Abstract

The six major mountain ranges in South Africa support critically important ecosystem services—notably water production—and are rich in biodiversity and endemism. These mountains are threatened by detrimental land uses, unsustainable use of natural resources, climate change, and invasive alien plants. Invasive alien plants pose substantial and rapidly increasing problems in mountainous areas worldwide. However, little is known about the extent of plant invasions in the mountains of South Africa. This study assessed the status of alien plants in South African mountains by determining sampling efforts, species compositions and abundances across the six ranges in lower-and higher-elevation areas. Species occurrence records were obtained from three databases that used various approaches (roadside surveys, citizen science observations, focused botanical surveys). Most mountain ranges were found to be undersampled, and species composition assessments were only possible for two ranges. The majority of abundant alien plants in both the lower- and higher-elevation areas were species with broad ecological tolerances and characterised by long distance seed dispersal. These prevalent species were mostly woody plants—particularly tree species in the genera Acacia, Pinus, and Prosopis—that are contributing to the trend of woody plant encroachment across South African mountains. We suggest improved mountain-specific surveys to create a database which could be used to develop management strategies appropriate for each mountain range.

Highlights

  • The six major mountain ranges in South Africa were determined using the topographical positional index and roughness surfaces (Figure 2)

  • The EGE has the highest elevations in South Africa, while—of the other mountain ranges—only the Cape Fold Mountains (CFM) exceeds 2000 m; the Western Great Escarpment (WGE), Southern Great Escarpment (SGE), Tropical Cuestas (TC) and GCM are all < 2000 m (Figure 3)

  • Elevational difference is more important for our purposes than absolute elevation, as the former provides the basis for determining surface area for invasion potential, and climatic partitioning and related potential invasion envelopes

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Summary

Introduction

The mountains of South Africa support critically important ecosystem services—. African mountains and their distribution across a strong climatic gradient in the region has resulted in diverse ecosystems and high local endemism [4,5,6]. This biodiversity is critical in supporting the livelihoods of rural local communities that are often poorer and more marginalised [7], and are directly reliant on natural resources, such as for agriculture and traditional medicine [8,9].

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