Invasive Futures

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.