Livestock systems/Data uncertainties limitations: Difference between revisions
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{{ComponentDataUncertaintyAndLimitationsTemplate | {{ComponentDataUncertaintyAndLimitationsTemplate | ||
|Status=On hold | |Status=On hold | ||
|Reference=FAO, 2012; Beusen et al., 2008; Bouwman et al., 2005; Seré and Steinfeld, 1996; | |||
|Description===Data== | |||
Data on animal stocks, milk production per animal, off-take rates and carcass weights, for the 1970–2005 period, are obtained from the [[FAO]] ([[FAO, 2012]]). Different animal production systems, and their total population and production have been defined in recent FAO publications ([[Seré and Steinfeld, 1996]]). For ruminants, these production systems include pastoral, mixed and landless production, for various agro-ecological zones. We aggregated the data to two broad groups: pastoral and mixed + landless production systems. The data are provided for 7 large world regions, which we subsequently disaggregated to the level of the 24 world regions in the IMAGE model ([[Bouwman et al., 2005]]). [[Seré and Steinfeld, 1996]] also provided data for the growth in animal populations and the production in each production system. | |||
==Uncertainties== | |||
There are several uncertainties involved in the calculation of livestock production in the different systems, both for historical years and scenarios. The first uncertainty is the aggregation level on the scale of countries and world regions, whereby all underlying heterogeneity is ignored. A second problem is the use of average data for carcass weight, off-take rate, and milk production for complete animal populations. In reality, animal populations include different age classes, and only part of a population is productive. Some calculations, such as on the energy requirement for maintenance, are a non-linear function of body weight. Using average values, therefore, may not be correct. | |||
A further uncertainty is associated with animal stocks. Methodology and frequency of data collection (e.g. by census) vary between countries, and are probably less certain for some developing countries than for industrialised countries. Uncertainties in this part of IMAGE as well as in other parts, such as those with respect to ammonia emissions, are strongly related to animal stocks ([[Beusen et al., 2008]]). | |||
The main uncertainties in construction scenarios concern agricultural demand ([[Agricultural economy and forestry]]), the distribution of production over the two systems, and production characteristics per system, including feed requirements and feed types. | |||
Limitations | |||
One important limitation is that the development of ruminant livestock system characteristics is purely following a scenario storyline and has no explicit link to the agricultural economy, or for example to land scarcity. This is partly due to the fact that livestock systems in the [[MAGNET model]], so far, have been represented rather weakly, and the model does not include explicit, physically based feed compositions. The two models are coupled only for the calculation of grassland area. | |||
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Revision as of 10:01, 16 December 2013
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