivia. It prefers semiopen habitats such as várzea, forest edge, and forest remnants, but can also be found in coffee plantations. It is generally common and its habitat preference makes it less vulnerable than many other Amazonian species. Consequently, it is considered to be of least concern by BirdLife International and IUCN.
This long-tailed species is generally green in color (both lutino and blue mutations are rare, but do exist in captivity) with a gray-brown head, a blue-tipped tail, and remiges that are dark gray from below, mainly blue from above. The bill is black, and it has a broad, bare, white (sometimes yellow-tinged) eye-ring. With a typical length of 25–28 cm (10–11 in) and a weight around 100 grams, it is slightly smaller than the sun conure. Many people call these conures minimacaws because they have skin near their beak and eyes, similar to the macaw.
It is social, and usually found in pairs or small groups. It may even flock with different species of conures. When food is plentiful, it may form flocks of up to 100 members. It eats fruit, seeds, and flowers, and searches decaying wood for insect larvae. It also ingests mineral-rich soil, e.g., from a clay lick, as a supplement. A pair raises their offspring together, nesting in woodpecker holes in trees or arboreal termite nests.
Consuming clay is believed to provide a mineral supplement and neutralise toxins in their diet. Their predators (along with many other neotropical parrots) include many birds of prey, monkeys, and in some cases, jaguars.
They do well in captivity. They are fairly easy to breed if provided with a durable nest box, and will lay up to three clutches per year. They are known to be quiet, compared to other conure species, but still very energetic and clownish, like most conures. These conures' lifespans range from 25 to 50 years, though their typical lifespans are usually 35–40 years.Recently, they have been sighted as a colony in coastal districts of Lima, Perú. They probably came as pets, and have settled in this city.Gurupa várzea
The Gurupa várzea (NT0126) is an ecoregion of seasonally and tidally flooded várzea forest along the Amazon River in the Amazon biome.Igapó
Igapó (Portuguese pronunciation: [igaˈpɔ], from Old Tupi: "root forest") is a word used in Brazil for blackwater-flooded forests in the Amazon biome. These forests and similar swamp forests are seasonally inundated with freshwater. They typically occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are found in a range of climate zones, from boreal through temperate and subtropical to tropical.
In the Amazon Basin of Brazil, a seasonally whitewater-flooded forest is known as a várzea, which is similar to igapó in many regards; the key difference between the two habitats is in the type of water that floods the forest.Marajó
Marajó (Portuguese pronunciation: [maɾaˈʒɔ]) is a large delta island in the state of Pará, Brazil. The island is bordered by the mouth of the Amazon river to the west and northwest, the Atlantic Ocean to the northeast and by the Pará River, a distributary of the Amazon to the east.
From approximately 400 BC to 1600 AD, Marajó was the site of an advanced Pre-Columbian society called the Marajoara culture, which may have numbered over 100,000 people at its peak. Today, the island is known for its large water buffalo population, as well as the pororoca tidal bore periodically exhibited by high tides overcoming the usual complex hydrodynamic interactions in the surrounding reaches of Amazon delta. It is the second-largest island in South America, and the 35th largest island in the world.
With a land area of 40,100 square kilometres (15,500 sq mi) Marajó is comparable in size to Switzerland. Its maximum span is 295 kilometres (183 mi) long and 200 kilometres (120 mi) in perpendicular width.Marajó várzea
The Marajó várzea (NT0138) is an ecoregion of seasonally and tidally flooded várzea forest in the Amazon biome.
It covers a region of sedimentary islands and floodplains at the mouth of the Amazon that is flooded twice daily as the ocean tides push the river waters onto the land.
The flooded forests provide food for a wide variety of fruit-eating fish, aquatic mammals, birds and other fauna.
It has no protected areas and is threatened by cattle and water-buffalo ranching, logging and fruit plantations.Monte Alegre várzea
The Monte Alegre várzea (NT0141) is an ecoregion of seasonally flooded várzea forest along the Amazon River in the Amazon biome.Mylossoma duriventre
Mylossoma duriventre, the silver mylossoma, is a species of freshwater serrasalmid fish endemic to tropical and subtropical South America. It grows to a maximum length of about 25 cm (10 in) and a weight of 1 kg (2.2 lb). It is the subject of a local fishery, being known as palu in Brazil and palometa in Venezuela (names it shares with several relatives).National Wetlands Inventory
The National Wetlands Inventory (NWI) was established by the United States Fish and Wildlife Service (FWS) to conduct a nationwide inventory of U.S. wetlands to provide biologists and others with information on the distribution and type of wetlands to aid in conservation efforts. To do this, the NWI developed a wetland classification system (Cowardin et al. 1979) that is now the official FWS wetland classification system and the Federal standard for wetland classification (adopted by the Federal Geographic Data Committee on July 29, 1996: 61 Federal Register 39465). The NWI also developed techniques for mapping and recording the inventory findings. The NWI relies on trained image analysts to identify and classify wetlands and deepwater habitats from aerial imagery. NWI started mapping wetlands at a small scale (1:250,000 map which covers an area the size of 128-1:24,000 USGS topographic maps or approximately 7,400 square miles). Eventually, large-scale (1:24K scale) maps became the standard product delivered by NWI. As computerized mapping and geospatial technology evolved, NWI discontinued production of paper maps in favor of distributing data via online "mapping tools" where information can be viewed and downloaded. Today, FWS serves its data via an on-line data discovery "Wetlands Mapper". GIS users can access wetlands data through an online wetland mapping service or download data for various applications (maps, data analyses, and reports). The techniques used by NWI have recently been adopted by the Federal Geographic Data Committee as the federal wetland mapping standard (FGDC Wetlands Subcommittee 2009). This standard applies to all federal grants involving wetland mapping to insure the data can be added to the Wetlands Layer of the National Spatial Data Infrastructure. NWI also produces national wetlands status and trends reports required by the United States Congress.Neacomys minutus
Neacomys minutus, also known as the minute neacomys, the small bristly mouse, or the minute spiny mouse, is a rodent species from South America in the genus Neacomys. It is found in Brazil.Orange-eyed flatbill
The orange-eyed flatbill or orange-eyed flycatcher (Tolmomyias traylori) is a species of bird in the family Tyrannidae. It is found in the Amazon (specifically in várzea forest) in south-eastern Colombia, eastern Ecuador, and north-eastern Peru. First recognized as a species due to its distinct voice, it was only described in 1997; the binomial commemorates the American ornithologist Melvin Alvah Traylor Jr. The International Union for Conservation of Nature has rated the conservation status of this species as being of "least concern".Orinoco softtail
The Orinoco softtail (Thripophaga cherriei) is a species of bird in the Furnariidae family.
It is endemic to the state of Amazonas in southwestern Venezuela. It has not yet been confirmed as occurring away from the type locality along the Río Capuana, a tributary of the Río Orinoco.
Its natural habitat is riparian tropical moist lowland forests, specifically várzea forest approximately 100 meters in elevation.
It is threatened by habitat loss.Purus-Madeira moist forests
The Purus-Madeira moist forests (NT0157) is an ecoregion in the central Amazon basin. It is part of the Amazon biome.
The ecoregion covers a stretch of flat and relatively infertile land between the Purus and Madeira rivers, extending to the Solimões River (upper Amazon) in the north. It is isolated from other regions by the seasonally flooded várzea forest along these rivers, and has a high degree of endemism among its flora and fauna.
The natural environment is relatively intact.
The BR-319 highway was built along the length of the ecoregion in the early 1970s, but rapidly deteriorated and is now closed.Purus várzea
The Purus várzea (NT0156) is an ecoregion of seasonally flooded várzea forest in the central Amazon basin. It is part of the Amazon biome.
The ecoregion is home to a vegetation adapted to floods of up to 12 metres (39 ft) that may last for eight months.
There is a great variety of fish and birds, but relatively fewer mammals.
Ground-dwelling mammals must migrate to higher ground during the flood season.
Threats include logging, cattle farming, over-fishing and mercury pollution from gold mining.