By 2050, cities are expected to house about 70% of the world's population. The United Nations' Sustainable Development Goals emphasize the need of making these cities safe and sustainable for everybody. Cities all throughout the globe are innovating to help address issues such as climate change. Tiny urban woods are one of the projects. Other ideas include renewable energy systems, green roofs, and bike sharing programs. Cities use a large proportion of the world's resources. Therefore, it is important that they become more sustainable so that everyone can live in harmony with their environment.