Chapter 1 Introduction
1.4 Objectives of the study
It is clear from the situation analysis presented above that freshwater ecosystems and the services they provide are seriously impacted by human activities across the region. In the study presented here we aim to provide an up-to-date baseline on the distribution and status of freshwater biodiversity across the region as a foundation for conservation and environmental decision making of relevance to freshwater species. Specifically, we will:
i) re-assess all freshwater species for the IUCN Red List, providing an index of change in the status of freshwater biodiversity (a Red List Index) since the baseline assessment was completed in 2009;
ii) evaluate the thirteen proposed freshwater KBAs against the KBA Global Standard and with the benefit of updated information on the relevant KBA trigger species;
iii) raise awareness and capacity for KBA designation in 6 countries of the hotspot and;
iv) demonstrate how the information can be used to identify a network of sites to best represent freshwater biodiversity throughout the hotspot.
Working through IUCN’s regional offices we will then ensure the findings are communicated to those NGOs involved in: i) conservation actions on the ground, ii) conservation planning at the National level, and iii) private sector companies interested in minimising their impacts on freshwater biodiversity. The project findings will also help donors, such as the Critical Ecosystem Partnership Fund (CEPF), direct their support to those species and sites in most need of conservation or restoration actions.
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Chapter 2
Assessment methodology
Starnes, T. 1, Sayer, C.A. 1
Contents
2.1 Selection of priority taxa ...15 2.1.1 Fishes ...15 2.1.2 Molluscs ...16 2.1.3 Odonates ...16 2.1.4 Decapods ...16 2.1.5 Plants ...17 2.2 Nomenclature ...17 2.3 Species mapping ...17 2.3.1 Range restricted species ...18 2.4 Assessment of species threat status...18 2.4.1 Data collation and quality control ...19 2.5 Red List Index ...19 References ...20
2.1 Selection of priority taxa
In the majority of cases, large-scale biodiversity assessments have focused on a limited range of taxonomic groups, most often including those groups that provide obvious benefits to humans through direct consumption, or the more charismatic groups, such as mammals and birds. In the case of aquatic systems, wetland birds, amphibians and fishes have received most attention. However, it is important that we take a more holistic approach by collating information to conserve other components of the food web that are essential to the maintenance of healthy functioning wetland ecosystems, even if they are neither publicly charismatic nor often noticed, as is generally the case for submerged species. As it is not practical to assess all species, a number of taxonomic groups have been prioritised for comprehensive assessment at the global scale (i.e. assessment of all described species within the taxonomic group on the global IUCN Red List of Threatened Species TM, www.iucnredlist.org) as part of IUCN’s global freshwater biodiversity assessment.
2.1.1 Fishes
Fishes are arguably the most important products (in terms of human use) of freshwater ecosystems at a global scale. In 2016 the total capture of fishes from inland waters globally was 11.6 million tonnes and this represents an 11% increase in comparison to the 2005–2014 average (FAO, 2018). Within
Africa, which accounts for 25% of global inland catches (FAO, 2018), fishes provide an important food source for over 400 million people and contribute essential proteins, fats, minerals and vitamins to their diets (Heck & Béné, 2005). As well as essential nutrition, this capture provides income for and supports the livelihoods of the poorest of communities, through both consumption and non-food uses (Dugan et al., 2010).
For the purposes of this assessment, freshwater fishes are defined as those species that spend all or a critical part of their life cycle in freshwaters. There are approximately 17,800 freshwater fish species globally (R. van der Laan pers. comm. 2019) and at present, global extinction risk has been assessed for approximately 51% (9,138 species) of freshwater fishes using the IUCN Red List Categories and Criteria (IUCN, 2019). A global freshwater fish assessment is currently under way with the aim of assessing all species for the Red List by 2021.
Lévêque et al., (1990) identified 558 fish species belonging to 180 genera and 61 families in the western Africa region.
This assessment was later updated by (Paugy, Lévêque &
Teugels, 2003), increasing the number of known species in the region to 584, within 192 genera and 64 families. Since 2010 an estimated 13 new species have been described, increasing the number of western African fishes to 597. This includes a number of predominantly marine species which
1 Freshwater Biodiversity Unit, Global Species Programme, IUCN (International Union for Conservation of Nature), David Attenborough Building, Pembroke Street, Cambridge, CB2 3QZ, UK
are also found in brackish water. In this current report we focus only on the freshwater fish species of which there are 555 species, from 164 genera and 49 families now recorded from western Africa. Of these, 10 species and one sub-species are not native to the region and one sub-species is a misidentification. The current assessment reported here focuses on described native species only.
2.1.2 Molluscs
Freshwater molluscs are one of the most diverse and threatened groups of freshwater taxa, and were found to be the group most at risk of extinction and most poorly known in the continental African assessment by Darwall et al. (2011), with 29% of species assessed as threatened and 30% assessed as Data Deficient (DD). Freshwater molluscs are mostly unobtrusive and are not normally considered to be charismatic, rarely attracting the attention of the popular media, unless in a negative light as some species are vectors in the transmission of human and livestock parasites and diseases. This is unfortunate as freshwater molluscs play a vital role in the provision of ecosystem services and are essential to the maintenance of wetlands, primarily due to their contribution to water quality and nutrient cycling through filter-feeding, algal-grazing and as a food source to other animals (Howard & Cuffey, 2006; Vaughn, Nichols &
Spooner, 2008; Vaughn, Gido & Spooner, 2004).
There are some 6,000–7,000 freshwater mollusc species described globally (MolluscaBase Eds., 2021). At present, the global risk of extinction has been assessed for approximately 57% (3,688 species) of described freshwater mollusc species on the IUCN Red List (International Union for Conservation of Nature (IUCN), 2021). The extinction risk of 83 species of freshwater mollusc native to the western Africa region was assessed according to the IUCN Red List Categories and Criteria (IUCN, 2012). A further 17 species had recently been assessed and were included in this report.
2.1.3 Odonates
Larvae of almost all species of dragonflies and damselflies (order Odonata) are dependent on freshwater habitats. The habitat selection of adult dragonflies strongly depends on the terrestrial vegetation type, and their larvae develop in water where they play a critical role with regards to water quality, nutrient cycling and aquatic habitat structure.
The larvae are voracious predators, often regarded as important in the control of insect pest species. A wide array of ecological niches is represented within the group and, as they are susceptible to changes in water flow, turbidity or loss of aquatic vegetation (Trueman & Rowe, 2009), they have been widely used as an indicator of wetland quality. There are approximately 6,300 extant described species of odonate
but, even though the group is well studied and relatively easily surveyed, it is believed that the actual number is closer to 7,000 species (Kalkman et al., 2007). At present, the global risk of extinction has been assessed for 85% (5,342 species) of described odonates (IUCN, 2021).
Odonate species selected for inclusion in this report encompassed all 307 species assessed on the Red List with all or part of their mapped range within the western Africa assessment region. This included 249 species with mapped ranges and a further 58 species with distributions
Odonate species selected for inclusion in this report encompassed all 307 species assessed on the Red List with all or part of their mapped range within the western Africa assessment region. This included 249 species with mapped ranges and a further 58 species with distributions