The Role of Wetlands

My previous post discussed water management in Nigeria, placing particular focus on the Bakolori Dam. To further investigate this topic, I chose to write about wetlands. Nigeria will again be used as main case study, enabling deep insight into wetland management and an understanding of the opportunities and challenges this particular country faces. 

What are wetlands?

Wetlands are extremely productive ecosystems that exists worldwide. In Africa, they particularly support farmers by enabling improved food production and providing a source of fish (see next section). While wetlands have been assigned various definitions, the probably most acknowledged description was coined by the Ramsar Convention on Wetlands. This intergovernmental treaty states that wetlands are “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres” (Ramsar, 2016: 9). In simpler terms, wetlands are ecosystems in which water is one of the main factors regulating animal and plant life. Therefore, wetlands can include a range of habitats: 

-      Marine (e.g. rocky shores, coral reefs)

-      Estuarine (e.g. tidal marshes, mangrove swamps)

-      Lacustrine (lakes)

-      Riverine (rivers and streams)

-      Palustrine (e.g. marshes, swamps)

-      Human-made wetlands (e.g. fish ponds dams, rice paddies)

Despite lacking data, Rebelo et al. (2010) estimated wetlands in Sub-Saharan Africa to cover approximately 4.7% of the total area. If lakes, rivers and reservoirs are included, this figure would rise to around 6%. However, 65% of these water resources are located in four major basins, namely Chad, Congo, the Niger River and the Nile River Basin.

In fact, floodplains make up the largest area of wetland types, followed by lakes with nearly 223,000 km². Reservoirs, on the other hand, constitute ‘only’ around 34,000 km² of the total area in Sub-Saharan Africa (Table 1). 

Table 1 – Distribution of wetland type across Sub-Saharan Africa (Adapted from Lehner and Döll, 2004)

Wetland Type	Area (km2)
Floodplain	692,631
Lake	222,978
Swamp forest	179,843
Intermittent wetland/ lake	135,038
Pan, brackish saline wetland	81,966
Coastal wetland	58,193
River	44,487
Reservoir	33,635

Given the Ramsar Convention’s aim to provide a framework for the wise and sustainable use of wetlands, a total of 413 sites in Africa are included in their list of international importance (Figure 1) (Ramsar, n/d). This list suggests that these sites are crucial for biodiversity and human life, and must therefore be conserved in order to maintain their ecological character. 

 

                Figure 1 – Ramsar wetlands of international importance in Africa (Ramsar, n/d)

Why should wetlands be conserved? – A case study from Nigeria

To demonstrate the significance of wetlands, I will use Nigeria’s Hadejia-Nguru wetlands as a case study. The floodplain is located in the north-eastern part of the country and is formed by two major rivers - the Hadejia river and the Jama’are river. These drain north-eastwards and flow through states such as Kano and Borno. The two streams join near the town Hadejia before continuing to lead to Lake Chad. Between the towns Gashua and Hadejia, the rivers flow through an area of low sand dunes, resulting in a drainage pattern and the wetland ecosystem (Adams and Thomas, 1996) (Figure 2 and 3). 

Figure 2 – Hadejia-Nguru wetlands (BirdLife, n/d)

      Figure 3 – Location of the wetland (Hadejia-Jama’are floodplain) (Adams and Thomas, 1996)

The climate of the area is dominated by the intertropical convergence zone, which creates a distinct dry season and rain season that lasts from May to September. In fact, 80% of the total runoff occurs in the months of August and September, emphasising the importance of these months to induce flooding and support local communities(Ibid.).

Given wetlands’ high productivity, they are extremely important for income generation and ensuring adequate nutritional standards. These environments support agricultural activity, allow for the grazing of livestock, provide non-timber forest products and fuelwood, and house fish populations for human harvest. Additionally, during the dry season, the wetlands provide a grazing ground for seminomadic pastoralists and provide an additional refuge for communities. Moreover, a notable benefit from the Hadejia-Nguru wetlands is their ability to recharge aquifers of the Chad Formation (Barbier and Thompson, 1998). These aquifers are widely used for agricultural and domestic purposes, and would suffer if replenishment slowed during the dry season. Therefore, one can again note the need for sustaining wetlands as they are able to mitigate the destructive impacts drought can have on subsurface water storage.

Consequently, the various advantages associated with wetlands underline that there must be a focus on wetland conservation. If these productive ecosystems lack protection, water- and food security for local communities becomes unstable and can pose challenges for human survival.  

Threats to wetlands

Despite the increasing recognition of wetlands' ecosystem services, the habitats are oftentimes degraded due to climate change and an imbalance between the growing demand for water and the limited supply of the resource. 

Firstly, a major risk for the Hadejia-Nguru wetlands are periods of drought. Global changes in climate increasingly stimulate such extreme weather events. Droughts not only seem to grow in occurrence, but also in duration. Long dry seasons can significantly reduce the discharge and flow of both the Hadejia and Jama’are rivers, essentially leading to a decrease in wet season floodplain inundation (Kimmage and Adams, 1992; Thompson and Hollis, 1995). Such reduced flooding has severe consequences for agricultural productivity and fish availability. 

Secondly, hydrology is affected by large-scale irrigation schemes that are implemented upstream. As discussed in my previous blog, dams alter the timing and size of floods, again challenging the state of food security. In Nigeria, multiple schemes have been proposed and initiated in the 1970s. Two dams, the Tiga Dam and the Challawa Gorge Dam, were constructed and are in full operation. Moreover, despite started construction of the Kafin Zaki Dam in 1903, work was halted after one year as a result of insufficient government funds. Like the other two dams, this project would have led to a great reduction in water supply and subsequent flooding in the wetlands. It has been estimated that the floods would not exceed 1500 km², directly comparable to the data obtained during the intense drought of the 1980s (Barbier and Thompson, 1998; Goes, 2001; Thompson and Hollis, 1995). Figure 4 demonstrates the historic original condition of the floodplain compared to the predicted scenario if the Kafin Zaki Dam had been implemented. It becomes clear that the natural flooding levels would greatly exceed those under dam presence. The graph thus visualises the risks posed to wetlands and highlights that the amount of water available would not be enough to support a total of three dams as well as maintain a healthy wetland ecosystem

Figure 4 – Flooding under the implementation of the dam (solid lines) compared to historic maxima (crosses) (Thompson and Hollis, 1995)

The dams consume large quantities of water that were originally destined for the Hadejia-Nguru wetlands. As explored in the Bakolori dam case study, food insecurity of downstream users may rise as reduced flooding causes wetland areas to decrease.

It can be concluded that both threats to wetlands, including droughts and large-scale irrigation schemes, can impact ecosystem productivity tremendously and subsequently threaten farming families’ livelihoods and survival during the dry season.  

Overall, I believe that it is extremely important to incorporate an assessment on wetland impacts into any planning strategy of water management schemes. Large dam and irrigation projects can significantly affect wetland presence, aquifer recharge as well as fish populations, reducing the ability of farmers to grow crops and harvest fish. As highlighted in my blogpost about the Bakolori project, a more holistic approach (i.e. Integrated Water Resource Management) can potentially be favourable for sustainable water use. Employing this management guideline in Nigeria could assist the conservation of the Hadejia-Nguru wetlands, and subsequently secure food availability for local communities. 

Thank you so much for reading my post!