Forest Health Checks in Northland Come Up with Encouraging Results
A series of annual health checks of Northland forests has come up with very encouraging results that show wild animal
control in the region is having the desired effect.
Bream Head Scenic Reserve at the tip of the Whangarei Heads has received possum control since 1993, which was
intensified in 1996. Vegetation monitoring was set up in 1993 to follow the response of the forest to the possum
control. The percentage of trees with possum browse has decreased from almost 100% in 1993 to 0% in 1999.
Trends in the condition of forests use information on possum densities to help interpret the vegetation monitoring data.
Possum densities are surveyed regularly in many Northland forests. In the case of Bream Head, possum numbers have been
kept in very low numbers since 1996, which has coincided with a rapid increase in forest health.
Northland Conservancy vegetation monitoring team members Kate McNutt and Patrick Whaley said the health checks were now
into their fifth year in some forests and all were showing strong signs of recovery following the removal of animal
pests like possums. The programme is hoping to expand into monitoring forest regeneration following the removal of goats
from Northlands forests.
"What we are doing with these monitoring programmes is moving away from the statistics of looking at how many animals we
have killed to looking at how healthy the bush is becoming," Ms McNutt said.
Forests like Bream Head, Waipoua, Whangaroa, Russell and Waima are among a large number being surveyed from December and
April each year by two fulltime DOC staff using a Landcare-Research developed system called the "Foliar Browse Index."
"What we have found is that in those forests where wild animal control work has taken place, the trees we survey have
shown very good signs of recovery," Mr Whaley said.
The system involves DOC staff checking on the health of a number of "ice cream species for possums like kohekohe,
pohutukawa, mahoe and pate which have been marked for surveying within the forests being monitored. The same trees are
checked every year.
The process has staff spending several months in the field gazing skyward to estimate the canopy density of these trees
and from this can determine the extent to which the trees have been browsed.
"The statistics we gather from this work enables the Department to answer management questions about how much possum
control is required to allow forests to recover and and remain healthy," Ms McNutt said.
"Its definitely work that would not suit most people as you end spending a lot of time in the field away from your home,
but we get to some awesome places in Northland that most people would never get to" she said.
For more information please contact Kate McNutt or Patrick Whaley on (09) 4380299