Promoting ecological awareness and sustainability of God's creation is now considered as a primary task of the CST. However, from its beginning with Rerum Novarum, CST emphasizes the promotion of social justice and equity, and highlights the dangers of economic inequalities between richer and poorer nations and the need for distributive justice. To that effect, human development was its central theme, which is favored by the dominion mandate and is known nowadays as the Anthropocene. Important documents like Gaudium et Spes and Populorum Progressio are illustrative for this anthropocentric stance, while less attention is given to the wellbeing of nonhuman creatures and natural ecosystems. Nevertheless, from Octogesima Adveniens onwards, the CST starts to look into environmental issues. Pope Francis' Laudato Si' in 2015 introduces a significant shift by referring to nonhuman creatures as ‘our fellow creatures’, thereby extending ‘intrinsic value’ to all nonhuman creatures. In his integral ecology, he promotes a sustainable and integral development that favors the wellbeing of both human and natural environments. In this article, we assess Laudato Si's view on sustainability and integral development in confrontation with the wider framework of the Planetary Boundaries's concept of sustainable development.