Salami, Ayobami T.
Ww
S VEGETATION MAPPING OF A PART OF DRY TROPICAL RAINFOREST OF
SOUTHERN NIGERIA FROM LANDSAT TM
ed AYOBAMI T. SALAMI
Institute of Ecology and Environmental Studies
Obafemi Awolowo university, Ile-Ife, Nigeria
E-mail:asalami@oauife.edu.ng
KEY WORDS: Classification, Ecosystems, Forestry, Land Use/Land Cover, Mapping
ABSTRACT
Vegetation in Nigeria, whether on topographical sheets or thematic maps, has generally been mapped from
aerial photographs. But aerial photographs are not generally available beyond the 70s in most part of the
country. Consequently, it has become difficult to assess the current ecological status of the biotic
environment. The main objective of this paper therefore is to demonstrate the potentialities of Landsat TM
in generating up-to-date information on the biotic environment in Nigeria. It shows the advantages and
limitations of high resolution satellite imageries in mapping vegetation of the heterogenous Landscape of a
developing country like Nigeria. The environmental implications of the study are highlighted.
1 INTRODUCTION
Vegetation mapping is one of the basic components of ecological data base of any region. Apart from
providing the benchmark data for forestry planning, the information that could be generated from reliable
vegetation map will also aid any programme on fuelwood energy conservation and assessment of
ecological status of forest ecosystem. However, Adejuwon (1967) lamented that vegetation has continued
to be inaccurately mapped in Nigeria. He contended that this is a result of faulty methods of data collection
as mapping in the field is a most difficult exercise. The situation has only changed a little, more than three
decades after this observation. In the same vein, Morain (1974) submitted that there seems to be no
reasonable means of providing timely and accurate data for vegetation mapping using traditional
approaches.
In response to this challenge, some attempts have been made to demonstrate the usefulness of aerial
photographs in mapping Nigerian vegetation. For instance, Larin-Alabi (1979) examined the potentialities
of air photos for studying Nigeria’s tropical forests. Also, Ikhouria (1993), produced a multidate map of a
part of Southern Nigeria from air photos of 1963 and 1973.
our corresponding concern with the preservation of the environment has encouraged the development of
other more sophisticated methods of remote sensing than conventional photography. This development
includes the emergence of satellite imageries such as Landsat and SLAR. But this led to the problem of
appropriate spatial scale. In line with this development, the federal government in the 70s, through the
Federal Department of Forestry initiated the Nigerian Radar (NIRAD) project. This employed Sidelook
Morris and Martin-Kaye (1973) noted that the ever increasing demands of the earth’s natural resources and
Airborne Radar (SLAR) to obtain Radar imagery covering the whole of the country. However, since the
scale of the imagery is 1:250,000, it is more useful for small scale mapping.
The advent of high resolution satellite remote sensing, using SPOT P mode, SPOT XS and Landsat TM in
the 80s, has opened up new possibilities which have not been adequately exploited by researchers and
environmentalists in Nigeria. This has been due mainly to lack of the required hardware and software
facilities as well as the technical know-how of digital image analysis, necessary for such studies. This paper
is thus an attempt to demonstrate the application of Landsat TM to vegetation mapping in Nigeria.
It shows advantages of the new technology-digital image processing over the analogue procedure that has
been predominantly employed by Nigerian researchers, while mapping the country's vegetation.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 1301
