Mapping wetland characteristics for sustainable development in Harare: The case of Borrowdale West, Highlands, National Sport stadium and Mukuvisi Woodlands wetlands

Wetland ecosystems are under threat from agriculture and urbanisation, affecting water supply and quality in urban areas like the City of Harare. With the need to protect wetlands that remain, the spatial extent of the Highlands, Borrowdale West, Mukuvisi and National Sports wetlands was established. LANDSAT and SPOT Satellite imagery were used to map the spatial extent on the wetlands and to take note of the temporal changes that occurred between 1989 and 2009. Supervised classification was used to classify the images. High resolution Google earth imagery were then downloaded and used as baseline data for mapping the wetlands using the Cowardin wetland classification system 1979 and the Land Capability Classification system for wetness. Maps showing the physical characteristic of the wetlands were then produced. Results indicated that area under wetlands has been shrinking over the years. Using the wetland classification system it was found out that much of the area under wetland should not be used for any other landuse purpose other than wetland protection. However the study found out that urban expansion projects are currently modifying the wetlands. The Highlands wetland has been drained and road construction is currently in progress while a Hotel is under construction on the National sports wetland covering 287 012 m2 of the wetland. This study provides information on the current physical state of the wetlands, which can be the basis for wetland protection and management by policy makers and managers. Key Words:  Wetland, Spatial extent, Physical characteristics, Classification, Landuse, Protection and Managemen

Occurrence and diversity of arbuscular mycorrhizal fungi colonising off‐season and in‐season weeds and their relationship with maize yield under conservation agriculture

Weeds are responsible for major crop losses worldwide but can provide beneficial agroecosystem services. This study aimed to elucidate how arbuscular mycorrhizal fungi (AMF) in weeds respond to host identity and conservation agricultural practices. The study was carried out at two locations in Southern Africa during off-season and in-season maize cultivation. Off-season AMF root colonisation, diversity indices and community composition significantly differed among weed species at both locations. Glomus sp. VTX00280 explains most of the AMF community differences. In-season, implementation of conventional tillage with mulching alone (CT + M) or together with crop rotation (CT + M + R) resulted in a 20% increase in AMF colonisation of the constantly occurring weed species, Bidens pilosa (BIDPI) and Richardia scabra (RCHSC), com- pared with conventional tillage plus rotations (CT + R). The diversity of AMF was highest under no-tillage plus mulching (NT + M). Off-season and in-season AMF structures of both BIDPI and RCHSC were not related, but 39% of the taxa were shared. Structural equation modelling showed a significant effect of the cropping system on weed AMF diversity parameters and weed and maize root colonisation, but no significant influence of weed root AMF traits and maize colonisation was detected on maize yield. This may be explained by the improvement in weed competitive ability, which may have offset the AMF-mediated benefits on yield. Our findings highlight that implementing M and CR to CT and NT positively affected weed AMF colonisation and diversity. The similarity between the off-season and in-season AMF composition of weeds supports the fact that weeds functionally host AMF during the non-crop period

Cyclodextrin-Based Nanofibers and Membranes: Fabrication, Properties and Applications

Cyclodextrin (CD)-based electrospun nanofibers have become critical role players in the water treatment arena due to their high porosities, small diameters, high surface area-to-volume ratio and other unique properties they exhibit. Investigations demonstrate that nanofibers containing CD molecules can be facially blended with other polymeric species and/or photocatalytic and magnetic nanoparticles to enhance their rates of adsorption, inclusion complexation and selective photodegradation. These properties make them excellent candidates for the removal of water pollutants. On the other hand, the electrospinning process has become the method of choice in the fabrication of various types of CD nanofibrous mats due to its versatility, cost-effectiveness and its potential for the mass production of uniform nanofibers. CDs and CD-derivatives have also found application in membrane technologies, particularly in mixed matrix and thin film composite membranes. CD-blended membranes display improved performances in terms of selectivity, rejection, permeation and flux with reduced fouling propensities and can be used for drinking water purification and removal of emerging micropollutants. This chapter critically reviews CD-based electrospun nanofibers looking at their production, characterization methods and various applications. The use of CDs as membrane materials and how they can be fully explored in water treatment are also investigated

Diel activity patterns of vector mosquito species in the urban environment: Implications for vector control strategies

Mathematical models have been widely used to study the population dynamics of mosquitoes as well as to test and validate the effectiveness of arbovirus outbreak responses and mosquito control strategies. The objective of this study is to assess the diel activity of mosquitoes in Miami-Dade, Florida, and Brownsville, Texas, the most affected areas during the Zika outbreak in 2016–2017, and to evaluate the effectiveness of simulated adulticide treatments on local mosquito populations. To assess variations in the diel activity patterns, mosquitoes were collected hourly for 96 hours once a month from May through November 2019 in Miami-Dade County, Florida, and Brownsville, Texas. We then performed a PERMANOVA followed by a SIMPER analysis to assess whether the abundance and species richness significantly varies at different hours of the day. Finally, we used a mathematical model to simulate the population dynamics of 5 mosquito vector species and evaluate the effectiveness of the simulated adulticide applications. A total of 14,502 mosquitoes comprising 17 species were collected in Brownsville and 10,948 mosquitoes comprising 19 species were collected in Miami-Dade County. Aedes aegypti was the most common mosquito species collected every hour in both cities and peaking in abundance in the morning and the evening. Our modeling results indicate that the effectiveness of adulticide applications varied greatly depending on the hour of the treatment. In both study locations, 9 PM was the best time for adulticide applications targeting all mosquito vector species; mornings/afternoons (9 AM– 5 PM) yielded low effectiveness, especially for Culex species, while at night (12 AM– 6 AM) the effectiveness was particularly low for Aedes species. Our results indicate that the timing of adulticide spraying interventions should be carefully considered by local authorities based on the ecology of the target mosquito species in the focus area

Effects of maize residue and mineral nitrogen applications on maize yield in conservation-agriculture-based cropping systems of Southern Africa

Conservation agriculture (CA) and no-till (NT)-based cropping systems could address soil degradation and fertility decline in southern Africa. A multi-location and multi-year experiment was carried out between 2008 and 2014 to assess the effects of different levels of maize residue biomass (0, 2, 4, 6 and 8 t ha−1) and nitrogen (N) fertilizer (0, 30, 90 kg ha−1) on maize performance under no-tillage. In some sites, different (N) fertilizer levels were superimposed to test their effects on maize grain yield and leaf chlorophyll content under different maize residue biomass levels. The different residue levels had no significant effect on maize yield in most growing seasons. Maize residue cover increased grain yield in eight out of 39 site-years across the sites used. However, in some sites, maize yield decreased with increases in residue level in cropping seasons that had average to above average rainfall. At a few sites maize yield increased with increase in residue level. Seasonal rainfall pattern influenced the effect of different residue levels on grain yield at most sites. Nitrogen fertilizer increased maize yield regardless of the residue level applied. This study demonstrates that mulching with maize residues in CA/NT systems results in limited maize yield gains – at least within the first 6 years in different agro-ecological conditions of southern Africa

Interventions to reduce pesticide exposure from the agricultural sector in Africa: a workshop report

Despite the fact that several cases of unsafe pesticide use among farmers in different parts of Africa have been documented, there is limited evidence regarding which specific interventions are effective in reducing pesticide exposure and associated risks to human health and ecology. The overall goal of the African Pesticide Intervention Project (APsent) study is to better understand ongoing research and public health activities related to interventions in Africa through the implementation of suitable target-specific situations or use contexts. A systematic review of the scientific literature on pesticide intervention studies with a focus on Africa was conducted. This was followed by a qualitative survey among stakeholders involved in pesticide research or management in the African region to learn about barriers to and promoters of successful interventions. The project was concluded with an international workshop in November 2021, where a broad range of topics relevant to occupational and environmental health risks were discussed such as acute poisoning, street pesticides, switching to alternatives, or disposal of empty pesticide containers. Key areas of improvement identified were training on pesticide usage techniques, research on the effectiveness of interventions targeted at exposure reduction and/or behavioral changes, awareness raising, implementation of adequate policies, and enforcement of regulations and processes