Photo credit: geoftheref
New Zealand has long been associated with the eco-travel movement, having implemented a number of eco-friendly practices in their tourist industry over the course of many years. Just about any outdoor activity can be enjoyed in an eco-friendly manner, from whale watching and bird watching to trekking, biking, and caving. There are hundreds of New Zealand guide and outfitting companies that specialize in eco-tourism; most of them care deeply about sustaining their local habitats and work with both local and national conservation organizations to promote sustainability.
Black Cat Cruises, an established marine tourism guide company in Lyttelton and Akaroa, is a great example of how conscientious many New Zealand guide companies can be. They use new and efficient engines and energy efficient lighting for their fleet, plan routes that travel the least distance, train all their staff in environmental awareness, and employ locals to reduce commuting times (among a host of other eco-friendly steps that can be found here).
New Zealand is renowned for its organic farming industry, with established internship programs for tourists who want to stay awhile and really get to know the local culture. Willing Workers On Organic Farms (WWOOF) is the largest and most established network of organic farming opportunities in New Zealand with hundreds of listings to choose from.
The indigenous Maori culture set the tone for properly living within the means of the land many hundreds of years ago and provide a unique opportunity for eco-tourists to see how these practices have influenced New Zealand culture as a whole. Respect Nature Tours is one outfitter that works closely with Maori by hiring them as guides, using Maori-run accommodations and supporting local Maori preservation programs.