Research & reports

Beaven Utete · Journal of Water Resources and Ocean Science · Zimbabwe

The ecological integrity of the peri-urban Chiraura River system in Zimbabwe was assessed through multivariate analysis of physicochemical parameters and the resident macroinvertebrate community. Monthly collections were conducted over five months from November 2011 to March 2012 at six sites, recording 1209 macroinvertebrates. Unsustainable anthropogenic activities, including industrial, domestic, and urban agricultural activities, were found to affect the water quality of the Chiraura River through run-off and increased effluent.

Patrick F. Banga · · Zimbabwe

Unsanctioned urban agricultural activities in Emakhandeni High Density Suburb of Bulawayo, Zimbabwe, negatively impact biodiversity. Researchers interviewed 100 people and conducted field visits, finding that the majority of cultivators operate outside existing laws and guidelines. This leads to progressive land degradation, massive deforestation, soil erosion, dried wetlands, lowered water table, and compromised groundwater quality due to pesticides and inorganic fertilizers.

S. A. Materechera · African Journal of Agricultural Research · Africa

A study of soil salinity in irrigated fields used for urban agriculture in a semi-arid region of South Africa. It compares sodium levels (19.3 vs. 9.8), pH (7.13 vs. 6.3) and electrical conductivity ECe (22.1 vs. 7.9 dS/m) between topsoil and subsoil layers, finding that calcium, magnesium and potassium (unlike sodium) were higher in the top than the subsoil layer, while pH and ECe did not differ significantly by depth overall. By irrigation method, basin irrigation produced the highest accumulation of calcium, magnesium, potassium and sodium, followed by drip and then sprinkler irrigation, with the same ranking (basin > drip > sprinkler > control) for pH and ECe; sprinkler irrigation was the only method showing higher pH and ECe at 10-20 cm depth than at 0-10 cm. The study concludes that irrigation is increasing soil salinity and points to the need for sound irrigation water management, particularly appropriate irrigation scheduling.

Karin Ahrné, Jan Bengtsson, Thomas Elmqvist · PLoS ONE · Sweden (Stockholm)

This study investigated bumble bees in allotment gardens along an urbanization gradient from inner Stockholm to rural areas. Findings showed that bumble bee diversity decreased with increasing urbanization, from approximately eight species in rural areas to five to six species in urban allotment gardens. Higher variability in the abundance of certain species in the most urban areas suggested a potentially weaker reliability of the pollination ecosystem service in areas strongly influenced by human activity.

Andreas Buerkert, Eva Schlecht, Martina Předotová, Rodrigue V.C. Diogo, Katja Kehlenbeck, Jens Gebauer · eScholarship (California Digital Library) · Sub-Saharan Africa

This study analyzed urban and peri-urban agriculture (UPA) systems in major Sub-Saharan African cities, measuring carbon, nitrogen, phosphorus, and potassium fluxes and conducting biodiversity studies. In Niamey, low-input gardens showed annual gaseous carbon emissions of 20-25 t ha-1, predominantly CO2, and high-input gardens irrigated with wastewater had annual CO2-C emissions of 27 t ha-1, with N2O as a major nitrogen loss contributor. Animal manure stored in the open was subject to large carbon and nitrogen losses, indicating environmental tradeoffs. However, UPA gardens in Niamey maintained a large variety of fruit and vegetable species, with richness increasing with garden and household size and commercialization.

Stefan Dongus, Dickson Nyika, Khadija Kannady, Deo Mtasiwa, Hassan Mshinda, Laura Gosoniu, Axel Drescher, Ulrike Fillinger, Marcel Tanner, Gerry F. Killeen, Márcia C. Castro · Geospatial health · Tanzania (Dar es Salaam)

A cross-sectional survey in urban Dar es Salaam, Tanzania, investigated the influence of agricultural and geographical features on Anopheles larvae presence. The study found that agricultural areas, covering over 5% of the 16.8 km2 study area, had a 1.7 times higher proportion of habitats containing Anopheles larvae compared to other areas. However, breeding sites originating from urban agriculture accounted for less than a fifth of all malaria vector breeding sites in the city.

Shane R. de Solla, Pamela A. Martin · Environmental Toxicology and Chemistry · United States

Because many reptiles oviposit in soil within agricultural landscapes, this study evaluated the toxicity of two commonly used nitrogenous fertilizers — urea and ammonium nitrate — to snapping turtle (Chelydra serpentina) egg survivorship. Eggs were incubated, unmanipulated and under ambient conditions, in a community garden plot treated with urea at realistic rates up to 200 kg/ha in 2004 and ammonium nitrate up to 2,000 kg/ha in 2005, and separately in covered laboratory bins designed to minimize nitrogen loss through volatilization or leaching. In the field, neither urea nor ammonium nitrate affected hatching success or development, despite ammonium nitrate showing overt toxicity to native plants. In the laboratory, however, both fertilizer exposures reduced hatching success, lowered body mass at hatching, and reduced post-hatching survival compared with controls. The authors attribute the field's lack of toxicity to leaching and atmospheric loss of nitrogen in soil, and conclude that nitrogenous fertilizers likely have little direct impact on turtle eggs deposited in agricultural landscapes.

Fabio Bontadina, Pascale Contesse, Sandra Gloor · DORA WSL (Swiss Federal Institute for Forest, Snow and Landscape Research) · Switzerland (Zurich)

This study analyzed attitudes towards urban foxes in Switzerland using a nationwide survey and questionnaires for households and allotment gardeners in Zurich. While 60% of Swiss respondents were against urban foxes, only 40% in Zurich were; however, 70% of gardeners opposed them, with 55% reporting damage caused by foxes, which negatively correlated with fox acceptance.