irrigation land appears to also raise the risk of conflict over land. Irrigated areas have higher predictability in terms of agricultural production as opposed to rainfed areas and the productivity gains from irrigation (or rents) are likely to be concentrated, making them more “lootable”. Thus, during periods of heightened fragility irrigated areas may be a “high-value” target for political groups engaged in conflict looking to gain income/ food security from land-grabs.

# _5.2.2 Empirical Approach: The Spark as a Shock_

The presence of irrigation, however, may be correlated with various characteristics such as the presence of crops, local climate conditions and population density, which may be driving the observed differential trends in Figure 3. To control for these, the relationship between conflict and the presence of irrigation during the post-Arab Spring period of heightened fragility is next examined in a difference-in-difference framework through an empirical specification that that controls for covariates of irrigation that might be influencing the observed differential trends. Specifically, the following regression is estimated: c c i i i i i i where the outcome of interest ii c c i is an indicator variable that equals 1 if a battle event occurs in ii ii ii ii ii ii cciicctt = ββ ln(i iieeii + 1) × SSccPPtt + γγ XX + ωωWW + δδ + αα + εε grid-cell in country in a given year . The variable i i i is a time-invariant measure of the area in ii cciicctt each grid-cell that was irrigated in the initial period, while is a dummy variable that takes on a value ii of 1 if t refers to the years after 2011. ii cc<sup>12</sup> tt The coefficient captures the differential trend in conflict between iieeii ii cells with high-irrigation and low-irrigation grid-cells in the post-Arab Spring period. Additionally, ii SSccPPtt is a ββ set of time-invariant cell-specific characteristics that may be correlated with the presence of irrigation and ii XX includes log of population at the start of the period as well as dummies to indicate the presence of wetlands, croplands, pasture lands, rivers and the homelands of ethnic groups that historically relied on agricultural livelihood strategies. allows for the effects of these characteristics to vary in flexible form over the period of the analysis. i is a vector of time-varying controls for rainfall and temperature to ii γγ control for differences in climate over time and across grid-cells. Lastly i is a set of country-year fixed effects, and a set of grid-cell fixed effects that account for average differences in other unobserved WW δδ characteristics. All errors are clustered at the grid-cell level.<sup>13</sup> ii αα Table A3 presents the results. For the G5 Sahel countries, there is a statistically significant and large positive increase in the likelihood of conflict breaking out in grid-cells where more irrigated land is observed and unchanged by multiple controls.<sup>14</sup> This is not found to be true for the rest of the countries in Western or Sub-Saharan Africa. The evidence does suggest the existence of differential trends in North Africa, which

> 12 The use of c (i i i + 1) instead of c (i i i ) is to ensure that gridcells with zero irrigation are not dropped from the analysis. Alternate specifications such as c (i i i + 0.1) , c (i i i + 0.01) , inverse ii ii hyperbolic sine of irrigated area (which is defined for zero) or the inclusion of a simple dummy to indicate the iieeii iieeii ii ii presence of any irrigation also produce similar results. iieeii iieeii

13 In additional results not reported here, we also confirm that our results are robust to the use of standard errors estimated after accounting for spatial autocorrelation.

> 14 See Table A3. Columns 1 – 4 sequentially include controls for country-year fixed effects, grid-cell fixed effects, timeinvariant controls, as well as controls for weather. A stable coefficient indicates that the relationship is robust to the inclusion of a rich set of controls. Columns 5 – 8 and 9 – 12  estimate the same regression for the rest of Western Africa and the rest of Sub-Saharan Africa, and show that there is no differential change in conflict trends between irrigated and non-irrigated grid-cells in these countries. Columns 13 – 16 show the differential trends in North Africa, but the magnitude decreases by half after controls are added in columns 15 and 16.

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