Proceedings of the Second International Symposium on Fire Economics, Planning, and Policy: A Global View
Economic Analysis in the Control of Fuel
Loading in Mediterranean Forest
Ecosystems: Prescribed Burning, an
Alternative to Mechanical Methods1
Francisco Rodríguez y Silva 2
Abstract
The management of fuel loading is a vitally important activity in fire prevention programmes
in Mediterranean forest ecosystems. The study and analysis of the issue, and the relevant
planning and operational management activities have been established as a permanent
requirement, both in time and space. The control of fuel loading makes it possible to obtain a
spatialized reduction in the energetic intensity of potential fires where control and
maintenance operations have been undertaken, and allows fire suppression resources to be
moved around in a safe and efficient manner.
Control methods based on the mechanical removal and subsequent disposal of the
residue have traditionally been, and continue to be the most common means of forest
management. The progressive introduction of results based management drawing on scientific
investigation in subjects such as fire behavior and the effects on the natural environment,
opens up the possibility of gradually introducing the use of fire in Mediterranean areas in the
form of prescribed burning as an extremely efficient tool in programmes aimed at controlling
fuel loading. Expertise in forestry models of prescribed burning management provide for the
safe, ecological, efficient and effective use of fire as a very useful tool in preparing forest
ecosystems to prevent fire.
Data is currently data available from a management and experimental project cofinanced by the European Union and the Junta de Andalucía (1997-2000) which studied
methods of applying prescribed burning in Mediterranean ecosystems. Efforts should
subsequently be aimed at progressively introducing the methods developed in the
management programmes funded out of annual budgets by the government agencies
responsible for the prevention of forest fires. An analytical study providing comparative cost
data for mechanical systems and prescribed burning, with special emphasis on describing the
properties of the distinct kinds of management based on fuel modeling criteria, will facilitate
the incorporation, and therefore the applicability of fire as a tool in the removal of excess fuel
loading. This paper considers the costs of both systems and presents a decision matrix to be
consulted when activities are planned with the aim of dealing with fuel loading in
Mediterranean ecosystems.
Before turning to the above-mentioned focus on the costs of the two systems of fuel
loading control, it is necessary to set out the methodology employed in designing the
fundamental technical requirements to be taken into account when faced with the task of
drawing up a region-wide plan with a view to long-term permanency. Such a plan involves
setting up a system directed at specific units in the area drawing on support from the
1
An abbreviated version of this paper was presented at the second international symposium on
fire economics, policy, and planning: a global view, 19–22 April, Córdoba, Spain.
2
Professor, Fire Sciences, University of Córdoba, Avda. Menendez Pidal, s/n Apdo 3048
14080 Córdoba, España; email: ir1rosif@uco.es.
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governmental procedures and funding required to ensure the ordered management of yearly
burning programmes. The shift within the regional burning plan to the use of prescribed
burning, guided by the requirement that it be ecologically acceptable and involve spatialtemporal distribution, represents a transfer of the studies and experience accumulated through
investigation to their practical implementation in real world forest management situations as a
preventative and frequent tool in the fight against forest fires.
Introduction, Materials, Methods
Background and basic premises
The project aims to define the activities, procedures and operative stages required in
order to execute and experiment with prescribed burning. A regional plan can be
drawn up within a framework made up of five separate sections.
x
The first section covers the gathering of data, measurements and reconnaissance
of the land with a view to selecting the forest areas in which it is appropriate to
establish prescribed burning as a tool for controlling fuel loading. Representative
plots are then identified within those areas to be used for experimenting with the
prescription and subsequent burning. All the information from the selected
forestry areas and plots are registered and referenced by means of geographical
information systems. This first section ends with a methodological design for
planning, and subsequently evaluating the burning.
x
A second section covers the development of procedures to be adopted in
carrying out burning, depending fundamentally on local conditions such as
topography, vegetation types, spatial distribution and the load of fuel models,
activities and land use by the inhabitants, meteorology and soil conditions.
Different procedures are drawn up to ensure the burning is carried out in a safe
and ecologically compatible manner, depending on the characterization of each
forest area and the individual peculiarities of each selected plot. This section
therefore covers the burning of the selected plots and testing of the existing
methods for igniting, spreading and controlling the fire.
x
A third section covers the drawing up and publication of the technical
documentation and manuals required to implement the Regional Prescribed
Burning Plan. The documentation includes the correct procedures and the
technical forms to be filled in before undertaking each separate step in the
burning, from preventive planning (evaluating and inspecting the areas to be
burnt, planning the burning, prescribing the burning) to the burning itself and
subsequent evaluation.
Once the management and experimental project aimed at defining a Regional
Prescribed Burning Plan has been concluded, a regional map must be drawn up
identifying appropriate areas for use of the prescribed burning system as a low-cost
tool for removing excess fuel. The identification of the procedures to be followed
when carrying out burning will also allow these techniques to be extended to the
management of controlled burning (brush land burning and the burning of slash and
waste from forestry activity and treatments), thus providing the best, safest and most
effective techniques for burning in the ideal area at the right time in meteorological
conditions which guarantee that the burning is under permanent control.
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Proceedings of the Second International Symposium on Fire Economics, Planning, and Policy: A Global View
Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
Survey and evaluation of the area. Taking data,
measurements, selecting areas and plots, burning plans and
evaluation.
The opportunities to carry out prescribed burning in forest areas and natural parks are
determined by means of "Prescribed Burning Management Areas"(PBMA) in each
individual area. The analysis and examination of these areas must take into account
two separate criteria. Firstly, there are natural criteria, where a study is made of the
general existing conditions created by the topography, the spatial distribution of
forest vegetation, the spatial distribution of the modeling of forest fuels, the effects of
local weather conditions, the presence of natural barriers, the level of floor cover and
hydrology. Secondly, there are anthropic criteria, where human influence on the fire
regimes is analyzed, i.e., the historic risk defined by the frequency and causation of
recorded fires, as well as land uses and the ground cover. This information is
obtained from the forest fire statistics database. The PBMAs are defined as areas
which are found to be appropriate for the implementation of spatial-temporal
programmes for the control of forest fuel by means of the structured and planned use
of prescribed burning, following an inspection of the land and an analysis of
parameters affecting the spread of fire, while ensuring ecological compatibility,
preventive rate of return and safety, as well as control of the energy and dynamic
force of the fire. Once the natural and anthropic criteria have been applied, the
following objectives should be borne in mind when specifying appropriate areas for
the use of prescribed burning:
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
A decrease in the energy and dynamic force of any fires which may arise.
Optimized effects of soils and water on the productivity and profitability in the
balance sheet for natural processes.
The protection of intrinsic natural values, both in terms of flora and fauna.
A reduction in forest fires caused by uncontrolled brush burning.
A reduction in forest fires caused by uncontrolled burning of grazing land.
The maintenance of existing fire prevention infrastructure at a local level.
A reduction in the risk of forest fires originating in areas used by the public.
The protection of items of interest.
The protection of areas bordering on sites of logging activity.
The protection of areas bordering on estates containing plantations.
The protection of forest areas bordering on farmland crops.
The protection of forest areas bordering on waste disposal sites.
Ordered management of competing vegetation.
An improved habitat for wildlife.
Improved silvopastoral activity.
Renewal of the vegetation.
Within the selected Prescribed Burning Management Areas (PBMA), certain
areas are defined as ‘Prescribed Burning Management Units’ (PBMU). These are
given priority in the burning program and contain the individual ‘Prescribed Burning
Blocks’ (PBB), which are identified in accordance with the plan implementing the
proposed objectives. The Units should not be any larger than 500 ha. The proposed
aims of prescribed burning in each individual block can respond to differing
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Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
objectives. The factors taken into account in identifying Units are the frequency of
forest fires and the potential hazard associated with the combustibility of the forest
vegetation, which is determined according to the ignition rates and the dynamic and
energetic behavior of the fires (Rodríguez and Silva, 1995)
The individual Prescribed Burning Blocks (PBB) are identified once an
assessment has been made of the forest system’s ecological suitability and
compatibility in respect of fires characterized by medium intensity energy values. To
that effect, each of the PBMAs must have a complete fire behavior study in order to
establish the prescriptions to be borne in mind when planning the burns, depending
on the ecological conditions in the forest system. Burning must only be carried out
where specific and tabulated conditions are met for each ‘Forestry Model for
Prescribed Burning’ (FMPB), these being determined by the project. The FMPB is
created by defining, classifying and standardizing the plant cover found in the
PBMUs, from the perspective of the specific conditions required to proceed safely,
efficiently and in an ecologically compatible way with ordered burning. Each model
must include a description of the structure and combustibility of the existing plant
cover, the local meteorological conditions under which it is feasible to carry out
prescribed burning, the rate of dynamic propagation with which the burning process
should develop spatially, the appropriate time of year in which to undertake burning,
the size of the burn, the frequency of the burns, the methods to be used in igniting
and controlling the burn, the necessary manpower and equipment and other specific
recommendations.
The technical and planning procedures outlined above have been drawn up for
application in each and every one of the existing priority action areas. The results
determine the location of each of the zoned categories where the annual prescribed
burning programmes will operate. Regional planning will cover all the Prescribed
Burning Management Areas which require this tool as a procedure to control fuel
loading and reduce the risk of forest fires. Based on the knowledge obtained from the
experimental burns carried out throughout the project, each of these areas will be
provided with the set of rules and protocols contained in Forestry Models for
Prescribed Burning for the appropriate and effective application of prescribed
burning.
Results and discussion
The results presented in this paper consist of forestry models specifically
drawn up for the management of prescribed burning in Andalusia. The
Forestry Models for Prescribed Burning have been obtained from a
breakdown of the Behave fuel models. The models which have been drawn up
have taken the following factors into consideration: the existence of a timber
canopy, the horizontal continuity of the fuel, the diameter of the fuel and the
vertical continuity between the distinct vegetation strata. The final
classifications thus obtained for the identification of forestry models for
prescribed burning are set out below.
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Proceedings of the Second International Symposium on Fire Economics, Planning, and Policy: A Global View
Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
A. No timber canopy to be protected.
FMPB
1
5
7
8
14
Description
Non-wooded or very sparsely wooded grassland, with little or no horizontal fuel
continuity.
Non-wooded high brush (1.5-2m) with horizontal continuity.
Medium-sized brush (1-1.5m), horizontally discontinuous.
Medium-sized brush (1-1.5m) with horizontal continuity
Debris, together with herbaceous plants or brush of differing sizes.
B. Under a timber canopy which must be protected.
FMPB
2
3
4
6
9
10
11
12
13
15
Description
Herbaceous fuel (<60cm) with low brush content.
Herbaceous fuel (<60cm) with low brush content and vertical continuity with the
tree crowns.
Taller herbaceous fuel (>60cm) with vertical continuity with the tree crowns.
Large-sized brush (1.5-2m), vertically discontinuous. The feasibility of burning is
determined by the difference in height between the two strata.
Brush capable of incorporation in model 5 of the Behave system.
Brush capable of incorporation in model 6 of the Behave system.
Brush of the model 5 kind with a certain degree of vertical continuity with the tree
crown.
Brush of the model 6 kind with a certain degree of vertical continuity
Litter
Debris
An information file has been prepared for each of the 15 Forestry Models for
Prescribed Burning (FMPB) to provide guidance on executing the burn. The file
contains the following information: the general characteristics of vegetation, times of
the year for burning, environmental conditions for burning, physiographical
conditions, ignition methods, cost, and photographic classification. As an example,
the file for type 10 FMPB is provided below.
FORESTRY MODEL FOR PRESCRIBED BURNING TYPE
10:
Description of the model:
Brush consistent with Behave model 7, under a timber stratum. There is distinct
discontinuity between the brush and timber strata, and therefore the possibility of
damaging the timber crown is low, although greater than in type 9 FMPB. These are
the ideal conditions for prescribed burning due to its ease of execution and low cost.
The surface fuel consists of:
Medium height brush (1 to 1.5m), covering 50 to 75% of the surface area.
Herbaceous plants covering a surface area that can be over 50%.
Pine needles or litter from trees, adding fine and dead elements to the fuel
mix.
Total floor coverage is over 75%.
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Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
The fuel loading in this model varies between 15 and 20 Ton/Ha of dry material.
The roundwood diameter of the fuel loading in the experimental plots for the type 10
FMPB is:
Fuel Moisture
1-h
10-h
100-h
1000-h
Live
% of the total load
50
5 – 10
0-5
0-5
40
Specific composition:
The specific composition in areas where this particular model has been located is:
Tree stratum: Pinus pinaster. Shrub stratum: Ulex Baeticus, Erica arborea,
Phlomix purpurea, Cistus sp. Herbaceous stratum: Brachypodium officinalis
Burning seasons:
Burning under this model is feasible either in Autumn or Spring. All burns
undertaken in the experimental plots took place in March and April with acceptable
results, although autumn burns would probably have obtained improved results with
respect to the amount of fuel removed. The average reduction in the quantity of fuel
as a percentage of the original amount was 50% in Spring. Cistaceous plants in
almost all the plots had a negative influence on the level of fuel eliminated.
Fire environment:
The ideal burning conditions for type 10 FMPB is:
Temperature
Relative humidity
Fine Dead Fuel Moisture
Wind speed
Live fuel humidity
15 –25ºC
50-75%
8-14%
0-10 Km/h
75 -125%
Ignition methods:
The ignition method in this model is determined by environmental or physiographical
factors. It is advisable to use backing fire on slopes of over 15% in order to reduce
flame length.
Cost:
Drawing on the data obtained in the experimental plots for this model, it is
recommended that this particular type of burning is organised into plots of at least
0.65 Ha. This ensures that the burns will be more cost efficient than any other type of
silvicultural treatment for fuel reduction.
Employing the structure of the file for the type 10 FMPB, the whole information
file puts together the documents for the remaining fourteen models, thereby
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Proceedings of the Second International Symposium on Fire Economics, Planning, and Policy: A Global View
Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
providing a working document which makes it easier to locate the data required to
draw up an operational burning plan. A comparative analysis between the costs of the
prescribed burning technique and traditional methods is a vital strategy in
disseminating an operational procedure which has not been considered in the past as
a preventative silvicultural treatment. The so-called traditional methods for
eliminating excess fuel loading consist of at least three stages; clearance (either
manual or mechanical), removal and piling and, finally, the elimination of the waste
product (by burning or shredding). In contrast to this sequence of operations,
prescribed burning provides considerable savings in both money and the time needed
to carry out the work. The savings are generated by the fact that prescribed burning
achieves in one single step what the traditional methods took three to achieve.
A cost analysis comparing prescribed burning and traditional
procedures.
Having presented the analytical procedure for obtaining the forestry models for
prescribed burning, it is now necessary to employ tables of comparative data to
analyze the cost per hectare for each method of removing forest fuels with the aim of
reducing the potential hazard of forest fires and their spatial development with
extreme characteristics. The traditional methods of forest fire prevention through
measures dealing with forest fuel are based on eliminating the loading (kg/m2) of
surplus plant material, either through manual (tools or brush cutters) or mechanical
means (tractors), its subsequent removal and piling, and then a final stage where the
waste generated by these processes is either burnt or shredded. The forest fire
prevention method offered by prescribed burning unifies all three of the stages
required by the traditional methods, whether manual or mechanical, into one single
operation. This obviously creates significant savings in time and money.
Drawing up the necessary financial estimates before undertaking clearance work
aimed at preventing forest fires must be based on sound knowledge of the conditions
on the ground where the work is intended to take place. The lack of a database
detailing price per hectare, which includes important factors such as the density of
forest fuels, the slope of the land and the diameters of the base of the shrubs, leads to
important mistakes when preparing projects either due to an under or overestimation
of the work units required.
In order to avoid these miscalculations, the financial costs of all necessary steps
should be realistically measured and evaluated in order to ensure there is no need to
review costs upon carrying out the fire prevention treatments. The costs for the
traditional methods must therefore be calculated based on the following criteria:
A. Brush clearance. (Manual, by brush cutter, either mechanized or employing
a tractor ). Costs vary depending on:
1 The roundwood diameter at the base of the brush stems, <3cm, 3-6cm and
>6cm.
2. Slopes. Furthermore, depending on their physical position, the three measures
cited above for stem diameters are divided up according to the steepness of
the slope (s): s >50% and s <50%.
3. In addition, there are differences in cost on each slope depending on the
percentage of the area covered by forest vegetation.
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B. Combined silvicultural treatments, (clearance, pruning and selective felling).
This type of operation is considered to be subject to differences in cost depending on
the density of vegetation, classified as low density, medium density and high density.
C. Gathering and piling forest waste following cutting and removal activities.
As above, differences in cost for this operation are established according to the
amount of material to be removed: <8t/ha., from 8 to 15t/ha., from 15 to 25 t/ha.,
from 25 to 35 t/ha., from 35 to 45t/ha. and >45t/ha. Within each of these classes,
there are several costs depending on the slope: <30%, 30-50% and >50%.
D. Waste burning. This final stage of the tasks which make up the silvicultural
treatment for forest fire prevention is subject to cost variations which are calculated
on the basis of the same measures given above for material removed in gathering and
piling operations.
The experimental burns made it possible to determine the size of workforce
which can undertake the task safely and efficiently, providing initial data in order to
ascertain the ‘cost-effective burn area’. This variable is considered to depend on the
type of ‘Forestry Model for the Management of Prescribed Burning’, and therefore
on the characteristics which identify it.
The workforce which made it possible not only to develop the FMPBs, but also
to gather the data on cost and to determine the cost-efficient burn area for each of the
models, consisted of seven workers and one foreman, a forestry technician, two
drivers-mechanics for a vehicle with a 3,500 litre tank, fire suppression equipment
and, finally, a driver-mechanic assigned to a vehicle designed for capturing
meteorological data.
A. No timber canopy to be protected.
FMPB
Description
1
Non-wooded or very sparsely wooded grassland, with little or no
horizontal fuel continuity.
Non-wooded high brush (1.5-2m) with horizontal continuity.
Medium-sized brush (1-1.5m), horizontally discontinuous.
Medium-sized brush (1-1.5m) with horizontal continuity
Debris, together with herbaceous plants or brush of differing sizes.
5
7
8
14
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Cost-efficient
burn area
> or =1.7 ha.
> or =0.45 ha.
> or =1.8 ha.
> or =1.8 ha.
> or =1.5 ha.
Proceedings of the Second International Symposium on Fire Economics, Planning, and Policy: A Global View
Session 6B—Economic Analysis in the Control of Fuel Loading—Rodríguez y Silva
B. Under a timber canopy which must be protected.
FMPB
Description
2
3
Herbaceous fuel (<60cm) with low brush content.
Herbaceous fuel (<60cm) with low brush content and vertical
continuity with the tree crowns.
Taller herbaceous fuel (>60cm) with vertical continuity with the
tree crowns.
Large-sized brush (1.5-2m), vertically discontinuous. The
feasibility of burning is determined by the difference in height
between the two strata.
Brush capable of incorporation in model 5 of the Behave system.
Brush capable of incorporation in model 6 of the Behave system.
Brush of the model 5 kind with a certain degree of vertical
continuity with the tree crown.
Brush of the model 6 kind with a certain degree of vertical
continuity
Litter
Debris
4
6
9
10
11
12
13
15
Cost-efficient
burn area
> or =0.93 ha.
> or =1 ha.
> or =0.9 ha.
> or =0.4 ha.
> or =0.6 ha.
> or =0.65 ha.
> or =0.5 ha.
> or =0.65 ha.
> or =1.75 ha.
> or =1.5 ha.
A cost comparison per hectare in average slope and density conditions between
prescribed burning and traditional methods (manual and mechanised clearance and
waste disposal) highlights the competitive advantage of prescribed burning (where
the ecological conditions of the forest area are appropriate) over traditional methods.
Forestry Model of
Prescribed Burning
Cost of prescribed
burning. Euros/ha.
Cost of traditional
methods. Euros/ha.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
412.5
228.45
678.4
783.6
1,356.96
1,624.1
816.5
1,154.2
928.5
1,289.4
1,045.36
1,591.5
376.8
846.34
1,975.6
724.52
575.46
930.24
1.053.69
1,891.53
2,194.59
1,221.64
1,527.05
1,383.31
1,713.75
1,563.71
1,834.70
636.74
1,116.31
2,468.17
Cost differential
between traditional
systems and
prescribed burning.
1.75
2.51
1.37
1.34
1.39
1.35
1.49
1.32
1.48
1.33
1.495
1.15
1.68
1.32
1.25
Conclusions
The proposed methodology makes it easier to identify the ideal forest areas for the
use of prescribed burning, the level of ecological response of each of the forestry
models for prescribed burning, the technical procedures and the cost data which,
converted into prices, make it possible to draw up annual proposals for prescribed
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burning as part of a region-wide plan. This would enable the use of prescribed
burning on a regular basis as a preventative tool for the control of fuel loading in
forest fire prevention programmes.
Acknowledgment
The author wishes to thank the Consejería de Medio Ambiente de la Junta de
Andalucía and Eimfor (contractor for this project) and its team of technicians who
were responsible for managing project no. 9761ES0050, entitled “Prescribed burning
techniques for controlling fuel loading”, presented by the Consejería de Medio
Ambiente under the aegis of Council Regulation (EEC) No. 2158/92 of 23 July 1992
on the protection of the Community's forests against fire.
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