Using palaeoecology and system dynamics to inform conservation of a biodiversity-rich, but endangered, ecosystem

摘要

Ecosystem Services (ES) upon which all humankind depends, come from ecological infrastructure (Cumming et al., 2014; Millennium Ecosystem Assessment, 2005) - i.e. healthy mountain catchments, wetlands, corridors of natural habitat, which together form a network of interconnected structural elements in the landscape. Plant biodiversity offers important provisioning ESs in the Cape Floristic Region (CFR), South Africa. The CFR is one of the world's 25 biodiversity hotspots (Goldblatt and Manning, 2000; Low and Rebelo, 1996; Mittermeier et al., 1998; Myers et al., 2000) and it contains >9000 plant species, of which ca.68% are endemic (Manning and Goldblatt, 2012). Human impact threatens its unique plant biodiversity with about 30% of CFR vegetation already transformed (Cowling et al., 1997; Fairbanks et al., 2000; Myers et al., 2000), making the CFR a global conservation priority. Current threats to biodiversity include urban development, agriculture, the spread of invasive alien plants and anthropogenic climate change (Allsopp et al., 2014; Goldblatt and Manning, 2000; Myers et al., 2000), however this landscape has been impacted by humans and climate variability for millennia (Fig. 1). For example, the San hunter-gatherers were in the region from at least 25 000 BP to the historical period, while the Khoikhoi pastoralists introduced livestock to the Western Cape from approximately 2000 BP (Boonzaier, 1996; Deacon, 1992). The arrival of, and colonisation by, European settlers from the mid-17th century onwards resulted in increased grazing, the introduction of crop cultivation and increased burning. In the 20th century, agricultural intensification increased environmental impacts in some areas, while others became nature reserves and stewardship schemes aimed at conserving the CFR's unique biodiversity (Bergh and Visagie, 1985; Hoffman, 1997; Newton, 2008). Furthermore, over the last ca. 10 000 years the CFR has experienced much climate variability (Fig.1): ranging from warmer and dryer conditions during the Mid-Holocene altithermal (9000-5000 BP) (Meadows and Baxter, 1999) and the Medieval Climate Anomaly (900-1400 CE), followed by the cold and wet Little Ice Age (1400-1800 CE) (Nicholson et al., 2013); with the latter part of the 20th century characterised by a warming trend due to anthropogenic climate change (Cronin et al., 2003; Haensler et al., 2010).