Little was taken but thieves were in the building for two hours. Windows stays and a door lock were damaged.
Pukenui Forest Trust ranger Bevan Cramp said the charitable trust operated purely on donations, so the theft was "a kick in the guts for sure".
"The GPS being taken means we have one less person on the ground at any given time. These are needed particularly by volunteers when its necessary to find traps, bait stations or any other point of interest."
The trail cameras were used to detect pests that may not be going into traps.
Cramp said without them, there was an increased probability of predators going undetected, which could detrimentally affect native species, including Pukenui's growing kiwi population.
Also, the theft of the projector prevented the trust and rangers from doing educational visits within the community, including spreading the responsible dog ownership message, which was vital for the success of the kiwi.
Whangārei Quarry Gardens manager Guy Hessell said thousands of dollars was going to be put into extra security whereas it should be going into buying plants.
"This feels like someone stealing from the Whangārei public. This is a community garden and the public volunteer hundreds of hours, which is done with a lot of love. This is gutting," Hessell said.
"It's a big community asset that we need to manage carefully with our limited funds."
Night-time security patrols are more frequent since the thefts.
Quarry Gardens marketing and events officer Kerry Marinkovich said five security cameras captured the break-ins and police were investigating.
"We remove money from the site every night after this happened the first time, so our donation box is now empty at the end of each day, leaving nothing of much value to steal."
Marinkovich said the ongoing cost of repairing windows and doors was outrageous for a non-profit organisation.
"We are now having to fork out for a loud alarm that will hopefully act as more of a deterrent, but comes at a significant cost to us.
"It is heartbreaking to face this situation on a frequent basis. We are trying our best to provide our community with a space of peace and beauty - and we are struggling to make ends meet."