With regards to DoC - can you PM me and let me know exactly what type of work your OH is looking for - is it policy office job or is it hands-on work? That will depend on who he speaks to since DoC is pretty big in Welly. I'll find out a contact once I know what he's interested in.
With regards to GWC (Greater Wellington Council) which also encompasses where I'd think the majority of the jobs are for environmental work I'd phone the following number & ask for the head of whichever department your OH is interested in:
http://www.gw.govt.nz/section18.cfm? as you can see there are a lot of environmental related departments!
T 04 384 5708
Its a lot easier to get through to people here on the phone without being given the 3rd degree & they'll probably give you a name if they aren't there & their e-mail address. (Don't be surprised if people are still on holiday until the end of Jan if you phone now - its quite normal in NZ for people to take part or the whole of Jan off.)