Vegetation change observed from on-ground repeat photography, Macquarie Island - 1980-2021

Brief description

Repeat photography from locations across Macquarie Island were visually compared to detect and categorise temporal changes in vegetation for each site. Photographs of the same scene in 1980, 2009 and 2014 were used. Terrain variables were used as predictor variables to investigate potential drivers of different types of vegetation change. Satellite-derived vegetation indices were compared with the on-ground photography for the latter period.

Dataset derived from visual analysis of a collection of repeat photography images from Macquarie Island. Three images from different years were compared for each location: 1980, 2009, 2014. Changes in vegetation were recorded for two change periods: 1980-2009 and 2009-2014.

MI Plateau 35year photo series_GPSdata and notes_Aug15_COPY.xlsx
Photograph metadata (location, dates, etc)

photochangesplateau.xlsx
Observed changes for each photopoint

photochanges_georef_3class.csv
Reclassified change data

WorldView_SVI_change_terrain.xlsx
Spectral vegetation indices (SVIs) derived from WorldView satellite sensor for photopoint locations. Calculated using ENVI software. NDVI - Normalized Difference Vegetation Index. MTVI - Modified Triangular Vegetation Index. SGI - Sum Green Index.

JScott photos 1980-2014.kmz
Location of photo points (i.e. location of photographer)

Shapefiles
ESRI shapefiles of point locations of centrepoint of 'photo zones', i.e. the subjectively defined areas where change was recorded within the viewshed of each photograph.

data
R files detailing data analysis plus csv files of data used for analysis.

Classes of vegetation/landscape:
Grass - short grassland (not Poa tussock) vegetation dominated by Agrostis, Luzula, Deschampsia, Festuca
Pleu - Pleurophyllum hookeri
Poa - Poa foliosa
Ace - Aceana magellanica and A. minor
Stilb - Stilbocarpa polaris (syn. Azorella polaris)
Bare - bare ground
Moss - bryophytes
Poly - Polystichum vestitum
Az - Azorella macquariensis
Az dieback - dieback of Azorella cushion plants (present/absent)

Change classes:
decrease
no change
increase

Data files use 0/1 values for binary data
0 = true/absent
1 = false/present
999 = NA/no data
e.g. GrassInc80 with a value of 0 means no increase in grass observed in the 1980-2009 period,
AceDec09 with a value of 1 means Acaena spp. did decrease in the 2009-2014 period,
landslide = 0 means site (polygon) not impacted by a landslide

Some datasets have been recoded to 4 categories:
0/1/2/3 value for decr/stable/incr/NA(unknown)
e.g. Poa80 = 0 means Poa foliosa decreased in the 1980-2009 period,
Bare09 = 1 means bare ground stable (no discernible change) over 2009-14