Biodiversity-Centric Habitat Networks for Green Infrastructure Planning: A Case Study in Northern Italy

Reviewer 1’s comments

Authors’ response

GENERAL COMMENTS

1

In general, this is a well written paper on an interesting topic, with a particularly strong discussion of the implications of the research presented here and excellent conclusions.

We thank Reviewer 1 for the kind words and appreciation of our work.

MATERIALS AND METHODS

2

Assigning Habitat Crossing Costs.

Please provide more information about how these were scored.  From the current manuscript, there is no way that someone else could replicate this study because the scores are not explained.  What specific factors were considered when assessing habitat similarity and how were they weighted?  How did you determine the similarity of vegetation composition, e.g. did you sample a given area (e.g. some number of 1 m2 plots) and extrapolate?  Or was this more based on gestalt, i.e. your impression of the plant community?  What successional stages were used as categories?

Scores were assigned to pre-existing CORINE habitat categories by local expert zoologists and botanists (now specified more clearly at L168 and L173-176) based on literature and on their own knowledge. We realized that, in the previous version, we did not underline sufficiently the limitation represented by the implicit degree of subjectivity of this method. We therefore added a section in the discussion acknowledging this limitation, but also underlying the fact that methods based on local ecological knowledge, such as our own, are increasingly considered important for conservation planning (L319-323). We also included an additional supplementary Excel file, detailing the crossing cost scores for all animal species and focal plant habitats; these scores could potentially be used to generate ecological networks in other areas that host similar communities and habitats, improving the usefulness and transparency of our methods and results.

3

‘Extensive agriculture areas were not included among anthropic impact areas.’

More information about the agricultural areas in the study area is needed.  Here those areas are considered not to have “anthropic impact“ (l. 205), which is clearly not correct.   In fact, agriculture is a primary driver of global biodiversity losses.  Please explain why you consider these particular agricultural areas to be habitat that is good for biodiversity.  Perhaps start by explaining the crops (a vineyard, for example, is a very different place from a farm growing wheat),  and the practices followed to increase biodiversity in the farmlands.

We apologize for our somewhat unclear wording; of course, we did not mean to imply that agriculture is not impactful to biodiversity. We simply wanted to underline the fact that extensive and low-input agricultural areas, if properly managed, can act as important habitats for a variety of wild species even though they are not completely impact-free. In fact, our experts selected extensive and low-input agricultural areas as ideal node habitats for one of our focus animal species, the European green lizard. For those reasons, we only focused on intensive agriculture when mapping agricultural impacts in our study. We expanded and modified this section of the text to better explain our reasons, also citing relevant literature (L222-229).

4

L. 229. Please explain exactly what is included in ‘other impactful land use types’ in line 229.

We added the specific types of impactful land use (intensive agriculture, intensive agriculture with seminatural residuals, perenni-al crops, alien vegetation) (L249-251).

RESULTS

5

Fig. 2. I cannot understand the maps in figure 2.  Are the white areas meant to be soil sealing (a) and intensive agriculture (b).   If so, please put that in the legend.  Also, the white is difficult to see against the yellow that indicates the study site, and I cannot make out the stepping stones (green).  How about making the background color white and the things you want a reader to be able to distinguish in different colors?  You could omit the grey, and possibly add a map of Italy showing the location of the site.

We realize that the explanation for this figure (now labeled Figure 3) was somewhat lacking. Different colors indicate different network components (red for nodes, blue for corridors, green for stepping stones), while color intensity indicates the incidence of either soil sealing or intensive agriculture in each individual node, corridor or stepping stone. This means that highly impacted elements (in terms of % of impacted area) are depicted with darker colors, while lightly impacted elements have lighter colors. We opted not to alter the general features of this figure, as we thought it was the best way to showcase the three impact gradients simultaneously. As one of the main goals was to give a general idea of impact distribution within the study area, we also deliberately retained the lower visibility of lightly-impacted elements if compared with the darker highly-impacted elements. We however slightly altered the legend and greatly expanded the figure caption, in order to better explain the symbology and improve clarity.

We also thank Reviewer 1 for the suggestion of adding a map of Italy for better showcasing the location of the study area; we added this element in the new Figure 1, which shows the general features of the study area.

MINOR CORRECTIONS

6

L. 38    Use ‘counteract’ rather than ‘contrast.’

Done.

7

L. 40. Comma goes after ‘areas,’ not after ‘planned.’

Done.

8

L. 44-45.  ….synonymous ‘with’ rather than not synonymous of (standard usage)

Done.

9

Ll. 57-58. --- this burden by allowing to focus.   I’m not sure what you mean here, but someone has to be doing the focusing, e.g. ‘by allowing managers to focus…’

We added “conservation managers” to the sentence (L62).

10

L. 107.  Correct to ‘In the case of….’

Done.

11

L. 152 ‘habitats’

Done.

12

L. 308  The percentage…remains (not ‘remain’)

Done.

Reviewer 2’s comments

Authors’ response

GENERAL COMMENTS

1

The manuscript presents an interesting method to be discussed by the scientific and academic community, especially because it is an area of opportunity in regard to the analysis of green infrastructure networks. However, the manuscript presents some content deficiencies that must be corrected for publication, which I list below:

We thank Reviewer 2 for the kind words and appreciation of our work. In the following sections, we respond in detail to the concerns raised by the reviewer and illustrate how we integrated their suggestions into our manuscript, hopefully to a degree that enables its publication.

ABSTRACT

2

Abstract. It lacks the general objective written explicitly. Then, the method and briefly what it consists of (the steps). The results based on the general and specific objective; they must show the main findings (quantitative information). The lines intended for the conclusion in the abstract must be directly supported by the results.

We modified some sections of the abstract according to Reviewer 2’s suggestions; especially focused on expanding the methods section, briefly describing its key steps (L19-22) and included some results to support the conclusions (L23-24).

MATERIALS & METHODS

3

Materials and Methods. Although authors mention that “We focused on the maintenance of the basic conditions for ecosystem services provision in the long time, namely natural habitat availability and the related biodiversity” (Lines 89-90), authors do not provide a conceptual explanation of the relationship that exists between target species and habitats, and the maintenance of ecosystem services; that is, how these properties support ecological functions and processes, and these support ecosystem services. This must be detailed and explained with bibliography.

We now realize that the sentence was somewhat misleading; while it is widely accepted that biodiversity conservation is linked with ecosystem services enhancement (as we state in the initial part of the manuscript), our study focused on a GI for biodiversity, rather than on quantifying ecosystem services. We slightly altered the sentence to reflect our goals more accurately (L94-95).

4

Study area. Authors should include and explain a map with the main characteristics: land use and vegetation, rivers and water covers, and human infrastructure, in order to know how the study area is integrated. In addition, the projection system (UTM coordinates or Lambert conic) must be included.

We added a new Figure 1 showcasing the main features of the study area, and its location in Italy. We did not include the mapping of the 75 CORINE vegetation types, as it would have made the map unreadable; we did however include the mapping of the main land cover types (agriculture, urban/industrial, natural habitats, alien vegetation), as well as the Isonzo-Vipacco river, which is central to the area and the project. We also added information about the projection system we used (L113-114).

5

Ecological Network. The authors need to add what the differences between the habitat categories consist of.

We added a sentence briefly explaining the categorization method of CORINE BIOTOPES, and cited a relevant reference (L136-139).

6

Building the ecological network. The authors need to add a couple of images illustrating how they did each of the steps and what they consist of.

We added two supplementary figures (Figure S1-S2) detailing the main steps of the network-building process. We now reference the new figures in relevant parts of the text.

MINOR CORRECTIONS

7

Results. Authors need to revised the text highlighted in the PDF (L55-56, L66-68, L129, L244-247, L252, Table 1).

We asked a native English speaker colleague to revise the highlighted text, applying minor corrections when needed. We corrected a very minor mistake in a reported percentage (the mistake did not influence results or conclusions in any way – L267). Finally, in the section about anthropic pressures results, we now also cite supplementary tables containing relevant data (L280-289).

Reviewer 3’s comments

Authors’ response

GENERAL COMMENTS

1

The manuscript deals with a very important topic, i.e. green infrastructure network planning at the regional scale and outside of urban settings. In the decade dedicated to ecosystem restoration, the concept of GI is of utmost important. I found the umbrella species approach incorporating also a high number of plant species compelling. I found the paper very well written, and suggest a minor revision.

We thank Reviewer 3 for the kind words and appreciation of our work.

2

The paper deals rather with GI designation than planning (except for the Discussion), as no new habitat nodes, links or stepping stones are designated. For this, I would change the title of the ms accordingly.

INTRODUCTION

3

L45 I would insert GI into the text as follows: ’in a landscape GI network’

Done.

MATERIALS & METHODS

4

L155 The Supplement could be complemented with the assigned costs of each Corine habitat type for each animal species.

We included an additional supplementary Excel file, detailing the crossing costs for all animal species and focal plant habitats.

5

L171 Please give some details on how you defined nodes. What was the minimum size of the nodes? What was the maximum threshold distance between two nodes?

Nodes were based on the initial CORINE BIOTOPES habitat categorization in relation with the specie/habitat needs, and we did not apply a threshold for size or minimum distance. When mapping the corridors we did, however, remove very short corridors (including less than 10 cells of the original grid). This information was lacking from the previous version due to an oversight, but we now added it to the manuscript (L191-192 and L201-202).

6

L188 How were the nodes and stepping stones differentiated from each other? As I understood they were from the same habitat types. Why were not all stepping stones defined as nodes?

We apologize for being insufficiently clear. Nodes and stepping stones were actually chosen among different habitat types: habitats that were already identified as nodes for at least one of the focal species or plant habitats were not considered in stepping stones selection. We added this information to the text (L207-208).

RESULTS AND DISCUSSION

7

L248 Are NAs not zeros in Table 1?

Information about anthropic impacts other than soil sealing were obtained from the CORINE habitat mapping, the same source we used to map nodes and stepping stones. As such, there is no overlapping and thus no information about the incidence of these other impacts in nodes and stepping stones, although it is assumed to be low. We added this information to the caption of Table 1, for additional clarity.

8

Planning based on the demands of species with a wide array of ecological needs may overestimate the functionality of the network for single species with specific habitat use. This possibility could be acknowledged in the text.

We agree, and for that reason we had suggested in the conclusion section that the same method could be also applied to a limited number of sensitive species to better tailor the network to their needs. We expanded the sentence to explicitly include the consideration suggested by Reviewer 3 and clarify the multi-species approach potential (L399-403).