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By making this comparison of the subjective values of-the écologists 
with the other parameters it is possible to indicate which of these 
other parameters can be used directly, with the aid of aerial photographs, 
to determine the value of different habitats for the purpose of conservation. 
CONCLUSION 
Based on the results of this study, suggestions can be made regarding the 
use of aerial photographs for the collection of. ecological data in both 
upland and Lowland environments. 
In the upland study area, the main difficulties of interpretation 
were encountered in mountain top habitats where it was in some cases 
impossible to distinguish between areas of bare ground, and the very 
pale toned Rhacomitrium-Empetrum and Nardus Communities which often provide 
only a sparse cover. It is suggested that true colour aerial photography 
might offer a better opportunity for differentiating between vegetation 
and bare rock, and also between different types of Artic-Alpine vegetation 
and geomorphological features, since on black and white air photos the 
difficulty is in distinguishing between subtle shades of grey. The 
photographic scale of 1:10,000 used was found to be too large for the 
purposes of the study, with often only one or two vegetation boundaries 
occurring over the area of one print. A scale of 1:15,000 for the 
upland study area would have meant the handling of fewer prints with a 
negligible loss of accuracy. 
In the lowland study area, the inability to distinguish freshwater marsh 
and permanent pasture was considered to be a serious limitation of the 
photography used. In a lowland region, wetlands may be isolated remnants 
of semi-natural vegetation and an important habitat for fauna. Permanent 
pasture, as opposed to arable and lay pasture, is often very important 
for wildlife and may be very rich floristically due to the length of time 
it has remained unchanged. It is thought that false colour infra-red 
photography would be more successful for identifying freshwater marsh and 
permanent pasture if, in the latter case, some criterion were adopted 
for defining the age, related to air photo appearance, of permanent pasture. 
The photographic scale of 1:10,000 was thought to be suitable for the type 
of area studied, with greater complexity of land uses and habitat types 
than in the upland area. 
These observations are based on the findings of one study and should be 
treated as a guideline for ecological surveys for application at the 
generalised level. Present survey methods are subject to the limitations 
imposed by present technology and air photo availability in the field of 
remote sensing as well as by the lack of standardised criteria for evaluation 
in the ecological field. However, the urgency at the present time to attach 
objectively defined conservation values to the whole of the countryside would 
suggest the need to develop a method based on specified criteria. 
ACKNOWLEDGEMENTS 
The authors would like to thank Dr. D. A. Goode of the Nature Conservancy 
Council who contributed enthusiastically to the ideas instigating this 
programme of research, and gave subsequent advice. 
Thanks are also due to Dr. P. Thompson, of the Department of Civil Engineering, 
Aston University for help and advice with computer programming involved 
in this study. Financial assistance was obtained from the Science 
Research Council and the Nature Conservancy Council.