There's a warning dozens of our native species could become extinct if the Government keeps scrimping on conservation spending in this year's Budget.

Department of Conservation (DoC) funding has dropped by more than $50 million a year since National came to power.

And a huge increase in tourism numbers has also left DoC staff struggling, often being forced to divert their attention away from core work due to a lack of funding.

Auckland University of Technology Tourism Professor Simon Milne warns it's crucial we maintain our clean, green image.

"Unless we resource and protect these natural environmental features, protect the biodiversity of the country, then the chances are we are going to suffer in the long term through a decline in visitor numbers.

"Another option would be perhaps to take a more user-pays type approach, to have the tourism industry contributing money in some way, depending on how they use these particular resources," Mr Milne says.

Forest and Bird's Kevin Hackwell says DoC is really starting to feel the pinch.

"Well over half of the budget is going into servicing huts, track, etcetera, and a huge amount of staff resources," Mr Hackwell says.

"There are now, on a good day, 3000 people walking across Tongariro Crossing. That involves an awful lot of work by Department of Conservation staff."

The Greens' Kevin Hague warns we need to take urgent action -- more than 140 native species face extinction, and they can't all be saved through corporate sponsorship.

Newshub.