Underpinnings of fire management for biodiversity conservation in ...

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Compartmentalised track networks
Figure 2.7 illustrates the most comprehensive compartmentalised model track network possible,
in which all points are visited to satisfy access requirements. The relative danger to hypothetical
firefighters is set to nil as there are alternate routes away from every point (intersections of two or
more lines on the grid). Compartmentalisation is complete. However, the relative cost as indicated
from edge-length alone is at a maximum – 40L – almost double the minimum of about 21L of Figure
2.6; thus all other networks have a cost between these two values.
Figure 2.7 The grid of 16 square cells with the number of tracks (solid lines) needed to define every cell. In this case there are
40 sides to the cells (some shared), so the total length is 40L. The number of dead ends to tracks among the total of 25 corners
and intersections is nil. There are numerous intersections.
Can we reduce the track length and retain or improve safety, while retaining groups of cells (cell
clusters), all with perimeter tracks? It can be declared that reaching the perimeter track implies safety
in this model system. If this were to be more realistic, the model system would have to expand well
beyond the area of jurisdiction and consider the tracks and roads surrounding the study area. There
are numerous alternative track designs for grids with a perimeter track but only two more follow.
In Figure 2.8a, all the tracks lead directly to the perimeter edge. The whole network is
compartmentalised, there is no dead end and the track length is 28L – instead of 21L in Figure 2.6,
or 40 in Figure 2.7. There are six exits to the perimeter. In Figure 2.8b, track length has increased by
4L, but there are more exits to the perimeter. There are also eight cell clusters rather than 4. This may
be regarded as safer for firefighters than Figure 4a as there are options for travelling in contrasting
directions from the interior to the perimeter, according to the direction from which the fire is
approaching. The second diagram implies that fires could be confined to cell clusters, and because
there are more of these clusters kept smaller on average. Thus these simple models suggest that
there are cost implications with length of track, and trade-offs between access, firefighter safety and
potential for confining fires to a group of cells.
Fire and adaptive management Underpinnings of fire management for biodiversity conservation in reserves