Charcoal production as a managment tool against bush encroachment: vegetation dynamics

Abstract

Bush encroachment has become a worldwide phenomenon and a concern for the world’s arid and semiarid biomes. Savannas are turning into shrublands and thickets as evident in Namibia. This change in vegetation communities has direct consequences on the functioning of ecosystems and on services delivered by these systems. In Namibia, millions of hectares (ha) of arable land have been invaded by native bush species which vary in densities and structures. This affected area represents 32% of Namibia’s terrestrial territory, and about 57% of Namibia’s productive arable land. The agricultural (red meat) sector has been experiencing an economic loss of at least N$ 1 billion annually. Historically, drivers of bush encroachment inter alia include overstocking by grazer, suppression of fires, reduced browsers populations and climate variability. Different methods have been used to try to control the spread of encroaching bushes. Methods used to try and combat bush encroachment includes biological means, the use of chemicals and mechanical means. Most of these methods proved to be inefficient to farming. Charcoal production since the 1990’s, has created an incentive for farmers to remove excess bushes by producing charcoal as a by-product from rangeland rehabilitation. This process is believed to be more selective, environmental friendly and a cost-effective way of combating bush encroachment. This study was therefore conducted to measure vegetation structure, plant density and composition, species diversity and evenness in response to the charcoal production on farm Pierre, situated in Outjo District, Namibia. Systematic sampling methods were used to collect data in 400m2 plots and 1m2 quadrats along transects placed in a representative Treatment area and Control area. The study results showed that bush thinning through charcoal production has led to the improvement of vegetation species diversity, veld ecological condition and facilitated a better grass biomass production. The tree density in the Treatment area was reduced by 51.4% and the grass density was 100% more than in the Control area. The veld ecological condition in the Treatment area, based on grass population dynamics was 168% more than in the Control area. The study also found that there was also a moderately strong negative correlation between tree density and grass density. To ensure that bush thinning for charcoal production remains a sustainable tool for bush encroachment control, key issues such as the reduction in unselective harvesting of large trees and improving on aftercare following bush harvesting need to be addressed by all stakeholders, especially the charcoal producer. This can be done through voluntary means or by developing policies that give incentive’s to aftercare treatment and to selective harvesting of problem trees.