River mangroves commonly grow as a shrubby hedge along river banks
The river mangrove Aegiceras corniculatum belongs to the family Myrsinaceae. The species is distributed throughout South East Asia, and extends from southern New South Wales along the east coast of Australia and along the west coast from Cape York to Shark Bay.
It is a common mangrove arround the Obolo Nation and of southern Queensland, occurring along banks in the upper tidal reaches of creeks and rivers where it is frequently encountered as an understorey beneath stands of grey mangrove. It may also form pure, dense stands in the centre and landward zones of mangrove forests.
River mangrove grows on poorly drained mud that is periodically inundated by saline or brackish water.
River mangrove occurs as a bushy shrub 2 to 3 m high but may occasionally grow to a small tree with several slender trunks up to 6 m high.
The bark is rough and dark grey or black.
Leaves are spoon-shaped with a rounded tip, and are glossy green above and paler green below. They occur alternately along the stem, while the surface is covered with minute salt glands that excrete salt from the plant.
Clusters of white flowers may appear with a smell similar to rotten bananas.
Roots along the soil surface are exposed to air at low tide and help the uptake of oxygen. Prominent lenticels (air pores) at the base of each trunk also help with atmospheric gas exchange.
Salt encrustation on the leaves is an identifying feature of the river mangrove.
Flowering and fruiting
Most flowering occurs in late spring and early summer with minor flowering all year.
The single-seeded fruit is small, curved, elongated and fleshy, and appears between summer and autumn. Seeds germinate on the tree (vivipary).
Healthy plants can tolerate fresh and salty water. Salt is extruded by glands on the leaves, which accumulates over time resulting in a fine film of white salt crystals on leaf surfaces. These crystals are most often seen during prolonged dry weather and are the primary characteristic by which river mangrove can be identified.
River mangrove trunks were used as stakes in the culture of oysters and the trees are still a major source of pollen for beekeepers. This species provides valuable habitats for juvenile commercial and recreational fish, and is suitable for the rehabilitation and stabilisation of river banks and estuaries.
A study on the industrial uses of the Mangroves, con
ducted by (FENCO) in 1976 indicated that Rivers State is roughly cropped of 30,000 hectares of such species with approximately 5.6 cubic meters of wood. In fact this provides a clear vegetative zone along the entire coastline, stretching through most riverine towns and villages like Bonny, Buguma, Okrika to mention a few.
This Mangrove forests which comprise of three major different types of tree species, is predominantly stocked with the species locally called ‘Angala’ by the people of ‘Wakirike’ Kingdom. The ‘Angala’, a tropical tree growing in swamps with visible extensive breathing roots, forms a clear vegetative band along the entire coastline, stretching through coastal towns and fishing villages of most riverine communities in Rivers State.
In respect to forestry activities in Rivers State, one could rightly conclude that successive governments at both state and local levels have not done enough to pursue effectively programmes in the area conservation, research and adequate protection of the abundant mangrove forest situation in the State.
With the conception that the mangrove forest has the ability of natural regeneration, a notion which exposes the mangroves of Rivers State to brutalization and under-utilization as merely sources of fire-wood, fish trap making and poles for local building construction.
This neglect and apparent under-utilization of the abundant mangrove forests resources of the State is considered by forestry experts as an economic waste. It has thus become an issue upon which it is difficult to further be silent. Riverine communities cannot afford to lose capacity to foresee and forestall particularly in a time like this in which the consequences of ‘Nigeria’ oil exploitation have continued to pose grave concern to the people.
The conservation and allowable exploitation of the mangrove forests resources to redress this situation should be seen as a vital commitment to Rivers State.
It is possible that the apparent lack of seriousness towards the conservation and sustainable exploitation of the mangrove forests in Rivers State, is brought about by inaccessibility and perhaps unacceptability due to lack of sufficient technical knowledge of the swamp and mangrove socio-economic potentialities. It is for this reason that qualified and practicing foresters should be detailed by the respective local government councils to educate co-operatives, business executives and the general public on the viability and sustained management of the abundant mangrove forests, in addition to state government participation.
Mangrove forest can be managed to serve as adequate protection of coastal shore-lines against flood and erosion, drought and fire. It can also be used to control water quality for human and agricultural uses. For instance, mangrove highly populated areas such as the ‘Wakirike’ environment can serve a good process for waste recycling, and could be put into other uses like fish/wild life conservation, maintenance of scenic beauty for recreation and tourism. It is a known fact that mangrove forests can transform barren matter into a colony of living organisms. The Avicenis germimans ‘Okor’ and Languncularia racemosa ‘Atabaka two of the three major mangrove tree species highly populated in Rivers State are known for their ability to trap soil, silt and their own dead leaves in their aerial roots. The trapping of matter, creates an ideal conditions for the multiplication of organisms. Consequently, the submerged banks are colonized by shrimp larvae and plankton. Their roots and crown canopy is known to provide a conducive habitat for fish hatchings. Mangrove trees are also useful for the production of timber for building construction, sleepers for railway tracks, pit-props for mines, electric and telephone transmission poles, fish traps, racks and various raw materials for wood based industries.
Mangrove trees particularly the Rhizophora racemosa, is very medicinal. Barks, leaves and roots of Rhizophora, which is classified into three distinct species namely: Rhizophora racemosa; Rhizophora harrisonii and Rhizophora Mangle, is locally administered to the sick by herbalists.
It is envisaged with high optimism that mangrove tree species can be very useful to modern medical researches. Okrikans, in time immemorial knew that apart from the mangrove trees, the mangrove ecozone is an important source of proteinous sea food. It is the natural habitat of the crustacean, molluses and fishes such as crab (ipa), lobster (ipoli), periwinkle (isam) and mud-skippers (ichila) and also the spawning, nursery and feeding ground for other coastal fin-fishes.
Crustaceans are the most conspicuous group of marine animals habitating the ‘Wakirike’ mangrove ecozone. For instance, Fiddler crabs (akanga) are quite characteristic of the mangrove swamp forests as they burrow into the soft mud and at low tide, when the ground is exposed, they emerge in large numbers with a rhythmic display of body movement believed by Okrikans to be beckoning on the tide to come back. Different species or crabs are found in different substrate of the ecosystem. Some of these are eaten by man, while others form the food chain of other animals and could be used as bates in fishing traps .
It is not just the saline flord and fauna that is of benefit to Okrikans in the mangrove ecosystem. Animals of terrestrial origin also inhabit the mangrove swamps. They include: reptiles, small and large animals and birds such as crocodiles (seki), iguana (awakiba); monkeys (ibuko), tortoise (ikaki), antelopes (tubara), hippopotamus (otobo) and kingfisher (akiama), wood pecker (arukara), dove (okuku), weaver-bird (pulopulo-feniba), etc.
Unfortunately, these species of fishes, reptiles, animals and birds are getting near extinction, resulting from the continued environmental maladjustment.
The mangrove ecosystem of ‘Wakirike’ Kingdom is variously subjected to the activities of oil prospecting, dredging and construction companies prominent amongst which is the gas flaring and marine effluent discharges pollution by SPDC and NNPC, major operatives within the zone. The volume of carbondioxide and effluent discharges into the ‘Wakirike’ air and water environment, is silently battled by the luxuriant green, vegetation and the swampy nature of the mangrove ecosystem in playing its role as purifier of air and water qualities for human and agricultural use.
The riches derivable froin the mangrove ecosystem are immeasurable. Nevertheless, the mangrove ecology is relatively ‘Very fragile and once destroyed, it takes many years to recover. We therefore, will like to call on the Federal Ministry of Environment to consider the establishment of a Mangrove Forests Research Centre for Rivers State. When established, this body will certainly indicate too, the quick and easy way the riches buried in these mangrove forests could be converted into commercial use. It may equally be pertinent to call Rivers State University of Science and Technology, to supplement whatever work such a centre will do, by developing extra interest in carrying out its own research into the diverse uses of the mangrove forests and the industries that should spring from them.