EPOW Ecology Picture of the Week -- Forest Wetlands of Tropical Africa

Explanation: Welcome to the heart of the Congo River Basin in central tropical Africa. We are flying over an immense stretch of unbroken rainforest in Salonga National Park, the second largest tropical forest park in the world and the largest in Africa. Below we see diverse canopies of flooded forests and the occasional stream and river.

Then, suddenly, the forest parts and in the middle of the jungle appears a large wetland along the edges of one of the smaller rivers.

Short video of flying over a "bais" wetland in flooded rainforest,
in the central Congo River Basin, tropical Africa.

Wetlands in central tropical Africa are variously called bais (pronounced like "buys"), ésobés ("ay-sow-bays"), salines, swampy meadows, elephant baths, and other names. The name bais is Pygmy.

These are relatively rare habitats for an amazing variety of plants and animals. The ecology of these wetlands is poorly studied and most are likely not even mapped and known.

Bais are rare wetland openings in the vastness of the central African rainforest.
In Ivindo National Park in the central African country of Gabon, bais were only
recently discovered, in 2000, one of which has the largest concentration of
observable elephants and gorillas in the country.

In one reference, J.P. Vande weghe (2004) noted that there two types of bais: one type occurs along rivers, such as the example in this week's main photo, and another type occurs completely within the forest far from major water sources, likely as a water-saturated local basin. Bais can be as small as just a few hectares up to nearly 100 ha (250 ac) in size.

These large bais are of the second type noted by Vande weghe -- they have
formed in a low-lying area far from a major water source
and are maintained by the trampling by large animals.

Bais might begin with a locally flooded streamside or low-lying area, but decades of use by large ungulates, particularly forest elephants, forest buffalos, and red river hogs will serve to enlargen and maintain the wetlands. This is one kind of key ecological function of such wildlife species, in that they create and maintain habitat for other species. Vande weghe noted that elephants and buffalo in particular compress the soil and churn plants, organic matter, clay, and humus to a depth of at least 20 cm (8 inches). The bare soil is then colonized by a variety of semi-aquatic annual plants such as Bacopa crenata, Lindernia numnulariifolia, Torenia thouarsi, and many others. In turn, invertebrates, birds, reptiles, amphibians, and mammals are attracted to the area.

In slightly elevated situations, where the bais site is less often flooded, a meadow habitat rich in nitrogen-tolerant plants will form. Animals will be attracted to eat the plants and then spread their dung across the meadow, further introducing other plant seeds to the site. Such Bacopa meadows, caused by trampling by buffalos and elephants, attract gorillas, antelope, forest hogs, and other large animals, which further maintain the meadow openings by grazing and trampling. In this way, water, animals, plants, and nutrients become an inextricable web of life, and each conditions the site for the other.

In this color-enhanced view of the edge of one of the bais,
notice the strata and layers of different vegetation stretching from
the water to the forest: aquatic, semi-aquatic, herbs and grasses,
riparian shrubs, and then finally the forest cover itself.
This diversity provides for many resources and habitats
for a wide variety of wildlife.

Some bais are saline, that is, salty, and large mammals are attracted by, and consume, the mineral salt. The salt from such "salt licks" comes from water evaporation leaving behind the salts of animal droppings and urine.

Forest wetlands of tropical Africa are amazing and delicate places where the functions of plants, animals, hydrology, and soil chemistry support and maintain each other. Without this intricate web of dependency, the system would surely simplify and habitat would be lost for many forms of life. Perhaps there is a lesson here for us to learn in our more stark and sterile urban environments.

A world of beauty and incredible isolation! To get to this
bais in Salonga National Park in the Congo takes a day's
hike through flooded swamp forest -- after you have flown
several hours from the nearest city, landed on a dirt strip,
hiked to the nearest village and river, and boated another
two hours, just to get to the trailhead in the swamp forest!

Information:
Vande weghe, J. P. 2004. Forests of central Africa. Nature and man. Lannoo Publishers, Tielt, Belgium.

EPOW - Ecology Picture of the Week