A biodiversity target based on species extinctions

doi:10.1126/science.aba6592

GSTDTAP > 气候变化

DOI	10.1126/science.aba6592
	A biodiversity target based on species extinctions
	Mark D. A. Rounsevell; Mike Harfoot; Paula A. Harrison; Tim Newbold; Richard D. Gregory; Georgina M. Mace
	2020-06-12
发表期刊	Science
出版年	2020
英文摘要	Although worldwide loss of biodiversity arising from human activities is widely known, policy has been unable to arrest the decline ([ 1 ][1]). Much of this failure can be attributed to a lack of mainstreaming of biodiversity in public policy (2, pp. 741–762) and limitations in raising the profile of biodiversity loss for politicians and the public. Of the 20 Aichi Biodiversity Targets (ABTs) established in 2010 by the Convention on Biodiversity (CBD), only four show good progress, whereas 12 related to the state of nature show worsening trends ([ 1 ][1]). With the 2020 target date for the ABTs now upon us, it is critical to define a post-2020 agenda to arrest the loss of biodiversity. This will require a target, underpinned by a clear global goal for biodiversity, that can be readily communicated to galvanize both political will and public support. Similarly to how the climate change community uses a single indicator (global mean temperature change) and a target (maximum 2°C rise relative to preindustrial levels) as a rallying point for policy action and agreements, we propose a 2°C-like target for biodiversity (see table S1): a measurable, near-term target of keeping described species extinctions to well below 20 per year over the next 100 years across all major groups (fungi, plants, invertebrates, and vertebrates) and across all ecosystem types (marine, freshwater, and terrestrial). Although there are many comprehensive proposals that seek to contribute to the post-2020 agenda ([ 3 ][2], [ 4 ][3]), they focus on achieving conservation actions, such as increasing the coverage of areas dedicated to wildlife, or maintaining intact wilderness, rather than specifying required outcomes for biodiversity ([ 5 ][4]). As such, there is a real risk, as with some of the 2020 ABTs, that targets will be met, yet biodiversity will continue to decline ([ 5 ][4]–[ 7 ][5]). We propose an alternative approach that draws on the theory of change (see tables S1 to S3). We suggest that the overall impact of a post-2020 biodiversity framework should be the goal of achieving the CBD 2050 vision of “Living in harmony with nature.” However, measuring progress toward this goal requires a communicable and actionable indicator and target, which for biodiversity has proven challenging. ![Figure][6] Targeting an extinction rate Extinction rates (E/MSY) across a variety of taxonomic groups for different historical periods are related to the proposed extinction rate target for the next 100 years and the aspirational target (background extinction rates) from 2120. Bars show the full range of possible values for E/MSY when E, S, and Y are represented by ranges of possible values (see Table S4 for the data sources). Data encompass all plants, animals, and fungi unless indicated otherwise. GRAPHIC: X. LIU/ SCIENCE As a largely political construct, supported by science, the 2°C climate policy target adopted by the United Nations Framework Convention on Climate Change (UNFCCC) was not intended to represent the multiple dimensions of the climate system and the diverse impacts of climate change. The target has the great advantage of being communicable to a nonscience audience and so supports understanding of the ambition in limiting climate change. Similarly, we argue that a comparable simple and measurable indicator is needed to support biodiversity policy with a specific and easily communicated target against which policy responses can be developed and tested. As with the global mean temperature metric for climate change, a single biodiversity metric will inevitably mask considerable spatial variation in the status of biodiversity and ignore many of the complexities inherent in ecological systems. However, as with climate change, a communicable, 2°C-like target for biodiversity should be supported by a broader range of indicators and targets that more fully describe the state of biodiversity and its drivers of change. A single biodiversity metric needs to be both relevant and effective for the goal, as well as being easy to measure and communicate. With this in mind, we propose a metric based on the rate of species extinction. Current species extinction rates clearly exceed those that were characteristic of the past, and projected future extinction rates are much higher still, even given large uncertainties ([ 8 ][7]). Over the coming decades, some continuing loss of species is inevitable given the current human domination of Earth's systems, so we suggest an ambitious but achievable rate: keeping described species extinctions to well below 20 per year over the next 100 years (see the figure). Thereafter, once there is stabilization of human impacts, we suggest that a rate closer to background rates (i.e., prehistorical rates) should be the aspiration (see the figure). The figure of 20 extinctions per year is based on a target to reduce extinctions to 10 per million-species-years applied to the estimated 2 million species described by science (see the figure and the supplementary materials). The 10 per million-species-years is the threshold adopted in the planetary boundaries framework ([ 9 ][8]). This threshold was used to reflect the addition of a large uncertainty bound to the upper estimate of natural background extinction rates of 1 per million-species-years ([ 9 ][8]). In proposing this single metric, we are not suggesting that it is sufficient on its own to describe the changing state of biodiversity, or to guide conservation policy, or ecosystem management on the ground. However, we suggest that the extinction rate is a necessary element of any biodiversity policy target and that it embraces the core concerns that most people have about biodiversity loss. Our justification for basing a global target only on the rate of species extinction is twofold. First, extinction fully incorporates the most fundamental aspect of biodiversity loss. Each species embodies distinct genetic diversity, usually shaped and developed over millions of years of independent evolution. The total body of extant species is the diversity of life on Earth. The extinction of a species represents an irreversible loss, a measurable reduction in the diversity of life on Earth, and is the ultimate concern for conservation. Although changes in species abundance or to ecological communities may be of equivalent concern ([ 10 ][9]), they are in principle, at least, reversible and recoverable. The extinction rate incorporates loss of species and of genetic diversity and therefore two of the core components of the CBD definition of biodiversity. Second, species extinction is widely understood and easy to communicate. There is widespread public concern about extinctions, as was demonstrated recently by the emphasis on the number of species at risk of extinction in the media coverage of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Global Assessment ([ 1 ][1]). There are collaborative networks recording the world's known and extinct species ([www.gbif.org/what-is-gbif][10] and [www.catalogueoflife.org][11]) and a program of work to catalog species close to extinction and to monitor extinctions as they take place ([www.iucnredlist.org][12]). We anticipate that targets such as we propose would stimulate new data and innovative approaches to monitoring and modeling the status of the world's species. We recognize that measuring only the extinction rate can miss many changes to biodiversity that are of great importance to people and that underpin the sustainable flow of ecosystem services. It would be possible, in principle, to meet a simple target to reduce the rate of species extinction and yet see wholesale and damaging changes to life on Earth. At the extreme, a single, small population of each species, maintained somewhere (perhaps in a protected area), would result in no extinctions, yet could place ecosystem functioning at risk everywhere and fail to meet most people's vision for life on Earth. Achieving our target could therefore have some perverse solutions, just as achieving the 2°C target can be achieved through actions such as solar radiation management, which treat symptoms, but do not address the root problem. Implementation, therefore, requires effective policy scrutiny. Current extinction events are, in any case, recorded [e.g., the annotation of “possibly extinct” by the International Union for Conservation of Nature (IUCN)], and this can contribute to more precautionary reporting. In addition to the global extinction rate, additional targets will be needed to ensure that biodiversity meets functional and cultural roles that are especially relevant at local and national scales. This will require countries to develop national targets that are relevant to their own circumstances. For climate change, national targets are defined by Nationally Determined Contributions (NDCs), which outline governmental action toward overall climate mitigation. Likewise, Nationally Determined Contributions for Biodiversity (NDCBs) could provide an action-based context for better protection and management of biological resources and provide governments with a framework within which they could act to achieve global biodiversity targets, including to reduce extinction rates. Governments also need to monitor the effects of NDCBs in real time and use models that project into the future, to evaluate compliance with policy implementation and fine-tune their policy responses. We are not suggesting that the species extinctions target would be allocated to countries in a top-down policy process. NDCs are voluntary, but monitored through the (independent) Climate Action Tracker to check if countries' national targets (which are decided by each country) collectively achieve the global target. One could envisage something similar for biodiversity where country NDCBs for actions within their own country boundaries and actions related to teleconnections are related to both national and global targets. This might lead to a “Biodiversity Action Tracker” or something similar. Then, as with the UNFCCC, an iterative review process would encourage countries to increase their ambition if collectively the global targets were not being achieved. Generally, countries with the most critically endangered species have the best opportunity to take direct action to mitigate the direct drivers pushing them toward extinction. Hence, national extinction targets need to be clear and sum up to the shared global ambition. Because the proposed global target concerns the number of species becoming extinct within 100 years, it follows that a national target will need to refer to national responsibilities toward reducing the number of global extinctions. National responsibility refers to the geographic location where removal of direct pressures on a species needs to occur, e.g., responsibility for reducing the rate of habitat loss for species in the Atlantic Forest of Brazil would lie in Brazil. Many other approaches, including the ABTs, also focus at the national level. We feel that it is important to highlight the need for national responsibility for the global target. In a world increasingly interconnected by trade and the impacts of consumption, the drivers of biodiversity loss often originate, at least in part, in other countries because of consumer demand ([ 11 ][13]). It is important, therefore, for nations to recognize the displacement effects of consumption patterns on biodiversity, along with the moral responsibility to act on this problem. Hence, it is equally important for nations to commit to the direct conservation of species beyond their national borders, because the risk of species extinctions is not equally distributed geographically. A commitment to support biodiversity in other parts of the world would mirror (and complement) efforts to alleviate poverty through international actions that foster development and would tackle the asymmetries inherent in financially poor countries often being biodiversity rich. Thus, the national responsibility for the recovery of species may best be addressed with financial aid, trade agreements, and other means to reduce indirect pressures. A refreshed vision that lays out an achievable ambition to reverse the decline in biodiversity is urgent. The time is right; there is currently a set of important preconditions to underpin successful policy development and implementation. Examples include the policy-relevant information from IPBES assessments, the ambitious goals embodied in the UN Sustainable Development Goals (SDGs) for 2030, and an emerging consensus that links biodiversity recovery to climate change mitigation and adaptation, and to sustainable development and human well-being, as well as the increasing public awareness and demand for action. Together these provide a valuable opportunity and one for which the world has all the necessary actors and institutions to exploit. There is a lot of debate about how effective the NDCs have been (which is relevant to assessing how effective NDCBs might be). However, in the end, the effectiveness of outcomes is strongly dependent on governmental willingness to act. This affects any indicator. The advantage of having a single, simple indicator as we propose here is that it makes lack of achievement toward the target more visible. It also makes clear that national governments have responsibility for reducing extinction rates everywhere. There is an important role for science in supporting this policy process by advancing understanding of some of the key elements of the theory of change. We need better understanding of the impact of policy actions on biodiversity outcomes and how this supports policy goals, e.g., through a Biodiversity Action Tracker. We need better modeling and futures analyses (target-seeking and ex-ante scenarios) to understand how sets of time-dependent actions encapsulated in alternative development pathways can move us toward the vision ([ 2 ][14]). We also need scientific advances to investigate what levels of biodiversity loss are damaging for ecosystem functioning, and to fill knowledge gaps about the complex interactions between species extinctions, biodiversity, ecosystem functioning, and ecosystem services. We recognize that a single indicator cannot capture the multiple dimensions of complex systems, and this holds as much for biodiversity assessment as it does for climate change. Ultimately, however, we need to catalyze both policy and public support for biodiversity and its preservation, and to do this we need an indicator and target that readily communicate the urgency of the problem to multiple audiences and enable monitoring of progress. Our proposal for a 2°C-like target for biodiversity based on the rate of global species extinctions attempts to provide a simple, measurable, and easily communicated target against which policy responses can be established and tested. Adoption of such a target globally, and its elaboration and implementation nationally, would help integrate the biodiversity and climate change agendas, which is critical for protecting and managing nature sustainably in achieving the SDGs. [science.sciencemag.org/content/368/6496/1193/suppl/DC1][15] 1. [↵][16]1. E. S. Brondizio, 2. J. Settele, 3. S. Díaz, 4. H. T. Ngo IPBES, Global Assessment Report on Biodiversity and Ecosystem Services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, E. S. Brondizio, J. Settele, S. Díaz, H. T. Ngo, Eds. (IPBES Secretariat, Bonn, Germany, 2019). 2. [↵][17]1. M. D. A. Rounsevell, 2. M. Fischer, 3. A. Torre-Marin Rando, 4. A. Mader Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, The Regional Assessment Report on Biodiversity and Ecosystem Services for Europe and Central Asia, M. D. A. Rounsevell, M. Fischer, A. Torre-Marin Rando, A. Mader, Eds. (IPBES Secretariat, Bonn, Germany, 2018). 3. [↵][18]1. E. Dinerstein et al ., Sci. Adv. 5, eaaw2869 (2019). [OpenUrl][19][FREE Full Text][20] 4. [↵][21]1. J. E. Watson et al ., Nature 563, 27 (2018). [OpenUrl][22] 5. [↵][23]1. P. Visconti et al ., Science 364, 239 (2019). [OpenUrl][24][Abstract/FREE Full Text][25] 6. 1. L. Boitani et al ., PLOS Biol. 6, e66 (2008). [OpenUrl][26][PubMed][27] 7. [↵][28]1. D. P. Tittensor et al ., Science 346, 241 (2014). [OpenUrl][29][Abstract/FREE Full Text][30] 8. [↵][31]1. V. Proença, 2. H. Pereira , “Comparing extinction rates: Past, present, and future” in Encyclopaedia of Biodiversity (Elsevier, 2017). 9. [↵][32]1. W. Steffen et al ., Science 347, 1259855 (2015). [OpenUrl][33][Abstract/FREE Full Text][34] 10. [↵][35]1. G. M. Mace et al ., Nat. Sustain. 1, 448 (2018). [OpenUrl][36][CrossRef][37] 11. [↵][38]1. A. Marques et al ., Nat. Ecol. Evol. 3, 628 (2019). [OpenUrl][39] Acknowledgments: We thank A. Arneth, N. Burgess, S. Butchart, A. Purvis, P. Visconti, and J. Watson for comments. M.D.A.R. acknowledges financial support of the Helmholtz Association. T.N. acknowledges funding from the Royal Society. The authors declare no competing interests. [1]: #ref-1 [2]: #ref-3 [3]: #ref-4 [4]: #ref-5 [5]: #ref-7 [6]: pending:yes [7]: #ref-8 [8]: #ref-9 [9]: #ref-10 [10]: http://www.gbif.org/what-is-gbif [11]: http://www.catalogueoflife.org [12]: http://www.iucnredlist.org [13]: #ref-11 [14]: #ref-2 [15]: http://science.sciencemag.org/content/368/6496/1193/suppl/DC1 [16]: #xref-ref-1-1 "View reference 1 in text" [17]: #xref-ref-2-1 "View reference 2 in text" [18]: #xref-ref-3-1 "View reference 3 in text" [19]: {openurl}?query=rft.jtitle%253DScience%2BAdvances%26rft.stitle%253DSci%2BAdv%26rft.aulast%253DDinerstein%26rft.auinit1%253DE.%26rft.volume%253D5%26rft.issue%253D4%26rft.spage%253Deaaw2869%26rft.epage%253Deaaw2869%26rft.atitle%253DA%2BGlobal%2BDeal%2BFor%2BNature%253A%2BGuiding%2Bprinciples%252C%2Bmilestones%252C%2Band%2Btargets%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fsciadv.aaw2869%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 [20]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6MzoiUERGIjtzOjExOiJqb3VybmFsQ29kZSI7czo4OiJhZHZhbmNlcyI7czo1OiJyZXNpZCI7czoxMjoiNS80L2VhYXcyODY5IjtzOjQ6ImF0b20iO3M6MjM6Ii9zY2kvMzY4LzY0OTYvMTE5My5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30= [21]: #xref-ref-4-1 "View reference 4 in text" [22]: {openurl}?query=rft.jtitle%253DNature%26rft.volume%253D563%26rft.spage%253D27%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 [23]: #xref-ref-5-1 "View reference 5 in text" [24]: {openurl}?query=rft.jtitle%253DScience%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.aav6886%26rft_id%253Dinfo%253Apmid%252F30975769%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 [25]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzNjQvNjQzNy8yMzkiO3M6NDoiYXRvbSI7czoyMzoiL3NjaS8zNjgvNjQ5Ni8xMTkzLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [26]: {openurl}?query=rft.jtitle%253DPLoS%2Bbiology%26rft.stitle%253DPLoS%2BBiol%26rft.aulast%253DBoitani%26rft.auinit1%253DL.%26rft.volume%253D6%26rft.issue%253D3%26rft.spage%253De66%26rft.epage%253De66%26rft.atitle%253DChange%2Bthe%2BIUCN%2Bprotected%2Barea%2Bcategories%2Bto%2Breflect%2Bbiodiversity%2Boutcomes.%26rft_id%253Dinfo%253Apmid%252F18351805%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 [27]: /lookup/external-ref?access_num=18351805&link_type=MED&atom=%2Fsci%2F368%2F6496%2F1193.atom [28]: #xref-ref-7-1 "View reference 7 in text" [29]: {openurl}?query=rft.jtitle%253DScience%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.1257484%26rft_id%253Dinfo%253Apmid%252F25278504%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/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzNDYvNjIwNi8yNDEiO3M6NDoiYXRvbSI7czoyMzoiL3NjaS8zNjgvNjQ5Ni8xMTkzLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ== [31]: #xref-ref-8-1 "View reference 8 in text" [32]: #xref-ref-9-1 "View reference 9 in text" [33]: {openurl}?query=rft.jtitle%253DScience%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.1259855%26rft_id%253Dinfo%253Apmid%252F25592418%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 [34]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjE2OiIzNDcvNjIyMy8xMjU5ODU1IjtzOjQ6ImF0b20iO3M6MjM6Ii9zY2kvMzY4LzY0OTYvMTE5My5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30= [35]: #xref-ref-10-1 "View reference 10 in text" [36]: {openurl}?query=rft.jtitle%253DNat.%2BSustain.%26rft.volume%253D1%26rft.spage%253D448%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fs41893-018-0130-0%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=10.1038/s41893-018-0130-0&link_type=DOI [38]: #xref-ref-11-1 "View reference 11 in text" [39]: {openurl}?query=rft.jtitle%253DNat.%2BEcol.%2BEvol.%26rft.volume%253D3%26rft.spage%253D628%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
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/274453
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Mark D. A. Rounsevell,Mike Harfoot,Paula A. Harrison,et al. A biodiversity target based on species extinctions[J]. Science,2020.
APA	Mark D. A. Rounsevell,Mike Harfoot,Paula A. Harrison,Tim Newbold,Richard D. Gregory,&Georgina M. Mace.(2020).A biodiversity target based on species extinctions.Science.
MLA	Mark D. A. Rounsevell,et al."A biodiversity target based on species extinctions".Science (2020).