Pope Leo XIV will mark the 10th anniversary of the landmark encyclical Laudato Si’ when he opens a conference today at the Vatican celebrating his predecessor’s reframing of the ecological crisis as an issue of central moral concern to Catholics, and to those of other faiths and none 

This celebration of Laudato Si could not be more timely. Despite the crises of climate and nature becoming increasingly evident, the willingness of our political leaders to work together to address them is waning.  

A moral voice on climate  

In 2015, the publication of Laudato Si’ – on Care for Our Common Home – by Pope Francis – helped galvanise and broaden the ongoing international effort to address climate change. The encyclical certainly started an ecumenical and interreligious dialogue and triggered numerous joint initiatives and deliberations among many people of good will, regardless of their religious beliefs, starting with scientists, including through the Pontifical Academies of Sciences and Social Sciences. This meant that the document was incisive and scientifically rigorous, providing a closely argued treatise on the causes of and solutions to the ecological crisis facing humanity and the planet.  

Moreover, it encouraged greater integration between environmental and social issues, starting from what Pope Francis called integral human ecology. The Encyclical also framed the issue in clear, unambiguous moral terms. It focused on the deep connections between ecological crisis and social iniquity. For me, this represented a turning point in how climate change and nature loss should be considered, putting justice at its centre.   

Pope Francis not only brought the moral authority of his magisterium to the climate issue – it was also clear that the protection of the environment was a subject that he cared deeply about. I was at a meeting at the Pontifical Academy of Sciences attended by the Pope when he raised his concerns about a news article he had just read describing the thawing of permafrost in Alaska. This personal interest added a passion that everyone could perceive. But the Pope's Encyclical was not limited to expressing concern; it also sought to educate and build capacity: a perhaps surprising but highly relevant objective at this time of cultural drift. 

Momentum at Paris  

Without doubt, Laudato Si’ contributed substantially to the momentum building for what was to be the breakthrough Paris Agreement on Climate Change, struck at COP21 at the end of 2015. By mobilising Catholic and other faith communities around the world, it helped create pressure on politicians to adopt an ambitious pact at the Paris climate negotiations. It stressed the importance of tackling global warming and ecological destruction as a shared human responsibility, not as a partisan issue.  

But it was also a practical document, as well as a theological one, and it has served to galvanise action – including within the Catholic church. In 2020, Pope Francis announced that the Vatican City State would commit to becoming net zero by 2050, helping to lead by example.  

It was also followed by Laudate Deum, a shorter exhortation that is more direct, urgent and challenging in tone. It emphasised the lack of progress since Laudato Si’ and criticised a reliance on illusory technological solutions and political inaction.  

But it also continued to stress how social justice must be central to efforts to address climate change, and how care for the poor and vulnerable is inseparable from care for the earth.  

A reminder of what is at stake – and what is possible, together 

As Pope Leo prepares to mark the anniversary of Laudato Si, there are two elements to the encyclical that I believe should resonate particularly strongly at this moment in time. The first is that it refutes the idea – which is gaining ground among some evangelical faith groups – that Creation is at the disposal of mankind, to do with as we wish. Instead, it stresses that we are its custodians.  

The second is the importance of cooperation. At a time when the very concept of multilateralism is under attack, when the strongest countries seek to do as they please, and the weakest do as they must, it is vital to remember that climate change recognises no borders, and we have a duty to work together to tackle it. Our solutions will ultimately need to be global.  

This is an important concept that we share at WWF, under our motto of “together possible”. The dual challenges of climate change and nature loss cannot be overcome by individuals, communities, governments or businesses working in isolation, but only by our coming together to protect our common home.