An upcoming conference being held at the Vatican examining the link between climate change and human trafficking is a reflection of the importance that ending modern slavery holds for Pope Francis, according to one of its organizers.

Presenting the meeting on "Modern Slavery and Climate Change: The Commitment of the Cities," Archbishop Marcelo Sanchez Sorondo, chancellor of the Pontifical Academy for Social Sciences, showed a copy of the handwritten letter Pope Francis had sent him suggesting that his office focus its efforts on the issue of human trafficking.

Pope Francis has been committed to combating human trafficking ever since he was Archbishop of Buenos Aires, when he established an annual Mass for the victims of human trafficking.

In a Sept. 23, 2011 homily, he stressed that "Jesus has not come to propose a theory of freedom," but rather "stands with our brothers and sisters who live under slavery."

"We have been taught that slavery has been abolished, but you know what? It is not true, because in the city of Buenos Aires slavery is not abolished. In this city slavery is present in different forms," the then-Cardinal Bergoglio said. And he gave as examples exploited workers, and the women and children forced into prostitution, and thus deprived of their dignity.

All these topics have been among the core issues of his pontificate.

The first time it was raised was during the speech Pope Francis gave Dec. 12, 2013 to a group of ambassadors newly accredited to the Holy See. The Pope underscored that it is a disgrace that persons "are treated as objects, deceived, assaulted, often sold many times for different purposes and, in the end, killed or, in any case, physically and mentally harmed, ending up discarded and abandoned," adding that the issue worries him very much.

Then on March 5, 2014 he sent a message to the faithful in Brazil on the occasion of the Annual Lenten "Fraternity Campaign," whose theme was "Brotherhood and human trafficking."

"It is not possible to remain indifferent before the knowledge that human beings are bought and sold like goods," Pope Francis wrote. "I think of the adoption of children for the extraction of their organs, of women deceived and forced to prostitute themselves, of workers exploited and denied their rights or a voice, and so on. This is human trafficking!"

The anti-human trafficking effort took an ecumenical angle when Pope Francis signed an agreement March 18, 2014 with Anglican Archbishop Justin Welby, by which the Church and the Anglican Communion will support an anti-slavery, anti-human trafficking initiative, the Global Freedom Network. The agreement was also underwritten by a Sunni scholar on behalf of the grand imam of al-Azhar University in Cairo.

The Pontifical Academy for Social Sciences took the floor Nov. 2-3, 2014, organizing a workshop on 'Trafficking in Human Beings: Modern Slavery.' Upon the close of the seminar, conference organizers issued a "joint statement based on the suggestions presented by the participants," which included proposals for media, religious institutions, civil organizations, and the business sector to work together in order to combat human trafficking.

One month later, Dec. 2, 2014, Catholic, Orthodox, Anglican, Jewish, Muslim, Hindu, and Buddhist leaders signed a Joint Declaration of Religious Leaders Against Modern Slavery as a public statement of their commitment to work together in spiritual and practical action to eradicate this crime against humanity and restore dignity and freedom to its victims.

In the mean time, the Pope had chosen the theme of the 2015 World Day of Peace, "No longer slaves, but brothers and sisters," thus making human trafficking one of the core issues of Vatican diplomacy during the year.

The Pontifical Academy for Social Sciences organized Apr. 27, 2015 a conference on "Trafficking with a special focus on children," together with the Swedish embassy to the Holy See.

The upcoming conference with the mayors of some 70 prominent cities worldwide is intended to combine environmental issues with human trafficking issues, through Pope Francis' approach.

In the encyclical Laudato Si', Pope Francis had in fact backed this combination between ecology and human trafficking issues.

In paragraph 91 of the encyclical, Pope Francis wrote that "a sense of deep communion with the rest of nature cannot be real if our hearts lack tenderness, compassion and concern for our fellow human beings. It is clearly inconsistent to combat trafficking in endangered species while remaining completely indifferent to human trafficking, unconcerned about the poor, or undertaking to destroy another human being deemed unwanted. This compromises the very meaning of our struggle for the sake of the environment."

This way, Pope Francis has brought his care for the victims of human trafficking to a higher lever. From care for victims, to diplomatic effort, up to a theological approach based on the notion of 'human ecology'.

These are the steps Pope Francis has undertaken in combating human trafficking, on the basis of his past experiences as Archbishop of Buenos Aires.