Wetlands

Flooded forests, rivers, lakes, and other wetlands cover about 14% of the Amazon Basin. These aquatic ecosystems support major fisheries, and supply food, water and other resources critical to the Amazon countries. The map presented here is based on "Hess et al. 2003. Dual-season mapping of wetland inundation and vegetation for the central Amazon basin” (Remote Sensing and Environment 87: 404-428).

 

The Amazon Basin has the most extensive and diverse freshwater wetlands in the world. In large part the high wetland biodiversity is linked to the extensive flooded forests where aquatic and arboreal life comes together during the long annual floods. Amazonian wetlands range from small glacier-fed streams in the high Andes above 4,000 meters or more to the largest river in the world that is flanked by floodplain lakes, flooded forests and floating herbaceous communities. Finally, the Amazon River  supplies an enormous estuary with freshwater and even pushes the Atlantic out to sea.

The area now recognized as wetlands in the Amazon has increased greatly with the advent of satellite imagery and, depending on exactly how wetlands are defined, as much as 800,000 km2 or 14% of the lowland Basin could possibility be classified as wetlands. Some areas dominated by wetlands exceed 50,000 km2, such as the palm-dominated swamps in the Marañón and Ucayali basins of Peru and the Llanos de Mojos savannas of eastern Bolivia in the Madeira Basin.

Although the Amazon River floodplain accounts for less than 2% of the Amazon Basin, it nevertheless covers a disproportional 12% of the basin’s wetlands. During the highest water levels, approximately 85,000 km2 of the main Amazon River floodplain is inundated. During the lowest water levels floodplain area is decreased by about 45%, and consists mostly of permanent channels and lakes. The savanna area of the Llanos de Mojos of Eastern Bolivia is the single largest wetland (92,000 km2) in the Amazon Basin. Other large contiguous wetlands include Bananal Island between the Tocantins and Araguaia rivers (59,000 km2) and the Roraima savannas through which the Branco River flows in northern Brazil (16,000 km2).

In general, the recognition of wetlands as fragile and, thus, in need of special and specific conservation action has been slow in the Amazon basin. In the last 3-4 decades, conservation efforts have largely centered on upland deforestation, with the unintended consequence of not integrating upland and wetland management efforts. A lack of widely recognized and used terms for wetlands in both Spanish and Portuguese also hinders their conceptualization. Uplands and wetlands should always be considered together to the extent possible in order to preserve ecosystem functions.

Definitions

The first step to conserving a wetland is to define it. There are many definitions of wetlands, usually revolving around what the stakeholder is interested in. Academic hydrologists and ecologists usually emphasize flooding as the main marker; botanists focus on vegetation as a clear marker of certain wetland types; and soil scientists center their definitions on soil properties. Although the word “wetlands” is commonly used in English and generally understood by the general public, its equivalents in Spanish (humedal) and Portuguese (paisagens aquáticas or áreas húmidas) are more ambiguous and rarely conceptualized by the general public.

Scientists often emphasize the need to standardize definitions but this has rarely, if ever, happened at national or state levels. Political units often have very different types of wetlands and obviously would be most interested in those in their jurisdictions. The danger of endless debate about what is a wetland can also hinder the development of wetland policy, such as when, say, the wetland definition does not include rivers, which many classifications do not.

All Amazonian countries are signatories to the Ramsar [CC3] [m4] Convention on Wetlands (RCW), whose principal premise is the importance and fragility of wetlands. RCW uses a very general definition:

 

“Wetlands are areas where water is the primary factor controlling the environment and the associated plant and animal life. They occur where the water table is at or near the surface of the land, or where the land is covered by water.”

This definition is general enough to include everything that is aquatic and leaves more specific definitions to local areas where some combination of local, scientific, and legal definitions may be required to advance wetland conservation. Academics are usually the main group suggesting that unifying definitions are necessary, principally because it would theoretically make it easier to classify wetlands over large areas, especially in the academic framework, such as limnology or botany, in which they work. Examples of definitions that favor the presence of plants include:

“A wetland is an ecosystem that arises when inundation by water produces soils dominated by anaerobic processes and forces the biota, particularly rooted plants, to exhibit adaptions to tolerate flooding.” (Paul A. Keddy, Wetland Ecology: Principles and Conservation)

“A wetland is an ecosystem that arises when inundation by water produces soils dominated by anaerobic processes and forces the biota, particularly rooted plants, to exhibit adaptions to tolerate flooding.” ([CC5] [m6] Paul A. Keddy, Wetland Ecology: Principles and Conservation)

In the United States the complexity of defining wetlands legally can be seen by the diverse definitions that the federal government and each state use. A couple of examples suffice to illustrate this complexity:

“Wetland is a generic term for all the different kinds of wet habitats–implying that it is land that is wet for some period of time, but not necessarily permanently wet.” (United States Geological Survey – USGS)

“Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. For purposes of this classification, wetlands must have one or more of the following three attributes: (1) at least periodically, the land supports predominantly hydrophytes (plants specifically adapted to live in wetlands); (2) the substrate is predominantly undrained hydric (wetland) soil; and (3) the substrate is non-soil and is saturated with water or covered by shallow water at some time during the growing season of each year”. (The U.S. Fish and Wildlife Service)

The definitions adopted by different political entities can have important implications in terms of wetland regulations. By keeping the general definition of wetland broad, we can further specify specific conditions in regulations relevant to jurisdictions and other factors, while at the same time being inclusive enough in terms of protection of wetlands as a whole.