The conventional view of peacemaking is to focus on changing the environment to achieve peace. Such a view advocates the use of institutions, laws, economic structures, military power, etc., to create an environment in which peace can flourish. Buddhists do not oppose such a view, but stress the greater urgency of transforming the mind of the individual.
To transform our minds, we must understand the intimate relationship between the environment and the mind. Buddhists believe that if a person's mind is not pure and calm, whatever advanced technology he may possess, however pleasant the environment he may enjoy, he will not be happy. On the other hand, if a person's mind is pure and calm, even in a tumultuous and confusing environment, he or she can ride out the storm without losing composure. In the midst of disaster, he or she will not suffer, and will be able to help others.
Furthermore, if our minds are compassionate, we will tend to see the environment as deserving of our concern, and take steps to purify it through activism. The Buddha said, "The world changes according to our state of mind." In this way, environmental activism can be seen as an indirect result of cultivating meditation.
Source : "A Pureland on Earth"