Johan Rockström is a Swedish scientist internationally recognized for his work on global sustainability issues. Rockström is one of the pioneers of work on planetary boundaries first published in 2009. Rockström's work has defined nine planetary systems that help cushion our impact on the world, including the ozone layer, fresh water, biodiversity and a stable climate. The 9 planetary boundaries presented are considered fundamental to maintaining a "safe operating space for humanity". He has published more than 150 articles in areas ranging from land and water use to global sustainability. He is ranked among the most cited researchers in the world by Clarivate Analytics.