Vrieling Anton

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  • Preprint
    Early assessment of seasonal forage availability for mitigating the impact of drought on East African pastoralists
    ( 2015-11) Vrieling, Anton ; Meroni, Michele ; Mude, Andrew G. ; Chantarat, Sommarat ; Ummenhofer, Caroline C. ; de Bie, Kees (C.A.J.M.)
    Pastoralist households across East Africa face major livestock losses during drought periods that can cause persistent poverty. For Kenya and southern Ethiopia, an existing index insurance scheme aims to reduce the adverse effects of such losses. The scheme insures individual households through an area-aggregated seasonal forage scarcity index derived from remotely-sensed normalized difference vegetation index (NDVI) time series. Until recently, insurance contracts covered animal losses and indemnity payouts were consequently made late in the season, based on a forage scarcity index incorporating both wet and dry season NDVI data. Season timing and duration were fixed for the whole area (March-September for long rains, October-February for short rains). Due to demand for asset protection insurance (pre-loss intervention) our aim was to identify earlier payout options by shortening the temporal integration period of the index. We used 250m-resolution 10-day NDVI composites for 2001-2014 from the Moderate Resolution Imaging Spectroradiometer (MODIS). To better describe the period during which forage develops, we first retrieved per-pixel average season start- and end-dates using a phenological model. These dates were averaged per insurance unit to obtain unit-specific growing period definitions. With these definitions a new forage scarcity index was calculated. We then examined if shortening the temporal period further could effectively predict most (>90%) of the interannual variability of the new index, and assessed the effects of shortening the period on indemnity payouts. Our analysis shows that insurance payouts could be made one to three months earlier as compared to the current index definition, depending on the insurance unit. This would allow pastoralists to use indemnity payments to protect their livestock through purchase of forage, water, or medicines.
  • Preprint
    The El Niño – La Niña cycle and recent trends in supply and demand of net primary productivity in African drylands
    ( 2016-07) Abdi, Abdulhakim ; Vrieling, Anton ; Yengoh, Genesis T. ; Anyamba, Assaf ; Seaquist, Jonathan ; Ummenhofer, Caroline C. ; Ardö, Jonas
    Inter-annual climatic variability over a large portion of sub-Saharan Africa is under the influence of the El Niño-Southern Oscillation (ENSO). Extreme variability in climate is a threat to rural livelihoods in sub-Saharan Africa, yet the role of ENSO in the balance between supply and demand of net primary productivity (NPP) over this region is unclear. Here, we analyze the impact of ENSO on this balance in a spatially explicit framework using gridded population data from the WorldPop project, satellite-derived data on NPP supply, and statistical data from the United Nations. Our analyses demonstrate that between 2000 and 2013 fluctuations in the supply of NPP associated with moderate ENSO events average ±2.8 g C m-2 yr-1 across sub-Saharan drylands. The greatest sensitivity is in arid Southern Africa where a +1oC change in the Niño-3.4 sea surface temperature index is associated with a mean change in NPP supply of -6.6 g C m-2 yr-1. Concurrently, the population-driven trend in NPP demand averages 3.5 g C m-2 yr-1 over the entire region with densely populated urban areas exhibiting the highest mean demand for NPP. Our findings highlight the importance of accounting for the role ENSO plays in modulating the balance between supply and demand of NPP in sub-Saharan drylands. An important implication of these findings is that increase in NPP demand for socio-economic metabolism must be taken into account within the context of climate-modulated supply