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. 2019 Jan 17;14(1):e0210642.
doi: 10.1371/journal.pone.0210642. eCollection 2019.

Better soils for healthier lives? An econometric assessment of the link between soil nutrients and malnutrition in Sub-Saharan Africa

Ezra D Berkhout  1 , Mandy Malan  2 , Tom Kram  1
Affiliations

Better soils for healthier lives? An econometric assessment of the link between soil nutrients and malnutrition in Sub-Saharan Africa

Ezra D Berkhout et al. PLoS One. .

Abstract

Malnutrition, the suboptimal consumption of essential nutrients like zinc, severely affects human health. This burden of malnutrition falls disproportionally heavy on developing countries, directly increasing child mortality and childhood stunting, or reducing people's ability mending diseases. One option to combat malnutrition is to blend missing nutrients in crop fertilizers, thereby increasing crop yields and possibly the nutrient density in harvested crop products, thus enriching crop products destined for human consumption. But, the effectiveness of so-called agronomic fortification remains ill-understood, primarily due to a paucity of field trials. We hypothesize that, if at all this is an effective strategy, there should exist a causal link between malnutrition and natural variation in the quality of soils to begin with. Until now, data limitations prevented the establishment of such a link, but new soil micronutrient maps for Sub-Saharan Africa allow for a detailed assessment. In doing so, we find statistically significant relations between soil nutrients and child mortality, stunting, wasting and underweight. For instance, a simultaneous increase in soil densities of copper, manganese and zinc by one standard deviation reduces child mortality by 4-6 per mille points, but only when malaria pressure is modest. The effects of soil nutrients on health dissipate when malaria pressure increases. Yet, the effects are fairly small in magnitude suggesting that except for a few regions, agronomic fortification is a relatively cost ineffective means to combat malnutrition.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Estimated concentrations of zinc and manganese in soils across Sub-Saharan Africa.
Data based on Hengl et al. [18]
Fig 2
Fig 2. Marginal effects (90% CI) of soil nutrient increase on child mortality.
The graphs display 90% confidence intervals of the marginal effects of greater soil nutrient densities on child mortality. Panel a displays the effects of factor 1 (Cu, Mn and Zn), panel b of factor 2 (Ca and Mg) and panel c of factor 3 (N and OMC).
Fig 3
Fig 3. Marginal effects (90% CI) of soil nutrient increase on child stunting.
The graphs display 90% confidence intervals of the marginal effects of greater soil nutrient densities on child stunting. Panel a displays the effects of factor 1 (Cu, Mn and Zn), panel b of factor 2 (Ca and Mg) and panel c of factor 3 (N and OMC).
Fig 4
Fig 4. Marginal effects (90% CI) of soil nutrient increase on child wasting.
The graphs display 90% confidence intervals of the marginal effects of greater soil nutrient densities on child wasting. Panel a displays the effects of factor 1 (Cu, Mn and Zn), panel b of factor 2 (Ca and Mg) and panel c of factor 3 (N and OMC).
Fig 5
Fig 5. Marginal effects (90% CI) of soil nutrient increase on child underweight.
The graphs display 90% confidence intervals of the marginal effects of greater soil nutrient densities on child underweight. Panel a displays the effects of factor 1 (Cu, Mn and Zn), panel b of factor 2 (Ca and Mg) and panel c of factor 3 (N and OMC).
Fig 6
Fig 6. Regions with low micronutrient densities, high population densities, or both.
The figure shows regions where soil densities of zinc (panel a), manganese (panel b) or copper (panel c) are low (<25% percentile) and population density is high (>95% percentile). Data on zinc, manganese and copper densities are from Hengl et al. [18], data on population density is from Center for International Earth Science Information Network—CIESIN—Columbia University [33].
Fig 7
Fig 7. Variation in malaria pressure across Sub-Saharan Africa.
Figure shows variation in malaria pressure based on the malaria stability index developed by Kiszewski et al. [35]. A low malaria stability index (in green) indicates low malaria pressure.
See this image and copyright information in PMC

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