Reconciling population and biodiversity in Lake Manyara basin, Tanzania

The Lake Manyara Basin is a biodiversity hotspot that is also economically important in the context of local food supply and tourism. Different parties (local users, nature conservationists, politicians) have various interests, leading both to ecosystem threats and social issues linked to land and water use. The management concerns have been addressed in a study led by Luc Janssens de Bisthoven (CEBioS, Royal Belgian Institute of Natural Sciences) within the framework of UNESCO’s MAB (Man and Biosphere) programme aiming to sustainably develop sensitive areas. Water use and distribution, participation of all interested parties and governance were identified as key priorities to be developed in order to evolve towards a management that is owned by all parties involved and has a positive impact on the sustainable development of the Lake Manyara basin.

Lake Manyara Workshop with all parties involved © RBINS/CEBioS

Lake Manyara is a shallow saline lake with a varying surface (maximum 480km2) in the heart of the Lake Manyara UNESCO Biosphere reserve in the Northern Tanzanian Rift Valley. It is situated in a closed basin with no natural outlet, that is being fed by 9 rivers. The Lake Manyara National Park is a well-known biodiversity hotspot. Being home to more than 390 bird species, it is classified as an Important Bird Area. Around 200 mammal species occur in the Park and a list of endangered fish species roam the waters.

The observation of natural diversity can also be combined here with visits to the iconic Maasai pastoralist communities. Therefore, it is no surprise that the Lake Manyara National Park is part of the famous ‘Northern safari circuit’ that attracts many tourists every year, contributing to the region’s economic development.

Malachite Kingfisher, Lake Manyara National Park © RBINS/CEBioS

The Manyara Management Challenge

However, the management of this lake has proven to be a challenge since it is also an epicenter of human activity with about 18 000 inhabitants (2015 census) around the lake depending on it. The lake itself is used for fishing, the North and the rift valley to the South of the lake are characterized by irrigation  agriculture, the uplands all over the catchment area are mostly used for rain-fed agriculture by various ethnicities, and the drier savannas are used for cattle grazing by pastoralists (mainly Maasai). While Lake Manyara is thus crucial to the region, it has been shown to suffer from issues of social, economic and environmental nature, such as decreasing water levels, erosion, and water and land conflicts.

The observed problems affect both the biodiversity (e.g. mass mortality of flamingos and other species that depend on the lake) and the social and economic situation. This creates a vicious circle in which water conflicts between livelihood groups and between humans and wildlife increase, and the revenue of tourism is also reduced. This in turn influences people’s acceptance of nature conservation actions.

Brainstorm during a Lake Manyara Workshop with all parties involved © RBINS/CEBioS

Identification of Issues and Solutions

The challenge for scientists and managers lies in reconciling the needs of the local population with the need for the protection of biodiversity. The research that was conveyed in order to identify key actions for the development of the Lake Manyara Basin suggests a unique plural and multifocal approach. This was the outcome of two participative workshops in December 2015 and 2016 that gathered 40 participants and 13 structures from several scientific disciplines, NGOs, local user groups and managers. Together, the participants identified 12 issues which have to be addressed: demographical factors, siltation, erosion, river dry-up, deforestation, destruction of water sources, human activities near the lake, water capture before the water reaches the lake, heavy rainfall causing erosion, evaporation, trampling and grazing. Subsequently, a decision support system in service of an integrated management plan was suggested. The results were published in the Journal of Environmental Management in April 2020.

Co-management and Conservation

The analysis showed that water use and distribution, participation of all interested parties and governance are the aspects that should be prioritized. The fact that there is no dedicated Manyara water board and that the Manyara catchment basin is managed by different authorities (with different spatial and functional scales) leads to discrepancies in management options. This leaves the door open to a grey zone of interpretation and enforcement and may result in corruption and land use conflicts.

“Our study aims to provide a continuous boost to encourage all parties to mobilize adequate national and international policies and resources. This should be done in a context of trust or ‘honest advocacy’ to develop a decision support system with a holistic and transformative vision.” states Luc Janssens de Bisthoven, lead author of the paper and coordinator of the CEBioS programme (Capacities for Biodiversity and Sustainable development) of the Royal Belgian Institute of Natural Sciences. “This is the only pathway towards management owned by all parties involved and with a positive impact on the sustainable development of the Lake Manyara basin”.

Hippopotamus, Lake Manyara National Park © RBINS/CEBioS

The paper on the social-economic situation of the Lake Manyara Biosphere Reserve in the Journal of Environmental Management is the outcome of a VLIR-UOS funded North South Project promoted by Prof. Luc Brendonck (KU Leuven) and co-promoted by Luc Janssens de Bisthoven (CEBioS), and part of the EVAMAB activities financed by BELSPO to support the UNESCO Man and the Biosphere Programme. The work also included researchers of UHasselt, the Open University of the Netherlands and others.

Results of temperature measurements at lake Nokoué


Reporter Katrijn Baetens

The team got back to the lake the 11th of November to pick up the thermometers left at the three stations. The one at the yatch club unfertunately was not sealed properly, so no data could be retrieved. Also the one at the west of the lake did not provide us with good data, here the issue was a malfunctioning of the thermocouple itself. The data logger in the center gave results for 7 days, the light was not switched on when retrieved, this sensor used rechargeable batteries.

The results of the 6 day temperature measurements:


Temperature evolution in the center of lake Nokoué Benin, Oct 2019
Average daily temperature and precipitation in Cotonou October 2019

From the results it is clear that their is mostly a clear day-night cycle observed in the surface temperatures of the lake except during the night of 17 and 18 October. The average temperatures of the atmosphere in the region did not explain why there was a decrease in overall surface temperature, an increased precipitation rate could have induced the observed temperature drom. Further research is necessary.

Our first experiences with the Arduino based equipment are good, however, to compete with the professional equipment , a better solution for powering the device should be found. Also proficient care should be given to sealing up the system and making sure the sensor is properly working.

Reanalysis of the first results

Sunday 13th of October 2019

After 10 busy days full of working and adjusting our work, we finally managed to make the temperatures measured at the port presentable and in a good format.

After ten days of hard work the team (Zacharie, Katrijn, Sylvain, Wilfried, Medard and field expert Victor) finally have the confidence to test there sensors in the field

After reanalysing the data of 3 and 4 October and comparing them with the GPS shield output we can come up with the following results:

Results of the sensor left at the port of Cotonou

The conclusion of these measurements is that the system is too unstable to produce good results and the gps module uses a lot of battery. After removing the GPS module and stabilizing the system we found the following results:

The conclusion of these measurements is that the addition of shock absorbers  proved very beneficial, there was one power cut that happened during the recollection of the system. The results can be positioned in time in a reliable manner.

On monday, when we will analyse the results gathered during the weekend, we will see if these conclusions can be hold in a real experimental set up.

Putting the system to the test

Friday, October 11th 2019

Report and pictures: Medard Honfo, Katrijn Baetens

After several days of preparation, a stable system was developed so we have the confidence to put the system to the test on the lake itself. After the last verifications our team (Zacharie Sohou, Katrijn Baetens, Medard Honfo, Sylvain Amoussou) and Mr Victor Okpeitcha,an oceanographic ingeneer of IRD/IRHOB took “une pirogue”, a local type of boat, to deposit three thermometers. The stations were next to existing stations of IRD/IRHOB, this will help the validation of our system and avoid double work.

Map of the positions were the sensors are released.
Station 1 (yellow) in the middle of the canal.
station 2 (orange) in the middle of the lake, this was not evident, luckily we got help from local fishermen
Station 3: A permanent station installed by IRD/IRHOB (blue)

Methodology used to install the sensors:

Step 1: fix a perforated pipe in the water

Step 2: Put the sensor inside, the sensor will float on the water

Step 3: close the system and put a lock on it

Fixing the sensors was not always straightforward

Production of more sensors and connection to the internet

Thursday October 10th 2019

Reporter: Wilfried Sintonji

Photos: Katrijn Baetens et Wilfried Sintonji

Today the students working on this project have assembled and configured their sensors independently. They also tested other types of containers made of local materials.

The new container type indeed was waterproof
The students working together to get the configuration of their sensor right.

Today we finally managed to attach the module system to our sensor, unfortunately we did not arrive to make it reliable enough to attach it to the operational system.

The first succesfull messages sent by the sensor

We ended the day by recollecting the second testtype we deposited at the port yesterday.