The announcement, only three days after the former Clutha-Southland MP received a knighthood in the Queen's Birthday Honours, came at a function in Lake Hayes last night.
The gathering included many volunteers from the 15 community groups the trust oversees and supports.
Sir William said his support for the trust was his contribution to the Predator Free 2050 goal of ridding the country of possums, rats and stoats.
''Predator Free NZ is a brilliant generational challenge to restore our environment.
''I support Wakatipu Wildlife Trust because this community effort makes the vision possible in this beautiful landscape, and it's our bit of the national mission.''
Formed nearly a year ago, the trust is an environmental charity with the goal of creating and expanding predator-free zones throughout the Wakatipu Basin to bring back native wildlife and birdsong.
It is an umbrella group for 15 community groups engaged in trapping projects from the head of Lake Wakatipu to Kingston.
The volunteers have caught more than 1600 rats, possums and stoats in the past 12 months.
Trust executive officer Ting Zhang said recent grants from the Department of Conservation and Queenstown Lakes District Council, along with fundraising from community groups, meant the number of traps would soon increase to nearly 1000 around Lake Wakatipu.
''Our ultimate vision is to have zero gaps among the communities, expand up mountainsides and reserves, and link up with trapping programmes beyond the Wakatipu region in order to save wildlife everywhere.''
