Reducing is the most important of the three R's. Human consumption--of food, energy, and other goods and services--is tied to greenhouse emissions, which in turn drive climate change. Reducing consumption can thus mitigate climate change by limiting greenhouse gas emissions associated with the production of goods and services.
Reusing, the second of the three R's, is better than recycling because it saves the energy that comes with having to dismantle and re-manufacture products. It also significantly reduces waste and pollution because it reduces the need for raw materials, saving both forests and water supplies.
The last of the three R's, recycling reduces the need for extracting (mining, quarrying and logging), refining and processing raw materials all of which create substantial air and water pollution. As recycling saves energy it also reduces greenhouse gas emissions, which helps to tackle climate change.