School of Agriculture, Environment, Water and Natural Resources Management (JA)

Sustainable woodland management and livelihood options in a charcoal producing region: An agent-based modelling approach

Tue, 15 Oct 2019 00:00:00 GMT

Sustainable woodland management and livelihood options in a charcoal producing region: An agent-based modelling approach Kiruki, Harun M.; van der Zanden, Emma H.; Zagaria, Cecilia; Verburg, Peter H. Woodland resources provide livelihoods for millions of people in Africa. Concerns about the impact of human utilization of woodlands have led to vigorous debates on woodland degradation. Ecological and socio-economic empirical data and understanding of the socio-ecological system have been synthesized in an agent-based model (ABM) to explore different woodland management options for a dynamic, semi-arid region in Kenya. In our simulations we accounted for the impacts of drought frequency, charcoal price changes, improved management practices and taxation of charcoal for a 20-year period to assess woodland changes in a spatially explicit way and evaluate the numbers of actors that can benefit from charcoal harvesting as a livelihood option. The model is based on an agent typology derived from 150 household interviews that focused on livelihood strategies and decision-making processes. Furthermore, the model integrates knowledge from vegetation plots and focus group meetings. From the model simulations we learn that favorable prices, improved management and taxation do not directly have the anticipated impact on woodland resources, as the improved conditions lead to fewer constraints on involvement in charcoal making. This reduces the positive impacts of these measures on the woodland quality but, at the same time, allows a larger number of actors to benefit from charcoal harvesting. Results show a very strong decrease in woodland area under the base scenario thereby reducing possibilities for households to supplement their incomes with charcoal making. Increased droughts and low prices for charcoal lead to early depletion of woodlands and reduction in livelihood options. Taxation stabilizes the number of charcoal producers but does not stop the depletion of woodland area. Woodland loss can only be prevented by controlling the number of charcoal makers and the amount of charcoal harvesting. https://doi.org/10.1016/j.jenvman.2019.07.016

Are standard tests sensitive enough to evaluate effects of human pharmaceuticals in aquatic biota? Facing changes in research approaches when performing risk assessment of drugs

Sun, 01 Feb 2015 00:00:00 GMT

Are standard tests sensitive enough to evaluate effects of human pharmaceuticals in aquatic biota? Facing changes in research approaches when performing risk assessment of drugs Aguirre-Martínez, G. V.; Owuor, Margaret A.; Garrido-Pérez, C.; Salamanca, M. J.; Del Valls, T. A.; Martín-Díaz, M. L. Nowadays, the presence of pharmaceutical products in aquatic environments is not only common, but is also of significant concern regarding the adverse effect they may produce to aquatic biota. In order to determine the adverse effects of caffeine (CAF), ibuprofen (IBU), carbamazepine (CBZ) and novobiocin (NOV), at environmental occurring concentrations, standardized endpoints applied in current guidelines were evaluated in four organisms including bioluminescence response in Vibrio fischeri, growth inhibition in Isochrysis galbana (marine water) and Pseudokirchneriella subcapitata (fresh water) and fertilization and embryo-larval development in Paracentrotus lividus. To reach this aim bioassays were implemented by exposing organisms to water spiked with drugs dissolved in DMSO (0.001% v/v). Risk characterization was performed, calculating the environmental impact of drugs by calculating environmental concentration and predicted no effect concentration ratio (MEC/PNEC). Results indicate that acute toxicity was found above environmental concentrations in the order of mg L−1 for bacteria bioluminescence, microalgae growth inhibition and sea urchin fertilization. However, teratogenicity was observed on sea urchin after exposure to environmental concentrations of drugs at 0.00001 mg L−1; at this concentration CBZ and IBU were found to reduce significantly the embryo-larval development compared to controls (p < 0.01). The risk calculated for selected drugs suggested they are harmless for aquatic environment except when applying the embryo-larval development endpoint. Endpoints applied in this study showed the necessity of using more sensitive responses, when assessing risk of pharmaceuticals in aquatic environments, since endpoints applied in current guidelines may not be suitable. https://doi.org/10.1016/j.chemosphere.2014.05.087

Salinity and salt fluxes in a polluted tropical river: The case study of the Athi river in Kenya

Thu, 01 Aug 2019 00:00:00 GMT

Salinity and salt fluxes in a polluted tropical river: The case study of the Athi river in Kenya Kitheka, Johnson U. Study region This study was undertaken in the Athi-Sabaki river basin in Kenya in East Africa. Study focus The study focused on the determination of the influence of streamflow variability on salt fluxes. This involved monitoring of river discharge and river salinity in the period between 2012 and 2018. New hydrological insights : This study demonstrates that Athi-Sabaki river discharges significant quantity of salt to the sea. There are significant seasonal and inter-annual variations in salt fluxes that are due to variations in river discharge and rainfall in the basin. The relationship between streamflow variations and variations of salinity in the river was inverse with highest salinity concentrations and fluxes occurring during low flow conditions. The river salinity and TDS concentrations decreased with an increase in river discharge due to dilution effect and flushing of salt from the river. The highly polluted sub-basins draining through the City of Nairobi exhibited relatively higher salinity and salt fluxes as compared to non-polluted ones draining rural areas. The total salt flux in the basin ranged between 29 × 103 and 261 × 103 tons year−1. The relatively high salinity and salt fluxes were attributed to the discharge of wastewaters, seepage of groundwater and irrigation return flows. The study calls for water pollution control, sustainable irrigation and landuse practices in the basin. https://doi.org/10.1016/j.ejrh.2019.100614

Agroforestry and soil health: A review of impacts and potential for sustainable agriculture

Mon, 16 Feb 2026 00:00:00 GMT

Agroforestry and soil health: A review of impacts and potential for sustainable agriculture Manono, Bonface O.; Mwami, Boniface M. Soil health is the sustained ability of soil to function as a vital ecosystem that supports plants, animals, and humans. Conventional agricultural practices, such as intensive tillage and monocropping, degrade soils by depleting organic matter, causing erosion, and reducing biodiversity. agroforestry systems, by contrast, mimic natural ecosystems and offer a viable solution to restore and protect this crucial resource. The purpose of this review was to explore agroforestry’s effects on soil health in the context of sustainable agriculture. by restoring and building soil health, the review revealed that agroforestry provides a solution to combat soil degradation, enhance biodiversity, and increase agricultural sustainability. Benefits to soil are diverse and include improving its physical, chemical, and biological aspects, which boosts ecosystem services and resilience. despite its clear advantages, agroforestry has not been widely adopted. challenges to adoption include time lag for trees to mature, insecure land tenure and lack of expertise and institutional support. overcoming these barriers through supportive policies, financial incentives and farmer participatory approaches offers clear pathways towards more resilient and profitable farming systems. this will require site-specific studies to optimize species selection and system designs compatible with local conditions. long-term agroforestry success is determined by aligning site-specific conditions (soil, slope, climate) with appropriate species selection, expert management, and farmer knowledge. in conclusion, intentionally combining trees and crops provides a powerful solution for building resilient soil ecosystems and ensuring agricultural sustainability. https://doi.org/10.3390/earth7010031