 I'd like to share one idea about managing water scarcity for food security, focusing on sub-Saharan Africa. The world's population has been increasing continuously and this has been translated into more mouths for food. And agriculture and food production needs a lot of water. Actually, right now, just for irrigation itself, they use about 70% of withdrawn water resources. And as a consequence, many rivers and lakes are drying up. So we are facing great challenge to produce more food with limited water resources. Then the question is where we should focus on to produce more food with per drop of water. Food production is not just for local consumption, it is also for international trade. At the moment, the international traded food accounts for about 15% of the total production. And international trade carries virtual water, which is the water used for production, during the production. North America and South America and Oceania are the major food exporters and also the virtual exporters. Asia and Africa are the major importers of food, also the importers of virtual water. In this map of water scarcity, as you can see, actually the major water scarcity regions are in the middle latitude of northern hemisphere. And in sub-Saharan Africa, there isn't physical water scarcity. However, in sub-Saharan Africa, yield, crop yield is very low, typically one third of the global average. And why it is that? We did a lot of studies on the factors influencing the yield growth in sub-Saharan Africa. And crop models are widely used for this kind of investigation. And coupling it with the GIS, we can do a large-scale simulation and find out what factors are important for crop growth. This slide actually shows one of our research result, which is simulated result for maize yield in sub-Saharan Africa. The total height shows the range of the yield. The red line shows the average yield of maize at this moment for the whole continent. And then the second bar actually shows if we increase the water supply to meet the demand by the crops, what will happen? It shows actually it doesn't have much impact on yield because yield doesn't increase much. The third bar actually shows when we increase the fertilizer supply to meet the demand of crops, and then you can see the yield jumps by a big margin. But the range is still very large because this means the range or the yield is unstable. And the last one, last bar actually shows that the yield is stable with water supply and sufficient fertilization. And here we want to show the technology and know how actually there, we know how to improve the yield. For sub-Saharan Africa, if we can double the yield, then the sub-Saharan Africa would not need to import cereal anymore. If we can triple the yield, then there will be surplus for export. So with many regions in the world having water scarcity and the increasing production becomes more costly and sub-Saharan Africa is a new source for the future food supply and virtual water supply to alleviate water scarcity in other regions. So a Chinese entrepreneur once has said, give me Africa and I can feed the world. He's wrong, he cannot have Africa, but he's right in a way that Africa does have the big potential to provide food to the world. And the challenge is how to unleash this potential in a sustainable and equitable and economically way.