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.
The large rivers that separate the ecoregion from surrounding regions prevent many species from migrating from or to other regions, making a distinctive environment with various endemic species.[3]
The Purus-Madeira moist forests are bounded by the Purus várzea ecoregion along the Purus and the Monte Alegre várzea along the Solimões and Madeira.
The Madeira-Tapajós moist forests lie on the east shore of the Madeira.
To the south there are stretches of Iquitos várzea in the Southwest Amazon moist forests.[2]
Physical
The ecoregion covers an almost entirely flat area of 17,404,720 hectares (43,008,000 acres) in the lower Amazon basin.
The plain holds large meandering rivers that have formed many oxbow lakes, and a great many small streams, all subject to annual flooding.[1]
Elevations range from 20 to 60 metres (66 to 197 ft).
It is within the low Amazon Basin, an area of soft sediments that emerged from five to two million years ago.
Soils are acidic and low in nutrients, mostly sandy podzols or hydromorphic clay soils.[3]
The Köppen climate classification is "Am": equatorial, monsoonal.[4]
Average temperatures range from 21 to 32 °C (70 to 90 °F) with a mean of 27 °C (81 °F).
Temperatures are fairly constant throughout the year.
Average annual precipitation is 2,200 millimetres (87 in).
Precipitation is lowest in July with an average of 32.8 millimetres (1.29 in) and highest in March with an average of 321.2 millimetres (12.65 in).[4]
Flora
Most of the vegetation is seasonally flooded tropical lowland rainforest.[1]
The flora have high biodiversity and endemism.
In the north the forest is dense with a canopy of 30 metres (98 ft) and emergent trees of up to 45 metres (148 ft).
There is a dense understory.
In the south the canopy is more open and the understory less dense.
In the extreme south the moist forest meets patches of wooded savanna.[3]
The World Wildlife Fund classes the ecoregion as "Relatively Stable/Intact".[3]
Most of the environment is undamaged, apart from the south.
A paved road (BR-319) was built along the length of the region from Humaitá to Manaus, but it proved impossible to maintain and was closed.
The Trans-Amazonian Highway crosses the southwestern end of the region from Humaitá to Lábrea and has caused deforestation to create pasturage and agricultural fields.
The southern area is threatened by controlled and uncontrolled fires.
Mining in the upper sections of the Purus and Madeira rivers causes pollution and habitat destruction.[3]
During the period from 2004 to 2011 the ecoregion experienced an annual rate of habitat loss of 0.32%.[6]
Global warming will force tropical species to migrate uphill to find areas with suitable temperature and rainfall.
Low, flat ecoregions such as the Purus-Madeira moist forests are extremely vulnerable.[7]
Coca-Castro, Alejandro; Reymondin, Louis; Bellfield, Helen; Hyman, Glenn (January 2013), Land use Status and Trends in Amazonia(PDF), Amazonia Security Agenda Project, archived from the original(PDF) on 2016-03-19, retrieved 2017-03-24
