Remarkably , we already possess the technology to solve almost all of our problems .The twenty-first century will likely see a swish from fossil fuels to more sustainable energy sources, such as photovoltaics, solar thermal electric generation , and biomass conversion. Whereas the paper of this book comes from trees , the paper of the future may well come from fast-growing weeds . More and more we are recycling waste products . In some parts of the world , progress is being made on stemming the human population explosion that aggravates almost every problem faced by humans today.