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If resource information is available, it was gathered on a single disciplinary
basis and the study and measurement of natural change phenomena was not in
cluded. An indication of the lack of adequate 'historical' data is shown by
the airphoto coverage of Canada. Most of the country was covered once and
selected parts of the developed areas were covered more frequently. Except
for the ERTS coverage this leaves many areas in the north, where presently
large scale developments are contemplated, without data on natural environ
mental change.
To predict impact it is necessary to study the effect of similar
activities in the past on similar ecosystems in similar ecoregions. The amount
of historic data, as discussed earlier, is quite limited and in many situations
we may not be able to learn from the past. However, natural models may exist
which may be indicative of the situation after planned actions have taken place.
These models should be selected on the basis of ecological similarity between
the model and the expected future situation in the areas where the change will
occur. For example, South Indian Lake in Northern Manitoba is a part of a large
hydroelectric development. Fig. 4 C shows the present situation as indicated by
an ERTS band 5 image. The Lake will be flooded; based on a detailed biophysical
survey it is predicted that the amount of eroding clay shoreline will increase
from about 5% to about 75% and this is similar to the present situation in the
highly turbid South Bay area. Based on this similarity one could predict that
the turbidity levels in the rest of the Lake may reach the levels of South Bay.
The ERTS satellite is well suited for the purpose of finding such
representative natural models especially in water and it can also monitor man
made change in a general way. It may act as a surveillance or warning tool that
some impact is occurring, but it will probably not provide adequate detail for
impact assessment (Fig. 5 D, F, G). Much of this work will have to be done
from aircraft by means of special sensors and supported by ground truthing.
However, ERTS can provide the basis for extrapolation of this information over
a large area.
Almost any surface change resulting from man's activities can be
monitored by using aircraft and satellite remote sensing and ground truthing:
land use change, crop response, urban sprawl, new roads, hydrolines, logging
areas, forest regeneration, etc. Fig. 3 shows a number of examples of smelter
smoke damage, logging areas and new road development. ERTS can demonstrate
some of the cause and effect relationships related to land management; Fig. 2
shows the connection between clearing of forest cover, erosion on sloping lands
and spring flooding in lowlands in the Whitmud River watershed. Imagery from
the ERTS-1 satellite has been used to revise small scale maps in the wilderness
areas of Canada. New roads, railroads, hydroelectric transmission lines and
reservoirs which are all part of the development of the north can be detected
on ERTS imagery and can be plotted with sufficient accuracy for the revision
of 1:250,000 topographical maps and 1:500,000 aeronautical charts (Fleming, 1974).
ENVIRONMENTAL PROTECTION SURVEILLANCE
While surveillance in support of resources management activities is
conducted to determine the true ecosystem impacts, surveillance is also carried
out to determine the effectiveness of measures which are being used to protect
the environment.