A spatial model of land use and forest regeneration in the Ituri forest of northeastern zaire

Abstract

A model of land-use change in the Ituri tropical moist forest of Zaire was developed to examine the changes in forest structure brought on by the recent concentration of formerly dispersed horticulturalist villages along a road. This cell-space model uses eight land-use categories: road, village, active shamba (field), farm-bush, Musanga forest, old seral forest, climax forest and forest islands. The model consists of two main parts: forest succession and shamba selection. Forest succession is determined deterministically by time since cultivation. Climax forest returns to the open ‘farm-bush’ class with a probability of 0.0025 per year. Shamba selection for each village involves the age of a cell, travel time to the cell from the village, and whether the cell is in the village's usufruct. A usufruct is the territory a village holds in trust for future generations. Productivity of each site is a function of the number of years fallow allowed. Simulations using various parameter combinations were done starting in 1940 (the approximate time of road construction), and lasting from 45 to 250 years. Corroboration of the model was done by comparing model results with transects of vegetation types taken in 1983 and Landsat imagery from 1985. For the situation with no population growth, the model predicts a more open habitat near the road, but able to support the villages indefinitely. With 5% population growth, the area near the road is converted almost entirely to farm-bush and Musanga forest in 45 years, productivity of the shambas is decreased, and the area must be abandoned after about 80 years.