Since the turning of the century, global governments have been increasingly implementing conservation interventions which, if sustained and expanded during the next few decades, could lead to a substantial recovery of the abundance, structure and function of marine life, a new study1 finds.
Marine biodiversity faces many threats today, including overharvesting, the destruction of coastal habitats, pollution and climate change. The situation is critical especially because healthy marine systems provide us with innumerable benefits. They are the livelihoods of many coastal communities providing millions of jobs, they are fundamental to our quest of ending world’s hunger, and they play a key role in climate change mitigation.
Cumulative human pressures during the past two centuries have caused a major decline in marine biodiversity. Figure credits: 1
Nonetheless, a new study published this month in Nature by a group of internationally renowned marine experts found that it may not all be doom and gloom for marine life, after all. Global action for the conservation of marine biodiversity has been increasing in the recent decades, significantly lowering human pressure on the ocean.
“Based on the case studies examined, we provisionally propose three decades from today (2050) as a target timeline for substantial (that is, 50–90%) recovery of many components of marine life, recognizing that many slow-growing, severely depleted species and threatened habitats may take longer to recover, and that natural variability may delay recovery further”, the authors of the study say.
The global rise in the establishment of marine protected areas is an example of successful conservation actions which have been implemented in the recent decades. In 2000, only 3.2 million squared km (0.9%) of the ocean was protected compared to 26.9 million squared km (7.4% of ocean area) today.
Time evolution of the Marine Protected Areas declared around the world. Video credits: 1
Similarly, the conservation status of 47% of 124 well-assessed marine mammal populations has greatly improved during the past decades. From humpback whales (a few hundred individuals in the 1960s, forty thousand today), to northern elephant seals (twenty breeding individuals in the 1880s, more than two hundred thousand today), great seals (increasing by 1,410% since the 1970s), and southern sea otters (about fifty individuals in the 1910s, several thousand at present). Even most sea turtles have been showing signs of recovery, with rises in nesting populations ranging from 4 to 14% per year, though their populations remain endangered today.
“Many fish stocks that are subject to management interventions display positive trends, and globally aggregated stock assessments suggest a slowing down of the depletion of fish stocks” the authors explain in their paper.
While conserving ocean biodiversity is still possible and actually probable if current positive policy interventions are continued and enhanced, it is instead impossible to restore the exact marine ecosystems of the past. “Efforts to rebuild marine life cannot aim to return the ocean to any particular past reference point. Our records of marine life are too fragmented to compose a robust baseline, and the ocean has changed considerably and—in some cases—irreversibly, including the extinction of at least 20 marine species. We argue instead that the focus should be on increasing the abundance of key habitats and keystone species”, the authors conclude.
With the increasing global effort documented, the possibility to rescue the ocean’s biodiversity and its invaluable services to people is not so obsolete. These trends bring some optimism in current debates, especially because most marine conservation policies have been introduced in the last few decades and we are yet to see the results of many of them, which will become more obvious in the near future.
However, compared to other threats to marine life, pollution and climate change are actually worsening and risk cancelling out conservation efforts if they remain unaddressed, the research shows.
Addressing these two main issues will be central not only to ocean recovery, but also to global sustainability and the wellbeing of future generations.
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- Duarte, C.M., Agusti, S., Barbier, E. et al.,2020. Rebuilding marine life. Nature. 580, 39–51. https://doi.org/10.1038/s41586-020-2146-7