Vegetation map of South Africa, Lesotho and Swaziland 2018: Progress on a historical national map of biodiversity since 2006

Abstract

The National Vegetation Map is a model of the historical extent of South Africa's vegetation. This model is a valuable resource for the management of South Africa's natural resources as it provides a baseline dataset forthreat assessments, national and provincial strategies, and conservation targets. Hence it is essential to ensure that the data is based on the best available information. However, mapping vegetation patterns nearly 300 years into the past can be a challenge as the data to inform the mapping of many regions is not available in South Africa and even the most advanced technology can only provide a snapshot of the current distribution of communities. The South African National Vegetation Map is updated periodically with improved data and the 2018 version, the third update since 2006, was recently completed. For this version we employed several different approaches to resolve coarsely mapped regions of the map. Techniques included a combination of surrogate abiotic maps, expert knowledge, mapping off orthorectified 1930's imagery. The map has also been improved by reducing errors. Previous versions included non-terrestrial features from other environments. However, stand-alone maps for these other environments were developed for the country's National Biodiversity Assessment 2018 and the vegetation map was edited to focus on terrestrial vegetation. We reported changes to the 2018 version of the National Vegetation Map and provided the rationale, data sources and contributing authors. We also quantified and corrected spatial and classification changes and errors since 2006. Changes made to the map using ArcMap 10.4included thefollowing:(i)thecorrection of spatialerrors;(ii)edits were made to existing vegetation type boundaries; (iii) new vegetation types were added where communities were too coarsely classified; (iv) polygons that overlapped withnon-terrestrial environments wereidentifiedorremoved; (v) non-terrestrial landscape features that mapped ocean or modern structures such as harbours were deleted. Changes between versions were quantified using ArcMap, R and Excel. Version 2018 had the largest changes by area, and number of types added and deleted since 2006. Changes in the 2018 version included the addition of 47 new types, boundary edits to 107 existing types, and the removal of 35 vegetation types and features, and affected nearly 5% of the total map area, compared to 2.6% and 0.5% for previous versions. Several sources of error were fixed and prompted protocols for future work. We have made progress in refining coarse areas of the map from 2006 to 2018. These progressive improvements lead to greater accuracy in National Ecosystem Assessments and National and provincial conservation planning.