Ashley Sparrow

A landscape-scale model of shrub and herbage dynamics in Central Australia, validated by satellite data

Abstract Ecosystem models have an important integrative role in allowing available data to be used to predict the potential impacts of changing climate or disturbance patterns. No such model has previously existed for the rangelands of Central Australia. In this paper we develop an ecosystem model for arid chenopod shrublands south of Alice Springs which takes account of inherent landscape heterogeneity and temporal variability, but which uses simple empirical relationships because of the small amount of available data on which to base any such model. The model is focused on the dynamics of simple herbage and shrub biomass pools; further breakdown of species composition is not attempted. Herbage dynamics are most dependent on grazing effects, as measured by distance from permanent watering points and average paddock stocking rate, and on the erosional status of the soil. Shrub dynamics are most sensitive to erosional status. The model is tested against historical Landsat MSS imagery transformed by a plant cover index. Correspondence is good, except on highly erosional sites which appear more dynamic than predicted. Further work is needed to quantify rates of soil erosion and deposition at different grazing levels, and of shrub growth and dieback in arid climates. Accurate means of assessing plant biomass from satellite imagery also require further development.

A model of soil moisture balance and herbage growth in the arid rangelands of central Australia

A simple model of soil moisture balance and herbage production in the arid and semi-arid rangelands of central Australia is presented. The model has few parameters and only requires inputs of rainfall and potential evaporation to model daily soil moisture and plant growth. Five landscape types were studied for over 2 years, and for up to four major growth events, to provide data for estimating parameters in the model. Moisture loss in the 0–500 mm soil profile has been modelled using an negative exponential function which depends on available soil moisture and is driven by daily rainfall and potential evaporation. The growth of herbage, whilst soil moisture is above wilting point, is a linear function of actual evapotranspiration, with the decay of plant material represented by a logistic curve.

Mediating boundaries between knowledge and knowing: ICT and R4D praxis

This article reflects critically on the use of a wiki as a data repository for knowledge transfer and as a mediating technical platform for social learning in the context of a multi-country programme of agricultural research for development. The wiki was designed to foster sustainable social learning and an emergent community of practice among biophysical and social researchers acting for the first time as co-researchers. Over time, the technologically mediated element of the learning system was judged to have failed. The article is based on an inquiry that asked ‘How can learning system design cultivate learning opportunities and respond to learning challenges in an online environment to support research for development practice?’ The article also considers the wider context and institutional setting in which the knowledge work took place.

Towards appropriate mainstreaming of “Theory of Change” approaches into agricultural research for development: Challenges and opportunities

Abstract Food insecurity persists in many parts of Africa and Asia, despite ongoing agricultural research for development (AR4D) interventions. This is resulting in a growing demand for alternative approaches to designing and evaluating interventions in complex systems. Theory of Change (ToC) is an approach which may be useful because it enables stakeholders to present and test their theories and assumptions about why and how impact may occur, ideally within an environment conducive to iterative reflection and learning. However, ToC is yet to be appropriately mainstreamed into development by donors, researchers and practitioners. We carried out a literature review, triangulated by interviews with 26 experts in African and Asian food security, consisting of researchers, advisors to programs, and donors. Although 17 (65%) of the experts had adopted ToC, their responses and the literature revealed four challenges to mainstreaming: (i) different interpretations of ToC; (ii) incoherence in relationships among the constituent concepts of ToC; (iii) confused relationships between ToC and project “logframes”; and (iv) limitations in necessary skills and commitment for enacting ToC. A case study of the evolution of a ToC in a West African AR4D project over 4 years which exemplified these challenges is presented. Five recommendations arise to assist the mainstreaming of ToC: (i) select a type of ToC suited to the relative complexity of the problem and focal system of interest; (ii) state a theory or hypotheses to be tested as the intervention progresses; (iii) articulate the relationship between the ToC and parallel approaches (e.g. logframe); (iv) accept that a ToC is a process, and (v) allow time and resources for implementers and researchers to develop ToC thinking within projects. Finally, we suggest that communities of practice should be established among AR4D and donor organisations to test, evaluate and improve the contribution that ToCs can make to sustainable food security and agricultural development.