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future scenarios and, in contrast to many conservation interventions, aims to be proactive
rather than reactive. It recognizes ecosystem heterogeneity, the importance of scale in under-
standing ecological patterns and processes, and the critical relationship between ecosystem
resilience and the integrity of its structure, diversity, and function (Rogers 2003). The operating
principles of least interference and the employment of the precautionary principle—taking
the low-risk approach where uncertainty is high. Central to the successful implementation of
SAM is an objectives hierarchy, which unpacks the key elements of the mission statement:
biodiversity, human benefits, wilderness, naturalness, custodianship (du Toit et al. 2003). For
example, the biodiversity and ecosystem objective is further broken down into various ecosys-
tem components of increasingly fine focus, including water, terrestrial, atmospheric, alien
species, and threatened species, which are themselves further unpacked (du Toit et al. 2003).
The finest level of the hierarchy are thresholds of potential concern (TPCs), which are opera-
tional goals that define the range of desired variability in key ecological parameters, such as
fire frequency, river flow, and tree density (Rogers 1997, Rogers and O'Keeffe 2003). Baseline
TPCs are developed by observation, monitoring, experiment, and consultation with multiple
stakeholders, guided by the local, national, and international policy context. TPCs are periodi-
cally reviewed, allowing response to new information, or changes in environmental, social or
political drivers. When a TPC is met, this triggers management action aimed towards moving
back to the desirable range, and/or the TPC is adjusted, in consultation with various stake-
holder groups, for example, representing policy makers at national, provincial, and local lev-
els, scientists, tourism and development, land-owners and local communities (Rogers and
Biggs 1999).
TPCs have potentially wide application in ecosystem management, but at present are not
widely used outside of the Kruger National Park. From the 1990s onwards, failed policies,
such as regular prescribed burning, elephant culling, and artificial water provision were over-
turned and replaced by TPCs that embraced flux and variability (van Wilgen and Biggs 2011).
For example, the old, equilibrium goal of stabilizing elephant populations at 7,000 by culling
was replaced by a TPC for elephants based on habitat condition, which allows loss of tree
cover of up to 80% locally or 30% park-wide, compared with the highest ever value.
But what was the 'highest ever' value and is the TPC realistic? Despite being managed and
to some extent monitored for over a century, this period of time is unlikely to be typical and
indeed may give a misleading impression because of the unusual conditions that prevailed in
the late nineteenth century, when intensive hunting and rinderpest had devastated animal
populations and had probably led to unusually dense tree cover (Carruthers 1995). Further-
more, following the founding of the Park there were many decades of intensive management,
including fire suppression and predator control, which would have impacted on herbivore
density and tree cover. The natural range of variability in the centuries preceding the colonial
era, was almost unknown (du Toit et al. 2003), creating a niche for comprehensive, palaeo-
ecological data that would establish how variable tree cover had been during past millennia
(Gillson and Duffin 2007).
Palaeoecological work carried out in the Kruger Park combined high-resolution fossil pol-
len data, radiocarbon dating, and multiple proxies (charcoal, diatoms, isotopes, and dung
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