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REMOTE SENSING APPLICATIONS OF GEOBOTANICAL 
PROSPECTING FOR NON-RENEWABLE RESOURCES 
by 
Richard W. BIRNIE 
Department of Earth Sciences 
Dartmouth College 
Hanover, NH USA 03755 
For centuries, observers have recognized that changes in surface 
vegetation sometimes reflect the subsurface geology. This Study, know as 
geobotany, has been used as a prospecting guide for potential deposits of 
non-renewable mineral resources. In the last decade, numerouse remote sensing 
experiments have detected physical changes such as vegetation density and 
chlorosis (yellow discoloration) in plant canopies and correlated these 
remotely sensed changes with the heavy metal content of the soil. 
Greenhouse experiments on various plants grown under controlled 
conditions and field studies of plants growing in their natural environment 
have confirmed that the reflectance properties of the vegetation change 
with heavy metal stress of the type expected at mineral deposits. Heavy metal 
stress is generally manifested by an increase in the reflectance of the 
vegetation in the visible part of the spectrum, and various investigators 
have interpreted this increase to result from a decrease in plant density 
or a decrease in the chlorophyll content of the stressed vegetation. 
  
For a remote sensing program to exploit these clear spectral 
responses of vegetation to heavy metal stress, airborne multispectral 
scanners that allow the rapid coverage of large areas with highly resolved 
spectra have been used. This author and his coworkers report that heavy 
metal stress is manifested by increased reflected radiance values in the 
visible part of the spectrum for lodgepole pine (670 nm) and douglas fir 
(560nm) , while William Collins and his coworkers at Columbia University 
report a spectral shift of 10-20 nm of the chlorophyll absorption edge in 
a conifer forest canopy. 
Remote sensing systems in space lack the high spatial and spectral 
resolution of the airborne and land based studies ; nevertheless, it is 
possible to detect geobotanical anomalies from space and correlate these 
anomalies with potential mineralized ground. This author and his coworkers 
have used Landsat digital data to map potential mineralized zones to the 
southeast of the Caraiba Mining District, Bahia State, Brasil. The Cu-Ni 
mineralization in the district is associated with mafic and ultramafic rocks 
intruded into Precambrian metasediments. The areal extent of the mafic rocks 
can be interpreted from Landsat digital data ; because the mafic rocks 
support denser stands of vegetation indeces (37-55) / (B7+B5)] and relatively 
low total brightness (particularly B44B5?), 
While work must be done on many different vegetation types under 
different kinds of heavy metal stress to determine the specific type and causes 
of the spectral responses, it is clear that remote detection of geobotanical 
stress is one of the methods that should be used in a mineral exploration program. 
Remote sensors must be designed to detect geobotanical stress, particularly the 
spectral regions associated with chlorophyll absorption in the visible part of 
the spectrum. 
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