Restoration and Rehabilitation of Degraded Ecosystems in Arid and Semi-Arid Lands. II. Case studies in Southern Tunisia, Central Chile and Northern Cameroon

background

This study compares non-human and human determinants of ecosystem degradation processes in three contrasted regions, as well as interventions tested in each. The three responses to ecosystem degradation under review are restoration, rehabilitation and reallocation as applied to ongoing projects in arid mediterranean region of southern Tunisia, the semi arid tropical savannas of northern Cameroon.

Research Goals & Methods

Vital ecosystem attributes (VEA) such as perennial and annual species richness, aboveground biomass, total plant cover etc., related to ecosystem structure and function, were used to compare the effects of non-human and human disturbances and of experimental interventions in different ecosystems to test hypotheses about ecosystems in a given phase of their trajectory.

Conclusions & Takeaways

In southern Tunisia it was observed that there was depletion of the seed banks of perennial species by the absence of nearby propagules. This absence seems particularly critical for trees and shrubs whose biomass is needed for energy and others considered keystone in the former arboreal steppe. Additionally, many Acacias and other nitrogen fixing legumes likely to be keystone species in arid and semi-arid ecosystems, are apparently pre-adapted to frequent and unpredictable disturbances. In northern Cameroon, human disturbances are presumed to be less longstanding and intense compared to the other countries. Nitrogen fixing and native trees are still present in small numbers, and seed sources of most ligneous native plants are still present. In conclusion, the authors suggest that the best way to insure sustainable agriculture in semiarid and arid lands is to pursue rehabilitation based on known or presumed structure and functioning of indigenous ecosystems that no longer serve purpose to anyone.