Blue carbon from the past forecasts the future

doi:10.1126/science.abc3735

GSTDTAP > 气候变化

DOI	10.1126/science.abc3735
	Blue carbon from the past forecasts the future
	Catherine E. Lovelock
	2020-06-05
发表期刊	Science
出版年	2020
英文摘要	When knowledge of a system is imperfect, thresholds are extremely useful tools for decision-makers. Sea level rise (SLR) threatens intertidal coastal wetlands because these aquatic plants will drown as water depths exceed their physiological tolerance limits. For mangroves—trees and shrubs that grow in tidal waters of the tropics or subtropics—the threshold for SLR has been elusive. On page 1118 of this issue, Saintilan et al. ([ 1 ][1]) deduce that the threshold SLR for mangrove ecosystems is 6 to 7 mm/year. This discovery can help inform decisions on how to sustain mangroves, which provide 200 million coastal people with essential ecosystem services. These include protection from intense storms and waves, reduction in the impact of coastal flooding, sequestering of carbon, improvement in water quality, and preservation of biodiversity and fisheries ([ 2 ][2]). Saintilan et al. studied ancient mangrove sediments to infer a threshold of relative SLR for mangrove tolerance. The term “relative” is used because the rate of SLR is determined not only by the increase in water volume of the oceans but also by subsidence or uplift of coastal land. Subsidence and uplift result, in part, from glacial isostatic adjustment, which describes a complex set of geophysical processes that vary geographically. The authors used sediment cores to collate the dates when mangrove vegetation first appeared in a variety of locations over the past 10,000 years. Mangroves can be detected from their distinctive, highly organic sediments, which reflect mangrove ecosystems' great productivity and conditions that favor preservation of vast quantities of organic carbon. The data obtained from sediment cores, sampled by a range of researchers from 78 sites on five continents, indicate that mangrove ecosystems did not develop unless relative SLR was less than 6 to 7 mm/year. The global mean rate of SLR is now 3.4 mm/year and is projected to exceed the threshold and reach ∼10 mm/year by 2100 under “business-as-usual” scenarios (greenhouse gas concentration trajectory Representative Concentration Pathway 8.5) ([ 3 ][3]). However, SLR could stabilize at ∼5 mm/year by the year 2100 under moderate-emissions scenarios in which countries reduce carbon dioxide (CO2) emissions ([ 3 ][3]). Clearly, reducing CO2 in the atmosphere is a first line of defense against passing the relative SLR threshold for mangrove persistence. However, in many mangrove locations, rates of relative SLR are already higher than 6 to 7 mm/year. Now, in the Anthropocene, subsidence of coastal land is also caused by extraction of oil, gas, and water ([ 4 ][4]). For example, the Mekong Delta of Vietnam is subsiding at a rate of 6 to 20 mm/year ([ 5 ][5]) and the Ganges-Brahmaputra Delta by 1 to 7 mm/year ([ 6 ][6]), which is accompanied by land erosion and saltwater intrusion. At the same time, sediment supply to the coast, which is vital to counteracting the effects of relative SLR as it contributes to raising the seafloor, has declined; this is because rivers are dammed and, in some cases, sediment has been mined and exported, all of which further increase the vulnerability of mangroves to SLR ([ 7 ][7]). Saintilan et al. also found variation around the mean threshold value of 6 to 7 mm/year, indicating that local factors, such as subsidence and sediment supply, drive location-specific relative SLR thresholds for mangroves. Reduction in extraction of water, oil, and gas from floodplains and enhancing sediment supply might avoid crossing the SLR threshold for mangrove persistence. Dam removal and the delivery of nourishing sediments and water to the coast are practiced in Europe and North America but have little uptake in the tropics ([ 8 ][8]). Improvement of water quality and reduction of overexploitation will help maintain mangrove health by facilitating strong root growth, which also contributes to vertical accretion ([ 9 ][9]). Balancing the freshwater and sediment needs of mangroves that provide natural ecosystem services against water storage, irrigated agriculture, and hydropower is an emerging series of trade-offs that policy-makers must face ([ 10 ][10]). One key consideration in these trade-offs is that under moderate SLR, mangroves mitigate CO2 in the atmosphere by storing it in the plants and sediment of the ecosystem (so-called blue carbon) ([ 11 ][11]). Saintilan et al. used their sediment core data to estimate the amount of CO2 sequestered over ∼1400 years of mangrove development and reached a conservative estimate of 85 Pg of stored carbon, which is larger than the estimated carbon stored in boreal peats as they developed through the same Holocene period. These historical estimates verify that sequestration of blue carbon in coastal ecosystems makes substantial contributions to the mitigation of global climate change ([ 12 ][12]). Without sufficient sediment and root growth to reduce the impacts of SLR, mangrove cover might be sustained through landward migration of mangroves onto floodplains. This would increase carbon sequestration, but landward retreat is complex and can be costly for governments and landholders ([ 13 ][13]). The threshold provided by Saintilan et al. , combined with knowledge of local factors that influence relative SLR, provides opportunities to develop time lines for decisions and actions that will maintain mangroves in the land-seascape. There are caveats to consider in the new study. Over the late Holocene, rates of SLR were mostly declining, whereas Earth currently faces accelerating SLR, which might alter the threshold. There could be lags in responses of mangrove cover to relative SLR that exceed the 6- to 7-mm/year threshold, and lags can vary with species traits and disturbance regimens, such as frequency and intensity of storms that exacerbate the impacts of SLR and which are predicted to intensify with climate change in many regions. Nevertheless, providing an evidence-based relative SLR threshold for mangrove survival can help stimulate solutions for coastal management. If nations and communities wish to harness the potential of blue carbon to mitigate climate change and to protect millions of people who depend on mangroves for shelter, flood protection, food, and fiber, then solutions for staying below the 6- to 7-mm/year relative SLR threshold should be the goal of civil society and governments. With reduction in CO2 emissions, equitable management of river water and sediment flows, limitations in water and oil extraction on floodplains, and conservation and planning for landward migration, mangroves can be maintained into the future. 1. [↵][14]1. N. Saintilan et al ., Science 368, 1118 (2020). [OpenUrl][15][Abstract/FREE Full Text][16] 2. [↵][17]1. E. B. Barbier et al ., Ecol. Monogr. 81, 169 (2011). [OpenUrl][18][CrossRef][19][Web of Science][20] 3. [↵][21]1. T. F. Stocker et al Intergovernmental Panel on Climate Change (IPCC), “Climate Change 2013: The Physical Science Basis. Working Group 1 Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change,” T. F. Stocker et al., Eds. (IPCC, 2013). 4. [↵][22]1. J. P. Syvitski et al ., Nat. Geosci. 2, 681 (2009). [OpenUrl][23][CrossRef][24][Web of Science][25] 5. [↵][26]1. P. S. J. Minderhoud et al ., Sci. Total Environ. 634, 715 (2018). [OpenUrl][27] 6. [↵][28]1. M. Becker et al ., Proc. Natl. Acad. Sci. U.S.A. 117, 1867 (2020). [OpenUrl][29][Abstract/FREE Full Text][30] 7. [↵][31]1. C. E. Lovelock et al ., Nature 526, 559 (2015). [OpenUrl][32] 8. [↵][33]1. L. Ding et al ., Chin. Geogr. Sci. 29, 1 (2019). [OpenUrl][34] 9. [↵][35]1. K. W. Krauss et al ., New Phytol. 202, 19 (2014). [OpenUrl][36][CrossRef][37][PubMed][38] 10. [↵][39]1. G. Grill et al ., Nature 569, 215 (2019). [OpenUrl][40][CrossRef][41][PubMed][42] 11. [↵][43]1. E. Mcleod et al ., Front. Ecol. Environ. 9, 552 (2011). [OpenUrl][44][CrossRef][45] 12. [↵][46]1. K. Rogers et al ., Nature 567, 91 (2019). [OpenUrl][47][CrossRef][48][PubMed][49] 13. [↵][50]1. C. R. Field et al ., Proc. Natl. Acad. Sci. U.S.A. 114, 9134 (2017). [OpenUrl][51][Abstract/FREE Full Text][52] [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #ref-6 [7]: #ref-7 [8]: #ref-8 [9]: #ref-9 [10]: #ref-10 [11]: #ref-11 [12]: #ref-12 [13]: #ref-13 [14]: #xref-ref-1-1 "View reference 1 in text" [15]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DSaintilan%26rft.auinit1%253DN.%26rft.volume%253D368%26rft.issue%253D6495%26rft.spage%253D1118%26rft.epage%253D1121%26rft.atitle%253DThresholds%2Bof%2Bmangrove%2Bsurvival%2Bunder%2Brapid%2Bsea%2Blevel%2Brise%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.aba2656%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [16]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEzOiIzNjgvNjQ5NS8xMTE4IjtzOjQ6ImF0b20iO3M6MjM6Ii9zY2kvMzY4LzY0OTUvMTA1MC5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30= [17]: #xref-ref-2-1 "View reference 2 in text" [18]: {openurl}?query=rft.jtitle%253DEcol.%2BMonogr.%26rft.volume%253D81%26rft.spage%253D169%26rft_id%253Dinfo%253Adoi%252F10.1890%252F10-1510.1%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [19]: /lookup/external-ref?access_num=10.1890/10-1510.1&link_type=DOI [20]: /lookup/external-ref?access_num=000290707600001&link_type=ISI [21]: #xref-ref-3-1 "View reference 3 in text" [22]: #xref-ref-4-1 "View reference 4 in text" [23]: {openurl}?query=rft.jtitle%253DNat.%2BGeosci.%26rft.volume%253D2%26rft.spage%253D681%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fngeo629%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [24]: /lookup/external-ref?access_num=10.1038/ngeo629&link_type=DOI [25]: /lookup/external-ref?access_num=000270355000011&link_type=ISI [26]: #xref-ref-5-1 "View reference 5 in text" [27]: {openurl}?query=rft.jtitle%253DSci.%2BTotal%2BEnviron.%26rft.volume%253D634%26rft.spage%253D715%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [28]: #xref-ref-6-1 "View reference 6 in text" [29]: {openurl}?query=rft.jtitle%253DProc.%2BNatl.%2BAcad.%2BSci.%2BU.S.A.%26rft_id%253Dinfo%253Adoi%252F10.1073%252Fpnas.1912921117%26rft_id%253Dinfo%253Apmid%252F31907308%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [30]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoicG5hcyI7czo1OiJyZXNpZCI7czoxMDoiMTE3LzQvMTg2NyI7czo0OiJhdG9tIjtzOjIzOiIvc2NpLzM2OC82NDk1LzEwNTAuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [31]: #xref-ref-7-1 "View reference 7 in text" [32]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D526%26rft.spage%253D559%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [33]: #xref-ref-8-1 "View reference 8 in text" [34]: {openurl}?query=rft.jtitle%253DChin.%2BGeogr.%2BSci.%26rft.volume%253D29%26rft.spage%253D1%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [35]: #xref-ref-9-1 "View reference 9 in text" [36]: {openurl}?query=rft.jtitle%253DNew%2BPhytol.%26rft.volume%253D202%26rft.spage%253D19%26rft_id%253Dinfo%253Adoi%252F10.1111%252Fnph.12605%26rft_id%253Dinfo%253Apmid%252F24251960%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [37]: /lookup/external-ref?access_num=10.1111/nph.12605&link_type=DOI [38]: /lookup/external-ref?access_num=24251960&link_type=MED&atom=%2Fsci%2F368%2F6495%2F1050.atom [39]: #xref-ref-10-1 "View reference 10 in text" [40]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D569%26rft.spage%253D215%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fs41586-019-1111-9%26rft_id%253Dinfo%253Apmid%252F31068722%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [41]: /lookup/external-ref?access_num=10.1038/s41586-019-1111-9&link_type=DOI [42]: /lookup/external-ref?access_num=31068722&link_type=MED&atom=%2Fsci%2F368%2F6495%2F1050.atom [43]: #xref-ref-11-1 "View reference 11 in text" [44]: {openurl}?query=rft.jtitle%253DFront.%2BEcol.%2BEnviron.%26rft.volume%253D9%26rft.spage%253D552%26rft_id%253Dinfo%253Adoi%252F10.1890%252F110004%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [45]: /lookup/external-ref?access_num=10.1890/110004&link_type=DOI [46]: #xref-ref-12-1 "View reference 12 in text" [47]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D567%26rft.spage%253D91%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fs41586-019-0951-7%26rft_id%253Dinfo%253Apmid%252F30842636%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [48]: /lookup/external-ref?access_num=10.1038/s41586-019-0951-7&link_type=DOI [49]: /lookup/external-ref?access_num=30842636&link_type=MED&atom=%2Fsci%2F368%2F6495%2F1050.atom [50]: #xref-ref-13-1 "View reference 13 in text" [51]: {openurl}?query=rft.jtitle%253DProc.%2BNatl.%2BAcad.%2BSci.%2BU.S.A.%26rft_id%253Dinfo%253Adoi%252F10.1073%252Fpnas.1620319114%26rft_id%253Dinfo%253Apmid%252F28790190%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [52]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoicG5hcyI7czo1OiJyZXNpZCI7czoxMToiMTE0LzM0LzkxMzQiO3M6NDoiYXRvbSI7czoyMzoiL3NjaS8zNjgvNjQ5NS8xMDUwLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==
领域	气候变化 ; 资源环境
URL	查看原文
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/273427
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Catherine E. Lovelock. Blue carbon from the past forecasts the future[J]. Science,2020.
APA	Catherine E. Lovelock.(2020).Blue carbon from the past forecasts the future.Science.
MLA	Catherine E. Lovelock."Blue carbon from the past forecasts the future".Science (2020).