North Africa in particular is considered the poorest of all African sub-regions in terms of water resources. Except for the Egyptian Nile River Basin, permanent rivers can only be found in the northern part of Morocco, Algeria and Tunisia. Moreover, the increasing demand on water, strictly linked to economic and demographic developments, constitutes a major pressure to these ecosystems. The need to integrate freshwater biodiversity considerations and improve data availability to decision makers for development and planning processes is therefore a priority for sustainability in the short, medium and long term.
North Africa Freshwater Biodiversity
Freshwater habitats and biodiversity are recognized to be under serious threat at global level. Monitoring freshwater basins is therefore important to prevent the loss of these ecosystems. In this assessment, five freshwater taxa, representing a range of trophic levels within the food webs that support wetlands, have been selected in order to evaluate the status and distribution of northern African freshwater biodiversity and, as a consequence, the quality of northern African basins.
Freshwater fish, molluscs, dragonflies and damselflies, crabs and aquatic plants have been identified as priority taxa representing the food web and indicators for the overall conservation status of wetland ecosystems. Regional and international experts in collaboration with the IUCN Species Survival Commission (SSC) Specialist Groups participated in a preliminary workshop in Rabat (Morocco, February 2007) to collect available data from existing literature on these selected species. Two experts evaluation workshops were then held, one in Porto (Portugal, October 2007) and one in Tabarka (Tunisia, February 2009) to contrast the information, which was then standardized by the IUCN Red List Unit and the Mediterranean Species Programme according to the 2001 IUCN Red List Categories and Criteria: Version 3.1 (IUCN 2001).
The tables below show the classification for the North African freshwater groups assessed at the regional scale. Among the 877 evaluated taxa, 247 (28%) are listed as threatened with extinction, out of which 7% are Critically Endangered (CR), 8% are Endangered (EN), and 13% are Vulnerable (VU); of these threatened taxa 45% are freshwater molluscs, 27% freshwater fishes, 24% dragonflies and 24% aquatic plants. Of the total number of taxa assessed, 9% is Near Threatened (NT), 42% is Least Concern (LC), and 14% is classified as Data Deficient (DD). If compared to similar evaluations implemented in eastern Africa (Darwall et al. 2005) and southern Africa (Darwall et al. 2008), North Africa results have revealed that it is the region with the highest known rate of extinction for freshwater species in the African continent: 2% (1 fish and 17 molluscs) of species native to the region are already extinct at the global level, and 4% are no longer present locally. Moreover, almost half of the 199 (23%) endemic species are threatened with extinction.
Freshwater species richness
The most important areas having the highest number of freshwater species assessed are the Middle and High Atlas and the Riff mountains in Morocco, with 385 species; the Subtropical Numidia, with 344 species; and the Egyptian Nile River with 268 species.
Distribution of threatened species
The most important areas in terms of the number of threatened freshwater species are in the North of Morocco and the Atlas mountains, hosting 53% of the species assessed as threatened; the northern coasts of Algeria and Tunisia, with 25% of the threatened taxa; and the Nile River basin, in the southern part of the assessed region, with 13% of the threatened taxa.
Distribution of endemic species
Endemicity in the region is strictly linked to aquatic plants, freshwater molluscs, and freshwater crabs, which are the groups with the highest proportions of unique species. In the Middle and High Atlas, in the Betico-Rifan arc in Morocco, the Kabylia-Numidia region in Algeria and the Kroumiria Mountains in Tunisia, 54% of the regionally freshwater endemic species are present. In spite of these areas being theoretically placed under protection through the establishment of parks and natural reserves, the level of effective protection is often low and degradation sometimes very significant.
Distribution of extinct species
The Nile River basin stands out for being the region where the highest number of North African species has gone extinct, with a total of 28 species.
Habitat loss and degradation: The excessive use of underground water for domestic, industrial and agricultural purposes has resulted in an increase of underlying saline waters and has led in many occasions to the degradation and final disappearance of surface water bodies. Moreover, the construction of dams regulating the few large river systems in the region affects almost 14% of the freshwater species assessed. In total, 207 freshwater taxa are at risk of extinction due to habitat loss and degradation in North Africa; in the Maghreb, large scale river habitat destruction due to excessive water extraction has already reached catastrophic proportions, with a 34% of the threatened freshwater species found to be affected by this.
Pollution: Pollution has been identified as the second most important cause of freshwater species extinction in the region, affecting more than half of the regionally threatened fauna and flora assessed. In the areas where its impact is higher due to uncontrolled waste disposal from agricultural, domestic and industrial human activities, ground and surface waters suffer an increase in nutrients’ concentration. This brings about an excessive growth of algae which, depleting the water of available oxygen, cause the death of many species inhabiting the basin (a phenomenon known as (eutrophication).
Natural disasters: Increasingly frequent and severe drought and flooding episodes, which bring further sediments into freshwater areas, are putting aquatic habitats under a strong pressure. Up to 26% of the threatened species assessed are currently affected by droughts and this tendency is likely to continue in the future with climate changes.
Human disturbance: As a result of tourism and outdoor recreational activities, human disturbance has been identified as a relevant cause of threat affecting 24 aquatic plant species (11% of the threatened species).
Changes in native species dynamics: Aquatic plants living on the ground are the most affected, as they have to compete for space, light and soil nutrients.
Harvesting and over-exploitation: Over-fishing is threatening at least 5 species of freshwater fish in the region, as some have a commercial value at local and national level, and for exports. Over-harvesting threats also 23 aquatic plants, 6 of which are classed as threatened.
Invasive alien species: Invasive alien species have a considerable impact on some indigenous species, through competition for resources, predation, as well as food competitors. They can also breed with native species producing individuals called “hybrids” (phenomenon known as hybridization).
Conclusions and recommendations
The study on freshwater biodiversity in North Africa has brought to life the high level of threat and endemism of freshwater species present in the North Africa region. The percentage of species regionally threatened is very high (28%) and this stresses the fact that freshwater species are facing serious challenges. Furthermore, North Africa biodiversity displays a high concentration of endemic species, a 47% of which is threatened with extinction. The alarming status of these species in the region is an indicator of the degraded status of their freshwater habitat and highlights the responsibility of North African countries to develop and implement conservation actions to preserve these essential resources. The main conservation priorities identified to preserve North African freshwater species from extinction are:
- Applying the Integrated River Basin Management (IRBM) approach to ensure the future of rivers and wetlands;
- Adopting sustainable agricultural and waste management techniques to reduce water pollution;
- Enforcing legislation to protect threatened freshwater species and their critical habitats;
- Preserving habitats and species by identifying Key Biodiversity Areas to protect;
- Raising awareness on the importance of biodiversity data to promote a sustainable use and management of wetlands;
- Increasing research efforts, in particular on the species assessed as Data Deficient.