People who cut down trees on river banks could face prosecution.
The warning comes from the Hawke's Bay Regional Council, which is concerned about the cutting and destruction of river edge flood protection trees around the region.
Operations engineering officer Vince Byrne said more people were targeting the protective trees for firewood.
"The cutting of trees on river berm land is prohibited and HBRC will be taking stern measures to apprehend and prosecute the offenders."
People have been prosecuted in the past because the trees along the region's rivers are a primary defence in mitigating flood flows.
"In the first instance, they protect and hold the riverbank, and secondly they slow water flow between the trees and the stop bank, which reduces erosion on the stop banks," Mr Byrne said.
One of the flood protection methods used by the council to enhance the tree line protection was to fell live trees, leaving them attached to their stump. This practice is called "layering or lopping" and encourages the tree to sucker into the river bank and form a dense permeable edge protection barrier.
Mr Byrne is urging anyone who sees people taking trees from the river bank to call HBRC as soon as they can.