Indigenous Vegetation Health and Extent

 
 

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What is being monitored?

 
Anticipated Environmental Result:
  • Retained or increased land area in indigenous vegetation.
Monitoring:
  • To biennially survey, using aerial photography, the indigenous vegetation cover throughout the Lakes A Zone.

Purpose of monitoring

The health and extent of indigenous vegetation in the Lakes A Zone provides an overall picture of the state of ecosystems and habitat of the area. Monitoring trends in the extent and health of indigenous vegetation provides information for better management of the Lakes A Zone.

Reports available

 
 

Current trends

Extent of indigenous vegetation in the Lakes A Zone

About 74% (25,504 ha) of the area of Lakes A Zone in 2006 was covered in indigenous vegetation. In 2011 the extent of this vegetation increased by a net 57 hectares. The total (gross) increase in this time was 95 ha and the total decrease or ‘loss’ was 38 ha, which equates to a net 57 ha increase.

Despite being an increase, 57ha is less than 1% of the total area of indigenous vegetation in the Lakes A Zone. Further analysis would need to be undertaken examine where the losses have occurred, and determine whether they are natural, legal/illegal, or otherwise. The location and cause of this loss needs to be examined as the rules of the Lakes A Zone require retention of indigenous vegetation.

Table 1 shows the changes to the extent of vegetation according to their structural class. The loss of Mossfield in particular is of concern as Mossfield is listed as a national priority for protection in the New Zealand Biodiversity Strategy (Ministry for the Environment, 2000) as it is an ‘originally rare’ ecosystem. The report states that ground truthing is needed to determine whether it is a ‘real’ change or loss, or whether it is due to difficulties in assessing changes through aerial photography.

 

Table 1. Extent of indigenous vegetation present in the Lakes A Zone, Rotorua District, for each vegetation class, based on 2006 and 2011 aerial photographs. (Note: figures are rounded to one decmal point)

Health of indigenous vegetation in the Lakes A Zone

A total of 110 sites were surveyed to determine health of indigenous vegetation, using aerial photography analysis. Most sites surveyed for vegetation health (canopy health) scored a 1 or 2 (on a scale of 1-4 where 1 is healthiest). Overall, vegetation health in the Lakes A Zone did not change significantly from 2006 to 2011.

An excerpt from the report says the followings the following on indigenous vegetation health:

 
"The canopy condition at each point was assessed using the following scale:
  • Appears healthy (90- 100% green canopy cover);
  • Obvious signs of canopy defoliation (1-2 dead trees present);
  • Some loss of canopy species evident;
  • Appears dead (90-100% loss of canopy cover).
The above scale allowed assessment of forest decline to be made and to assess whether forest is trending to shrub/treeland (i.e. loss of forest health)."

Table 2: Canopy condition scores in 110 randomised polygons across indigenous forest vegetation cover in the Lakes A Zone in 2006 and 2011.

"Canopy condition declined in nine polygons(sites) but improved in eleven polygons (sites). In all cases, change was only one level (i.e. 3 to 2), and no drastic deterioration of forest canopy was evident."

"Canopy condition declined in both fragmented patches of forest sampled, indicating that fragmented forest may be under greater pressure than forest buffered by contiguous cover. Forest in the Settlement Zone showed no change in condition."

 
To view the full report click here.
 

Page reviewed: 03 Jul 2019 10:12am