GIS Unit - Mount Oku and Ijim Ridge (Cameroon)

Monitoring vegetation cover changes in Mount Oku and the Ijim Ridge (Cameroon), using satellite and aerial sensor detection.

Kniphofia reflexa

Kniphofia reflexa

Introduction

This project was initially a collaboration between the Royal Botanic Gardens, Kew, and the Department of Geomatic Engineering, at University College London. Susana Baena, working towards her MSc dissertation for a degree in Geographical Information Science, began studying the magnitude, rates of change, and temporal/spatial distribution of forest cover in the area of Mount Oku and the adjoining Ijim Ridge. The GIS Unit at Kew with Birdlife International have further developed this study.

Mount Oku and the Ijim Ridge is the largest remaining patch of montane forest in west Africa. It has exceptional levels of endemism amongst flora (for example, Kniphofia reflexa shown in the photograph) and fauna – especially amongst birds. For this reason, since 1987 an important conservation project managed by Birdlife International has been working in the area, aiming to reduce forest loss and to improve agricultural practices.

The conservation project is currently known as the "Kilum-Ijim Forest Project". The aim of this study is to assess the reserve performance by monitoring the vegetation cover, comparing the forest extent before and after the conservation project started.


Mount Oku forest
Forest

Project description

The Kilum-Ijim forest lies at the centre of the Bamenda Highlands in north-western Cameroon (location of the study area). This region includes the mountains and highland areas of the border region between Nigeria and Cameroon; Mount Oku is the highest point within this region at 3011 m above the sea level.

 

The majority of the area enclosed by the Kilum-Ijim boundary is at an altitude of over 2000 m. The vegetation is highly influenced by this altitude: above 2000 m, where the study area is mainly located, it consists of montane forest mixed with montane grassland and subalpine communities. Below this, most of the submontane forest has already disappeared due to clearance for agriculture.


False colour Landsat Mount Oku
False colour Landsat ETM and composite of the region (vegetation is bright red)

Data and methods

The project, studying the changes in vegetation cover over time, was carried out using remote sensing imagery (satellite images and aerial photographs). The methodology involved different processing techniques for both satellite images and aerial photography in order to create a time-series of images (1958-2001). Each of the satellite images in the data set was classified to delimit the forest boundaries. In the case of aerial photographs, before any analysis could be performed they had to be orthorectified using a DEM derived from a Radarsat stereo pair. The forest boundaries for these photographs were then defined by on-screen digitising and converted to raster format. All the images showing the forest extension for the different dates studied were combined in a GIS environment to perform subsequent analysis.


MountOku_veg_change
Vegetation changes

Results

The results show strong spatial patterns of deforestation between 1958 and 1988 (more than 50 % of the montane forest was lost in this period) followed by a regeneration period starting in 1988, just after the Conservation Project was created. In this last 1988-2001 period, 7.8 % of the 1988 extent of montane forest has been recovered, mainly on the eastern side of the mountain. The forest vegetation boundary in the north-east has been held at the 1988 level, while in the east it has recovered and extended by 800 m (until 1995). From 1995 the forest boundary has remained static and marks the limits of the reserve. In the western boundary, the reserve limits have also been held at the 1995 level; regeneration is still taking place inside these limits. Also see the animation.


Animation

This animation shows the change in vegetation from 1958 to 2001. Eastern forest is seen to recover after 1988 (reserve was put in place in 1987). The western forest seem to be recovering to some degree.


Mount Oku in 3D

Digital elevation model of the region, overlaid with the false coloured Landsat ETM and imagery (vegetation is bright red).

3D animation

By using the digital elevation model (DEM) it is possible to produce a three dimensional representation of the region. You will need a VRML plugin to view it we recommend Cortona or Cosmo. If you are having difficulties viewing this scene, try this small globe, to test your system.

Mount Oku VRML (615 Kb) with Landsat image as below

Mount Oku deforestation animation in 3D (Very large file 6.05 Mb)

 



 

Mount Oku boundary
Mount Oku reserve boundary

Kilum-Ijim Forest Project

The "Kilum-Ijim Forest Project" started in 1987, when the most dramatic deforestation in the area occurred. Its establishment has been followed by a regeneration period. After 1995 the rate of regeneration (3.9%) significantly exceeded the deforestation, and the forest area has increased by 10.6%. These results, showing the excellent reserve performance, are of major importance to the Kilum-Ijim communities, since the reserve is under their direct management.

 


Acknowledgements

We are especially indebted to Helen Papadaki (UCL) for her help in the processing of aerial photography and digital elevation models, and to Jeremy Morley (UCL) for his suggestions during the course of this study. Thanks are also due to Dr. Martin Cheek (RBG Kew) for contributing field knowledge and valuable information on the vegetation of the area. Help from Russell Fox (Ordnance Survey) and Ben Pollard (Kew) is also gratefully acknowledged. We are grateful to Rob Freeman (QINETIQ) and EROS Data Center (USGS) who supplied the satellite data, also to Norman Lamont of the MOD for supplying the aerial photographs.

Image processing was performed in the GIS laboratory at UCL (Geomatic department) and at the GIS unit (RBG Kew). This study was supported by Earthwatch and Darwin Initiative grants to Royal Botanic Gardens, Kew under the "Conservation of the Plant Diversity of western Cameroon" project 

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