Fieldwork in riparian forests

Fieldwork around Kitui, along Nzeeu and Kalundu river was conducted from 11th-27th March 2016 together with students and scientists from Germany and Kenya; developing and set-up of our study-design, collection of data, data preparation and provisional data analysis and data interpretation. Conclusive data analyses will be conducted in Germany.

The two selected rivers south of Kitui, Nzeeu and Kalundu river, tributary streams to the Athi river system, are important life-lines (for many animal and plant species), but also provide important ecosystem services for the human being, setteling along these rivers. The former riparian vegetation became strongly degraded due to human demographic pressure and caused a subsequent transformation of indigenous riparian vegetation into agricultural plots. In the meanwhile, major proportions of former riparian vegetation became invaded by the exotic plant species Lantana camara. Apart from direct destructions of former habitats, climate change (dryer and warmer climatic conditions) are assumed to negatively affect this region. These factors strongly modify and shape the current environmental conditions in this semi-arid region, which negatively affect food security and ecosystem functions, as well as the persistence of many endangered plant and animal species (see Habel et al. 2015).

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Riparian forests provide important linear corridors throughout semiarid savannas of East Africa. Some species can exclusively found in this vegetation type. However, rapid habitat destruction caused a severe decline of biodiversity, like a loss of many typical riparian forest species. Various studies indicate a significant relationship between species´ abundance and population density. In consequence, landscapes of low quality may finally loose a major proportion of its pristine biodiversity, as observed for the Kenyan endemic Hindes Babbler, Turdoides hindei (Habel et al. 2015).

Apart from the provision of pristine habitat structures for endangered species, still intact reparian forests provide various important ecosystem services and ressources for the local human population: Ground water (for food crop production), fertile soil as well as soil to produce bricks, wood for charcoal and brick production as well as for timber. Thus, the preservation of intact environments along streams are of relevance for both – endangered species and the human being. Thus, integrative conservation strategies considering both (nature and human) are crucial.

Due to the rapidly growing human population in Kenya (particularly along rivers), riparian vegetation occurs today in small and isolated remnants. This trend negatively affect habitat availability, habitat quality, and various ecosystem functions. Previous studies showed that especially riparian habitat specialists (adapted on riparian vegetation) suffer under ongoing habitat destrcution as most of potentially remaining habitat patches are too small and isolated, and thus are no more suitable for many species (potential versus effective habitat size) (more details see Habel et al. 2015). This may finally lead to a complete loss of a major proportion of biodiversity, and to a severe reduction of life-quality for the local human population. The following figure indicates suitable habitat patches (in orange and red) for four riparian bird species – T. hinde is the most specialised bird species and thus is assumed to suffer the most under ongoing habitat deterioration.

SDMs_Drei Flüsse_Vier ArtenDespite ongoing habitat destruction, the riparian vegetation still holds highly diverse biodiversity. During an ornithological excursion along Kalundu river we found more than 60 bird species in only three hours. In the meanwhile, some of these bird species are using the exotic invasive Lantana camara thicket as surrogate habitat, even the highly endangered Kenyan endemic Hindes Babbler Turdoides hindei (Teucher et al. 2015). However, to ecological value of exotic invasive species and its general relevance to act as novel ecosystem remains questionable, especially when focusing on the mass of biodiversity – arthropods.

During the following two weeks we divided the participants into five working groups, supervised by five German scientists, and supported by collaborators from Kenya: Social sciences (Rebecca Rogers), Land cover mapping (land cover change detection) (Mike Teucher), vegetation ecology (Christine Schmitt), Rapid Ecosystem Function Assessment REFA (Sebastian Meyer), and animal ecology (Jan Christian Habel). Data assessments were conducted by nine German students (Lisa Otten, Dennis Saler, Jana Holler, Dominik Meyer, Vinzenez Eichinger, Wieland Feuerabendt, Rebekka Honecker, Marie Heuberger, Christine Geelhaar, see picture below, with Jan C. Habel and Onesmus Kioko) and four Kenyan students, two from SEKU (Jane Evelyn Mutunga and Mery Cheruto), and two from PU (Mwanzi Obeka Bonventure and Agnes Koamboka Ombati). Furthermore, four researchers and technicians from the National Museums of Kenya and from SEKU assisted us in the field: Morris Mutua, Kennedy Matheka and Onesmus Kioko from the NMK, and Danson Maseka Kioko from SEKU.

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Further details on distinct working packages and the repsective field work are explained in the following:

Land cover mapping: High resolution, georeferenced aerial pictures were produced along a 15km strip of Nzeeu and Kalundu river, covering 300m river banks on both sides of the rivers. Data collection was split into more than 100 flight missions. This detailed land cover assessment was performed with a DJI Phantom 2 quadrocopter and a GoPro HERO 4 camera. This dataset will create important background information for many other working packages, but also forms an independent research package, which evaluates the degree of vegetation degradation and the spatial configuration of the remaining riparian thicket patches. Temporal comparative analyses on land cover changes will be analysed using historical aerial pictures, taken by the British Royal Airforce during the 40s, 60s and 80s (picture below – remark: Nzeeu river on the left, Kalundu river on the right, with Wikililye in the centre), kindly provided by the Survey of Kenya.kitui_15_2862Animal ecology: In the animal ecology working package we mainly focused on habitat needs and the movment behaviour of selected riparian bird species. We used VHF telemetry (Pib-tags) to track 11 typical riparian bird species over a period of two weeks. Based on these occurence points (from triangulation), in combination with the detailed land cover map (provided from the working package described above), we will be able to detect potential barriers and corridors for these species. One of the targeted species here was the highly endangered Kenyan endemic Hindes Babbler Turdoides hindei. These data will allow to evaluate habitat preferences and might provide valuable information about how to design human-wildlife-corridors along rivers of semiarid south-east Kenya.

Rapid Ecosystem Function Assessment: Intact functions in an ecosystem are the pre-requisite for both, high quality habitats for endangered, endemic species as well as for ecosystem services used by the local human population. A rapid ecosystem function assessment describes the condition of an ecosystem by assessing selected parameters. REFA protocols, developed by Sebastian Meyer, are cost and time efficient and thus can be applied easily all over the world (in terrestrial but also marine ecosystems, see Lefcheck et al. 2016). The REFA working group set 90 20x20m plots along the Nzeeu river, with 100m distant from each other. The following parameters were collected: abundance and biomass by measuring seed removal and collecting flying arthropods with pan traps (see pictures below), biomass of ground dwelling arthropods using pit fall traps, and the degree of predation with artificial caterpillars.

Vegetation ecology: Vegetation structure and species composition were assessed along 100m transects, 300m distant from each other. Species assessments were conducted at Nzeeu and Kalundu river (a comparative approach, with Nzeeu river being highly degraded and Kalundu river still representing intact pristine vegetation structures). As plant diversity is very high, only woody species with dbh (diameter at breast height) considered. Based on these data the group is interested to analyse (i) the degree of invasion by exotic plant species and (ii) the legacy of former pristine vegetation still available in highly degraded environments. This working package was conducted under supervision of Christine Schmitt, in collaboration with scientists from National Museums of Kenya.

Social sciences: 200 interviews were conducted with farmers cultivating along the Nzeeu river. 50 farmers were interviewed randomly and anonymously in each of 4 pre-defined zones (covered by the land-mapping of the drone – see above). The questionnaire was designed to gain knowledge on four main issues: 1) Socio-demographic data of farmers and side conditions (age, gender, education, children, landownership); 2) Land-use (production of goods, reasons for production, size of fields, problems of farming); 3) Awareness & Attitudes (familiarity with conservation terms, environmental awareness, attitude towards protection of species, information/media usage); 4) Willingness (Effort to protect nature, willingness of changing farming techniques, involvement in protection actions along the river). Two teams of students were conducting the interviews – each team consisted of 1 Kenyan and 1 German student. Special thanks goes to the two Kenian students and the German TUM students, particularly to Christine Geelhaar, for their strong commitment. Besides the 200 interviews, we also got 3 experts to answer questions on the current management situation of the Nzeeu river.

What was remarkable was the kindness of participating farmers and their families. Only one out of the 200 approached farmers was not willing to undertake the questionnaire. All other participants placed chairs for all of us to sit and we received a great variety of fruits. Many times, the group sitting around us grew fastly, as neighbours and family members came to see what was going on. We enjoyed the discussions and amazing hospitality of the people and hope that our results and insights will help to develop effective and sustainable management strategies to ensure both: the protection of the highly valuable nature and the fulfillment of people’s needs.

In a next, concluding step, each working group will analyse their data and will subsequently combine the own data-set with the findings from other working packages – to profit from potential synergies. This will allow to improve the explanatory power of single working packages and will produce a complete picture on human needs and nature conservation for this region. Joint-data-sets will allow to indicate potential knowing-doing-gaps, and to analyse the relevance the gap between institutions and the local people. Joint data-sets will give valuable indication on potential ecological effects from habitat destruction and degradation on (i) ecosystem functions (and subsequent life quality), (ii) vegetation structure, and (iii) the persistence of biodiversity.

Finally, we will translate these scientific findings into practical advices: How to improve the environmental conditions (and thus human livelihood) along such rivers. Particularly we are interested to recommend specific pristine tree species which are useful for the local human population (ecosystem functions and the cultural legacy) and which also provide important habitat structures for rare species (evidences from animal and vegetation ecology). Practical management advices will be elaborated hand in hand with local insitutions, as the National Environmental Management Authority, NEMA, the Kenyan Forest Service, and other stakeholders located in the Kitui County. IMG_7933During the stay in the field, the students were hosted in a local Kenyan family, the Mutuas, located in the middle of our study region. We would like to thank for their great hospitality throughout the time, and the unique chance for sharing the Kenyan way-of-life with us!

We are looking forward having a second fruitful activity very soon in Freising, Germany!