Towards an Integrated Approach to Wildfire Risk Assessment: When, Where, What and How May the Landscapes Burn

Round 1

Reviewer 1 Report

The addressed topic is focal and of great interest to Fire readers.

The contents are organized in the usual sections and follow a logical sequence.

The results are derived from the application of the methods described.

References are adequate and abundant and some of them are recent. However, I miss the reference to some recent works published in the Fire journal

The only relevant issue that should be rethought is the title of the article, because by mentioning "... and with what consequences?", the title does not correspond to the real content of the manuscript.

Furthermore, a minor review is essential in order to improve the article (two figures could be revised to improve readability):

-       Fig. 2: improve quality and add scale and north,

-       Fig. 7: improve the quality of legibility of the legend.

Author Response

Reviewer1

The addressed topic is focal and of great interest to Fire readers.

The contents are organized in the usual sections and follow a logical sequence.

The results are derived from the application of the methods described.

References are adequate and abundant and some of them are recent. However, I miss the reference to some recent works published in the Fire journal

The list is already quite extended and based on most important information known by the authors. 5 recent references proceed from Fire.

The only relevant issue that should be rethought is the title of the article, because by mentioning "... and with what consequences?", the title does not correspond to the real content of the manuscript.

The last sentence has been removed

Furthermore, a minor review is essential in order to improve the article (two figures could be revised to improve readability):

-       Fig. 2: improve quality and add scale and north,

Done

-       Fig. 7: improve the quality of legibility of the legend.

The right map legend text has been increased.

Reviewer 2 Report

Congratulations on a strong piece of work. I especially liked the comprehensive review of wildfire risk assessment. This is a real strength of the paper.

The discussion of the development of the FirEURisk tool is also interesting. Some of the documentation of its components could possibly be shortened to reduce the length of the paper. 

In addition, I was extremely disappointed to see the paper end without presenting an actual example of the final risk product. In my opinion, this needs to be done  (even if it is only a hypothetical scenario if the product is not yet in operational use or if you are planning a separate paper to illustrate its operational use in the future).

Doing so would also help clarify the scale of the final product and would also help in terms of improving its interpretation. This latter point should be made clear in the paper.

Enclosed below are other comments that I had:

143-144: This is not a complete sentence.

152: "Finally, Risk ..." should be "Finally, risk..."

160: Perhaps the scale should be briefly discussed here?

216: There's an extra space in "affect   fire" here.

Subsection 2.2.3 Vulnerability: Should some discussion on prevention tools as a way to modify an area's vulnerability appear somewhere here?

Section 2.3: A lot of this section distracts from the risk focus. Could some parts be shortened or moved to an appendix?

346-373: Note that Wotton and Martell (2005) that you cite later explicitly  track lightning strikes over space time and incorporate holdover into their modelling framework.

553: The wording "As regards provisioning services..." is not clear. Please revise.

584-585: What is the intuition behind this formula? I ask because shouldn't the marginal loss just be discounted back to the time of interest? The formula is more complicated. Hence, something else is being done. This should be explained to the reader. Moreover, what is the rationale for commonly setting is the discount rate to 2%?

587 and elsewhere after equations: Don't indent lines like "where..." that appear after the equations.

642: Typo: "This Is the..."

684: Please elaborate on what is meant by "synthetic" in this context.

697-706: This could use a reference or two.

738: What is meant by common risk scale? Why is this needed? And, are there limitations/considerations to think about when different variables are mapped to a common scale?

756 and elsewhere: This formula for the probability of the union of two independent events is essentially considered general knowledge and likely doesn't need to be references.

761 (equation 3): Strictly speaking, is this actually ignition occurrence? I would interpret this as the occurrence of one fire. The given formula is the probability of a human-caused fire, or a lightning-caused fire, or both human AND lightning. The latter is the ignition of two fires. Please clarify the intuition behind the use of this forumal.

763-769: There is a difference between fire occurrence prediction and fire susceptibility modelling: the latter produces relative output where the former produces properly calibrated probabilities of fire occurrence. This should be made clear since some of the references here do fire occurrence prediction where others are modelling fire susceptibility.

784-786: This needs to be reworded. In particular, how can an assessment system reduce exposure or vulnerability? It is simply assessing something, it isn't actually an action being taken to reduce something.

823: What is meant by "a proper mean"? Consider rewording.

835: The writing "Public Messaging, that is..." is not a proper sentence.

828-854: There is inconsistent formatting of the elements in this  list. Specifically, should the first part of each of these paragraphs be formatted the same way when introducing each technique?

855-884: This part could use some citations to references.

972: Typo: "...emerging threat [273].." (extra period)

1064-1078: This writing should be improved. In particular, please communicate to the reader what the specific interpretation of Burn-P3 output is? (I view it as a spatially explicit map of the relative risk of burning in the very near future--i.e., in an upcoming fire season).

1064-1078: Furthermore, note that recent work has examined how Burn-P3 predictions from correspond with actual burned areas, noting areas of concern for its use and of its limitations; see Beverly and McLoughlin (2019, Forest Ecology and Management). 

1104: Perhaps mention that a recent review of wildland fire risk research in Canada appears in Johnston et al. (2020, Environmental Reviews)?

1257-1263: What is the temporal scale of the EWRA risk index?

Figure 2: Same as above. Please add a description of the temporal scale to the caption for this figure.

1342: Please explain or add a reference to explain what is mean by a "bilinear model for the residual errors".

1377 (equation 4 and related writing): Please explain the rationale behind this formula. In particular, what do the distributions of the individual FireMetrics and ValuesAtRisk components look like and then what does the distribution of their product look like? Could one of those two marginal distributions drive what happens in their product?

1460-1481: What is the temporal scale for the ignition model? Is it a fire occurrence prediction model or a fire susceptibility model? (See earlier comment about this distinction.) If it's the former, how was it calibrated to produce proper probabilities as predictions? And, finally, what were the specific sub-seasons and the rationale for how they were chosen?

1605-1615: What about other values, such as industrial values or infrastructure?

1749-1770: The mathematical notation here could be improved. For example, t₀ instead of t0, t_i instead of ti. Also, the index i is not explained nor does it appear in equation (6).

1811-1817: Some of the units presented here need to be fixed with proper superscripts/subscripts.

1865-1875: Please provide a visual example of the output so that the reader can visualize and interpret it. This could even be a hypothetical scenario. But, it is needed. Otherwise, the paper builds up to this point but then never shows the final product.

Author Response

Reviewer2

Comments and Suggestions for Authors

Congratulations on a strong piece of work. I especially liked the comprehensive review of wildfire risk assessment. This is a real strength of the paper.

The discussion of the development of the FirEURisk tool is also interesting. Some of the documentation of its components could possibly be shortened to reduce the length of the paper. 

We tried to avoid double referencing in sections 2 and 4. The former is a general review of existing knowledge on the different variables while the latter are the specific decisions taken for the FirEUrisk assessment system.

In addition, I was extremely disappointed to see the paper end without presenting an actual example of the final risk product. In my opinion, this needs to be done (even if it is only a hypothetical scenario if the product is not yet in operational use or if you are planning a separate paper to illustrate its operational use in the future).

The integration of the different indices may be done in may different ways, including the preferences of the different potential end users. However, to comply with the reviewer comment, we have include a first integration approach, based on our expert knowledge on the field.

Doing so would also help clarify the scale of the final product and would also help in terms of improving its interpretation. This latter point should be made clear in the paper.

Done

Enclosed below are other comments that I had:

143-144: This is not a complete sentence.

We have deleted it, as the definition was already included in the following sentence.

152: "Finally, Risk ..." should be "Finally, risk..."

done

160: Perhaps the scale should be briefly discussed here?

Since this is an introductory section, dealing with general natural hazard terminology, extending the sentence may distract the reader from the main focus.

216: There's an extra space in "affect   fire" here.

corrected

Subsection 2.2.3 Vulnerability: Should some discussion on prevention tools as a way to modify an area's vulnerability appear somewhere here?

This topic is covered in section 2.7

Section 2.3: A lot of this section distracts from the risk focus. Could some parts be shortened or moved to an appendix?

We think that this revision is useful to understand better the impact on risk assessment of how the different risk variables are generated, both in terms of temporal and spatial scales.

346-373: Note that Wotton and Martell (2005) that you cite later explicitly track lightning strikes over space time and incorporate holdover into their modelling framework.

This reference was included in the text, but explicit mention is now shown in section 2.3.1

553: The wording "As regards provisioning services..." is not clear. Please revise.

Modified

584-585: What is the intuition behind this formula? I ask because shouldn't the marginal loss just be discounted back to the time of interest? The formula is more complicated. Hence, something else is being done. This should be explained to the reader. Moreover, what is the rationale for commonly setting is the discount rate to 2%?

The mathematical formulation for the cumulative loss is assumed to be shaped using an hyperbolic function rather than a geometric function. This assumes that the discount rate is not constant but decreasing over time to penalise less the future benefits of the ecosystem recovery accruing over a very long period of time (50 to 100 years from the time of the damage). We are quoting here a paper published by Roman et al. in 2012, where they use 2% as a standard value quoting other papers. In any case, we have further clarified the sentence and explained that the small discount rate used should be in the order of 1 to 3% in assessing environmental projects because benefits generated over a long period of time would not have any positive impacts in the appraisal in case of adoption of interest rate generated by private market (5% to 10%).      

587 and elsewhere after equations: Don't indent lines like "where..." that appear after the equations.

done

642: Typo: "This Is the..."

corrected

684: Please elaborate on what is meant by "synthetic" in this context.

We have modified the word synthetic by integrated.

697-706: This could use a reference or two.

[Hong, 2018 #7003; Oliveira, 2020 #6872] references introduced

738: What is meant by common risk scale? Why is this needed? And, are there limitations/considerations to think about when different variables are mapped to a common scale?

We have added the explanatory sentence “that is assigned risk values with a common metric”. Having a common metric is necessary to generate integrated indices, otherwise the different risk variables could not be combined.

756 and elsewhere: This formula for the probability of the union of two independent events is essentially considered general knowledge and likely doesn't need to be references.

The formula refers to a specific study where the probabilistic rule was applied to a wildfire risk analysis. We consider it is worth to keep it, but we have removed a similar one in line 1856

761 (equation 3): Strictly speaking, is this actually ignition occurrence? I would interpret this as the occurrence of one fire. The given formula is the probability of a human-caused fire, or a lightning-caused fire, or both human AND lightning. The latter is the ignition of two fires. Please clarify the intuition behind the use of this forumal.

We have followed the addition law of probability, or the sum rule. That is, the probability that an event in A or B will happen is the sum of the probability of an event in A and the probability of an event in B, minus the probability of an event that is in both A and B. That is the probability that a fire anywhere in the target region can be ignited either by a human or by lightning, not necessarily by both.

763-769: There is a difference between fire occurrence prediction and fire susceptibility modelling: the latter produces relative output where the former produces properly calibrated probabilities of fire occurrence. This should be made clear since some of the references here do fire occurrence prediction where others are modelling fire susceptibility.

It is not clear to us what the reviewer means here. We have not used fire susceptibility as a risk concept in the paper, but rather fire hazard-danger, defined as “the estimation of the likelihood that a fire ignites and propagates” (line 183). This can be done from inductive (historical fire records) or deductive (physical models) approaches. We are referring in lines 763-769 to studies aiming to estimate ignition probability.

784-786: This needs to be reworded. In particular, how can an assessment system reduce exposure or vulnerability? It is simply assessing something; it isn't actually an action being taken to reduce something.

The sentence was changed to “how well it defines the exposure or vulnerability of the target area”.

823: What is meant by "a proper mean"? Consider rewording.

Mean was changed to Median.

835: The writing "Public Messaging, that is..." is not a proper sentence.

These paragraphs were originally bullets, but they were not properly formatted in the MDPI template. The sentence was changed to: “Public Messaging, which involves communicating important information to lay people, particularly…”,

828-854: There is inconsistent formatting of the elements in this list. Specifically, should the first part of each of these paragraphs be formatted the same way when introducing each technique?

Sorry again, as indicated before, this was originally a bullet list.

855-884: This part could use some citations to references.

Some have been added

972: Typo: "...emerging threat [273].." (extra period)

Corrected

1064-1078: This writing should be improved. In particular, please communicate to the reader what the specific interpretation of Burn-P3 output is? (I view it as a spatially explicit map of the relative risk of burning in the very near future--i.e., in an upcoming fire season).

We clarified the interpretation of Burn-P3 output in the following manner: “This measure [BP] provides a spatially explicit, gridded estimate (i.e., per analysis cell) of the likelihood of fire occurrence for one year (often the upcoming fire season).”

1064-1078: Furthermore, note that recent work has examined how Burn-P3 predictions from correspond with actual burned areas, noting areas of concern for its use and of its limitations; see Beverly and McLoughlin (2019, Forest Ecology and Management). 

We thank the reviewer for this comment, noting that the assessment of the predictive accuracy of BP is indeed an important challenge in fire modelling studies. Yet this issue is beyond the scope of this section, which simply aims to review the approaches used for fire risk assessment in different countries.

1104: Perhaps mention that a recent review of wildland fire risk research in Canada appears in Johnston et al. (2020, Environmental Reviews)?

This paper was already quoted, see ref 298

1257-1263: What is the temporal scale of the EWRA risk index?

EWRA assesses the structural risk based on a climatological analysis of data from 2003 to 2020. This was cited already, but further clarified in the new version

Figure 2: Same as above. Please add a description of the temporal scale to the caption for this figure.

Corrected

1342: Please explain or add a reference to explain what is mean by a "bilinear model for the residual errors".

This text was added:

A purely geo-statistical approach was performed to a 1km×1km grid by using AIC-based stepwise regression [329] with topological and geographical parameters (altitude above sea level, latitude, longitude and distance to the Atlantic Ocean and Mediterranean Sea). Finally, a bilineal model was applied to the residual errors obtained by comparison of the geo-statistical approach and the original ERA5Land grid point values.

In other words, for each hour of the target days, a stepwise regression is used to obtain the interpolation function of ERA5Land data to a 1-km x 1km grid using as selection method the likelihood function as described in Akaike (1980), using the R stat package. The interpolated data are subsequently compared with the original ERA5Land ones in order to obtain the residual errors that are then interpolated with a bilinear model to obtain the final values for the target grid.

1377 (equation 4 and related writing): Please explain the rationale behind this formula. In particular, what do the distributions of the individual FireMetrics and ValuesAtRisk components look like and then what does the distribution of their product look like? Could one of those two marginal distributions drive what happens in their product?

The main purpose of this equation is to easily identify the grid points with higher values of exposure, and exposure results from the product between the chosen fire metric value and the chosen exposed element quantity (e.g. fireline intensity and number of buildings). It is assumed that both fire metric and exposed element have always a similar weight and it is possible to have one of the components of exposure driving the final value and this is part of the exposure concept. For instance, in case the quantity of exposed elements is low, but the fire metric is too high, the final exposure value will be very low. Moreover, this equation allows representing with the same dimensionless scale, and for all the selected fire metrics and exposed elements, the exposure potential spatial distribution, that can be used in the development of an integrated approach to wildfire risk assessment. This information was added in the revised manuscript (section 4.2.2).

1460-1481: What is the temporal scale for the ignition model? Is it a fire occurrence prediction model or a fire susceptibility model? (See earlier comment about this distinction.) If it's the former, how was it calibrated to produce proper probabilities as predictions? And, finally, what were the specific sub-seasons and the rationale for how they were chosen?

The previous lines (1449-59) explained that the model was trained from historical fire occurrence (70/30), defined by the ignition points obtained from satellite observations of burned areas. The model is a RF categorical predictive one, obtaining probability of ignition/no ignition. The final sentence was modified to clarify the length of the summer period considered in the models, although the paper only includes results from the global model, considering all months, which was the one used for the integration.

1605-1615: What about other values, such as industrial values or infrastructure?

In this version, only houses were considered, which are the most commonly affected by wildfires, since industries are uncommonly interfaced with forested areas.

1749-1770: The mathematical notation here could be improved. For example, t₀ instead of t0, t_i instead of ti. Also, the index i is not explained nor does it appear in equation (6).

Done

1811-1817: Some of the units presented here need to be fixed with proper superscripts/subscripts.

Done

1865-1875: Please provide a visual example of the output so that the reader can visualize and interpret it. This could even be a hypothetical scenario. But, it is needed. Otherwise, the paper builds up to this point but then never shows the final product.

Included in the new figure 14

Reviewer 3 Report

This is a very intresting concept paper. I propose the acceptance of the article. Some remarks for the authors are to introduce the "megafires" terminology as the last decades concern scientific community. Moreover, in the introduction part add a paragraph and discuss the post fire accelerated concequences especially from recent studies over the Mediterranean basin.

Author Response

Reviewer3

This is a very interesting concept paper. I propose the acceptance of the article. Some remarks for the authors are to introduce the "megafires" terminology as the last decades concern scientific community. Moreover, in the introduction part add a paragraph and discuss the post fire accelerated consequences especially from recent studies over the Mediterranean basin.

A sentence was added to the introductory section

Round 2

Reviewer 2 Report

Thank  you for the detailed responses to my original comments. Again, I still very much like this paper and think it will be a great addition to the literature. What follows below are three remaining comments (one major and two minor) which, once addressed, would make the paper suitable for publication in my opinion.

Major Comment:

My original review included the following comment: "lines 1064-1078: Furthermore, note that recent work has examined how Burn-P3 predictions from correspond with actual burned areas, noting areas of concern for its use and of its limitations; see Beverly and McLoughlin (2019, Forest Ecology and Management)."

The authors response was: "We thank the reviewer for this comment, noting that the assessment of the predictive accuracy of BP is indeed an important challenge in fire modelling studies. Yet this issue is beyond the scope of this section, which simply aims to review the approaches used for fire risk assessment in different countries."

My response to this lack of revision to address this concern is as follows:

I strongly disagree about this point being left out. Otherwise, this section as written makes it seem like Burn-P3 is adopted Canada wide, which it isn't! Burn-P3 is not officially part of the Canadian Forest Fire Danger Rating System, it is modelling tool developed by some researchers in Canada. Moreover, the section this material appears in is called  "Analysis of existing wildfire risk assessment system". The term "Analysis" implies it's not just a summary or review of what may be used. Consequently, a statement should be made to discuss the concerns for its use and of its limitations as was discussed by Beverly and McLoughlin (2019, Forest Ecology and Management). My suggestion is to end the corresponding paragraph (lines 1339-1353 in the revised version) with something like the following:

"The limitations of Burn-P3 as a burn probability modelling tool as well as concerns for its use have also been discussed by researchers [cite Beverly and McLoughlin 2019 here]"

Minor Comments:

Lines 1345-1347: This needs rewording. Fire occurrence has a very specific meaning in the wildland fire science literature and this sentence, as written, conflicts with that definition. Specifically, the term "fire occurrence" is used to refer to the occurrence of one or more fires. Here, in the Burn-P3 context, the output does not represent occurrence; it represents the likelihood of that grid cell burning (i.e., a fire occurring in it OR a fire that started somewhere else spreading into that cell).

My original review also included the following comment: 

1865-1875: Please provide a visual example of the output so that the reader can visualize and interpret it. This could even be a hypothetical scenario. But, it is needed. Otherwise, the paper builds up to this point but then never shows the final product.

The authors' response was:

Included in the new figure 14

However, there is no figure 14 in the revised version I downloaded from the online review system. There are two Figure 13s. I believe the second such figure needs to be renamed figure 14, along with any corresponding text (e.g., line 2346).

Author Response

Thank you for the detailed responses to my original comments. Again, I still very much like this paper and think it will be a great addition to the literature. What follows below are three remaining comments (one major and two minor) which, once addressed, would make the paper suitable for publication in my opinion.

 Major Comment:

My original review included the following comment: "lines 1064-1078: Furthermore, note that recent work has examined how Burn-P3 predictions from correspond with actual burned areas, noting areas of concern for its use and of its limitations; see Beverly and McLoughlin (2019, Forest Ecology and Management)."

The authors response was: "We thank the reviewer for this comment, noting that the assessment of the predictive accuracy of BP is indeed an important challenge in fire modelling studies. Yet this issue is beyond the scope of this section, which simply aims to review the approaches used for fire risk assessment in different countries."

My response to this lack of revision to address this concern is as follows:

I strongly disagree about this point being left out. Otherwise, this section as written makes it seem like Burn-P3 is adopted Canada wide, which it isn't! Burn-P3 is not officially part of the Canadian Forest Fire Danger Rating System, it is modelling tool developed by some researchers in Canada. Moreover, the section this material appears in is called  "Analysis of existing wildfire risk assessment system". The term "Analysis" implies it's not just a summary or review of what may be used. Consequently, a statement should be made to discuss the concerns for its use and of its limitations as was discussed by Beverly and McLoughlin (2019, Forest Ecology and Management). My suggestion is to end the corresponding paragraph (lines 1339-1353 in the revised version) with something like the following:

"The limitations of Burn-P3 as a burn probability modelling tool as well as concerns for its use have also been discussed by researchers [cite Beverly and McLoughlin 2019 here]"

Response: we followed the renewed suggestion by the reviewer and made two changes: [1] we reworded the title of section 3 to "Review of existing wildfire risk assessment systems". [2] We added the following text to the section about Burn-P3 to highlight concerns about it performance:  "...This estimate provides a simple proxy for wildfire hazard, but it is not without limita-tions, as burn probability estimates derived from Burn-P3 have limited predictive power of actual burnt areas in subsequent years (REF0 , but see REF1 )."

Minor Comments:

Lines 1345-1347: This needs rewording. Fire occurrence has a very specific meaning in the wildland fire science literature and this sentence, as written, conflicts with that definition. Specifically, the term "fire occurrence" is used to refer to the occurrence of one or more fires. Here, in the Burn-P3 context, the output does not represent occurrence; it represents the likelihood of that grid cell burning (i.e., a fire occurring in it OR a fire that started somewhere else spreading into that cell).

Response: we replace the term 'the likelihood of fire occurrence' with 'the likelihood of a grid cell burning'.  

My original review also included the following comment:

1865-1875: Please provide a visual example of the output so that the reader can visualize and interpret it. This could even be a hypothetical scenario. But, it is needed. Otherwise, the paper builds up to this point but then never shows the final product.

The authors' response was:

Included in the new figure 14

However, there is no figure 14 in the revised version I downloaded from the online review system. There are two Figure 13s. I believe the second such figure needs to be renamed figure 14, along with any corresponding text (e.g., line 2346).

Response: Indeed, we apologize for this error. Now it is corrected. The generation of the integration process has been expanded and the map commented as well.