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368 | IAASTD Global Report

Table A.5.12 Major uncertainties in the mapped Seré & Steinfeld (1996) classification

Model component

Uncertainty

Model Structure

•   Based on thresholds associated with human population density and length of growing period
•   Also based on land-cover information that is known to be currently weak with respect to cropland identification
•   The global classification is quite coarse, and no differentiation is made of the mixed systems

Parameters

Inputs:
•   Land cover, length of growing period, human population density, irrigated areas, urban areas
•   Observed or modeled livestock densities
Outputs:
•   Areas associated with grassland-based systems and mixed crop-livestock systems (rainfed and irrigated), broken down by AEZ (which can then be combined with other national or sub-national information, such as poverty rates)

Driving force

Even at the broad-brush level, population change and climate change will not be the only drivers of land-use change in livestock-based systems, globally

Initial condition

Some validation of the systems layers has been carried out for current conditions, but more is needed

Model operation

Assembling the input data and running the classification is not an automated procedure. It requires separate sets of FORTRAN programmes for estimating changing agroclimatological conditions; and various sets of ArcInfo scripts for spatially allocating population data and rerunning the classification

measures of MSA, each in relation to different degrees of pressure exerted  by various pressure  factors  or driving forces. The entries in the database are all derived from stud­ies in peer-reviewed literature, reporting either on change through time in a single plot, or on response in parallel plots undergoing different pressures.
     The current version of the database includes data from about 500 reports: about 140 reports on the relationship between species abundance and land cover or land use, 50 on atmospheric N deposition (Bobbink, 2004), over 300 on the impacts of infrastructure (UNEP, 2001) and several lit­erature reports on minimal area requirements of species.

 

     The driving forces (pressures) incorporated within the model and their sources are as follows:
•     Land cover change (IMAGE)
•     Land use intensity (IMAGE / GLOBIO3)
•     Nitrogen deposition (IMAGE)
•     Infrastructure development (IMAGE / GLOBIO2)
•     Climate change (IMAGE)

Climate change is treated differently from other drivers in GLOBIO3, as the empirical evidence compiled in GLOBIO dose-response relationships so far is limited to areas that are already experiencing significant impacts of change (such as

Table A.5.13 Level of confidence for scenario calculations

 

 

 

 

 

 

 

 

 

 

 

 

Level of Agreement/ Assessment

High

Established but incomplete •   Agricultural and land-use intensification processes

Well-established •   Impacts of human population densities on agricultural land-use

Low

Speculative •   Climate change scenarios •   Human population change scenarios •   Impacts of changing climate on agricultural land-use

Competing Explanations •   Different or expanded sets of variables as drivers of system intensification

 

Low

High

Amount of Evidence (Theory, Observations, Model Outputs)

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