Wetlands and Ecosystem Services

Wetlands Importance for providing Ecosystem Services in Africa

This third blog will move on from wider context of seasonal variability in climate and water availability to look at a specific example of Ecosystem Service in the context of Africa, floodplain wetlands. The importance of these areas is closely linked to the variability described in my previous blog.  Discussion of this will help to illustrate exactly what an ecosystem service is and how it works, and begin to look at a few of the consequences of such a conception.

Floodplain wetlands provide such useful insights as a case study of water as an ecosystem service in Africa as they impacted by several specific and unique aspects of African ecosystems and topography, whilst providing an array of complex services linked to this.

These wetlands can be found across Africa, although they are of particular significance in regions which experience high seasonal variability, areas which are made up predominantly of the Savanna eco-region and sub-tropical steppe, shown below in the diagram of Baileys Eco-Regions. This shows the distribution of Wetlands of International Significance, also known as Ramsar sites, within these various eco-regions (Rebelo, et al., 2010).

Fig. 2 Baileys ecoregions and the location of Ramsar wetland sites Source-Rebelo Article

Wetlands provide a host of ecosystem services, both in direct human usages of water, such as domestic, industrial and irrigation use, but also through helping provide ‘forage and hunting resources, wood resources, grazing, fish and agricultural produce’ (Adams, 1993). Furthermore, they also contribute to natural processes such as aquifer recharge, flood control and through nutrient transfer, aspects which are incredibly important but are harder to assess in terms of ecosystem services, and so may be overlooked.

It is within dryland Africa that the economic importance of wetlands is greatest, so much so that their impact is described as being ‘out of all proportion to their size’ (Adams, 1993). This is as they help to regulate the impacts of seasonal variability in precipitation in Africa, as topography, past sediment deposition and erosion lead to flooding of certain areas. The length of inundation varies massively, but regardless helps to regulate ecosystem service provision as they delay and lower the peak of flood flows, whilst helping to produce outputs that serve communities in differing ways throughout the year.

For example in several river basins in Nigeria, such as the Hadejia-Jama'are, at the peak of inundation crops like rice and sugar cane which can tolerate flood conditions are planted, whilst once the waters begin to recede other crops such as millet and sorghum are cultivated. Likewise, communities often integrate usage of wetland and dryland areas, utilising crops that require labour at different times of year, as is the case in Sierra Leone, where communities have 'one foots in the wetland and another in the dry'(Adams, 1993).

From this list of usages it is clear these wetland areas play a crucial role as an ecosystem service. This is supported with the outputs from this various ecosystems having been valued. For example in Kilombero Valley in south-western Tanzania, the areas wetlands were calculated to provide up to 66% of the average households US$ 518 income, accounting for a significantly larger portion in poor households. Furthermore, this is without even accounting for consumed staple crops. Similarly, the overall economic output from the Hadejia-Nguru wetlands in north-eastern Nigeria has been valued at US$37 million per annum, equating to $51 per hectare and $13,000 per metre cubed of water (Barbier, 1993). 

Although these values provide an insight into the incredible economic and developmental significance the wetlands play in Africa, they also demonstrate some issues. These valuations are based solely on agricultural, fuel-wood and fisheries benefits, and as alluded to earlier, many other important aspects for valuation are ignored. This suggests the flaws and limitations of these ecosystem service valuations, especially as they can have stark impacts on informing policy on sustainable utilisation of these resources. These are important issues, which can have telling impacts on wetlands management, and are something which I will come back to in my next blog!