We have talked about two kinds of transitions already, demographic and energy. Let's talk about three others, well, the forest transition, agricultural transitions, and nutrition transitions. What are the forest transition? To understand forest transition, we have to understand the relationship between forest cover increase and deforestation. Just as Malthus predicted, that the birth rate of people is much faster, and therefore population grows much faster compared to the death rate and compared to food production. The dominant understanding of forest cover change, as population grows, we'll see a decline in forest cover. As time passes, we'll see forest cover declining. However, one of the most surprising changes in forest cover is that in many parts of the world, including in some poor countries or middle income countries such as China and India, we see forest cover increasing despite the population increasing. What explains this change, this empirical phenomenon where despite increasing pressure from more people, land cover and forest cover are increasing? The basic explanation for increasing in forest cover as rather than declines, it is because of what people do and the technological changes that are taking place. As the numbers of people increase, and after they have cut down a large area of forests, they realize that in fact forest do provide many different benefits that they need. Therefore, instead of cutting down trees to make use of them for their daily use or for their different needs, people begin to plant trees so as to increase the amount of wood available for their daily needs or for their different uses. This plantation, this effort to create new forest is what leads to increases in forest cover and despite the increasing numbers of people. It happens because of an increase in awareness that forests are important, products that forests provide for human use are important to maintain. It occurs also as a result of changes in institutions related to land so that when people plant trees, they can take benefit of and take advantage of the new forests that emerge. It's also a result of changes in economic incentives and how wood products become more expensive as a result of created scarcity of products from forests. So as a result of all of these different forces occurring together, forests becoming economically more valuable, as their extent declines, there is an incentive for many people to plant trees and to increase the area under forest cover. This is what leads to the forest transition. The agricultural transition is similar in its origins to the forest transition or any of the other transitions that we have talked about till now. At the root of agricultural transition are changes in technologies and in institutions and in behavior. So recall again Malthus' prediction, which was that we should not see increases in food production taking place as quickly as increases in population. But what has happened in stead in many countries is that we have new food production technologies that have rapidly increased the amount of food human societies can produce. In South Asia, for example, the adoption of Green Revolution technology by many farmers, not only far outpaced population increases, it created an enormous surplus for the Indian government to even be able to export food crops. Again, in the case of agricultural transition, the result that you have large amounts of food being produced, large numbers of agricultural commodities being produced, that result is occurring because of changes in technologies that enable larger amounts of food to be produced from the same area of land. They are a result of changes that human beings make in their production decisions by adopting new seeds, by adopting high-yielding varieties of crops, by adopting inorganic fertilizers to increase the fertility of soils, and by using pesticides and irrigation to reduce pests on the one hand and to provide plants more water to improve and to make more stable output from agriculture possible. The agricultural transition has happened in a large number of countries, certainly most of the Western European and North American countries. It has also happened in East Asia, in South Asia, and is happening in some countries in Africa as well. It is occurring because of the result of the adoption of new policies by governments, because of the technological changes in agricultural crops that I have already described, and because of choices that farmers make to earn better living from agriculture. The simplifications are, as a result of improvements in agricultural output, we are no longer confronted with the nightmare scenario that Malthus portrayed of widespread famines and loss of human lives because food production cannot keep up with population increases. The final transition I want to talk about is the nutrition transition. The nutrition transition is closely related to the agricultural transition. What it means is that we have more food available per capita today, despite a much larger population on the planet than was the case 20 or 30 or 50 years ago. Instead of the crisis of hunger that killed many people in the past, and which continues in fact, to kill many people today, we simultaneously also have a crisis of obesity. As people are able to eat more food, and as a result of eating more food, gain weight that is not as healthy for them as lower amount of food may be. The increasing obesity is occurring not just in rich countries, but also in poor countries. A much larger number of adults suffer from the risk of obesity than from the risk of hunger. Whereas in 1980, there were only 250 million people at risk of obesity. About 30 years later, this number had increased almost by three to four times. At the same time, we also know that in poor countries, a large proportion of the population is undernourished. The increasing obesity or the nutrition transition is also a result of changes in diets of people in both rich and in poor countries. It is a much more homogeneous diet, and often it comprises a lot of different processed foods rather than non-processed foods. The amount of food people are eating, the amount of calories they are consuming, has also increased substantially. So for all of these reasons, we are seeing a nutrition transition underway. It is creating greater risks to human populations as a result of obesity than has been the case in the past, and even greater than is the case of risk from hunger.