Assessing uncertainties in global cropland futures using a conditional probabilistic modelling framework

Engström, Kerstin; Olin, Stefan; Rounsevell, Mark D. A.; Brogaard, Sara; van Vuuren, Detlef P.; Alexander, Peter; Murray-Rust, Dave; Arneth, Almut

doi:https://doi.org/10.5194/esd-7-893-2016

Articles | Volume 7, issue 4

https://doi.org/10.5194/esd-7-893-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/esd-7-893-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 7, issue 4

Research article

|

17 Nov 2016

Research article |

| 17 Nov 2016

Assessing uncertainties in global cropland futures using a conditional probabilistic modelling framework

Kerstin Engström, Stefan Olin, Mark D. A. Rounsevell, Sara Brogaard, Detlef P. van Vuuren, Peter Alexander, Dave Murray-Rust, and Almut Arneth

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Final revised paper (published on 17 Nov 2016)
Preprint (discussion started on 15 Mar 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'esd-2016-7', Anonymous Referee #1, 09 May 2016
RC2: 'Remark 16 in RC1', Anonymous Referee #1, 13 May 2016
RC3: 'Anonymous Referee #2', Anonymous Referee #2, 01 Jun 2016
AC1: 'Response to reviewer 1', Kerstin Engström, 25 Jun 2016
AC2: 'Response to reviewer 2', Kerstin Engström, 25 Jun 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (14 Jul 2016) by James Dyke

AR by Kerstin Engström on behalf of the Authors (14 Jul 2016) Manuscript

ED: Referee Nomination & Report Request started (19 Jul 2016) by James Dyke

RR by Anonymous Referee #1 (28 Jul 2016)

Suggestions for revision or reasons for rejection

Dear authors,

thank you for your comments and the revised manuscript. I find the improved manuscript much more readable and you successfully addressed my major concerns. I just have the following minor remarks:

Answer to comments 4-5, manuscript p.5 and Appendix A2:
Thanks for a much improved description of the crop yield calculations.
Just for further clarification: Do I understand correctly that technological development only affects the yield gap and not potential yields? And that potential yield is only influenced by climate? Or is there any technological development in yield potential, too? (breeding etc ...). It would be good if you could add a clarifying sentence in section 2.2.

Answer to comment 7: I generally concur with your justification. Just one minor aside: You write "Additionally, using normal distributions reduces extreme outcomes as the probability of sampling at the tails of several distributions is greatly reduced." Well, this is not a pro argument per se, since avoiding outcome extremes can be wrong or right depending on what the correct (unknown) distributions would be ...

Answer to comment 8: Just a correction: Sobol' sequences can work with a large variety of distributional assumptions. They do indeed produce uniformly distributed variates, but these can be transformed into most other distributions using e.g. the inverse transform method.

Answer to comment 19 / p.4 l. 3ff.: Unfortunately, the sentence regarding SPAs does not explain at all whether or not they play any role in your model. It interrupts the description of the scenario matrix without really explaining the connection. Maybe something like: " We use the SSPs as reference scenarios without introducing any specific mitigation policies (as could be done using SPAs, for example)." would be better, in case it fits what you did?

p.14, l. 25: The use of "however" does not make sense to me here.

p.14, l. 28: This sentence seems to convey that in both scenarios (F1 and F3) the total cropland area was -41% in 2000 and increased to 58% in 2010. I guess what you rather want to say is that the change of cropland areas differs strongly between the two scenarios. (A somewhat similar problem at the end of line 31)

p.15, l. 1: The comma and "and" are a bit confusing here. Should there be an "and" where the comma is? Or could there be an Oxford comma in front of the existing "and"? In other words, do you enumerate 2 or 3 considerations here?

p.15, l. 5: "equally important .... than ..." is gramatically incorrect, I guess.

p.15, l. 6: no comma before if, and clearer: "if these sources" or "if both sources"

p. 15, l.9: At the end of the sentence one wonders, which sources were not so important: The pretty general "differences in socio-economic scenario assumptions" and "uncertainties in interpreting model input parameters" are the main sources of uncertainties, rather than which other sources?

p. 15, l.18: Could the last sentence be worded more clearly and strongly: "This leads us to conclude that very different worlds can result in very similar cropland futures at the aggregated global scale as lon as they share low to medium population development.", or would that change meaning?

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RR by Anonymous Referee #2 (03 Aug 2016)

ED: Publish subject to minor revisions (review by Editor) (11 Aug 2016) by James Dyke

AR by Kerstin Engström on behalf of the Authors (16 Aug 2016)

ED: Publish as is (06 Sep 2016) by James Dyke

AR by Kerstin Engström on behalf of the Authors (13 Sep 2016)

Short summary

The development of global cropland in the future depends on how many people there will be, how much meat and milk we will eat, how much food we will waste and how well farms will be managed. Uncertainties in these factors mean that global cropland could decrease from today's 1500 Mha to only 893 Mha in 2100, which would free land for biofuel production. However, if population rises towards 12 billion and global yields remain low, global cropland could also increase up to 2380 Mha in 2100.