Environments2015, 2(3), 338-357; doi:10.3390/environments2030338 (registering DOI) - published 6 July 2015 Show/Hide Abstract
Abstract: Since the paper by Giller et al. (2009), the debate surrounding the suitability of conservation agriculture (CA) for African smallholders has remained polarized between proponents and opponents. The debate also gave rise to a few studies that attempted to identify the “niche” where CA would fit in the region, but the insight offered by these studies has been limited. In this paper, we first analyze the rationale of adoption where it occurred globally to define “drivers” of adoption. Our analysis suggests that CA has first and foremost been adopted under the premises of being energy-saving (time and/or power), erosion-controlling, and water-use efficient, but rarely to increase yield. We then define the niche where CA fits, based on these drivers of adoption, as systems where (1) the energy available for crop establishment is limited and/or costly (including labor and draft power); (2) delayed planting results in a significant yield decline; (3) yield is limited or co-limited by water; and/or (4) severe erosion problems threaten the short- to medium-term productivity of farmland. In Eastern and Southern Africa, this niche appears rather large and likely to expand in the near future. When implemented within this niche, CA may still be limited by “performance challenges” that do not constitute drivers or barriers to adoption, but limitations to the performance of CA. We argue that most of these performance challenges can (and should) be addressed by agronomic and socio-economic research, and provide four examples where the International Maize and Wheat Improvement Center (CIMMYT) and its partners have been successfully alleviating four very different challenges through research and development (R&D) in Eastern and Southern Africa. Finally, we describe an iterative and multi-scale R&D approach currently used by CIMMYT in Eastern and Southern Africa to overcome challenges associated with the implementation of CA by African smallholders. This approach could also be useful for other complex combinations of technologies aiming at sustainable intensification.
Abstract: A long-term study was carried out in the Zidyana Extension Planning Area (EPA), Malawi and in the Zimuto Communal Area, Zimbabwe, to evaluate the effect of different conservation agriculture (CA) systems on crop productivity, soil quality and economic performance. Maize productivity results from Zidyana showed that CA systems out-yielded the conventional system in seven out of nine cropping seasons. Labour savings relative to the conventional control ranged from 34–42 labour days ha−1 due to reduced time needed to make manual ridges and for weed control, leading to higher net benefits of 193–444 USD·ha−1. In Zimuto, yield benefits were apparent from the second season onwards and there was a much clearer trend of increased yields of CA over time. Greater net benefits (in USD·ha−1) were achieved on CA systems in Zimuto compared with conventional control treatments due to overall higher yields from CA systems. In Zimuto, both increased infiltration and a gradual increase in soil carbon were recorded, which may have contributed to the greater yield response of CA in this area. In Zidyana, yield increases were attributed primarily to enhanced water infiltration since no increases in soil carbon levels were measured. Farmers highlighted critical challenges to the adoption of CA. These will have to be addressed in future research and extension to provide effective solutions to farmers.
Abstract: The Río Tinto drains the eastern part of the Iberian Pyrite Belt (IPB), an area with a huge amount of massive sulphide deposits that has been mined for the last 4500 years. This river presents extreme conditions, with very high concentrations in solution of metals and metalloids and low pH values. Mining activities in the upper part of the watershed of the Río Tinto have been documented since historical times and a huge amount of widespread acid-producing mine residues exist in this area. Nevertheless, there is no consensus among the scientific community as to whether the extreme conditions of the Río Tinto are the result of natural processes or the intense mining activity in the region. Here we show, using numerous geological, archaeological and historical records, that the present quality of the Río Tinto is the result of mining activities, especially during the period 1850–2001, while natural processes of formation of acid rock drainage can be considered negligible.
Abstract: A study based on the physicochemical parameters and dissolved metals levels from three main rivers around Dhaka City, Bangladesh, was conducted in order to determine the present pollution status and their alteration trends with the seasonal change of discharge amount. The water samples were collected from the rivers Buriganga, Turag, and Shitalakkhya during both dry and monsoon seasons. Physicochemical analyses revealed that most of the water quality parameters exceeded the recommended levels set by the Department of Environment (DoE), Bangladesh, during both the dry and monsoon seasons. A very strong positive correlation was found between biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in all sampling points. Both BOD and COD values had a strong negative correlation with dissolved oxygen (DO) in the Shitalakkhya River. Most of the dissolved metals concentrations in the water samples were similar. However, the concentrations of different physicochemical properties varied with the seasons. The dry season had significantly higher contamination loads, which were decreased during the monsoon season. Anthropogenic activities, as well as the variation in river water flow during different seasons were the main reasons for this high degree of water pollution.
Abstract: This study explores the relationships between forest cover change and the village resettlement and land planning policies implemented in Laos, which have led to the relocation of remote and dispersed populations into clustered villages with easier access to state services and market facilities. We used the Global Forest Cover Change (2000–2012) and the most recent Lao Agricultural Census (2011) datasets to assess forest cover change in resettled and non-resettled villages throughout the country. We also reviewed a set of six case studies and performed an original case study in two villages of Luang Prabang province with 55 households, inquiring about relocation, land losses and intensification options. Our results show that resettled villages have greater baseline forest cover and total forest loss than most villages in Laos but not significant forest loss relative to that baseline. Resettled villages are consistently associated with forested areas, minority groups, and intermediate accessibility. The case studies highlight that resettlement coupled with land use planning does not necessarily lead to the abandonment of shifting cultivation or affect forest loss but lead to a re-spatialization of land use. This includes clustering of forest clearings, which might lead to fallow shortening and land degradation while limited intensification options exist in the resettled villages. This study provides a contribution to studying relationships between migration, forest cover change, livelihood strategies, land governance and agricultural practices in tropical forest environments.
Abstract: Urbanized areas of the southwestern/western United States are among the fastest growing in the nation and face multiple water resource challenges. Low impact development (LID)/green infrastructure (GI) practices are increasingly popular technologies for managing stormwater; however, LID is often not as common in the southwest/west due to the lack of regulatory and/or economic drivers. There is also a lack of performance evaluation of these practices, particularly at the field scale. This study focused on investigating the hydrologic and pollutant removal performance of field-scale LID/GI systems in arid/semi-arid climates. Nine typical practices were reviewed: rainwater harvest system, detention pond, retention pond, bioretention, media filter, porous pavement, vegetated swale/buffer/strip, green roof, and infiltration trench, as well as integrated LIDs. We evaluate these practices by a cost-effectiveness analysis and also recommend best practices for the arid/semi-arid area. The analysis provides data support and insights for future implementation of LID/GI in the southwest/west.