Fisheries in the Southern Border Zone of Takamanda - Impact ...

Landcover change in the Takamanda Forest Reserve, Cameroon:
1986-2000
1 Introduction
As with many areas of conservation interest, the
Takamanda Forest Reserve (TFR) is part of a dynamic,
human-influenced landscape. Although located in a fairly
remote region along the Nigerian border, the reserve is
surrounded by numerous small villages on its eastern and
southern sides, with three villages enclaved within the
reserve itself (see figure 2 in Chapter 1). Figure 1
graphically indicates the relative proximity of much of
the reserve to human settlements and movement.
Additionally, numerous old village sites scattered
throughout parts of the reserve indicate the extent and
fluidity of previous human settlements.
Until recently, access to the reserve was relatively
difficult, often requiring a day’s journey on foot to reach
either the southern boundary (from Mamfe) or the
northern boundary (from the Obudu Cattle Ranch in
Nigeria). Since the late 1980s, however, access to the
area has been improved with the completion of a largespan
bridge over the Manyu river at Mamfe. With this
bridge in place, both logging companies and the
government have constructed unpaved roads into the
region. The government has also made significant
progress on the long-awaited Mamfe-to-Akwaya road,
which may be completed within the next few years at
current rates of progress. A network of footpaths
currently connects most villages in the region to one
another.
Given the existing pattern of settlements and the
recently improved access to the region, we wanted to
examine recent landcover change in and around TFR.
Fortunately, the archive of high-resolution satellite
imagery for the region includes clear images from 1986
Dan Slayback
and 2000, allowing a study of landcover changes over
that 14-year period.
2 Methods
2.1 Data
Chapter 12
NASA’s Landsat series of earth-observing satellites have
been acquiring medium to high-resolution multispectral
earth imagery since 1972. Starting with the launch of
Landsat 4 in 1982, the satellites began carrying the 30meter
resolution Thematic Mapper (TM) instrument. The
resulting TM data archive, from 1982 to present, is the
most extensive global collection of high-resolution
imagery.
However, the archive contains relatively few cloudfree
images from the coastal areas of central Africa,
including the scene covering the TFR (identified as WRS
path 187 row 56). This is in part due to the extreme
cloudiness of the region and the satellite’s 16-day repeat
coverage (any scene is observed only once every 16
days). Also, previous data acquisition policies and
technical difficulties hindered the acquisition of imagery
over central Africa until the launch of Landsat 7 in 1999.
Fortunately, one relatively clear Landsat 5 image is
available from December 12, 1986. This image and a
clear Landsat 7 image from December 10, 2000 were
acquired for this analysis.
To ensure the precise image-to-image registration
required for detecting changes between an image pair,
both scenes were orthorectified (by the EarthSat
corporation). Orthorectification uses the known locations
of many ground reference points to remove the artificial
curvature of satellite-acquired imagery, which is an
artifact of the satellite’s viewing geometry. Further
preprocessing of the imagery was unnecessary; due to the
SI/MAB Series #8, 2003, Pages 173 to 179