Christian H. Roth

Farming Adaptation to Environmental Change in Coastal Bangladesh: Shrimp Culture versus Crop Diversification

AbstractnFarming in coastal Bangladesh includes rice/shrimp and rice/non-rice cropping systems. The former has been highly profitable but has exacerbated salinization of soil and water. We evaluate the relative profitability, riskiness, and sustainability of the two cropping systems, using data from two coastal villages in Khulna District. Shrimp cultivation was initially very rewarding. However, over 12–15xa0years, the cropping system experienced declining profitability, increased salinity, and adverse impacts on rice cropping and the local environment. From 2009, farmers adapted the system by changing the pond (gher) infrastructure, adopting delayed planting of a saline-tolerant rice cultivar, flushing out accumulated salt with freshwater during rice cropping, and allowing the soil to dry out after harvesting rice. The budgeting results show that with current management practices, the rice/shrimp system is economically more viable (higher returns to land and labour and less risky) than the rice/non-rice system. Soil analyses showed that while salinity was higher in the gher during the dry season, it was significantly reduced in the wet season and was very similar between the two systems (1–2xa0dS/m). Hence, as well as being more profitable and less risky, the rice/shrimp system may well be more sustainable than previously observed.

Household types as a tool to understand adaptive capacity: case studies from Cambodia, Lao PDR, Bangladesh and India

Supporting smallholder households to adapt to climate variability is a high priority for development agencies and national governments. Efforts to support climate adaptation in developing countries occur within highly dynamic contexts. Macro-level changes in national and regional economies manifest in dynamic local conditions, such as migration, changing household labour dynamics, market access and land-use options. Research aimed at developing adaptation options is often focused on particular activities or industries and struggles to take into account the broader, interrelated suite of household livelihood activities or the non-climate stressors driving change and adaptation. This paper explores the use of household types to (a) understand the diversity of household circumstances and (b) place agricultural adaptation options within the broader context of household livelihoods. Results from application in four countries are discussed, which highlight the utility of the method and identify broader level trends and drivers that are common challenges (experienced differently) across multiple contexts.

Optimising drainage from sugar cane fields using a one-dimensional flow routing model: a case study from Ripple Creek, North Queensland

Abstract Inundation of sugar cane fields in the Ripple Creek catchment is perceived by some cane farmers to be a major contributor to loss of production. To alleviate this inundation, drainage systems have been designed which are capable of removing surface water very rapidly. However, when the Herbert River is in flood this water may have nowhere to go. This combination of an efficient drainage system, the lack of an outlet for the water, and the growing of cane on land which may be unsuitable, has led to some farms facing extended periods of inundation. For this reason, proposals have been made to the Ripple Creek Drainage Board to modify the drainage system to produce a more equitable distribution of inundation. In this paper, we examined the application of the Mike-11 modelling system to the Ripple Creek catchment. We found that the modelled predictions of depth, discharge and velocity matched observational data collected as part of an intensive CSIRO monitoring program. The model developed was then used to examine the hydrologic impact of opening a new channel to divert flow into the Seymour River. We found that opening this channel had some impact on indundation in parts of the catchment, but that the impact depended on whether or not the Herbert River was in flood at the time.

Ein autoregressives Verfahren zur Bestimmung der gesättigten und ungesättigten hydraulischen Leitfähigkeit

Mit Hilfe der Augenblicksprofilmethode wurde die Wasserleitfahigkeit fur den wasserungesattigten Bereich (k) bestimmt. Dabei wurden Wassergehalte und Wasserspannungen als Funktion der Zeit und Tiefe an Stechzylinderproben gemessen. Die Messungen der Wassergehalte und Wasserspannungen erfolgten mit TDR-Sonden bzw. Druckaufnehmertensiometern. Das Untersuchungsmaterial umfaste 40 Bodenhorizonte mit einem weiten Spektrum in Textur und Lagerungsdichte. Neben den k-Werten wurden auch die gesattigte Wasserleitfahigkeit kf und die pF-Kurve bestimmt. n n n nAnhand dieser Daten wurde ein „autoregressives Verfahren“ zur Berechnung der k-Werte fur die Wasserspannungen 30, 60, 100, 300 und 600 hPa fur lehmige Sande, sandige, tonige und schluffige Boden entwickelt. Dabei wurde zunachst der k-Wert berechnet, der sich mit der grosten Genauigkeit anhand von Kennwerten der pF-Kurve ermitteln last. Bei der k-Wertberechnung der benachbarten Wasserspannungsbereiche geht neben den Kennwerten der pF-Kurve der bereits berechnete k-Wert mit ein. Auf diese Weise wird eine hohere Genauigkeit bei der Ermittlung der k-ψ-Beziehung zwischen Wasserleitfahigkeit und Wasserspannung erreicht, wie der Vergleich mit anderen Verfahren zeigt. n n n nAn autoregressive procedure to predict the hydraulic conductivity — Comparison of measured and predicted results n n n nAn instantaneous profile method was used to measure the unsaturated hydraulic conductivity. Relatively new techniques involving undisturbed soil samples instrumented with minitensio-meters and Time-Domain-Reflectometry (TDR) mini-probes were used for the experiments. The laboratory method allows a high spatial and temporal resolution. Laboratory measurements were carried out for 40 soil horizons with a wide spectrum of texture and bulk density. In addition, retention curves were measured using the standard pressure plate apparatus. Using this homogeneous set of data, an autoregressive model was developed which allows a stepwise calculation of the hydraulic conductivity for a water potential range of —30 up to —600 hPa. This model was developed for loamy sands, sandy, silty and clayey soils in conjunction with data from the retention curves. The calculation procedure starts with the determination of an initial unsaturated conductivity (k) close to field capacity, i.e., for water potential from —60 hPa up to —100 hPa. This first value is then used to predict other conductivity values using appropriate changes in soil water content corresponding to a defined range of the soil water potential. Subsequently, the hydraulic conductivities for higher and lower potentials were estimated considering the k value of the previous step in combination with the data of the retention curve of the next water potential range. n n n nThe advantage of this empirical model is the indirect consideration of soil structure, in contrast to the closed-form van Genuchten-Mualem (vGM) model. To demonstrate these effects on different fitting procedures, the vGM model was also used to describe soil hydraulic functions. The accuracy of both, the vGM model and the autoregressive one, were compared for various fitting procedures and soils.

Constraints to the capacity of smallholder farming households to adapt to climate change in South and Southeast Asia

Rural households in developing countries face a range of pressures to secure their livelihoods. Households feel the effects of changing rainfall patterns, droughts, cyclones, floods and increased temperatures, and draw on a wide range of resources to adapt but some households are better equipped than others. We explore the extent to which smallholder rural households might be able to adapt to the processes of increased climate variability or climate change through assessing their adaptive capacity using elements of the rural livelihoods framework. We involved almost 600 participants in discussions and interviews in India, Bangladesh, Cambodia and Lao PDR to explore the factors that condition their ability to adapt. We identified 36 key indicators of adaptive capacity, half were specifically related to climate change or climate variability, with others recognized as important in terms of overall livelihoods. “Experience”, “health” and “labour” (Human capital), “access to market” and “farmer networks/groups” (Social capital) were considered strongly enabling of adaptation, whereas “lack of training” (Human capital) and “soil quality/condition” (Natural capital) constrained adaptation. It takes time for households to recover from climatic events, but, households with better access to diverse resources, and a more balanced livelihood portfolio were better able to cope. Mechanisms to support adaptation involved supporting farmer groups, novel information networks, better access to markets and value chains, land ownership, improved financial and economic management, and credit options.