Non-Hydrostatic RegCM4 (RegCM4-NH): model description and case studies over multiple domains

We describe the development of a non-hydrostatic version of the regional climate model RegCM4, called RegCM4-NH, for use at convection-permitting resolutions. The non-hydrostatic dynamical core of the Mesoscale Model MM5 is introduced in the RegCM4, with some modifications to increase stability and applicability of the model to long-term climate simulations. Newly available explicit microphysics schemes are also described, and three case studies of intense convection events are carried out in order to illustrate the performance of the model. They are all run at a convection-permitting grid spacing of 3 km over domains in northern California, Texas and the Lake Victoria region, without the use of parameterized cumulus convection. A substantial improvement is found in several aspects of the simulations compared to corresponding coarser-resolution (12 km) runs completed with the hydrostatic version of the model employing parameterized convection. RegCM4-NH is currently being used in different projects for regional climate simulations at convection-permitting resolutions and is intended to be a resource for users of the RegCM modeling system.

The causes and consequences of fisheries conflict around the Horn of Africa

Fisheries conflict is an underappreciated threat to the stability and health of communities. Declining fish populations, rising demand for seafood, and efforts to reduce illegal fishing are increasing the risk that conflict over fisheries resources will undermine stability and peace. Here, we investigate the frequency, causes, and consequences of fisheries conflict in six countries around the Horn of Africa and East Africa (Tanzania, Kenya, Somalia, Djibouti, Eritrea, and Yemen) between 1990 and 2017. Fisheries conflict events were cataloged from news reports, and events were characterized by the date, location, actors, consequences, and drivers of the conflict. We found the rate of fisheries conflict is gradually increasing in the region, with spikes in conflict driven by the arrival of foreign fishing boats or international naval vessels. Conflict was caused primarily by illegal fishing, foreign fishing, weak governance, limits on access to fishing grounds, and criminal activities including piracy. Two-thirds of all conflict events occurred in Kenyan and Somali waters, with areas of high conflict intensity in the Lake Victoria region, near the Somali coastline, and in the southern Red Sea. During this period, 684 fisheries conflict events in the region resulted in over 400 fatalities, nearly 500 injuries, and over 4,000 arrests.

Modelling potential range expansion of an underutilised food security crop in Sub-Saharan Africa

Despite substantial growth in global agricultural production, food and nutritional insecurity is rising in Sub-Saharan Africa. Identification of underutilised indigenous crops with useful food security traits may provide part of the solution. Enset (Ensete ventricosum) is a perennial banana relative with cultivation restricted to southwestern Ethiopia, where high productivity and harvest flexibility enables it to provide a starch staple for ~20 million people. An extensive wild distribution suggests that a much larger region may be climatically suitable for cultivation. Here we use ensemble ecological niche modelling to predict the potential range for enset cultivation within southern and eastern Africa. We find contemporary bioclimatic suitability for a 12-fold range expansion, equating to 21.9% of crop land and 28.4% of the population in the region. Integration of crop wild relative diversity, which has broader climate tolerance, could enable a 19-fold expansion, particularly to dryer and warmer regions. Whilst climate change may cause a 37% – 52% reduction in potential range by 2070, large centres of suitability remain in the Ethiopian Highlands, Lake Victoria region and the Drakensberg Range. We combine our bioclimatic assessment with socioeconomic data to identify priority areas with high population density, seasonal food deficits and predominantly small-scale subsistence agriculture, where integrating enset may be particularly feasible and deliver climate resilience. When incorporating the genetic potential of wild populations, enset cultivation might prove feasible for an additional 87.2 - 111.5 million people, 27.7 – 33 million of which are in Ethiopia outside of enset’s current cultivation range. Finally, we consider explanations why enset cultivation has not expanded historically, and ethical implications of expanding previously underutilised species.