Abstract
In this study, we investigate and compare the response patterns of small mammal communities to increasing land use intensity in two study areas: private farmland at the southern boundary of Etosha National Park and smallholder farmland in Tsumeb agricultural area. Species richness, community composition and a standardized capture index (RCI) are compared between sites of (a) increasing grazing pressure of ungulates (Etosha) and (b) increasing conversion of bushland to arable land (Tsumeb). Within each study area, we found clear response patterns towards increasing land use intensity. However, patterns differ significantly between the two areas. Within the less-transformed area (Etosha), high land use intensity results in a decrease in the RCI but not species richness. Small mammal communities remain relatively stable, but ecosystem functions (e.g., bioturbation, seed dispersal) are weakened. Within the more-transformed area (Tsumeb), high land use intensity leads to a decrease in species richness and increasing RCIs of two common pest species. The disappearance of a balanced community and the dramatic increase in a few pest species has the potential to threaten human livelihoods (e.g., crop damage, disease vectors). Our comparative approach clearly indicates that Gerbilliscus leucogaster is a possible candidate for an ecological indicator of ecosystem integrity. Mastomys natalensis has the potential to become an important pest species when bushland is transformed into irrigated arable land. Our results support the importance of area-specific conservation and management measures in savanna ecosystems.
Highlights
African savannas are of high ecological relevance, but are vulnerable to human-induced disturbances [1,2]
Mastomys natalensis has the potential to become an important pest species when bushland is transformed into irrigated arable land
Our study reveals different response patterns of small mammal communities to increasing land use intensity in two distinct areas (Etosha area vs. Tsumeb area)
Summary
African savannas are of high ecological relevance, but are vulnerable to human-induced disturbances [1,2]. Owing to the agricultural potential of grassland systems and a growing human population, there is an increasing trend in the conversion of savanna ecosystems into profitable production systems for livestock or crop farming [3]. This can cause a dilemma between nature conservation and land use [4]. Many efforts are being made to significantly expand irrigation-based agronomic production in particular areas of the country This is the case of the so-called “Maize Triangle”, an area with relatively high precipitation, underground water for irrigation and fertile soils that is demarcated by the towns of Grootfontein, Tsumeb, and Otavi
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