Background
Freshwater ecosystems globally face mounting pressures due to climate change, pollution and excessive water abstraction. These ecosystems include intermittent rivers and ephemeral streams (IRES) which periodically cease to flow and may dry up completely during periods of drought. IRES provide water to both humans and wildlife and they also play a vital role in landscape hydrology and ecology, hosting unique flora and fauna. However, compared to perennial rivers, limited information is available regarding their biodiversity and ecology, especially within tropical African countries.
The Lake Manyara Basin in Tanzania, a UNESCO Biosphere Reserve, harbours a diverse array of IRES characterised by their highly variable flows. Little information is available on the biodiversity they harbour or the ecological function they play . There is an urgent need for studies that provide evidence-based scientific insights into the significance and distinctive biodiversity and ecology of IRES. These studies are instrumental in advocating for biodiversity conservation and the sustainable management of these vital ecosystems in the region for improved community livelihood. This project was designed to generate initial data to inform the development of more intensive research; and to engage with local communities to raise awareness of the importance of conserving these vulnerable habitats.
Emmanuel Julius sampling a stream with a kick net
Aims
The project had three objectives -
- To assess the occurrence, species diversity, and community composition of macroinvertebrates in IRES in the Lake Manyara Basin.
- To investigate key environmental factors that influence the macroinvertebrate species diversity, distribution and community composition in IRES.
- To conduct outreach programs aimed at raising awareness about the importance of and promoting the conservation of IRES .
What was done
Field Survey
A field survey was conducted from 3rd to 9th June 2024. Sampling was carried out at 11 sites along the Kiongozi (3), Makuyuni (4) and Tarangire (4) rivers. Water samples were taken and analyses were done for a range of parameters including electric conductivity, temperature, pH, total dissolved solutes, dissolved oxygen and major nutrients. Substrate composition (silt/mud, sand, gravel, cobbles and boulders) and riparian vegetation and land-use were visually assessed. Results from the analyses of water samples showed no significant differences among sites for some of the parameters measured. However, there were inter-site differences in temperature, electrical conductivity and phosphate levels. These differences are attributed to variations in climate and human activities such as livestock grazing.
Macroinvertebrates were collected in a semi-quantitative way using a kick net and following standard protocols. Findings revealed significant biodiversity within IRES, with variations in species composition influenced by water availability, substrate type, and anthropogenic activities. The macroinvertebrates recorded belonged to seven orders, including Odonata (dragonflies and damselflies), Hemiptera (true bugs), Coleoptera (beetles), Diptera (flies), Mollusca (snails), Decapoda (freshwater prawns), and Orthoptera (grasshoppers). Within these orders, a total of 15 families were identified, with notable families such as Gomphidae (clubtails), Notonectidae (common backswimmers), Palaemonidae (prawns), and Thiaridae (snails) being particularly prominent. This diversity reflects the dynamic and heterogeneous nature of the aquatic habitats provided by the IRES.
Conservation Education Workshop
On 2nd August 2024, a workshop on the conservation education of IRES was conducted at Tanzanite Hall, Makuyuni. The main objective of the workshop was to enhance awareness about IRES, their biodiversity, socio-ecological importance, threats they face, and potential conservation measures. The workshop brought together 33 stakeholders from diverse organizations, including Ward and Village Executive Officers, Village Environmental Committee members, the Tanzania Wildlife Association, Wildlife Management Areas, the Internal Drainage Basin Authority, Monduli and Babati District Councils, NM-AIST, Manyara Ranch, and representatives from local communities. More than 30 percent of participants were women and approximately 20 percent were youth.
Through increased awareness and stakeholder commitment, this workshop marked an important step toward the sustainable conservation of IRES in the region. The workshop underscored the socio-ecological importance of IRES in the Lake Manyara Basin, emphasizing their critical role in supporting biodiversity, livelihoods, and environmental stability. It also highlighted the urgent need to address threats to these ecosystems through collaborative and integrated conservation approaches. Strengthened community engagement, robust policy frameworks, and innovative research are essential to safeguarding IRES for future generations.
Challenges
Certain challenges were encountered during the project. The two main ones were restricted access to some sites and a lack of secondary information to guide activities. Restricted access to National Parks and remote IRES sites meant that it was not possible to make a comprehensive assessment of these ecosystems within the basin, especially given the limited resources and the short time available. The absence of adequate secondary data on river networks, hydrology and eco-hydrological processes of IRES in the basin constrained a thorough understanding of these systems.
Outcomes
The survey identified a diverse range of macroinvertebrates across the surveyed rivers confirming the ecological significance of IRES in the Lake Manyara Basin. The findings provide insights into the taxonomic composition, abundance, and functional roles of the observed macroinvertebrates. The data serves as important baseline information for further research and water management planning in support of environmental conservation.
The stakeholder workshop was successful in raising awareness among local communities and other stakeholders about the value of IRES and the need to conserve them. Several recommendations were made including the need to:
- Advocate for the recognition and integration of IRES into national water resource management policies.
- Establish comprehensive, long-term monitoring programs for IRES to track changes in biodiversity, hydrology, and ecosystem health.
- Expand conservation education initiatives to include a broader range of communities, emphasizing the role of IRES in supporting livelihoods and ecosystem services in the region. Engage local stakeholders in stewardship activities to ensure sustainable management.
- Invest in capacity building by training local scientists and researchers in advanced taxonomy, eco-hydrological assessments, and conservation science.
- Address data gaps by conducting detailed studies on the river networks, hydrological regimes, eco-hydrological processes, and biodiversity of IRES.
- Promote collaboration between government agencies, NGOs, research institutions, and local communities to develop and implement effective conservation and management strategies for IRES.