The mass arrival of cane toads in the delicate Kimberley region of Western Australia is the biggest environmental disaster to ever hit the region, Premier Colin Barnett says.



The Kimberley Toad Busters group, which claims to have captured more than 2.8 million cane toads in the Northern Territory and WA since 2005, says distinct flora and fauna is now under major threat.



The pests have begun marching south towards Broome and are endangering freshwater crocodiles, goannas, turtles and quolls, and many other native animals.



Mr Barnett said the spread of cane toads, which are estimated to have infiltrated about 50 per cent of the Kimberley in the past three years, was an environmental tragedy.



"It is an absolute tragedy, from a species introduced into Queensland and that has spread across," Mr Barnett told ABC radio on Wednesday.



"Despite valiant efforts by government and volunteers the procession continues on. It will destroy much of the native flora and fauna.



"The state government has had a program underway where many of the endangered species, both plant and animal, have been transferred to the islands off the Kimberley so at least they will survive.



"But it has been the greatest tragedy for the Kimberley we could have ever imagined."



The species was introduced into Queensland in 1935 and it has taken several decades to get this far west.



KTB founder and president Lee Scott-Virtue said the first toad arrived just east of the famous Bungle Bungles about a fortnight ago, and were expected to reach Kalumburu at the same time they reached Broome.



AAP