We assembled a time series of 20 Landsat thematic mapper images from 1982 t
o 1996 for Key Largo, Florida, to ascertain whether satellite imagery can d
etect temporal changes in coral reef communities, Selected reef and control
areas were examined for changes in brightness, spectral reflectance, band
ratios, spatial texture and temporal texture (Pixel-to-pixel change over ti
me). We compared the data to known changes in the reef ecosystem of Carysfo
rt Reef and terrestrial sample sites. Changes in image brightness and spect
ral-band ratios were suggestive of shifts from coral-to algal-dominated com
munity structure, but the trends were not statistically significant. The sp
atial heterogeneity of the reef community decreased in the early 1980s at s
cales consistent with known ecological changes to the coral community on Ca
rysfort Reef. An analysis of pixel-scale variation through time, termed tem
poral texture, revealed that the shallow reef areas are the most variable i
n regions of the reef that have experienced significant ecological decline.
Thus, the process of reef degradation, which alters both the spatial patte
rning and variability of pixel brightness, can be identified in unclassifie
d thematic mapper images.