In his continual effort to quell worldwide conflicts, Pope Francis Thursday chastised world leaders for lacking the will to make change, and also insisted true peace implies an “ecological conversion” or it won’t work.

In an annual message for the World Day of Peace, which is celebrated on Jan. 1, the pope implied that violence toward humanity and violence toward the planet go hand in hand.

“If a mistaken understanding of our own principles has at times led us to justify mistreating nature, to exercise tyranny over creation, to engage in war, injustice and acts of violence, we believers should acknowledge that by so doing we were not faithful to the treasures of wisdom which we have been called to protect and preserve,” he said.

Francis argued that the world is in need of “an ecological conversion” due both to the consequences of hostility toward one another and a lack of respect for the environment, often “seen only as a source of immediate profit, regardless of local communities, the common good and nature itself.”

He praised the recent October Synod of Bishops on the Amazon for the efforts it made to foster peace among communities and with the land. Each person, he said, is called to work for a better planet for future generations with responsibility for those at every level of society.

“All this gives us deeper motivation and a new way to dwell in our common home, to accept our differences, to respect and celebrate the life that we have received and share,” Francis said, adding that the ecological conversion he is calling for “will lead us to a new way of looking at life.”

This conversion, he added, “must be understood in an integral way, as a transformation of how we relate to our sisters and brothers, to other living beings, to creation in all its rich variety and to the Creator who is the origin and source of all life.”

“For Christians, it requires that the effects of their encounter with Jesus Christ become evident in their relationship with the world around them,” he said.

Instituted by Saint Pope Paul VI in 1968, the World Day of Peace is celebrated each year on the first day of January and is accompanied by a message from the pope sent to all foreign ministers around the world, which typically foreshadows the Holy See’s diplomatic tone during the coming year.

In his message, Francis pointed to global conflicts around the world, which he said are often sparked by an inability to respect differences, and urged people to learn from the past, pointing to the dropping of the atomic bombs in Hiroshima and Nagasaki as an example.

“Entire nations find it difficult to break free of the chains of exploitation and corruption that fuel hatred and violence,” he said, noting that often those who suffer most are “the innocent,” who become victims of humiliation, injustice and “the trauma born of systematic attacks on their people and their loved ones.”

“War, as we know, often begins with the inability to accept the diversity of others, which then fosters attitudes of aggrandizement and domination born of selfishness and pride, hatred and the desire to caricature, exclude and even destroy the other,” he said, adding that conflict is often fueled by “a perversion of relationships, by hegemonic ambitions, by abuses of power, by fear of others and by seeing diversity as an obstacle. And these, in turn, are aggravated by the experience of war.”

Peace and international stability are “incompatible” with efforts to “build upon the fear of mutual destruction or the threat of total annihilation,” he said, recalling his recent visit to Japan, where he visited Hiroshima and Nagasaki and met with survivors of the atomic bombs dropped there in 1945.

“Their testimony awakens and preserves the memory of the victims, so that the conscience of humanity may rise up in the face of every desire for dominance and destruction,” he said, adding that memory is a powerful tool in taking steps toward a better future.

Francis noted that the effort to achieve peace is often complicated due to private interests “between people, communities and nations,” which “are numerous and conflicting.”

“We must first appeal to people’s moral conscience and to personal and political will,” he said. True peace comes from the heart, he said, stressing that “political will must always be renewed, so that new ways can be found to reconcile and unite individuals and communities.”

Francis recently vented frustration over what he said is a lack of political will in implementing environmental protections called for by both the United Nations and his 2015 environmental encyclical Laudato Si.

Francis wrote in a message to the U.N. Climate Change Conference summit in Madrid, “We must seriously ask ourselves if there is the political will to allocate with honesty, responsibility and courage, more human, financial and technological resources to mitigate the negative effects of climate change.”

In his message for the World Day of Peace, he stressed that “the world does not need empty words but convinced witnesses, peacemakers who are open to a dialogue that rejects exclusion or manipulation.”

“In fact, we cannot truly achieve peace without a convinced dialogue between men and women who seek the truth beyond ideologies and differing opinions,” he said, and called for a more just and equitable economic system increasingly open “to forms of economic activity marked by quotas of gratuitousness and communion.”

“The peace process thus requires enduring commitment,” the pope said. “It is a patient effort to seek truth and justice, to honor the memory of victims and to open the way, step by step, to a shared hope stronger than the desire for vengeance.”