Woody plant encroachment in arid and mesic South African savanna-grasslands: same picture, different story?

Woody plant encroachment in South Africa’s savanna-grasslands has been considered a rangeland management problem since the early 1900s. This phenomenon, which has been observed globally, is particularly important in Africa given the extent of tropical grassy biomes on the continent and their importance for rural livelihoods. In this study, local and regional scale approaches were used to investigate woody cover change in South Africa across the important savanna-grassland rainfall threshold of 650 mm mean annual precipitation (MAP). The aim was to test this threshold using remote sensing and demographic surveys in order to better understand the patterns, mechanisms and drivers of encroachment. Rates of encroachment and population demographics of Vachelia karroo were compared at arid and mesic savanna sites in the Eastern Cape, using time-series analysis of historical aerial photographs in conjunction with field surveys. Changes in the extent of woodland vs. grassland were then quantified at a national scale (1990-2013) by combining optical and synthetic aperture radar remote sensing data. This produced the first map of woodland- grassland shifts for South Africa and provided the basis for a spatially explicit investigation of the key drivers of change. The local studies revealed higher rates of encroachment at mesic sites than at arid sites, with a correlation between drought and rate of encroachment at the arid site. Vachelia karroo seedlings and stunted saplings were more prevalent at mesic sites than at arid sites and the growth form of adult trees differed significantly between sites. The national remote sensing investigation showed that woodland replaced grassland in over 5% of South Africa’s savanna- grasslands between 1990 and 2014, at rates consistent with other global and regional studies. Spatially explicit models showed a pattern of incremental expansion of woodland along a ‘tree front’ and complex relationships between woodland increase and fire, rainfall, terrain ruggedness and temperature. Overall, the local and regional scale findings of this work highlight the importance of the savanna rainfall threshold (~650 mm MAP) and the presence / absence of fire in understanding savanna dynamics and woody cover change in the context of global drivers such as elevated atmospheric CO2

The bii4africa dataset of faunal and floral population intactness estimates across Africa’s major land uses

Sub-Saharan Africa is under-represented in global biodiversity datasets, particularly regarding the impact of land use on species’ population abundances. Drawing on recent advances in expert elicitation to ensure data consistency, 200 experts were convened using a modified-Delphi process to estimate ‘intactness scores’: the remaining proportion of an ‘intact’ reference population of a species group in a particular land use, on a scale from 0 (no remaining individuals) to 1 (same abundance as the reference) and, in rare cases, to 2 (populations that thrive in human-modified landscapes). The resulting bii4africa dataset contains intactness scores representing terrestrial vertebrates (tetrapods: ±5,400 amphibians, reptiles, birds, mammals) and vascular plants (±45,000 forbs, graminoids, trees, shrubs) in sub-Saharan Africa across the region’s major land uses (urban, cropland, rangeland, plantation, protected, etc.) and intensities (e.g., large-scale vs smallholder cropland). This dataset was co-produced as part of the Biodiversity Intactness Index for Africa Project. Additional uses include assessing ecosystem condition; rectifying geographic/ taxonomic biases in global biodiversity indicators and maps; and informing the Red List of Ecosystems

South Africa’s Red List of Terrestrial Ecosystems (RLEs)

Ecosystem level indicators are emerging as important pillars of the post-2020 global biodiversity framework of the Convention on Biological Diversity; at the same time, the IUCN Red List of Ecosystems (RLEs) is experiencing rapid global uptake. We applied a systematic RLE assessment to 456 terrestrial ecosystems in South Africa between 2017 and 2021. What sets South Africa apart in this endeavour is that an independently formulated ecosystem threat status indicator was developed between 2004 and 2008 and the list of threatened ecosystems (effectively a proto RLE) was integrated into the national environmental regulatory framework in 2011. Through this, Critically Endangered and Endangered types were afforded a form of statutory protection through increased regulation of land-use change activities. We describe the transition to the IUCN RLE framework and focus on both the technical steps of incorporating the best available data into a credible assessment, and the unique social and legal processes to ensure that the biodiversity conservation sector in South Africa understood and supported the proposed replacement of the existing list of threatened ecosystems (2011) with the RLE (2021). We discuss the policy development steps required in South Africa, and the pros and cons of maintaining a legislative link for RLE implementation

South Africa’s Red List of Terrestrial Ecosystems (RLEs)

Ecosystem level indicators are emerging as important pillars of the post-2020 global biodiversity framework of the Convention on Biological Diversity; at the same time, the IUCN Red List of Ecosystems (RLEs) is experiencing rapid global uptake. We applied a systematic RLE assessment to 456 terrestrial ecosystems in South Africa between 2017 and 2021. What sets South Africa apart in this endeavour is that an independently formulated ecosystem threat status indicator was developed between 2004 and 2008 and the list of threatened ecosystems (effectively a proto RLE) was integrated into the national environmental regulatory framework in 2011. Through this, Critically Endangered and Endangered types were afforded a form of statutory protection through increased regulation of land-use change activities. We describe the transition to the IUCN RLE framework and focus on both the technical steps of incorporating the best available data into a credible assessment, and the unique social and legal processes to ensure that the biodiversity conservation sector in South Africa understood and supported the proposed replacement of the existing list of threatened ecosystems (2011) with the RLE (2021). We discuss the policy development steps required in South Africa, and the pros and cons of maintaining a legislative link for RLE implementation

Taking state of biodiversity reporting into the information age – A South African perspective

South Africa’s National Biodiversity Assessment (NBA) is the primary tool for monitoring and reporting on the state of biodiversity, with a focus on spatial information and key indicators. The NBA distills information that informs policies and strategies, meets national and international reporting requirements, and helps prioritize limited resources for managing and conserving biodiversity. The three previous versions of the NBA (2004, 2011 and 2018) are in the form of detailed thematic technical reports and a synthesis report, served on a simple, static web page. Selected spatial products from the report are available via a dedicated web platform (http://nba.sanbi.org.za/). While all methods and data are clearly described in the technical reports, most of the underlying analyses are inaccessible, lacking reproducibility and transparency. This makes iterative updates to indicators or metrics challenging and inefficient, complicates version control, and exacerbates the risk of capacity, knowledge and data loss during staff turnover. To move the assessment process into the information age we aim to develop well documented and reproducible workflows, and to serve the indicators and their accompanying synthesis on an interactive web platform that facilitates uptake. Achieving these aims will deliver efficiency, greater transparency and trust in future NBA products and will strengthen communication and engagement with the content by the many different users of those products. While these visions will not be realized overnight, the skills and systems required to achieve them can be adaptively built towards an improved NBA that better serves the needs of our society

The bii4africa dataset of faunal and floral population intactness estimates across Africa’s major land uses

International audienceSub-Saharan Africa is under-represented in global biodiversity datasets, particularly regarding the impact of land use on species' population abundances. Drawing on recent advances in expert elicitation to ensure data consistency, 200 experts were convened using a modified-Delphi process to estimate 'intactness scores': the remaining proportion of an 'intact' reference population of a species group in a particular land use, on a scale from 0 (no remaining individuals) to 1 (same abundance as the reference) and, in rare cases, to 2 (populations that thrive in human-modified landscapes). The resulting bii4africa dataset contains intactness scores representing terrestrial vertebrates (tetrapods: ±5,400 amphibians, reptiles, birds, mammals) and vascular plants (±45,000 forbs, graminoids, trees, shrubs) in sub-Saharan Africa across the region's major land uses (urban, cropland, rangeland, plantation, protected, etc.) and intensities (e.g., large-scale vs smallholder cropland). This dataset was co-produced as part of the Biodiversity Intactness Index for Africa Project. Additional uses include assessing ecosystem condition; rectifying geographic/ taxonomic biases in global biodiversity indicators and maps; and informing the Red List of Ecosystems

bi4africa dataset - open source

The bii4africa dataset is presented in a multi-spreadsheet .ods file. The raw data spreadsheet (‘Scores_Raw’) includes 31,313 individual expert estimates of the impact of a sub-Saharan African land use on a species response group of terrestrial vertebrates or vascular plants. Estimates are reported as intactness scores - the remaining proportion of an ‘intact’ reference (pre-industrial or contemporary wilderness area) population of a species response group in a land use, on a scale from 0 (no individuals remain) through 0.5 (half the individuals remain), to 1 (same as the reference population) and, in limited cases, to 2 (two or more times the reference population). For species that thrive in human-modified landscapes, scores could be greater than 1 but not exceeding 2 to avoid extremely large scores biasing aggregation exercises. Expert comments are included alongside respective estimates

bii4africa dataset

The bii4africa dataset is presented in a multi-spreadsheet .xlsx file. The raw data spreadsheet (‘Scores_Raw’) includes 31,313 individual expert estimates of the impact of a sub-Saharan African land use on a species response group of terrestrial vertebrates or vascular plants. Estimates are reported as intactness scores - the remaining proportion of an ‘intact’ reference (pre-industrial or contemporary wilderness area) population of a species response group in a land use, on a scale from 0 (no individuals remain) through 0.5 (half the individuals remain), to 1 (same as the reference population) and, in limited cases, to 2 (two or more times the reference population). For species that thrive in human-modified landscapes, scores could be greater than 1 but not exceeding 2 to avoid extremely large scores biasing aggregation exercises. Expert comments are included alongside respective estimates