VI Annual Meeting of the African Economic History Network (AEHN)
Climate shocks in tropical Africa and Asia in the pre-carbon emission age
Did African farmers face greater insecurity?
Kostadis Papaioannou1
Wageningen University
&
Ewout Frankema
Wageningen University
Abstract
In this paper we exploit a new dataset of annual and monthly rainfall levels collected from local
meteorological stations set up by former colonial governments to re-assess the longstanding idea
that specific environmental conditions have hampered agricultural productivity growth in tropical
Sub-Saharan Africa more than in other regions of the world. We conduct a statistical test to venture
more deeply into the various aspects of rainfall variability, and especially the frequency and intensity
of rainfall shocks. We find that in the period of 1920-1940, that is before notable global
anthropogenic carbon releases, African farmers were confronted with greater climatological
instability. Rainfall shocks in tropical Africa were both more frequent and more severe than in
tropical Asia, translating into higher cultivation risks. Controlling for mean rainfall levels, these
shocks explain part of the variation in population densities on a district level, adding further
evidence to the idea that climatological instability has created adverse conditions for agricultural
intensification.
1
Acknowledgements. We are grateful for the financial support European Research Council under the
European Community’s Seventh Framework Programme (ERC Grant Agreement no. 313114) as part of
the project Is Poverty Destiny? A New Empirical Foundation for Long-Term African Welfare. Any remain mistakes
remain our own.
VI Annual Meeting of the African Economic History Network (AEHN)
1. Introduction
There is a longstanding idea in several strands of historical, economic and environmental
sciences literature that adverse environmental conditions have hampered long-term African
agricultural productivity growth, especially in the tropical parts of the sub-continent. Adam Smith
in his Wealth of Nations already alluded to the lack of opportunities for sea-bound trade and related
division of labour, as Africa had none of the great water inlets such as the Baltic or Mediterranean
seas to ‘carry maritime commerce into the interior parts of that great continent’ (1776, p. 30, quoted
in Bloom and Sachs 1998, p. 237). In the tradition of the Annales school, Fernand Braudel also
emphasized the importance of environmental conditions, or “geography”, in explaining divergent
development paths between Europe and Africa in the longue durée. According to Braudel, Africa’s
lack of navigable waterways inhibiting the commercialisation of subsistence economies (Braudel
1995; Sowell 1998). Indeed, the very idea that high transportation costs resulting from a highly
uneven spread of populations in large landlocked areas, have hampered long-term economic
development in Africa is a recurrent theme in studies of African development (Collier 2008; Gallup
et al. 1999).
That tropical regions have been, and still are, at a disadvantage in agricultural development
has been widely advocated. Farmers in tropical regions often face rapid nutrient depletion of soils
(torrential rains leach nutrients quickly), and a more limited scope for diffusion of domesticated
plant and animal species and related agricultural innovations (Diamond 1997, Hibbs and Olsson
2005). However, it has also been suggested that some environmental conditions were more adverse
to agricultural productivity growth in tropical Africa than in tropical Asia or America. Human, plant
and animal diseases have been thought to be more severe, such as the constraints on the use of
animal draft power, manure and transportation opportunities imposed by trypanosomiasis (Goody
1971, Alsan 2012, Frankema 2015). Soil compositions also appear to be more heterogeneous than
elsewhere, complicating attempts at land re-generation by farmers (Otsuka and Larson 2013). And
although most of the literature tends to emphasize distinctive differences in state capacity as the
key factor in explaining why tropical Africa, contrary to large parts of tropical Asia, failed to benefit
from green revolution technologies, it is also acknowledged that the environmental constraints to
productivity growth were, on the whole, higher in Africa than in Asia (Conway 1998, Djurfeldt et
al. 2005, Otsuka and Larson 2013, Frankema 2014).
Tropical Africa’s climatological conditions are considered to be particularly
disadvantageous for agricultural productivity growth. Sub-Saharan Africa is not just generally dryer,
with larger arid areas, rainfall patterns also tend to be more erratic (Bloom and Sachs 1998, p. 222).
In the past few decades the World Bank has composed drought indicators showing that a large
group of tropical African countries experiences droughts more frequently and that there are
VI Annual Meeting of the African Economic History Network (AEHN)
significant differences in rainfall variability with other parts of the tropical world. Yet, virtually all
climate studies focussing on variability concentrate on recent periods that are affected by global
climate change (Hsiang et al. 2013; Bulte and Klomp 2013; Dell et al. 2014.). There are very few
studies that systematically exploit historical data from meteorological stations, to explore whether
such differences in rainfall patterns have been of a more structural nature, independent of high
anthropogenic carbon emissions (Papaioannou 2015, Papaioannou and de Haas 2016).
This paper aims to re-assess the structural differences in rainfall variability between tropical
Africa and tropical Asia in the 1920s and 1930s, that is, before the era of high global anthropogenic
carbon emissions, using a new dataset of annual and monthly rainfall levels collected from local
weather stations set up by former colonial governments. We conduct several statistical tests to
venture more deeply into the various aspects of rainfall variability. We are especially interested in
the frequency and intensity of rainfall shocks (deviations from the mean). We find that in the period
of 1920-1940, African farmers were confronted with greater climatological instability. Rainfall
shocks in tropical Africa were both more frequent and more severe than in tropical Asia, translating
into higher cultivation risks.
In the second part of this paper we take this conclusion a step further by exploring the
links between rainfall regimes, including both the average annual spread of rainfall (unimodal or
bimodal) regimes as well as the shocks (deviations) from this regime, to test whether both aspects
correlate with historical densities of population on a district level. We find that, controlling for
mean rainfall levels, rainfall variability indeed explains an additional part of the variation in
population densities across tropical Africa and Asia. This adds further evidence to the idea that
climatological instability has created adverse conditions for agricultural intensification.
All these results lend further support to the idea that, underlying clear differences in
colonial state capacity, differences in rainfall variability played a role in the development of
agriculture in former European colonies in tropical Africa and Asia.