ISRIC Report 2012/02: Global changes of remotely sensed greenness and simulated biomass production since 1981

isric_report_2012_02.pdf (pdf, 4.29 MB)
Year of publication
ZG Bai, JG Conijn, PS Bindraban and B Rutgers
The global food- and eco-system will encounter unprecedented pressures over the next few decades, as agricultural production must increase by 70-100% to feed over 9 billion people by 2050. This is further compounded by the growing demand for non-food items such as biofuels and biomaterials. There is compelling evidence, however, that the productive capacity of cropland is degrading. Estimates of the rate at which this is happening, globally, and the costs incurred in terms of productivity and economic losses, and how this impacts on food security are extremely variable and uncertain because of (i) uncertainties in underlying information; (ii) lack of an objective definition of land degradation; (iii) methodological weaknesses to relate changes in productivity to land degradation or other variables (e.g. climate or management) and (iv) different system boundaries used in different estimates (types of land degradation accounted for; inclusion or not of off-site effects) (Pimentel et al., 1995; Trimble & Crosson, 2000; Lal, 2007; Wilkinson & McElroy, 2007; Sonneveld & Dent, 2007; Telles et al., 2011).
Even at the local level, it is still a challenge to quantitatively assess the effects of soil degradation on crop yields (WOCAT, As a consequence, land degradation appears to be underemphasized on national and international policy agendas (Nkonya et al., 2011) and the investments required to safeguard future food security are unknown. Land degradation is a phenomenon that leads to the decline in productivity of agro-based goods and ecosystems services. Yet, land can be used for a range of other functions like urbanisation and industry for instance, which are considered valuable but not contributing to agro-ecological functions. Balancing different functions is at the heart of any decision related to land use, certainly so as it affects people most that rely directly on land resources for their livelihoods.
If interpreted appropriately, up-to-date quantitative information about land degradation can support policy decision making on balancing such needs, including food and water security, economic development, environmental integrity and resource conservation. However, rather than doing this by the conventional approach of classifying areas affected by degradation and then determining its impacts, which incurs loss of information and fruitless discussions about class boundaries, a more integrated approach appears to be more
promising. This would aim at the assessment of changes in land attributes which, through the use of mechanistic models and supported by empirical findings could then be translated in changes in ecosystem functioning or goods and services (e.g. agricultural productivity, carbon storage, water regulation). This integrated approach is followed in a comprehensive modelling exercise ‘IMAGE-GLOBIO’ by PBL Netherlands Environmental Assessment Agency with explicit attention to the relation between economic activities and
Land may degrade due to a wide range of activities including changes in land use, unbalanced nutrient management, inappropriate soil tillage leading to erosion, salinization due to inappropriate irrigation or reduced precipitation etc. The productivity of land, i.e. the amount of biomass that can be produced, is affected by degradation. Yet, the relation between ‘land degradation’ and ‘biomass productivity’ is not straightforward and needs accurate understanding of soil processes in relation to climate, plant growth and
management. Higher level integration through the ‘IMAGE-GLOBIO’ approach will advance this primary relation between ecosystems/biodiversity, land productivity, economic development and poverty. The scope of this research relates specifically to land degradation and biomass productivity.
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