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The Health, Poverty and NDVI Connection Throughout West Africa

Paper Reviewed
Sedda, L., Tatem, A.J., Morley, D.W., Atkinson, P.M., Wardrop, N.A., Pezzulo, C., Sorichetta, A., Kuleszo, J. and Rogers, D.J. 2015. Poverty, health and satellite-derived vegetation indices: their inter-spatial relationship in West Africa. International Health 7: 99-106.

There is no doubt that elevated concentrations of atmospheric CO2 lead to enhanced plant photosynthesis and growth. This well-known fact has been confirmed over and over again in literally thousands of laboratory and field studies conducted by scientists over the past several decades. In recent years, however, the growth-enhancing benefits of atmospheric CO2 have been increasingly studied and observed in the real world of nature using Earth-orbiting satellites. Such instruments have the capability to remotely sense plant growth and vigor at altitudes miles above the Earth's surface; and they have generated a spatial and temporal record of vegetative change that now spans more than three decades. And what has that record revealed?

The take-home message of the satellite data is two-fold. First, at the global level, all recent studies show there has been a significant greening of the planet over the past few decades despite the occurrence of a number of real (and imagined) assaults on Earth's vegetation, including wildfires, disease, pest outbreaks, deforestation, and climatic changes in temperature and precipitation, which greening has more than compensated for any of the negative effects these phenomena may have had on the global biosphere during that time (Nemani et al., 2003; Young and Harris, 2005; Liu et al., 2010; De Jong et al., 2012; Eastman et al., 2013; Mao et al., 2013; Wu et al., 2014 ). Second, there is compelling evidence that the atmosphere's rising CO2 content -- which is considered by many to be the chief culprit behind concerns about the future of the biosphere via indirect threats projected to result from CO2-induced climate change -- is most likely the primary cause of the observed greening trends (Piao et al., 2006; De Jong et al., 2012; Andela et al., 2013; Donohue et al., 2013; Mao et al., 2013).

The observed CO2-induced greening of the Earth portends several obvious benefits for both society and nature. The increasing density and aerial coverage of vegetation, for example, helps to reduce the negative effects of soil erosion caused by the ravages of wind and rain. It also provides an increased source of food for both humanity and wild nature. Plant and animal biodiversity is also similarly stimulated, as vegetative productivity is highly correlated with biodiversity in natural habitats. And thanks to the recent work of Sedda et al. (2015), we now have another reason to celebrate CO2-induced greening -- it is helping to reduce poverty in developing nations.

Noting that reducing rural and urban poverty in developing countries was a "key target" of the United Nations Millennium Development Goals of 1990-2015, Sedda et al. set out to conduct a study to determine if satellite-derived Normalized Difference Vegetation Index (NDVI) data could be used to evaluate the degree to which this specific goal may or may not have been achieved. Based on NDVI data they obtained for a large area of West Africa, the team of researchers found that "the intensity of poverty (and hence child mortality and nutrition) varies inversely with NDVI," which findings, in their words, "highlight the utility of satellite-based metrics for poverty models including health and ecological components."

Because of the very positive connection that exists between landscape greening and atmospheric CO2 enrichment, as discussed earlier, it is quite plausible -- if not certain -- that the historic and ongoing increase in the air's CO2 concentration has played a significant role in the contemporaneous reduction in the portion of Earth's human population that has lived under poverty conditions, which currently stands at 21%, and which Sedda et al. say is "a reduction from 33% in 2000 and 43% in 1990," citing Ravallion (2012).

In light of these several observations, Sedda et al. conclude that since "the relative location of people in poverty and child mortality is dependent on the values of NDVI," a simple "accounting for NDVI can reduce the number of indicators required to measure the intensity of poverty," as well as to "improve the geographic targeting of pro-poor interventions," as a part of "the upcoming United Nations Sustainable Development Goals framework." But to its own disgrace, the United Nations simultaneously works to reduce the anthropogenic CO2 emissions that can raise the standard of living for all people of all countries.

Andela, N., Liu, Y.Y., van Dijk, A.I.J.M., de Jeu, R.A.M. and McVicar, T.R. 2013. Global changes in dryland vegetation dynamics (1988-2008) assessed by satellite remote sensing: comparing a new passive microwave vegetation density record with reflective greenness data. Biogeosciences 10: 6657-6676.

De Jong, R., Verbesselt, J., Schaepman, M.E. and De Bruin, S. 2012. Trend changes in global greening and browning: contribution of short-term trends to longer-term change. Global Change Biology 18: 642-655.

Donohue, R.J., Roderick, M.L., McVicar, T.R. and Farquhar, G.D. 2013. Impact of CO2 fertilization on maximum foliage cover across the globe's warm, arid environments. Geophysical Research Letters 40: 3031-3035.

Eastman, J.R., Sangermano, F., Machado, E.A., Rogan, J. and Anyamba, A. 2013. Global trends in seasonality of Normalized Difference Vegetation Index (NDVI), 1982-2011. Remote Sensing 5: 4799-4818.

Liu, S., Liu, R. and Liu, Y. 2010. Spatial and temporal variation of global LAI during 1981-20006. Journal of Geographical Sciences 20: 323-332.

Mao, J., Shi, X., Thornton, P.E., Hoffman, F.M., Zhu, Z. and Myneni, R.B. 2013. Global latitudinal-asymmetric vegetation growth trends and their driving mechanisms: 1982-2009. Remote Sensing 5: 1484-1497.

Piao, S., Friedlingstein, P., Cias, P., Zhou, L. and Chen, A. 2006. Effect of climate and CO2 changes on the greening of the Northern Hemisphere over the past two decades. Geophysical Research Letters 33: 10.1029/2006GL028205.

Ravallion, M. 2012. How Long Will it Take to Lift One Billion People Out of Poverty? World Bank, Washington, D.C.

Wu, D., Wu, H., Zhao, X., Zhou, T., Tang, B., Zhao, W. and Jia, K. 2014. Evaluation of spatiotemporal variations of global fractional vegetation cover based on GIMMS NDVI data from 1982-2011. Remote Sensing 6: 4217-4239.

Young, S.S. and Harris, R. 2005. Changing patterns of global-scale vegetation photosynthesis, 1982-1999. International Journal of Remote Sensing 26: 4537-4563.

Posted 14 August 2015