The next several generations will need all the resources of science to choose optimal pathways into the future. Humanity faces a number of unprecedented challenges that are in part driven by the rapid expansion of the human population and associated resource demands. The global human population was less than three billion in 1950 and expanded to six billion by 2000. It is projected to reach approximately 9.3 billion by the middle of the twenty-first century.
This means that in 100 years, human-driven resource demands will have at least tripled. The amount of arable land to support each person will have been reduced threefold, and many essential resources will be severely strained. Moreover, the by-products of human activity—such as CO2 emissions—are changing the global climate and threaten to have uneven and possibly devastating impacts in some regions of the world. A short list of major twenty-first century challenges includes the following:
water supply and quality,
global energy transition,
ecosystem and species preservation, and
equity and quality of life.
These challenges are global and do not respect national boundaries. In almost all cases, science can suggest potential mitigations or even solutions to these challenges, but to do so science must be able to present options based on the best current knowledge to decision-making communities around the globe. A fundamental goal of the international scientific organizations that are built on national science academies is to create a bridge between