Invasive species

Typha bed in the Hadejia-Nguru wetland in the Komadugu-Yobe sub basin in Nigeria
Portion of cluster of quelea birds around maga area of the basin

Invasive species, also called invasive exotics or simply exotics, is a nomenclature term and categorization phrase used for flora and fauna and for specific restoration-preservation processes in native habitats and has several definitions which includes;

  • The first definition, the most used, applies to introduce species (also called "non-indigenous" or "non-native") that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically. Such invasive species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland-urban interface from loss of natural controls (such as predators or herbivores). It has been used in this sense by government organizations as well as conservation groups such as the International Union for Conservation of Nature (IUCN).  The European Union defines "Invasive Alien Species" as those that are, firstly, outside their natural distribution area, and secondly, threaten biological diversity. It is also used by land managers, botanists, researchers, horticulturalists, conservationists, and the public for noxious weeds.
  • The second definition includes the first, but broadens the boundaries to include indigenous or native species, with the non-native ones, that disrupt by a dominant colonization of a particular habitat or wild land areas from loss of natural controls (i.e.: predators or herbivores).
  • Another definition identifies invasive species as a widespread nonindigenous species. This one can be too broad, as not every nonindigenous or "introduced" species has an adverse effect on indigenous environment.  A nonadverse example is the common goldfish (Carassius auratus), though common outside its native range globally, it is rarely in harmful densities to a native habitat.

Lake Chad basin

In the lake Chad Basin, prevalence of invasive species is identified as one of the seven priority regional environmental concerns in the basin Trasboundary Diagnostic Analysis (TDA). Others are variability of the hydrological regime and fresh water availability, water pollution, decrease viability of biological resources, loss of biodiversity, loss and modification of ecosystem and sedimentation in rivers and water bodies.

However, the problem is mostly seen in the komadougou-Yobe sub basin, Chari Logone sub system and the lake itself. In the KYB sub-system, there are two prominent invasive species, typha grass and quelea birds. In the Chari-Logone system it is water Hyacinth while the lake itself has been invaded by Typha and water Hyacinth.

Typha Grass

Typha bed in the Hadejia-Nguru wetland in the Komadugu-Yobe sub basin in NigeriaTypha grass is a species of water loving plant that can, under favorable condition (i.e. in shallow permanently inundated areas) proliferate and become difficult to control making it an invasive species. Under such conditions it out-competes almost all other plants.

In Hadejia-Nguru wetland in particular and other parts of Hadejia-Jama’are-Komadugu-Yobe Basin (HJKYB) in general, the inversion of Typha spp has for the past years constituted one of the most alarming threats to the economy and ecology of the area. In recent years, river channels, lakes and fadamas in the wetlands have been taken over by Typha along with many hectares of farmlands and potential grazing lands. On the Marma Channel and Nguru Lake (a section of Hadejia-Nguru wetlands) to mention an example, where Typha inversion is more severe, over two thirds of potential farming and grazing lands have been taken over by the plant. Conversely, it has also contributed to the desiccation of Burum Gana Channel, where about 60% of dry season irrigation farms are wasting. In addition, the grass provides a harbor for large flocks of Quelea birds (another invasive bird species in the basin) a cereal crops pest.

Impacts

The major environmental impact of weed infestation is the blockage, and in some instances even diversion of channels. This has led to parallel incidences of channel desiccation and inundation in the HNWs, the net consequences of which have been loss of livelihoods, poverty and resources use conflicts.

Quelea Birds

It is a small seed-eating bird which is a serious pest of sorghum and millet in much of central and West Africa. It has a grazing range of up to 500 km, which more than often crosses borders and thus, an international support/cooperation is required for its control.

The birds occur in colonies of up to millions which normally feed on grass seeds but in the absence of these seeds, they attack the crops mainly at Dough stage, sucking out the soft grain. Damage caused in individual field can be as high as 100 percent if no control measures are undertaken.

However, the two cereals mainly affected by the birds form part of the staple diet for the human population in the region and are grown in almost all parts of the region due to their drought tolerance.

Impacts

Portion of cluster of quelea birds around maga area of the basinQuelea birds destroy crops and thus resulting in losses in incomes and food stuff.

Furthermore, Spraying with the organophosphates has been the predominant means to control it for more than forty years. Birds of prey, owls and passerines have been commonly reported casualties of spraying over land. Moreover, organophosphates are known to have negative effects on aquatic invertebrates, in particular on populations of crustacea, which predicates against its use near water bodies. Non-target species may be affected directly by spraying, but predatory birds, scavenging birds and even mammals can be contaminated by secondary poisoning when they eat Quelea carcasses which can be found up to 20 km or more from the primary control site.

Root Causes

As identified in the Lake Chad Basin Transboundary Diagnostic Analysis (LCBC TDA). “The major cause of typha invasion in the KYB is a change in the hydrological regime, which turned a seasonal river into a perennial river. This in turn is the result of poor dam operation procedures and inefficient raw water intake structures, which put a lot of water in the river system during the dry season. The Kano City raw water intake structure on the KYB, for example, takes maximally only 5% of dam releases in the dry season effected on its account. The remaining 95% of the releases, at a maximum of 25 million cubic meters per second, and a minimum of 10 million cubic meters per second, provides unwanted dry season flows downstream. This is happening due to the absence of an integrated system of water resources management in the basin, which is illustrated by a poor enforcement of environmental protection regulations and the absence of sustainable development/wise use

of natural resources on the political agenda. There is in addition the issue of eutrophication as another immediate cause, which is driven by the lack of best practices in the use of agricultural chemicals, which itself is the result of the absence of an administrative framework for managing diffuse sources of pollution in agriculture. Quelea birds, on the other hand, have become more prevalent as crop pests due to the degradation and destruction of their grazing sites through uncontrolled expansion of farmlands and settlements, which are in turn the products of population pressure and low standards of environmental education and awareness”.

Objectives

  • Make an inventory of invasive species,
  • Foster regional commitment to the control of invasive species in a Biodiversity Protocol and other appropriate regional agreements,
  • Develop regional procedures for the study and management of invasive species, and
  • Undertake pilot demonstration of strategies/approaches for controlling invasive species.

Achievements

  • Promotion of typha grass briquetting technology as alternative source of energy and income generation in the typha proliferated areas of Hadejia –Nguru wetlands in Nigeria.
  • Planned project for the development of lake Chad through improving the hydraulic capacity of its tributaries which involve a technical study on invasive plants including assessment of the areas invaded, eradication techniques and cost estimate for its eradication.

Links

  • Promotion of typha grass briquetting technology as alternative source of energy and income generation in the typha proliferated areas of Hadejia –Nguru wetlands in Nigeria.
  • Planned project for the development of lake Chad through improving the hydraulic capacity of its tributaries which involve a technical study on invasive plants including assessment of the areas invaded, eradication techniques and cost estimate for its eradication