Just 27 percent of the forest that once covered the Wellington region is left.
A report from Greater Wellington Regional Council charts the decline of forests and highlights the dangers of further losses.
It said the biggest casualties were lowland forests, which had made way for farming and urban growth.
Report co-author Philippa Crisp said the loss of the forest was significant because it would have been a space for native fauna, such as birds and lizards.
She said some forests needed extra protection.
"Those are the main things, keeping stock out.
"In some cases people could do pest control but it's more just making sure we don't allow those … to degrade further."
Ms Crisp urged landowners to take charge and manage what remains and plant more.