Where flooding happens
Because of its vast area, not all parts of the Amazon Basin are subject to flooding at the same time. Generally, flooding occurs in the northern Amazon Basin (above the Equator) while floods are receding in the basin's southern part (below the Equator). Other parts can even experience two floods per year, which are different in intensity.
As the Amazon Basin floodwaters drain into the Atlantic Ocean, the water levels begin to fall and the forests "rise" again from the water. Wildlife reclaims its boundaries, and intense heat returns.
The importance of the Amazon floodplain forest
Flooding radically alters the forest landscape and is vital in dispersing sediment and in fertilizing the varzea. Heavy silt loads, primarily from the Andes, are a major factor in enriching soil for cultivation.
As the waters creep over the land, the habitats that are created make it possible for aquatic organisms to navigate gallery forests (found alongside the riverbanks) and to seek food there.
Tiny organisms called zooplankton are consumed by fish and reproduction rate is highest during high water. When the flood recedes, zooplankton is carried by the flow and is distributed to many rivers, providing a much needed food base for a range of aquatic wildlife.3
Floodplain forests, subject of unwanted attention
Floodplain forests are among the most threatened of all ecosystems in South America due to logging and forest clearing. Intensive logging and selective exploitation of the kapok
tree (Ceiba pentandra
) and virola
) are accelerating deforestation. In Peru, it is oil exploitaition activities that pose the gravest threat to floodplain forests.
areas are threatened by cattle ranching and the increase in the number of introduced water buffalo. In addition, over-exploitation of fisheries to supply growing urban centres in the region has the potential to cause the extinction of prized species and the loss of subsistence for traditional riverine dwellers.
The sustainability of these fisheries is tremendously important for the entire population of the Amazon, for whom fish are an essential part of their diet and culture.
Moreover, badly planned damming
could profoundly alter the beneficial aspects of flooding, disrupting many crucial ecological relationships.4
Meggars, 1998 in Kricher, 1997
Goulding, 1993 in Kricher, 1997
Goulding et al, 1996 in Kricher, 1997