Invasive and Exotic Species in the Restoration of Stochastic Agricultural Lands in Ethiopia

Abstract

Feeding inexorably increasing population is among the challenges confronting mankind. Marginal lands including mountainous and sloppy areas have been converted to agricultural land. The highland parts of Ethiopia (43% of the country’s total size) have been highly degraded. About 4 % had reached a point of no return. This has diminished food crop production capacity of the country. In addition, there is not extra marginal or forest lands to be converted to farmland as before. Hence, restoration of agricultural land is an urgent matter. Restoration increases agricultural system stability. Restoration can be done in various ways such as area closure (in areas with relatively large landholding size), erosion protection using physical structure and restoration using tree planting or combination of two or more of the interventions. But rural Ethiopia cannot afford to put land aside for restoration due to scarcity of farmland. A key question, then, is how to successfully and quickly restore the degraded landscapes in the country. This review work, therefore, analyzes the merit and demerit of exotic and invasive plant species in the restoration of agricultural land in Ethiopia.  Most Exotic species in Ethiopia are providing various socio-economic services. On the other hand, few are highly competitive and deny resources for native trees as well as for crops. Some of these invasive species have allelopathic characteristics and ooze inhibiting chemicals. They quickly colonize the area and deny the space for crops. The invasive species also lower the water table and also adversely affect the livestock sector however that agriculture and livestock sectors are complementary activities in Ethiopia. Absence of well-developed management techniques exacerbated the downside of invasive species. Many studies invigorate adverse impact of invasive species. The invasive plants use the opportunity of high disturbance of agricultural lands to outcompete with crops or co-existing native flora. Unless it is the last option using invasive species for restoration of agricultural land is not recommended. Regarding the exotic species such as Eucalyptus spp, Cuppressus lustanica, Gravillia robusta, Pinus radiata, there is mixed evidence on their role on restoration of agricultural land. The widely held negativity view of exotic plant species seems not right. The performance of exotic trees on the restoration of agricultural land varies from species to species. Some leguminous exotic species has a positive role in increasing soil nitrogen, moisture content, total SOC, physical property of soil, etc. Few such as eucalyptuses have over competing with crops and with co-existing native flora for the available water, nutrients, light, etc. Species such as Cuppressus lustanica has very high evapo-transpiration during wet season and suppress the growth of understory.  As compared to the native trees exotic species have less efficiency on the restoration of agricultural lands. This does not mean that all native plants have good performance than exotic plants. In general, before embarking to agricultural land restoration species selection that exactly fits the required purpose must be done.

Keywords: Restoration, invasive species, Exotic, Agricultural land