A Burning Question: Can Long-term Data Inform Fire Management in the Twenty-first Century? - Biodiversity Conservation and Environmental Change - page 73

which prevent fuel building up to dangerous levels, as well as generating landscape heteroge-
neity and a range of different habitats (North and Keeton 2008, Long 2009, Cumming 2011,
Turner et al. 2013). Understanding variability and resilience of ecosystems over time provides
a practical framework for managing fire based on long-term ecological function, rather than
the present-day snapshot, which might in no way be typical or sustainable (Keane et al. 2009,
Williams and Baker 2013). An understanding of the historic range of variability can guide
adaptive management approaches aimed towards maintaining fire regimes within Thresh-
olds of Potential Concern (TPCs) (see Chapter 2).
The ecosystem management approach is founded on the idea that ecosystems are disturb-
ance driven and dynamic at a range of temporal and spatial scales (see Chapter 1) (Grumbine
1994, 1997, Christensen et al. 1996, Pickett et al. 1997). In North America, the ecosystem man-
agement approach has been embraced in the management of forests. As a result, forest man-
agement goals are no longer simply about producing timber, but include increasing forest
structural complexity and spatial heterogeneity, maintaining landscape connectivity, and
protecting and restoring watershed integrity (North and Keeton 2008, Keane et al. 2009). The
1994 Crown Forest Sustainability Act (Canada) and the 2003 Healthy Forests Restoration Act
(USA) give legal basis for the ecosystem management approach, encouraging the restoration
of forest heterogeneity, ecological processes, and natural fire regimes where practical. The
Northwest Forest Plan established a suite of harvest strategies, ranging from uncut forests to
intensive industrial-scale logging, which combines ecological and economic goals in multi-
use landscapes (Chapin III et al. 2010).
The historical range of variability, sometimes known as the natural range of variability, and
the long-term disturbance regime, can provide an ecological basis on which to found fire
management programmes and to define the limits of acceptable change (Keane et al. 2002,
2009). However, as different forest types vary in their fire history, there is no one-size fits all
solution to fire management and site-specific insights from charcoal and tree-ring data are
needed when planning fire restoration and management programmes (Noss et al. 2006, Mil-
lar et al. 2007). Dry ponderosa pine and mixed conifer forests of the western and south-
western USA, are adapted to frequent, low-intensity surface fires, which control fuel loads.
These fires burn patchily and maintain the diversity of understory vegetation, create a range
of microhabitats, and provide pulses of soil nutrients (North and Keeton 2008). It is these fire
regimes that have been most disrupted by fire suppression, logging and grazing (Figure 4.9)
(Swetnam et al. 1999, Allen et al. 2003, Moore et al. 2011). Suppression of fire from the nine-
teenth century altered fuel loads and forest age structure, contributing to unusual pulses of
tree recruitment and occasional, intense crown fires, which may further increase in the
twenty-first century due to climate change (North and Keeton 2008). The restoration of these
forests requires not only fire management but also management of grazers and thinning of
younger stands of trees to restore stand densities to the former levels (Noss et al. 2006).
Mature trees and dead wood are retained, while removing or reducing grazing and reintrodu-
cing fire help to regenerate understory vegetation (North and Keeton 2008). The aim at larger
spatial scales is to restore a landscape mosaic that is heterogeneous and includes a range of
open and forested habitats of different ages.