Past, Present, and Future Climate Change: Can Palaeoecology Help Manage a Warming World? - Biodiversity Conservation and Environmental Change - page 107

mitigate or exacerbate climate change, by influencing rainfall and albedo, or feedbacks that
involve the combined effects of climate, fire, and vegetation (see Chapter 4). Furthermore,
there may be critical thresholds in species abundance or landscape fragmentation when
population viability is lost (With 2002, 2004, Magri et al. 2006, Gillson et al. 2008, Gavin et al.
2014). Local patterns of disturbance and biotic interactions play out across topographic,
edaphic, and hydrological templates at landscape scales, and are influenced by climatic driv-
ers at regional-global scales (Wu and Loucks 1995, Gillson 2004). Thus, the spatial patterns
and rates of change that are observed in ecosystems today are a result of the interactions
between extrinsic and intrinsic drivers acting hierarchically across a range of scales, and the
thresholds at which ecosystems reorganise (Wu and David 2002, Williams et al. 2011).
Identifying the thresholds and scales at which ecosystems reorganise is of crucial interest
to conservation planners and managers, but ecological studies rarely cover timescales that
are long enough to observe these dynamics (Gil-Romera et al. 2010). Threshold behaviour
can be identified in the palaeo-record, and can help in preventing undesirable changes and/
or adapting to new ecosystem processes and changes in ecosystem services (Gillson et al.
2008, Willis et al. 2010, Williams et al. 2011). The examples from the Altiplano of Bolivia and
from the greening of the Sahara, discussed previously, show the presence of alternate stable
states, maintained by local-regional drivers, with dramatically different outcomes for human
society and sustainability. In Mediterranean ecosystems, Gil-Romera et al (2010) found a
threshold response to fire and drought, whereby a forested landscape was replaced by a more
patchy vegetation structure with open elements. Similarly, fossil pollen data from savannas
has helped to unravel the interaction between fire, climate, and nutrients that drives transi-
tions between grassland, woodland and forest states (Gillson and Ekblom 2009a, Gillson
2004, Mayle et al. 2007, Rull 2009, Rull et al. 2013), while multiproxy data from Madagascar
showed how a combination of drought and changes in sea level caused ecosystem reorgani-
sation (Virah-Sawmy et al. 2009).
Studying these transitions helps to understand the interaction between climate and other
factors, and what happens when critical combinations of climate change, land cover change
and disturbance occur (Virah-Sawmy et al. 2009, Briske et al. 2010, Dearing et al. 2012a).
Understanding these interacting effects raises possibilities for ameliorating the effects of glo-
bal change through management interventions at local—landscape scales. For example, ris-
ing CO 2 is leading to the conversion of some savanna ecosystems to forest, with loss of
grassland habitat and grazing resources (Warman and Moles 2009, Hirota et al. 2011, Mayer
and Khalyani 2011, Staver et al. 2011a, b, Higgins and Scheiter 2012, Parr et al. 2012, 2014).
hough CO 2 cannot be controlled at the local-regional scales, fire management can contrib-
ute to the maintenance of savannas by preventing woody plant encroachment (Rull et al.
2013). For example, the savannas of the Noel Kempff National Park (NKMNP), in Bolivia, are
threatened by forest encroachment, associated with decreased fire (Mayle et al. 2007). The
palaeoecological record suggests that more burning may be necessary to conserve the endan-
gered species in the savanna vegetation.
Predicting threshold behaviour is important for biodiversity conservation and the man-
agement of ecosystems, because rapid change affects ecological function, biodiversity, and