CRC TRR 228 Project B01

Invasive Futures

The social ecology of rangelands in changing savanna ­environments

B01 Invasive Futures

Project Summary

The stewardship of rangelands in Africa is undermined by overstocking and land degradation, entailing the potential collapse of the existing social-ecological rangeland system. One key factor of rangeland degradation and key driver of their conversion to other land uses is the spread of alien invasive plant species that affect both the environment and pastoral livelihoods. Invasion has been observed to massively accelerate in recent years, with land management, conditions of water availability, and soil fertility shaping the observed spread dynamics. In addition, factors such as policies (Act to sedentarize nomadic pastoralists, Land Act), physical insecurity and violent conflicts, as well as infrastructure developments (road construction, geothermal development and associated “infrastructuring”) are likely to drive system shifts, which, in turn, may accelerate invasive spread dynamics.
The seasonal availability and quality of pasture are increasingly restricted by the expansion of crop agriculture and the establishment of wildlife conservancies. Further, rainfall variability drives seasonal and inter-annual variability in the availability and quality of forage. In addition, the undesired spread of the exotic invasive plants Parthenium hysterophorus, Opuntia spp. and Prosopis juliflora is negatively affecting (agro-) pastoral livelihoods in the Kenyan Rift Valley. Alien plant invasion thus impacts current and future land uses, accelerating social-ecological transitions in future crop- and rangelands.

Research Regions: Lake Baringo Area, Kenya

Traditional rangeland management systems in Kenya generally, and in the Baringo basin specifically, have been exposed to considerable external pressure as well as system-immanent drivers for change such as rangeland degradation and changing aspirations of the land users. Undesired spread of alien plant invasion impacts on current and future rangeland uses accelerating social-ecological transitions in the rangelands. Closely linked to the undesired spread of alien plant species, is the invasion by emerging vector-borne human and animal diseases while a number of other (mainly woody) unpalatable species is negatively affecting livestock mobility. Plant invasion (and the related spread of other harmful organisms) becomes thus a key element in future-making that will affect economic mobility and accelerate social-ecological transitions in future rangelands.

  • Which attributes and management practices favour enhanced invasion of alien plant species?

 

  • How does invasion affect the productivity of crop- and rangelands (forage availability and quality, crop yields)?

 

  • Which economic constraints, risks and opportunities affect aspirations and future-related behaviour (economic mobility)?

 

  • Which feedback processes and patterns of transformation emerge and how do poverty traps constitute barriers for future-making capacities (future rangelands)?
  • Analysis of digital elevation models
  • Monitoring of wells
  • Remote sensing soil moisture assessments
  • Field surveys
  • Geostatistical modelling
  • Isotopic analysis of topsoil organic matter
  • Mass-spectrometric analysis of stable isotopes
  • Analysis of fast-moving ecological threats (locusts and fall armyworm)
  • Behavioural-economic experimetns

a) Invasive spread: Prosopis has been established in the area since the 1980s. It is mostly found in the seasonally inundated plains, where 65% of households report being infested. Grazed pastures had much higher infestations than frequently cropped farmlands, and semi-nomadic pastoralists and agro-pastoralist households were more impacted by Prosopis infestation than cropland farmers.

Parthenium was reported by most pastoralists and many crop farmers to be an emergent problem in the area. It invades mainly moist places, along irrigation and drainage channels, and as ruderal plant along roadsides (water runoff from tarmac roads create moist niche environments). Parthenium is likely to expand north of Marigat supporting progressing infrastructure development and system shift from (agro-)pastoralism towards sedentary crop cultivation.

 

b) Environmental attributes: Results indicate that high stand densities or recent spread dynamics of Parthenium and Prosopis are closely linked with high soil moisture or with larger quantities of available water in the environment. Thus, seasonal dynamics of soil moisture are related to dynamics in seed germination, growth, and stand densities of the invasive plants. The relation between species vigor and recent spread dynamics appears further to be associated with soil fertility attributes such as relatively high soil C and N contents, with low C:N ratios in the soil organic matter, and, to a lesser extent, with plant available P.

 

c) Impact on households and livelihoods: An economic survey collected attributes of 530 households and aspirations of farmers and (agro-)pastoralists in the face of these invasive species and the related livelihood threats. Households generally aspire beyond their current status regarding income, assets, livestock, and social status. However, ecological shocks such as massive invasion dynamics of Prosopis and the emerging spread of Parthenium have negative effects on aspirations. Education, access to agricultural extension services, and households’ wealth status are additional determinants of aspiration formation. Cooperative membership contributes positively to the formation of income and asset aspirations.

 

d) Response strategies and land-use patterns: Coping with risks and uncertainties entails changes in livelihood strategies and shifts in production systems. Preliminary observations indicate that practices of future-making appear to be dominated by shifts from pastoral land use towards agro-pastoralism or even intensive crop farming. The extent of livelihood shifts further appears to depend on resource endowments and on physical, social, and educational infrastructure with better-off actors acting as pacemakers.

The integrated agro-economic project on invasive futures is linked to several CRC projects – such as “Future roads” (B05) which will together study the effects of progressing infrastructure developments around Lake Baringo on the spread dynamics of invasive plants and the effects of invasive spread dynamics as push - pull factors for system shift. A GIS-based analysis of soil-moisture maps and road constructions will provide input to the model for explaining current and projecting future invasive-species distribution. Together with project on “Future Infections” (B02) the project will use the invasive-spread mapping to target studies on vector populations for of arboviral spread and the emerging risks. Invasion-related arboviral infections may constitute an additional push force that can accelerate land-use changes.

Publications


Alvarez, M., Heller, G., Malombe, I., Matheka, KW, Choge, S. &

Becker, M. 2019. ‘Classification of Prosopis juliflora invasion in the Lake Baringo basin and environmental correlations’. African Journal of Ecology vol. 57(3), pp. 296-303. DOI

Alvarez, M., Curran, M. & Malombe, I. 2021. SWEA-Dataveg: A vegetation database for sub-Saharan Africa. Vegetation Classification and Survey. DOI

Agha, SB., Alvarez, M., Becker, M., Fèvre, EM., Junglen, S., Borgemeister C 2021. ‘Invasive alien plants in Africa and the potential emergence of mosquito-borne arboviral diseases—A review and research outlook‘. Viruses vol.13, pp. 32. DOI

Tabe-Ojong, M.P. 2022. ‘Ecological shocks and non-cognitive skills: Evidence from Kenya’, Ecological Economics, vol. 194, no. 107330 DOI

Tabe-Ojong, M.P., Hauser, M., Mausch, K. 2022. ‘Does Agricultural Commercialisation Increase Asset and Livestock Accumulation on Smallholder Farms in Ethiopia?‘, The Journal of Development Studies. DOI

Tabe-Ojong, M.P., Alvarez, M., Ihli, H., Becker, M., & Heckelei, T. 2021. ‘Action on Invasive Species: Control Strategies of Parthenium hysterophorus L. on Smallholder Farms in Kenya’, Environmental Management. DOI

Tabe-Ojong, M.P., Gebrekidan, B.H., Nshakira-Rukundo, E., Börner, J., & Heckelei, T. 2022. ‘COVID-19 in rural Africa: Food access disruptions, food insecurity and coping strategies in Kenya, Namibia, and Tanzania‘, Agricultural Economics, pp. 1– 20. DOI.

Tabe-Ojong, M.P., Heckelei, T. & Baylis, K. 2021. ‘Aspiration formation and ecological shocks in Rural Kenya. The European Journal of Development Research. (Online First Articles). Link

Tabe-Ojong, M.P., Mausch, K., Woldeyohanes, T., Heckelei, T. 2021. ‘Three hurdles towards commercialization: Integrating subsistence chickpea producers in the market economy’. European Review of Agricultural Economics. DOI

Tabe-Ojong, M.P. & Nshakira-Rukundo, E. 2021. ‘Religiosity and parental educational aspirations for children in Kenya,’ World Development Perspectives, Volume 23, 100349. DOI

Conferences & Working Papers

Conference contributions / Working papers / Papers under review

Alvarez, M., Kiboi, S., Becker, M. & Malombe, I. 2019. ‘Modelling potential dispersal of Prosopis juliflora in East Africa: Scaling and assembling correlations‘. Presentation at EMAPi, Prague.

Sainepo, B., Alvarez, M. & Becker, M. 2021. ‘Impact of Parthenium hysterophorus invasion on plant species composition and soil properties in grassland communities in the Njemps flats, Kenya’. Paper to be presented at the Joint International Grassland Congress/International Rangeland Congress 2021 virtual conference, August 2021.

Sainepo, B., Tabe-Ojong, M.P., Kiboi, S., Malombe, I., Becker, M., Heckelei, T. & Alvarez, M. 2019. Parthenium hysterophorus in East Africa: a numerical review’. Presentation at EMAPi, Prague, Czech Republic

Tabe-Ojong, M.P., Heckelei,T & Baylis, K. 2020. ‘Aspiration formation and ecological shocks: An exploratory analysis in rural Kenya‘. Paper presented at the Annual Meeting of the American Applied Economics Association (AAEA), Kansas City, July 26-28.

Tabe-Ojong, M.P., Heckelei, T. & Baylis, K. 2020. ‘Collective action and smallholder rural households: Implications for income and asset aspirations‘ Paper presented at the Annual Meeting of the American Applied Economics Association (AAEA) in Kansas City, July 26-28

Tabe-Ojong, M.P., Heckelei, T., Baylis, K. & Rasch, S. ‘How does collective action affect the aspirations of smallholder households?’ (working paper) Access Link

Tabe-Ojong, M.P., Rasch, S. ‘Income aspirations and livestock savings: Evidence of aspiration failure in Kenya’ (working paper) Access Link

Tabe-Ojong, M.P., Ihli, H., Alvarez, M., Becker, M., Heckelei, T. 2021. ‘Action on invasive species: control strategies of Parthenium hysterophorus L. on smallholder farms in Kenya’ (under review) Access Link

Tabe-Ojong, M.P. et al Coping with locusts and COVID-19 in rural Africa: An analysis of household-level coping strategies to food insecurity (under review) Access Link

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Team Members

Eca Bacud Portrait

Eva Salve Bacud

University of Bonn

Katherine Baylis Portrait

Prof. Dr. Kathy Baylis

University of California, Santa Barbara

Matthias Becker Portrait

Prof. Dr. Mathias Becker

University of Bonn

Thomas Heckelei Portrait

Prof. Dr. Thomas Heckelei

University of Bonn

Hanna Ihli Portrait

Dr. Hanna Ilhi

University of Bonn

Hellen Kamiri B01

Dr. Hellen Kamiri

University of Bonn / Karatina University

Daisy-Mutuku-B01

Daisy Mutuku

University of Bonn

Bernice-Sainepo-B01

Bernice Sainepo

University of Bonn

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