On his way to the hall, the Pope was asked to plant a tree in the United Nations Centre park.
"I was happy to carry out this simple symbolic act, which is so meaningful in many cultures," he said, adding that the act is both "an invitation to continue the battle against phenomena like deforestation and desertification" and "an incentive to keep trusting, hoping, and above all working in practice to reverse all those situations of injustice and deterioration which we currently experience."
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He noted the upcoming climate change conference in Paris, saying, "It would be sad, and I dare say even catastrophic, were particular interests to prevail over the common good and lead to manipulating information in order to protect their own plans and projects."
The Pope called for the upcoming conference to help develop a new energy system "which depends on a minimal use of fossil fuels, aims at energy efficiency and makes use of energy sources with little or no carbon content." At the same time, the poor and underprivileged must be taken into account, he said.
Therefore, the upcoming conference must have "three complex and interdependent goals: lessening the impact of climate change, fighting poverty and ensuring respect for human dignity."
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He warned that "the culture of deterioration and waste" has human victims, questioning whether the modern world is "growing accustomed to the suffering of others, as if it were something normal."
The Pope drew attention to an increasing number of migrants fleeing poverty that is aggravated by environmental degradation.
He also warned of urbanization accompanied all too often by social breakdown, drug trafficking and use, violence, and a loss of identity. Efforts must be made, he said, to work for the right to land, lodging and labor, as well as to promote city planning and maintenance that take into account views of local residents and alleviate poverty.