Regional opportunities for tundra conservation in the next 1000 years
Curation statements for this article:-
Curated by eLife
Evaluation Summary:
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. This detailed modelling study predicts dramatic losses of tundra area by the middle of the millenium even under an ambitious climate mitigation scenario and highlights considerable risks of extinction.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)
This article has been Reviewed by the following groups
Listed in
- Evaluated articles (eLife)
- Ecology (eLife)
Abstract
The biodiversity of tundra areas in northern high latitudes is threatened by invasion of forests under global warming. However, poorly understood nonlinear responses of the treeline ecotone mean the timing and extent of tundra losses are unclear, but policymakers need such information to optimize conservation efforts. Our individual-based model LAVESI, developed for the Siberian tundra-taiga ecotone, can help improve our understanding. Consequently, we simulated treeline migration trajectories until the end of the millennium, causing a loss of tundra area when advancing north. Our simulations reveal that the treeline follows climate warming with a severe, century-long time lag, which is overcompensated by infilling of stands in the long run even when temperatures cool again. Our simulations reveal that only under ambitious mitigation strategies (relative concentration pathway 2.6) will ∼30% of original tundra areas remain in the north but separated into two disjunct refugia.
Article activity feed
-
-
Author Response:
Reviewer #1:
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of the life-history of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. The videos show the main simulation results succinctly.
The life-history parameters of growth, reproduction, dispersal, establishment, and mortality are apparently tied to temperature, wind, and precipitation; however, the connections of life-history traits to these critical environmental variables does not appear fully described, except to state that growth is tied to temperature.
If space is limiting in the manuscript's Methods, some of the description of machine computations could be reduced and a fuller …
Author Response:
Reviewer #1:
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of the life-history of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. The videos show the main simulation results succinctly.
The life-history parameters of growth, reproduction, dispersal, establishment, and mortality are apparently tied to temperature, wind, and precipitation; however, the connections of life-history traits to these critical environmental variables does not appear fully described, except to state that growth is tied to temperature.
If space is limiting in the manuscript's Methods, some of the description of machine computations could be reduced and a fuller description of how warming, wind, and water are included in the model parametrization (rather than citing a previous paper behind a pay-wall) can be provided. For instance, Figure 3 is both a computational and a conceptual graphic. Many readers might prefer to understand how climate change is incorporated into LAVESI conceptually, at least as much if not more so than how much computational time is required to run it.
We thank the reviewer for the critical assessment of our manuscript. Following their suggestions, we will include more details about the forcing climate data link to the internal processes in the Methods section. We will add this at the end of the first paragraph, Model description and improvements. Our changes will include replacing the abstract conceptional Figure 3 with a more detailed version showing how climate variables and especially climate warming will impact the individual processes in LAVESI. Further, we will remove the model performance plots from Figure 3 and merge them into the appendix.
Reviewer #2:
This detailed modelling study provides important insight into longterm treeline advance into Siberian tundra ecosystems, quantifying the dramatic loss of tundra area of 70% even under ambitious mitigation scenario RCP2.6 by the middle of the millenium. It highlights considerable risk of extinction esp. of cold-climate tundra types.
Strengths:
- Emphasizes non-equilibrium of treeline position with climate conditions.
- demonstrates lead-lag effect of climate and treeline shift under warming, but also cooling conditions. The very slow recovery of tundra even under late millenium cooling highlights urgency of combating climate warming quickly
- Quantifies tundra loss, regions and speed of loss, highly relevant for science-based tundra conservation policies
We thank the reviewer for pointing out the key points of our study.
Weaknesses:
- Systematically discussing in the introduction or the appendix main limiting factors of tree establishment and growth relevant for the study area, and mentioning those finally implemented in the model would add considerable value (i.e. limiting factors that prevent tree establishment and growth, permafrost degradation, soil nutrient development, biotic interactions (herbivory)).
This discussion would increase traceability of methods and assessment of relevance of results, but also further emphasize how much this study is an improvement over previous studies by including some of this processes largely neglected earlier. Some of this very relevant information is mentioned in the response letter, but only partly introduced in the revised manuscript.
Following the recommendations of the reviewer, we will add a new paragraph with a more detailed presentation of implemented abiotic/biotic limiting factors in the Methods section. This will include either a statement of how these are explicitly considered, or argumentation as to whether these are implicitly part of other processes in LAVESI.
- Discussion of limitations of the modelling study is largely missing, including the following aspects:
- Is this vegetation model coupled with a climate model? If not, feedbacks of forest expansion with climate and permafrost are currently neglected. The model is tested along gradients in selected regions, but it remains uncertain if space-for-time approach will hold in the future and further north, esp. when large-scale feedbacks are included.
We did not couple LAVESI to a climate model so only climate forcing is used and the model can be run stand-alone with data from different sources. We will add in the Discussion the point about limitations of potential loss of space-for-time.
- What about disturbances and extreme weather conditions that might regionally impact treeline advance or tree survival? E.g. increasing tundra fire activity might strongly impact vegetation development. Also droughts/flooding might lead to regional vegetation impacts, esp. at seedling stage. Extreme events and related disturbances are predicted to increase under climate change and a discussion on how they might impact predictions by the model is needed. Are these factors all only short-term and neglectable compared to the long-term perspective modelled? If yes this should be mentioned.
The reviewer brings attention to a very important discussion. In our model, currently (tundra) fire is not explicitly simulated, however drought impact on growth and survival is considered, although flooding or waterlogging that may take place locally are not. The impact on predictions can be that the tundra colonization is even slower, further prolonging the time-lagged response. But in the long run, more extreme weather events could support a faster dieback and retreat of the treeline.
We will debate this in the Discussion section of the revised manuscript.
- Figures and their legends need to be checked and improved.
We will check and add further detail where necessary, both for improvement and understanding of the content.
-
Evaluation Summary:
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. This detailed modelling study predicts dramatic losses of tundra area by the middle of the millenium even under an ambitious climate mitigation scenario and highlights considerable risks of extinction.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)
-
Reviewer #1 (Public Review):
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of the life-history of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. The videos show the main simulation results succinctly.
The life-history parameters of growth, reproduction, dispersal, establishment, and mortality are apparently tied to temperature, wind, and precipitation; however, the connections of life-history traits to these critical environmental variables does not appear fully described, except to state that growth is tied to temperature.
If space is limiting in the manuscript's Methods, some of the description of machine computations could be reduced and a fuller description of how …
Reviewer #1 (Public Review):
Kruse and Herzschuh apply LAVESI, a machine-intensive and spatially-explicit simulation of the life-history of individual Siberian trees at the tundra-forest boundary, to call attention to the rapid reduction in the tundra biome as climate warming pushes forests toward the Arctic Ocean. The videos show the main simulation results succinctly.
The life-history parameters of growth, reproduction, dispersal, establishment, and mortality are apparently tied to temperature, wind, and precipitation; however, the connections of life-history traits to these critical environmental variables does not appear fully described, except to state that growth is tied to temperature.
If space is limiting in the manuscript's Methods, some of the description of machine computations could be reduced and a fuller description of how warming, wind, and water are included in the model parametrization (rather than citing a previous paper behind a pay-wall) can be provided. For instance, Figure 3 is both a computational and a conceptual graphic. Many readers might prefer to understand how climate change is incorporated into LAVESI conceptually, at least as much if not more so than how much computational time is required to run it.
-
Reviewer #2 (Public Review):
This detailed modelling study provides important insight into longterm treeline advance into Siberian tundra ecosystems, quantifying the dramatic loss of tundra area of 70% even under ambitious mitigation scenario RCP2.6 by the middle of the millenium. It highlights considerable risk of extinction esp. of cold-climate tundra types.
Strengths:
1. Emphasizes non-equilibrium of treeline position with climate conditions.
2. demonstrates lead-lag effect of climate and treeline shift under warming, but also cooling conditions. The very slow recovery of tundra even under late millenium cooling highlights urgency of combating climate warming quickly
3. Quantifies tundra loss, regions and speed of loss, highly relevant for science-based tundra conservation policies
Weaknesses:
1. Systematically discussing in the …
Reviewer #2 (Public Review):
This detailed modelling study provides important insight into longterm treeline advance into Siberian tundra ecosystems, quantifying the dramatic loss of tundra area of 70% even under ambitious mitigation scenario RCP2.6 by the middle of the millenium. It highlights considerable risk of extinction esp. of cold-climate tundra types.
Strengths:
1. Emphasizes non-equilibrium of treeline position with climate conditions.
2. demonstrates lead-lag effect of climate and treeline shift under warming, but also cooling conditions. The very slow recovery of tundra even under late millenium cooling highlights urgency of combating climate warming quickly
3. Quantifies tundra loss, regions and speed of loss, highly relevant for science-based tundra conservation policies
Weaknesses:
1. Systematically discussing in the introduction or the appendix main limiting factors of tree establishment and growth relevant for the study area, and mentioning those finally implemented in the model would add considerable value (i.e. limiting factors that prevent tree establishment and growth, permafrost degradation, soil nutrient development, biotic interactions (herbivory)).
This discussion would increase traceability of methods and assessment of relevance of results, but also further emphasize how much this study is an improvement over previous studies by including some of this processes largely neglected earlier. Some of this very relevant information is mentioned in the response letter, but only partly introduced in the revised manuscript.
2. Discussion of limitations of the modelling study is largely missing, including the following aspects:
- Is this vegetation model coupled with a climate model? If not, feedbacks of forest expansion with climate and permafrost are currently neglected. The model is tested along gradients in selected regions, but it remains uncertain if space-for-time approach will hold in the future and further north, esp. when large-scale feedbacks are included.
- What about disturbances and extreme weather conditions that might regionally impact treeline advance or tree survival? E.g. increasing tundra fire activity might strongly impact vegetation development. Also droughts/flooding might lead to regional vegetation impacts, esp. at seedling stage. Extreme events and related disturbances are predicted to increase under climate change and a discussion on how they might impact predictions by the model is needed. Are these factors all only short-term and neglectable compared to the long-term perspective modelled? If yes this should be mentioned.3. Figures and their legends need to be checked and improved.
-
