The Rio Declaration outlines 27 principles related to sustainable development and the environment that countries agree to uphold. The principles call for putting human needs at the center of development, respecting countries' sovereignty over their own resources while ensuring activities don't harm other countries or global commons, and meeting both environmental and development needs of present and future generations. They also stress the integration of environmental protection into development, international cooperation to reduce poverty and disparities, addressing the special needs of developing countries, and countries having common but differentiated responsibilities in addressing global environmental issues.