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MONITORING RECENT CHANGES IN EXTENT OF NATURAL FORESTS 
IN KENVA USING REMOTE SENSING TECHNIQUES 
by 
N. OCHANDA AND H. EPP 
KENYA RANGELAND ECOLOGICAL MONITORING UNIT 
MINISTRY OF ENVIRONMENT AND NATURAL RESOURCES 
P.O. BOX 47146, NAIROBI, KENYA 
ABSTRACT 
Mapping of the existing forest cover in Kenya was carried out to 
provide a complete and up to date inventory of the forest cover and to use 
this data base to monitor forest cover changes. The mapping covered an 
area of 1.37 million hectares with an estimated mapping error of 3.6%. 
Critical forest areas with high depletion rates were observed at 4 
years intervals starting from 1967. Much of the forest area was cleared 
in the peak period of 1972-1976 and this trend appears to have slowed down 
in the last few years. 
Mapping and monitoring of the forest cover changes was done through 
visual analysis of multi-date landsat satellite imagery and old aerial 
photographs augmented by some digital analysis and information from the 
topographic maps, overflights with light aircraft, and ground survey data. 
INTRODUCTION 
The conflicting land-use options within the agriculturally high 
potential areas of Kenya coupled with an increasing population are making 
a greater demand on the limited forest resources, causing rapid depletion 
in some areas. Major portions of the indigenous forest reserves are clear- 
cut after economically valuable trees are removed. The cleared areas do not 
regenerate quickly into indigeneous forest but are turned into subsistance 
level agriculture or exotic plantations or remain fallow (Miller 1979). 
Heavy pressure is being exerted on the indigeneous forests without a full 
awareness of the effects on the overall ecological stability. . 
A state of knowledge of the existing forest cover which is required 
for the correct appraisal of problems and determination of possible solutions 
could be improved by continued monitoring of the changes in areal extent | 
and the ecological status from the established base. Remote sensing 
techniques have been used to some extent to establish the data base by 
mapping the total forest cover (Doute et al 1981) and to monitor changes 
in areal extent of the selected critical forest areas (Ochanda et al 1981). 
The techniques have been applied with success in some countries 
(Miller, 1979; Lorenzo et al 1979) for mapping of clear-cut or deterioriat- 
ing forest areas. The limited access to sophisticated digital analysis and 
the inconsistent supply of the appropriate products of landsat coupled 
with the limitations of the Landsat sensors, limited the studies to mapping 
and monitoring broad changes in the forest cover. Improvements in the Land- 
sat sensor resolution to the level where three dimensional analysis is 
possible with high resolution, could enhance monitoring of the ecological 
status of the forests which is the much needed information for rational 
management. 
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