302 
INTRODUCTION 
The present rate of population growth and the use of our natural 
resources and living space have made man realize the limits of our planet. 
Development and growth seem unavoidable and natural resource planning based 
on ecological concepts is needed. With ecologically based resource manage 
ment we can hope to maximize long range benefits, social as well as economic, 
without unduly harming our life-sustaining ecosystems. 
Essential to such planning and management is knowledge about ecosystems. 
Only with this knowledge and the study of the impact of man’s past activities can 
we expect to predict the impact of our planned actions. Without this knowledge 
the evaluation of resource alternatives becomes ineffective and the expected 
benefits may prove to be too costly. The development of any region, whether in 
the economic, social or cultural sphere, is dependent upon the totality of the 
natural and human resources of that region. Its productivity is dependent, not 
upon the capabilities of soil and climate alone or upon the capabilities of living 
organisms alone, but upon specific relationships between living organisms and the 
total environment (Hills, 1970). 
In the past, airborne remote sensing has been found to be a most effective 
tool for the description and mapping of natural ecosystems (Thie, 1972, Johnson, 
1970). Remote sensing in the ultra violet, visible, thermal and microwave parts 
of the electromagentic spectrums has been correlated with many ecosystem 
parameters which are essential for describing and understanding these systems. 
New sensors which add new parameters are continuously being developed. For 
example, in Canada the Sensor Working Group stimulates the development of, among 
others, correlation spectrometers, a laser fluorosensor, Lidar, spectroscopic 
devices, and a soil moisture meter (MacDowall, 1973). It is however obvious that 
ground truthing remains a key to being able to properly describe ecosystem elements. 
Ecosystems are very dynamic, their elements and their interrelationships 
are ever-changing. To really understand these, repetitive surveys have to be 
carried out on hourly, weekly, monthly, yearly or multi-yearly basis. In fact 
without understanding the dynamics of natural changes of the environment, it 
will be impossible to adequately assess the impact of man’s activities on the 
environment. 
The survey of the natural dynamics of a large area, certainly in Canada, 
is only possible by means of remote sensing from aircraft and satellites in 
combination with selective ground truthing. While aircraft remote sensing provides 
more detailed information, the conduct of frequently repeated airborne surveys 
over all of Canada is politically as well as financially not feasible. Satellite 
remote sensing with its low resolution and regular 18-day cycle provides a rea 
sonable alternative, although it should always be used in combination with 
aircraft and ground truth data. 
MONITORING OF NATURAL ENVIRONMENTAL CHANGE 
The primary purpose of monitoring is to accumulate knowledge about 
ecosystems and the dynamic interrelationships between elements of these systems.