Deriving a Global Social Accounting Matrix from GTAP version 5 Data

This paper reports a method for converting version 5 of the GTAP database into a global SAM that is stored in GAMS data exchange (GDX) format or in a Header Array (HAR) format. The focus of attention is on the generation of a SAM representation of the GTAP database that is fully consistent with the GTAP model; as such the resultant SAM can be readily used to calibrate a version of the GTAP model that had been coded in GAMS. The GAMS code used to generate the SAM representation of the GTAP database is provided as a GAMS model library – this code has been tested with versions 5.0 and 5.3 of the GTAP database

Impact of Switching Production to Bioenergy Crops: The Switchgrass Example January 2005

This paper reports the results of a series of simulations that evaluate the general equilibrium effects of substituting crude oil by biomass, specifically switchgrass, in the production of petroleum in the USA. The simulations are inspired by debates over the implications for developing countries if agricultural policies in the USA are changed so that agricultural land is transferred from the production of cereals and other crops to biomass production. The results confirm expectations that such a policy shift would raise cereal and other agricultural prices, due to a general reduction in food production in the USA. However, the reduction in the demand for crude oil in the USA causes terms of trade effects that more than offset any potential benefits for developing countries due to the depreciation of their exchange rates, causing a general decline in economic welfare. Moreover, the declines in welfare are proportionately greater for developing countries due to their small levels of production of the commodities whose prices increase with the change in USA agricultural production

Tax policy to reduce carbon emissions in south Africa

Noting that South Africa may be one of the few African countries that could contribute to mitigating climate change, the authors explore the impact of a carbon tax relative to alternative energy taxes on economic welfare. Using a disaggregate general-equilibrium model of the South African economy, they capture the structural characteristics of the energy sector, linking a supply mix that is heavily skewed toward coal to energy use by different sectors and hence their carbon content. The authors consider a"pure"carbon tax as well as various proxy taxes such as those on energy or energy-intensive sectors like transport and basic metals, all of which achieve the same level of carbon reduction. In general, the more targeted the tax to carbon emissions, the better the welfare results. If a carbon tax is feasible, it will have the least marginal cost of abatement by a substantial amount when compared to alternative tax instruments. If a carbon tax is not feasible, a sales tax on energy inputs is the next best option. Moreover, labor market distortions such as labor market segmentation or unemployment will likely dominate the welfare and equity implications of a carbon tax for South Africa. This being the case, if South Africa were able to remove some of the distortions in the labor market, the cost of carbon taxation would be negligible. In short, the discussion of carbon taxation in South Africa can focus on considerations other than the economic welfare costs, which are likely to be quite low.Environmental Economics&Policies,Transport Economics Policy&Planning,Taxation&Subsidies,Energy Production and Transportation,Environment and Energy Efficiency

An Analysis of South Africa's Value Added Tax

In this paper, the authors describe South Africa's value added tax (VAT), showing that (1) the VAT is mildly regressive, and (2) it is an effective source of government revenue, compared with other tax instruments in South Africa. They evaluate the VAT in the context of other distortions in the economy by computing the marginal cost of funds-the effect of raising government revenue by increasing the VAT rates on household welfare. Then they evaluate alternative, revenue-neutral tax systems in which they reduce the VAT and raise income taxes. For the analysis, the authors use a computable general equilibrium (CGE) model with detailed specification of South Africa's tax system. Households are disaggregated into income deciles. They demonstrate that alternative tax structures can benefit low-income households without placing excess burdens on high-income households.

Aid, growth, and real exchange rate dynamics

Devarajan, Go, Page, Robinson, and Thierfelder argued that if aid is about the future and recipients are able to plan consumption and investment decisions optimally over time, then the potential problem of an aid-induced appreciation of the real exchange rate (Dutch disease) does not occur. In their paper,"Aid, Growth and Real Exchange Rate Dynamics,"this key result is derived without requiring extreme assumptions or additional productivity story. The economic framework is a standard neoclassical growth model, based on the familiar Salter-Swan characterization of an open economy, with full dynamic savings and investment decisions. It does require that the model is fully dynamic in both savings and investment decisions. An important assumption is that aid should be predictable for intertemporal smoothing to take place. If aid volatility forces recipients to be constrained and myopic, Dutch disease problems become an issue.Economic Theory&Research,Debt Markets,Currencies and Exchange Rates,Emerging Markets,

Bridging the disciplinary gap in conservation agriculture research, in Malawi. A review

Conservation Agriculture has emerged as a popular form of climate smart agriculture aimed at enhancing climate change resilience for smallholder farmers across Africa. Despite positive biophysical results, adoption rates remain low. It has been acknowledged that improved understanding of farmer decision-making is needed due to the variation in socio-economic and agro-ecological contexts which drives the research agenda to answer the question ‘what forms of Conservation Agriculture work, where, and why?’. To fully understand this question, we need to approach the study of Conservation Agriculture within complex farming systems by collating and integrating different forms of knowledge. In this paper, we discuss (1) a comparison of disciplinary approaches to evaluating Conservation Agriculture in Malawi, (2) the identification of the knowledge gaps that persist at the intersection of these disciplines and (3) recommendations for alternative and interdisciplinary approaches in addressing these knowledge gaps. With a focus on published studies from Malawi, we show that the Conservation Agriculture literature represents two distinct approaches to addressing the question ‘what forms of Conservation Agriculture work, where, and why?’, namely agro-ecological and socio-economic and that neither of these approaches can address the full scope of this question, in particular its ‘why’ component. To overcome these challenges, there is a need for access to compatible, comprehensive data sets, methodological approaches including farmer participation and ethnography, through on-farm trial research as a middle ground between disciplinary approaches

Prenatal mechanistic target of rapamycin complex 1 (mTORC1) inhibition by rapamycin treatment of pregnant mice causes intrauterine growth restriction and alters postnatal cardiac growth, morphology, and function

BACKGROUND: Fetal growth impacts cardiovascular health throughout postnatal life in humans. Various animal models of intrauterine growth restriction exhibit reduced heart size at birth, which negatively influences cardiac function in adulthood. The mechanistic target of rapamycin complex 1 (mTORC1) integrates nutrient and growth factor availability with cell growth, thereby regulating organ size. This study aimed at elucidating a possible involvement of mTORC1 in intrauterine growth restriction and prenatal heart growth. METHODS AND RESULTS: We inhibited mTORC1 in fetal mice by rapamycin treatment of pregnant dams in late gestation. Prenatal rapamycin treatment reduces mTORC1 activity in various organs at birth, which is fully restored by postnatal day 3. Rapamycin-treated neonates exhibit a 16% reduction in body weight compared with vehicle-treated controls. Heart weight decreases by 35%, resulting in a significantly reduced heart weight/body weight ratio, smaller left ventricular dimensions, and reduced cardiac output in rapamycin- versus vehicle-treated mice at birth. Although proliferation rates in neonatal rapamycin-treated hearts are unaffected, cardiomyocyte size is reduced, and apoptosis increased compared with vehicle-treated neonates. Rapamycin-treated mice exhibit postnatal catch-up growth, but body weight and left ventricular mass remain reduced in adulthood. Prenatal mTORC1 inhibition causes a reduction in cardiomyocyte number in adult hearts compared with controls, which is partially compensated for by an increased cardiomyocyte volume, resulting in normal cardiac function without maladaptive left ventricular remodeling. CONCLUSIONS: Prenatal rapamycin treatment of pregnant dams represents a new mouse model of intrauterine growth restriction and identifies an important role of mTORC1 in perinatal cardiac growth

Impacts of Conservation Agriculture on Soil Structure and Hydraulic Properties of Malawian Agricultural Systems

Sub-Saharan Africa (SSA) faces climate change and food insecurity challenges, which require action to create resilient farming systems. Conservation agriculture (CA) is widely promoted across SSA but the impacts on key soil physical properties and functions such as soil structure and hydraulic properties that govern water storage and transmission are not well understood. The aim of this study was to assess the impacts of long term (10–12 years) maize-based CA on soil hydraulic conductivity, water retention and pore size distribution. Root zone (0–30 cm depth) soil total porosity, pore size distribution, saturated hydraulic conductivity (Ksat) and plant available water capacity (PAWC) of conventional maize monocrop farming systems (CP) are compared with those of adjacent CA trials with either sole maize or maize intercrop/rotation with cowpea (Vigna unguiculata L.), pigeon pea (Cajanus cajan L.) or velvet bean (Mucuna pruriens L) in trial locations across central and southern Malawi. Results show that maize-based CA systems result in significant changes to soil hydraulic properties that correlate with improved soil structure. Results demonstrate increases of 5–15 % in total porosity, 0.06−0.22 cm/min in Ksat, 3–7 % in fine pores for water storage and 3–6 % in PAWC. Maize monocrop CA had similar effect on the hydraulic properties as the maize-legume associations. The values of Ksat for CA systems were within optimum levels (0.03–0.3 cm/min) whereas PAWC was below optimum (<20 %). There was no significant build-up in soil organic matter (OM) in the CA systems. The results lead to a recommendation that crop residue management should be more pro-actively pursued in CA guidance from agricultural extension staff to increase soil OM levels, increase yields and enhance climate resilience of sub-Saharan African farming systems