Abstract
Identification of conservation priorities is essential for conservation planning, especially as the biodiversity crisis develops. We aimed to support conservation prioritisation by addressing knowledge gaps for the genus Aloe in the Horn of Africa. Specifically, we developed a dataset of herbarium voucher specimens and occurrence data to estimate geographic distribution of 88 species of Aloe and used this to estimate extinction risk and establish the major threats to Aloe in this region. The resulting assessments, each published on the IUCN Red List, show that 39% of the species are threatened with extinction, and the principal threats are the expansion and intensification of crop farming and livestock farming, gathering of plants, and unintentional effects of logging and wood harvesting. We review ex situ conservation in botanic gardens and seed banks, revealing gaps in coverage and urgent priorities for collection, with 25 threatened Aloe species currently unrepresented in seed banks. Protected areas in the region offer limited coverage of Aloe distributions and the most recently designated protected areas are increasingly in regions that do not overlap with Aloe distributions. However, we show with a simple optimisation approach that even a modest increase in protected area of 824 square kilometres would allow representation of all Aloe species, although further data are needed to test the area required to ensure long-term persistence (resilience) of Aloe species.
Highlights
Human alteration of landscapes (Venter et al 2016), unsustainable use of wild species (Tierney et al 2014), expansion and intensification of croplands (Kehoe et al 2017) and increasing threats associated with a changing climate (Urban 2015) are all contributing factors to an ongoing biodiversity extinction crisis (Ceballos et al 2015; Díaz et al 2019)
Our assessment of Aloe from the Horn of Africa documented Red List status for 88 species, for which our best estimate is that 39% are threatened with a high risk of extinction
Most of the species classed as threatened (96%) were classified according to criterion B1 or a combination of B1 and B2, with just two species listed strictly based on area of occupancy (AOO) and one species listed under criterion D
Summary
Human alteration of landscapes (Venter et al 2016), unsustainable use of wild species (Tierney et al 2014), expansion and intensification of croplands (Kehoe et al 2017) and increasing threats associated with a changing climate (Urban 2015) are all contributing factors to an ongoing biodiversity extinction crisis (Ceballos et al 2015; Díaz et al 2019). Numerous global-scale approaches have been developed to identify species and sites of greatest importance for conservation (Brooks et al 2006)—including biodiversity hotspots (Myers et al 2000), Key Biodiversity Areas (IUCN 2016a), Alliance for Zero Extinction Sites (AZEs, Ricketts et al 2005) and Important Plant Areas (Darbyshire et al 2017)—as well as approaches that prioritise conservation based on other factors such as evolutionary history (Li et al 2018) Protecting these sites and associated species can be accomplished through the expansion of the protected area network (Butchart et al 2012, 2015). These prioritisation approaches depend on high-quality biodiversity data such as species inventories, species distribution maps and estimates of species’ extinction risk
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