Today is the annual "Earth Day", a secular holiday of sorts that encourages people to pay attention to the state of our world's environment and particularly the threats to the beauty and purity of our material world. That's all well and good and we should certainly do so
But Earth Day also gives us an opportunity to put enviromentalism in its broader context, informed by a Christian understanding of the nature of the human person and of the gift of creation. To do this, it's worth revisiting Pope Francis' encyclical, Laudato Si.
When it was released, the secular media generally portrayed Laudato Si as the Pope's "climate change encyclical". Some people reacted to the letter with horror because it dared to cast doubt upon the modern worship of mammon in the form of "captialism". But both of these reactions miss the point. Laudato Si challenges us to a personal and social conversion of heart, so that we can return to God's original plan for humanity and all creation
This central purpose of the encyclical is evident right at the beginning, when the Holy Father points out that the harms to our material world come from the sin in our hearts. And he notes that we have forgotten the fundamental truth that we are an intrinsic part of creation, formed from the "dust of the ground" (Gen 2:7), and that our lives depend on the material bounty of the Earth. This is evident to us, not just from divine revelation, but by a reasoned contemplation of nature itself
The theme of returning to God's original plan is woven throughout the encyclical. Again and again, Pope Francis comes back to the idea that the troubles of our world are the result of our sinfulness, particularly our loss of a sense of the universal moral law and the abuse of our freedom. We see this in the underlying causes of environmental and economic exploitation and degradation   a utilitarian and technocratic way of treating each other and the absence of solidarity between people
All these problems rest on a faulty understanding of the nature of the human person. Pope Francis sees clearly that our modern world considers man as a being whose entire existence is determined by self-interested material needs and pursuits, without regard to his relationships with others. When one looks at the modern domination of our society by the ethos of economic libertarianism and hedonistic autonomy, the diagnosis certainly rings true. The Holy Father calls this an "excessive anthropocentrism", a failure to understand our true place in this world, particularly our interlocking relationships with creation, or fellow beings, and our Creator
It is in his discussion of these relationships that we see most clearly the Holy Father's true Christian anthropology, and his perception that God's original plan is the antidote to our modern world's problems. In Chapter Two of the encyclical, Pope Francis sets forth an extended exegesis of the Scriptural passages that reveal God's intentions for creation. The key passage, paragraph 66, is so important that it needs to be quoted in its entirety:

The creation accounts in the book of Genesis contain, in their own symbolic and narrative language, profound teachings about human existence and its historical reality. They suggest that human life is grounded in three fundamental and closely intertwined relationships: with God, with our neighbour and with the earth itself. According to the Bible, these three vital relationships have been broken, both outwardly and within us. This rupture is sin. The harmony between the Creator, humanity and creation as a whole was disrupted by our presuming to take the place of God and refusing to acknowledge our creaturely limitations. This in turn distorted our mandate to "have dominion" over the earth (cf. Gen 1:28), to "till it and keep it" (Gen 2:15). As a result, the originally harmonious relationship between human beings and nature became conflictual (cf. Gen 3:17-19). It is significant that the harmony which Saint Francis of Assisi experienced with all creatures was seen as a healing of that rupture. Saint Bonaventure held that, through universal reconciliation with every creature, Saint Francis in some way returned to the state of original innocence.[40] This is a far cry from our situation today, where sin is manifest in all its destructive power in wars, the various forms of violence and abuse, the abandonment of the most vulnerable, and attacks on nature.

It is certainly important to pay close attention to the Holy Father's comments on the specific environmental depradations that have been inflicted upon creation, particularly in the developing nations. But the true significance of Laudato Si can be found in its call to recapture the remnants of God's original plan for humanity, so that we can live in peace and harmony with each other and with all creation. This has to begin, as the Holy Father said in last year's Message on World Day of Prayer for Creation, with "a serious examination of conscience and moved by sincere repentance," so that "we can confess our sins against the Creator, against creation, and against our brothers and sisters"
Today, the Holy Father got right to the heart of the matter, in the prayer he sent out on his Twitter feed:

Lord, bring healing to our lives, that we may protect the world and not prey on it, that we may sow beauty, not pollution and destruction.

May this be our prayer on Earth Day, and throughout the year.