The fact that sustainability science is interdisciplinary and concerns itself with the relationship between knowledge and practice, leads to a number of other implications. One, sustainability science is a science of trade-offs and co-benefits. We will talk about what each of these mean. But even the very basic meaning of trade-offs suggests that we need to think about more than one goal, and to understand what's the relationship between these two goals. You need to understand how we can manage to improve what we want on one goal without sacrificing what we want on another goal. When this is impossible, but it is not possible to achieve one without compromising the other, we have trade-offs in place. Now, given that sustainable development goals Number 17. So given that there are 17 different sustainable development goals, it would be very hard to imagine that we can achieve all 17 of them together. We need different actions to achieve different goals. But there are interactions among these goals. There are interactions between the goal of eliminating hunger or eliminating poverty on the one hand, and maintaining biodiversity on the other. There are tensions between the need to reduce climate change, to reduce the emissions that lead to climate change, and the goal of economic growth. So we need to think about when does it, the trade-offs are impossible to avoid, and what trade-offs we are willing to live it. The multiplicity of different Sustainable Development Goals, and their targets, and their Indicators suggests that trade-offs are inevitable when we are trying to work toward sustainability and development outcomes. Understanding and managing these trade-offs is a central part of what sustainability science is about, what sustainable development is about. The second element that comes across very clearly in sustainability science, because it focuses on sustainable development, is that it is a science of transitions. We need to understand how societal transitions take place. Because we are on paths, on trajectories of unsustainable development at present, you need to change that. But such societal change requires a deeper understanding of societal transitions and that is a central element also of what sustainability science is about. The third major focus on sustainability science also comes about as a result of its attention to translate research into practice. There's any amount of research that is being carried out, and which will never have an impact on the real world. Indeed, much research searches for how to become relevant to policymakers and to decision-makers. This need to understand implementation pattern as the third focus in sustainability science. Sustainability science is also an implementation science. Finally, because insights in sustainability science come from so many different sources, from so many different disciplines, it is necessary to bring these together, and to think about how to synthesize knowledge, and scientific insights from different fields. So these four imperatives of sustainability give rise to the four different emphasize in sustainability science, the need to understand and manage trade-offs, the need to think about societal transitions, the need to implement scientific findings into real-world decisions and practice. Finally, the need to synthesize knowledge from across multiple fields of scientific endeavor and investigation. What do we mean by trade-offs and benefits? As I said, interactions between different sustainability objectives, between the social, the economic, and the environmental across the different 17 development goals. Among the many different initiatives and interventions that we are attempting to achieve these goals. Interactions among these are all over the place, they are ubiquitous. Understanding these interactions, how they affect one goal versus another, how they may be contributing to achievement of multiple goals is critical, and is necessary for sustainability and development to be achieved. Interactions may occur between the goals. They may affect different groups of people in different ways. Some people may benefit and some people who may be harmed by different interventions. There are also interactions over time. We may achieve things more today and then not be able to do what we want tomorrow, or by sacrificing some goals today, we may be able to achieve them better tomorrow. So these interactions among goals, among people in different social groups, and across time are what trade-offs are about. They are what gives rise to trade-offs and they necessitate a deeper understanding of how trade-offs happen and how to manage different trade-offs. What exactly are trade-offs? We can define trade-offs very simply. Trade-offs happen when it is not possible to improve what we want to achieve in one arena, in one area, without making things worse off in another arena. When achievements with respect to one goal, with respect to one group of people, with respect to one time period, worsen the outcomes related to another goal, related to another group of people in a different time period. That is when trade-offs occur. What are some examples of trade-offs? Think about health versus leisure. If you have leisure, you may want to rest, but if you rest you may not be able to undertake exercise affecting your health over time. If you consume what you earn today, you may not be able to save. So consumption versus savings, there is a trade-off between them. When we tax one group of people to support another, there's a trade-off between the well-being of one group versus the well-being of another. When we try to grow our company without taking care of consolidating what we have already achieved, there is a trade off between growth and consolidation. So trade-offs are all over different spheres of our existence. They are present in many different ways and affect what we do and what we choose to do. Contrasted to the idea of trade-offs is the idea of co-benefits. Co-benefits happen when it is possible to improve outcomes in one area while outcomes in a different area don't change, or an outcomes in a different arena also improve. So when it's possible to improve outcomes from one group of people has also a different group of people at the same time, you can imagine that there are co-benefits occurring. We can undertake interventions to improve outcomes for hunger or poverty, and at the same time, also protect biodiversity or reduce the measurements, we are talking about co-benefits. What are some examples? If you use your leisure time, for example, to undertake physical activity, and you enjoy the physical activity, then you are also at the same time improving your health. Often we hear that there's a pleasure in giving, in donating what you can afford to others. There is a pleasure in giving. This is another example of a co-benefit. Often we can also focus on improving market share, but the goal at the same time improving profits. So co-benefits can happen. They are perhaps more rare compared to trade-offs. But both trade-offs and co-benefits occur in the real world as a result of the choices we make, as a result of the activities, and interventions we undertake. The goal of sustainability science is to understand better the trade-offs between different dimensions of sustainability, and different aspects, different goals related to development.