观点

恢复海洋生物

保护海洋生物的养护措施已经初见成效。通过开展这些行动,我们得以遏制物种数量的下降趋势,修复已经退化的海洋生态系统。但要普遍恢复海洋健康,我们必须更加积极地治理污染,防止过度捕捞并抵御气候变化带来的影响。

卡洛斯·M. 杜阿尔特(Carlos M. Duarte)

沙特阿拉伯阿卜杜拉国王科技大学(KAUST)海洋生态学家、塔雷克·艾哈迈德·贾法里红海生态研究教席负责人

就在不久之前,海洋生物多样性的前景还不容乐观。大型海洋动物的数量和重要海洋栖息地的范围损失将半,有些情况甚至更触目惊心。这些不仅是统计数据,也是我亲眼见证的惨痛局面。从北极到南极洲,从浅海海岸系统到深海,我曾目睹过海草草甸、红树林和珊瑚礁等诸多生态系统从退化到消失的过程。

然而在2010年前后,事态发生了转机。世界多地纷纷报告,研究工作发现了越来越多的成功迹象——流失速度放缓,甚至实现了复原。海洋修复项目在沿海各地如雨后春笋般涌现,海洋保护区的数量不断增长、规模持续扩大。不止我一人报告了红树林、水下草甸和盐沼等各类栖息地的恢复情况。座头鲸和象海豹等濒危物种的种群数量也有所增加。

为确定海洋生物发展趋势是否就此开始逆转,我对促成这些海洋保护成果的行动进行了第一次评估,其中时间最久的行动始于20世纪70年代。此次评估中的一些实例证明,海洋生物的生存情况确实正在好转。

在初步评估的基础上,我邀请顶尖海洋生态学家组建了一支团队,系统评估目前为止在恢复海洋生物方面取得的进展以及促成这些成果的行动。我们审查了重要栖息地的状况,其中包括海草草甸、红树林、盐沼、珊瑚礁、海藻林、深海生态系统和牡蛎礁等,也研究了鲸鱼、鲨鱼、海鸟和海龟等巨型海洋动物。

趋势逆转

2020年4月,《自然》科学杂志发表了我们的评估报告。报告表明,海草草甸、红树林、盐沼的流失速度已经放缓,而且在许多地区,这些栖息地的面积正在扩大。此外,许多大型海洋物种的种群数量正在增加,其中一些的回升规模相当可观。在我们评估的124个海洋哺乳动物种群中,47%的种群数量近几十年来显著增加,40%没有变化,只有13%的种群数量发生缩减。一些捕鱼区的情况也有改善,近20年来过度捕捞的现象减少了,可持续捕捞的鱼类种群比例则有所提高。

海洋生物获得的这些改善大多得益于20世纪70年代采取的政策和行动。这些政策要经过大约二三十年的落实才能实现预期成果,所以它们带来的益处才刚开始显露。

海洋生物的生存情况确实正在好转

事实上,假如我们能够借此良好势头采取必要行动,再接再厉,或许可以改变现状,恢复海洋生物。我们认为,海洋生物是可能实现显著恢复的,到2050年可以恢复到以往数量的70-90%。

这就需要对物种采取保护措施,因为大量海洋物种依然处于濒危状态,其中还包括一些极度濒危物种。我们还应对空间进行保护。2000年,只有0.4%的海洋面积受到保护,到2020年这一面积已接近10%,并有望在2030年达到30%。我们需要开展切实有效的恢复行动,逐步消除具有破坏性和损害性的做法,积极主动地推进保护工作。

治理污染和过度捕捞问题

我们还应消除各种形式的污染,包括过剩营养物质输入、持久性有机污染物和塑料等。在这方面,我们已经取得了一些成绩。由于在几十年前开始改用无铅汽油,海洋已摆脱了遭受全球铅污染的命运。这项功绩鲜为人知,却是值得称颂的。

由于改用无铅汽油,海洋已摆脱了遭受全球铅污染的命运

在捕捞问题上,我们必须保持理智,减少渔获量,以便恢复鱼类资源,同时打击非法捕捞和未经报告的捕捞活动。这就需要改进监管和执法,适当管理公海鱼类资源。这项工作已不再依靠渔船自主报告,随着卫星技术和人工智能的发展,我们如今可以监测海上的各种活动——不仅是非法捕捞,人口贩运和毒品贩运行为也能尽收眼底。发展可持续的水产养殖业,使之成为农业生产循环中的最后一环,还将有助于减轻野生种群承受的压力。

然而,我们是在气候变化这个大背景下取得上述成果的。假如不能减缓气候变化,不能实现或改进《巴黎协定》的目标,这些行动结出的成果就可能付之东流。重要的是,气候变化严重威胁到了珊瑚礁的恢复。由于海洋变暖已达临界值,比前工业化时代的平均温度高出大约1摄氏度,珊瑚礁已经出现大面积死亡的情况。

增加碳储存

在采取气候行动上,我们现在应把目光放得更加长远。要恢复海洋生物丰度,需扩大海洋中的生物碳库,从而助力减缓气候变化。恢复红树林、盐沼和海草草甸所产生的成效将尤为显著。这些生态系统的碳固存能力在整个生物圈中名列前茅,同时也是我们抵御气候变化、避免海平面上升和风暴频发的第一道防线。

要以具有成本效益的可靠方式开展上述行动,需要着眼于在科技研究领域推进实施解决方案。“联合国海洋科学促进可持续发展10年”(2021—2030年)为我们提供了一个绝佳出发点,增强了我们恢复海洋生物生存状况的能力。

这项修复工作需要大笔资金,预计平均每年要投入100—200亿美元。这个数字看似庞大,其实仅占全球国内生产总值的0.02%。而且,回报丰厚无比——估计每投入1美元,就能获利10美元。主要受益者将是保险公司、海产品公司、旅游业,以及众多依托海洋获取食物和庇护的社区。

单凭重建渔业这一项工作,全球海产品行业的年利润即可增加530亿美元。保护沿海湿地可以减少暴雨引发的洪水,每年能为保险业省下520亿美元。海洋生物恢复行动还将创造数百万由此获益的工作岗位,并实现关于水下生物的联合国可持续发展目标14 。

我们的目标是,到2050年显著恢复海洋生物丰度,这个目标虽艰巨,但并非天方夜谭,政府、企业、资源使用者和民间团体等诸多利益攸关方需要携起手来,围绕一项循证行动计划,建立全球伙伴关系。为支持这项事业,必须制定健全可靠的政策框架、科学和教育计划、量化目标、成果衡量标准和商业计划。私营部门,特别是依赖健康海洋进行发展的行业和公司,必须发挥重要作用。开展修复工作还应需要强大的领导能力,以促进伙伴关系、协调各方贡献并发挥协同作用,同时保持前进势头,消除阻碍,克服挫折。

如能成功恢复海洋生物生存状况,这将是人类实现全球可持续未来征程上的一座历史丰碑。我们不能为子孙后代留下一片片满目疮痍的海洋。取得成功,我们义不容辞。

 

拓展阅读:

绿海龟重归塞舌尔群岛

《海洋和海洋宝藏》,联合国教科文组织《信使》,1998年7-8月。

《珊瑚:地球健康的见证者》,联合国教科文组织《信使》,1994年7-8月。

《拯救鲸鱼》,联合国教科文组织《信使》,1970年8-9月。

 

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By Carlos M. Duarte

Until very recently, the future of marine biodiversity did not give us much to be optimistic about. We had lost about half of the biomass of large marine animals and the extent of key ocean habitats – even more, in some cases. This was not just based on statistics, but sadly, also my personal experience. From the Arctic to Antarctica, from shallow coastal systems to the deep sea, I had witnessed many ecosystems – seagrass meadows, mangrove forests and coral reefs that were degraded and then lost.

However, around 2010, something started to change. Increasingly, studies documenting successes – the slowing down of losses, or even recoveries – were being reported from multiple parts of the world. Marine restoration projects were mushrooming around the ocean, and marine protected areas were growing in number and size. And I reported, along with others, on the recovery of various habitats such as mangroves, underwater meadows, and salt-marshes. Endangered species, like humpback whales and elephant seals, also registered an increase in their populations.

To determine whether this was the beginning of a trend reversal, I conducted a first assessment of what actions had enabled these successes in marine conservation – the oldest of which dates back to the 1970s. This assessment confirmed that the recovery of marine life was underway in a number of cases.

On the basis of that initial assessment, I brought together a team of leading marine ecologists to systematically assess the progress, to date, in recovering marine life, and the actions that had enabled these successes. We reviewed the status of key habitats, including seagrass meadows, mangrove forests, salt-marshes, coral reefs, kelp forests, deep-sea ecosystems and oyster reefs. We also studied marine megafauna, such as whales, sharks, sea-birds, and sea-turtles.

Trend reversal

Our assessment, published in the scientific journal, Nature in April 2020, showed that loss rates of sea-grass meadows, mangrove forests, salt-marshes had slowed down and, in many areas, these habitats were expanding. Likewise the populations of many large marine species were improving, with some of them displaying impressive comebacks. Forty-seven per cent of the 124 marine mammal populations assessed have seen a significant increase in recent decades, no change was detected in forty per cent, and only thirteen per cent have decreased. Some fishing areas had also improved in status – with a reduction of overfishing in the past two decades, and an increase in the proportion of fish stocks that are sustainably harvested.

These improvements in the components of marine life were rendered possible, in many cases, by policies and actions that were adopted in the 1970s. We realized that their benefits are just becoming apparent, because it takes about two to three decades for those policies to yield the expected outcomes.

The recovery of marine life was underway in a number of cases

In fact, a tide change of ocean recovery is conceivable if we take the necessary actions to catalyse the momentum created by the policies put in place decades ago. We concluded that it is possible to achieve a substantial rebuilding of marine life, to between seventy per cent and ninety per cent of its past wealth by 2050.

This requires protecting species, as a large number of marine species continue to be endangered, some of them critically so. We also need to protect spaces. While in 2000, only 0.4 per cent of the ocean area was protected, this figure is approaching ten per cent in 2020, and is on course to reach thirty per cent by 2030. The protection needs to be active, driven by effective restoration action and the phasing out of destructive and damaging practices.

Fighting pollution and overfishing

We also need to remove all forms of pollution – from excess nutrient inputs to persistent organic pollutants and plastics. We have already achieved some wins in fighting pollution. The ocean is now restored from global lead pollution, thanks to the transition to unleaded petrol, which started several decades ago. This is a success that few are aware of, but one that must be celebrated.

The switch to unleaded petrol has rid the ocean of global lead pollution

We must harvest wisely, reducing catches to rebuild fish stocks, and fighting illegal and unreported fishing. This requires improved regulation and enforcement, and appropriate stewardship of fish stocks in the high seas. This is no longer dependent on self-reporting by fishing vessels, as improvements in satellite technology and artificial intelligence now allow monitoring activities at sea – not just illegal fishing, but also human and drug trafficking. Developing a sustainable aquaculture industry that closes the production cycle within the farm, will also help reduce pressure on wild stocks.

However, climate change is the backdrop against which our success plays out. Failure to mitigate climate change and to meet, or improve upon, the goals of the Paris Agreement will risk wasting many of the benefits of the actions being taken. Importantly, climate change poses the greatest risk for the recovery of coral reefs, which are already experiencing widespread mortality due to the extent of ocean warming – about 1 oC above the average temperature in pre-industrial times – already realized.

Increasing carbon storage

It is time for climate action to reach a new level of ambition. Rebuilding the abundance of marine life involves increasing the pool of living carbon in the ocean, therefore also contributing to mitigate climate change. The recovery of mangroves, salt-marshes and sea-grass meadows will be particularly effective, as these ecosystems rank highest in carbon sequestration mitigation across the biosphere. They are also our first line of defence from rising sea levels and increased storms because of climate change.

Solution-focused advances in scientific and technological research will be required to undertake the actions above in a cost-effective and reliable manner. The United Nations Decade of Ocean Science for Sustainable Development (2021-2030) provides a unique springboard to support our capacity to rebuild marine life.

This rebuilding will require significant investments, estimated at $10 billion to $20 billion per year. This may seem a steep amount, but it is a mere 0.02 per cent of global GDP. Yet, this investment is expected to generate significant returns – an estimated $10 for every dollar invested. The main beneficiaries will be insurance and seafood companies, and the tourism industry, along with the many communities that depend on the ocean for food and protection.

Rebuilt fisheries alone could increase the annual profits of the global seafood industry by $53 billion. Conserving coastal wetlands could save the insurance industry $52 billion annually, by reducing storm flooding. Rebuilding marine life will also create millions of beneficial jobs, and will achieve UN Sustainable Development Goal (SDG) 14, Life Below Water.

Substantially rebuilding marine life by 2050 is an achievable, if challenging, goal. It requires a global partnership of diverse interests – including governments, businesses, resource users and civil society – aligned around an evidence-based action plan. This must be supported by a sound policy framework, a science and educational plan, quantitative targets, metrics for success, and a business plan. The private sector must play an important role, particularly those businesses and corporations that benefit from a healthy ocean. Rebuilding also requires strong leadership to catalyse partnerships, align contributions and build synergies – while keeping up the momentum and overcoming roadblocks and setbacks.

Should we succeed, it would be a historic milestone in humanity’s quest to achieve a globally sustainable future. Leaving a devastated ocean to future generations is not an option. We have the moral obligation to succeed.

Carlos M. Duarte

Marine ecologist and Tarek Ahmed Juffali Research Chair in Red Sea Ecology at the King Abdullah University of Science and Technology (KAUST), Saudi Arabia.

The ocean: Time to turn the tide
UNESCO
January-March 2021
UNESCO
0000375277
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