A Global Estimate of the Size and Location of Informal Settlements

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

As the paper title reads, this paper presents a global estimate of the size and location of informal settlements. This is a very relevant topic, for it is possible that the typical characterization of slums as inner-city overcrowded settlements may be wrong, or biased.

The paper uses original and innovative explorative methods to try to assess the size and location of settlements, and this is also valuable, for it is quite difficult to harmonize uneven sources of data on settlements, housing and deprivation.

The paper has, yet in my opinion, two major flaws it needs to deal with.

1.    The selection of literature to address the characterization of slums and informal settlements is quite slanted, and it does not bring forth the debate that, since the early 2000 to say the least, abounds on it. The three following papers are a thumbnail of the rich debate that has been increasing in the last years:

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1468-2427.2007.00754.x

https://www.tandfonline.com/doi/abs/10.1080/01944360508976689

https://journals.sagepub.com/doi/full/10.1177/00961442221127057

 

The main problem here is the authors have not clearly positioned themselves vis-a-vis these debates, however they point out that slums are complex realities and that the concept has been instrumentalized for bad actions. The title describes informal settlements and yet the text uses slums commonly, and yet it seems that the concept is associated basically with housing deprivations (page 1 and later on). This reinforces the idea that slum is used as a vague placeholder that yet carries the pejorative intrinsic denominations from its original British meaning. This is visible when reading statements like the following:

 

“Slums are a structural feature of urbanization (p.1.)”: does it mean that urbanization needs to essentially be built of urban, rural and slum areas?

 

“their manifestation [of slums] is almost synonymous with the Global South (p.1)”. This is a normative view that sees slums as deviant to proper urbanization, which occurs in the global North. The work of Vanessa Watson and Edgar Pietersee and also Ananya Roy, to say a few, context this view of slums from the global North as having colonialist traits, as the “uneducated South” that needs more of the “modern North”. This does not mean that slums or substandard settlements are more prevailing in countries in the global North, but such sweeping affirmations goes beyond the description of particular housing deprivations to a blanket worldview.

 

“…provide estimates for needed slum land within the SDG framework (p.2)”: does this mean that the solution of future precarious urbanization is the provision of “slum land”, and not just land? This may also render visible how the concept of “slum” is overly essentialized, as if “slum lands” were the place where “slum dwellers” belong, regardless of wherever they go. This phenomenon (the essentialization of slums as an ethereal essence beyond it being the odd packaging that UN-Habitat has made of housing deprivations at an urban scale) takes place throughout the text in the naming of “global slum dwellers” (p.3; do local slum dwellers belong to a global community?), or “slum realities” (p.2).

 

In my view, the way to go out from this problem is to do two things: One, spend some time at the beginning properly dissecting this debate (which has clear methodological consequences, as different data sources like the Atlas of *Informality* use different concepts and operationalizations) – this should go beyond just saying that the concept of slums is impossible to be replaced (it is unclear what this means: is not the concept actually synonym of “housing deprivations”?.

 

After the clarification, the second path needed would be to choose a concept, and explain its characteristics – so it can be taken as a scientific concept. My impression is that there are two main paths possible for this.

-       The first option, which in my view is the most solid, is to use a scientific term that describes what you are broadly mapping, regardless of the term someone uses for a particular country and publication. In my view what the paper is describing is substandard settlements, in the sense that it is trying to map the settlements that different stakeholders, in different institutions and with different characterizations, name as not following the standards existing in those institutions or places for housing. This would allow to then deal with the irregularity of data acquired in a proper manner, and being able to describe the irregularity without having the risk of being inconsistent.

 

-       The second option is to use the term “slum” because it is the one used in international development (despite all the reaction against it), and establish that it is used as a synonym for housing deprivations. If done so, one would need to express the limitation that current data sets focus on the global South, even when formality of tenure and overcrowding also exist in the global North (see for example the broad work of Jake Wegmann: https://onlinelibrary.wiley.com/doi/full/10.1111/1468-2427.12444) and has not been reported because there is no data (think of illegal migrants working on agricultural lands in Europe, for example).

 

2.    The structure of the paper is, in the view of the reviewer, still unclear. Part of this is due to language, and part of this is due to the organization of information. Parts 3 and 4 mix current sets of data on slums of settlements-associated information. While it is understandable that the chapters want to showcase the limitation in data, it is not clear why the GADM is, for example, not placed under chapter 3. If chapter 4 wants to describe Data and Methods, then so be it; but so far it seems partially describing current data available on slums or urbanization, and partially describing Results (i.e. Table 3, Table 1). Chapter 5, Analysis, seems to be also a description of methods and parts of the results, even though results are on chapter 6, and they are very short (for orientation, results should be a considerable chunk of the paper, like 30 or 40% of the text). In particular, data processing is not well explained. I do understand that there are some interesting databases that are used. But what are the methods used to analyse data? And how is data processed? This later one is important, for the reader cannot interpret that once one has for example global data on slums and statistical analysis, then one gets the results – one should explain how one uses statistics to make data provide certain results. This is, for example, visible at the end of page 13, when it is said that “slum population would grow by 384.8 million inhabitants.” How is this figure achieved? Are authors applying simple arithmetic to calculate future slum dwellers based on current share of population living in slums, and applying it to future population? That would be, at the same time, something questionable, for it is understood that slums are not a fix factor of world population. This type of ellipsis takes place in other places of the text.

 

Furthermore, the role of figures in the paper needs to improve. The references of text to images and figures is insufficient. One should explain in more detail what are we seeing in the figures, and what should we be reading. One particular moment where this is crucial is in explaining how does the analysis of the 30 more or less cities becomes a global analysis shown from figure 5 onwards. Besides, figures are placed far away from where the text refers to them, and figures like table 4 and table 1 are simply not referred in the paper (!). All this gives the impression that the paper was submitted perhaps quickly, before carrying a thorough revision and giving some time to fully organize the content.

Comments on the Quality of English Language

There are two features that need improvement.

On the one hand, there is a widespread use of acronyms in the paper, which are defined in different moments. I would ask the authors to understand that readers and reviewers are not familiar with the daily use of these acronyms, and for this reason:

-       Acronyms should be defined (explained, or layouted) at the first use (i.e., “a lack of WASH, p.2)

-       One should reduce the use of acronyms to the minimum possible, just to make the text more readable.

The second aspect regarding the use of language in that I would encourage authors to consider the stylistic form of a scientific paper. Expressions like “Making the incomparable comparable” may want to express the size of the challenge in research at hand, but in a way the text does not deliver the breakthrough the title expresses (there are always challenges to harmonize data), and even posits the suspicion that one cannot indeed compare the incomparable.

Otherwise, a copy-editing of the text (ideally, a professional one) is recommended for the use of sometimes informal expressions, or ambivalent sentences (as, for example, in the “two broad ways to map slums”, which is followed by a string of four elements) in the text.

Author Response

We have addressed all your comments and refer to the attached file for details.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

See the attachment

Comments for author File: Comments.pdf

Author Response

We have addressed all your comments and refer to the attached file for details.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Major Comments:

1.      The English language quality of the manuscript needs extensive improvement. A lot of grammatical errors as well as misused vocabulary are seen, and the text is not even understandable in some places.

2.      The paper is written unprofessionally and is not well-organized. For instance, Abstract does not have a flow. It must be re-written to summarize the goal of the study, the novelty, the proposed methods, and the findings. As another example, figures should not be placed in Introduction section, and figure captions should be placed below figures, not above them. The whole manuscript needs a major overhaul.

3.      MDPI Format must be followed when revisions are being made, including referencing style, figures, tables, titles/subtitles, etc.

4.      Please make sure you clarify the progress made compared to previous studies, by defining the research gap, and how you propose to fill it in the Introduction section.

5.      Section 2 should be either merged with Introduction (section 1) or merged with the next section (current section 3), which can be named “Section 2. Data” together. The current section 4 can also be changed to “Section 3. Methods”.

6.      Sections 5, 6, and 7 can be merged to form “Section 4. Results and Discussion”.

 

Minor Comments:

1.      Some references are cited without the author names. Only titles of the works are listed.

2.      Abstract: “Some essential questions on the location and density of slums cannot be answered in the current data landscape”. It is not clear why this sentence is written. What are those questions?

3.      Abstract: “to estimate that only half of all slums are located within the administrative borders”. Is this the goal of the study or the result of the study? Please re-write the abstract.

4.      SDG Target 11.1 is not defined yet but used in abbreviation form.

5.      The chosen keywords are not appropriate. Using single general words such as “Global” and “Estimates” are not appropriate. Pease be more specific.

6.      Please do not use direct quotes, unless necessary: "represent one of the most enduring faces of poverty, inequality, exclusion, and deprivation".

7.      When starting new paragraphs, please use tab for spacing.

8.      What is the number 85 here? (UN‐Habitat 2003, 85)

9.      Please remove this: “Error! Reference source not found.”

10.  Can you use larger font size in the boxes in Figure 1? They are not readable now.

11.  Please enlarge Table 1 horizontally, and use larger font size.

12.  Title of Section 2 does not look correct. “Challenge of slums” means that the challenge is the slum itself. I think you were intending to introduce some challenge related to the slums.

13.  Please enlarge the small maps in Figure 4, in a way that they are easily visible, and their legends and scales are fully readable. Also, please name them as a, b, c, etc. and write an informative figure caption, explaining all of them.

In the Data Availability section, what do you mean by “based on positive approval of the source.”?

Comments on the Quality of English Language

The English language quality of the manuscript needs extensive improvement. A lot of grammatical errors as well as misused vocabulary are seen, and the text is not even understandable in some places.

Author Response

We have addressed all your comments and refer to the attached file for details.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I appreciate the effort of the authors to improve the paper, but frankly do not see a clear change from the previous version. The argument given by the authors, that the changes suggested by this reviewer would require extending the word limit, implies their understanding that the critiques provide were not related to the core argument of the paper. But this is the case: in my view the papers cannot make a paper about slums that at the same time has "informal settlements" in its title, and which conflates housing deprivation, substandard housing, issues of mobility, public space scarcity etc. I agree that authors go forth with the definition of UN-Habitat, but this would require to say it so, simply, and then carry out with the consequences of this terminological choice. Poverty, scarcity, precarity, hunger, needs, are related but not the same - the same applies to slums. The reason why this is important is because it creates the idea that we all know what we are talking about when we say slums, or informal settlements, etc, without needing to create conceptual boundaries - but what we may indeed may be characterizing is the denomination of urban settlements that is considered pejorative for different people.

 

The other aspect that has not been taken into account is the inference from 30 cases to the unexplained generalization worldwide. Data about slums in cities may be more present in larger cities, some regions, particular economies, and therefore the generalization to the world level will carry those biases. What if slums in small cities are closer to urban cores, especially in say sub-Saharan cities? The authors are right in that addressing these changes may require a different paper. But so I think that the generalization is unwarranted. To generalize world scenarios based on thirty cases is, frankly, insufficient, and if made, it would require a detail explanation of how the global case is inferred - technically, meaning what statistical methods - simple aggregation is not enough.

This calls to the need to reduce the expectations of the paper. I do consider that the quest for authors to better understand the geography of informal settlements is very relevant, but the thirty cases do not allow for a global picture. They may point to some patterns found from existing analyses, which global models could verify or reject, or which could be useful moving forward with policy. But all that is different than making a global assessment. One could see this from a survey perspective: how many slums should one analyze to establish statistical evidence of their geographical pattern? Given that there is almost 2 billion people living in slums, it seems to me obvious that 30 cases obtained by snowballing is not enough.

I do encourage the authors to submit this material to this or other journal, but changing the expectations of the research. The paper is clearly exploratory in nature, not explanatory; and this means that the ontological horizon it has should be adjusted to what it can demonstrate. There is in science a growing pressure to produce clear, global, simple arguments that can be broadly communicated with different audiences; yet science has to remain grounded to what the facts can tell. If the author remain grounded to the facts they will be able to say a lot of relevant things, but in my view not oversimplifed versions of complex phenomena like that of slums.

Comments on the Quality of English Language

There are still some inconsistencies in langugage, mostly informal ways of expression that in my view should be polished and tightened.

Reviewer 2 Report

Comments and Suggestions for Authors

the manuscript has been sufficiently improved to warrant publication in Urban Science

Reviewer 3 Report

Comments and Suggestions for Authors

Thanks for the revisions. Your efforts are appreciated.