Bid to Protect Key Links in the Food Chain
Marine protected areas cover 7.1 per cent of the Southern Ocean, but as some experts call for this to widen, a team of scientists are using tracking data to identify the biodiversity hotspots that most warrant protection.
To reach Sustainable Development Goal 14: ‘Conserve and sustainably use the oceans, seas and marine resources for sustainable development’, the UN set a target to protect 10 per cent of the world’s oceans within ‘marine protected areas’ (MPAs) by the end of 2020.
MPAs come in different forms, but are generally defined as parts of the marine environment that have been reserved and protected by law or by other effective means. Currently, only 3.6 per cent of the ocean lies within MPAs and only two per cent within strongly or fully protected areas. Defining such zones can prevent overfishing and resource depletion; protect endangered species; make ecosystems more resistant to climate change, and maintain biodiversity.
Expanding the coverage of MPAs as widely as possible is one way to protect biodiversity, but scientists and wildlife organisations are also calling for ‘ecological hotspots’ to be identified, which are of high conservation value – an approach that would optimise the utility of chosen areas. According to the World Wildlife Fund (WWF), ‘we need more marine protected areas in the right places – where the conservation need is most urgent and where the potential for their contribution, for both humans and wildlife, is highest.’
A collaboration of scientists from the Retrospective Analysis of Antarctic Tracking Data Project (RAATD) has used tracking data from marine predators to identify ecological hotspots in the Southern Ocean. The team collected data from 4,060 animals, spanning 17 species, including 12 seabirds and five marine mammals. They identified the preferred habitats of each species, before homing in on those that were frequently used by many other animals as well. This indicated areas with healthy food chains with high biological productivity and biodiversity – ecological hotspots that researchers dubbed Areas of Ecological Significance (AESs).
Tracking diverse marine predators allowed the team to get a broad picture of the ecological significance of ocean regions. ‘Merging tracking data from multiple predators to identify ecological hotspots has not really been done before. With data from our group of experts, we were able to assess the areas of the Southern Ocean that were significant across many levels of the food chain,’ says oceanographer Yan Ropert-Coudert, who co-led the study.
AESs were mostly located over the Antarctic continental shelf, and in two more northerly regions: one encompassing most of the Scotia Sea and surrounding waters, and the second covering the chain of sub-Antarctic islands from the Prince Edward Islands, through to parts of the Kerguelen Plateau.
Next, the team explored how their AESs were being affected by human-induced stressors. Using fishing data from the Global Fishing Watch dataset they found that the highest levels of fishing mostly occurred inside AESs: high-intensity fishing areas of the Southern Ocean occurred around the Falkland Islands (where squid and finfish are targeted); around South Georgia (krill and toothfish); at the West Antarctic Peninsula (krill); and over the Kerguelen Plateau (squid and finfish).
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is the international body responsible for the management of fisheries in the Southern Ocean. According to the study, 27 per cent of the AESs already fall within CCAMLR’s designated MPAs. If all proposed MPAs that are currently under review by CCAMLR were to be adopted, the number of AESs under protection would increase to 39 per cent. ‘The good news is that CCAMLR is doing quite a good job of encapsulating the AESs within their marine protected areas. Our evidence shows that they can continue this progress by accepting all of the marine protected areas currently under review,’ says Mark Hindell, study co-lead.
Compared to the 3.6 per cent of the world’s oceans under marine protected area status, the Southern Ocean – defined as ocean south of 40°S – is better protected, with 7.1 per cent falling within MPAs. This figure would jump to 11.2 per cent if all currently proposed MPAs were implemented. Although this is encouraging, Ropert-Coudert wants to see protection efforts smartened up. ‘The level of protection of the Southern Ocean is high by global standards, but it is essential that we protect the right regions that are important for the persistence of biodiversity,’ he says.
‘The AESs identified are clearly candidates for protection, and the implementation of proposed marine protected areas within the CCAMLR region would greatly increase the protection of important habitats in the Southern Ocean,’ concludes the RAATD study, recently published in Nature.
As ocean temperatures increase and the distribution of sea ice and ocean fronts are altered due to climate change, AESs are likely to move. To forecast this movement up to 2100, the team combined data from eight global climate models, which account for fluctuations in sea ice with predicted climate change trajectories. In the sub-Antarctic, AESs generally moved south with time, producing a net loss of AESs within marine protected areas. ‘The challenge is that climate change is dynamic and accelerating. Food chains are dynamic, and migratory species move. We need to designate marine protected areas that are dynamic, and responsive to climate-induced changes to ecological hotspots’ says Ryan Reisinger, study co-lead. ‘However, CCAMLR nations have to reach consensus, making dynamic marine protected areas very difficult to establish,’ he adds.
The researchers hope that scientists will continue to collaborate to identify regions that will optimise the protection of the Southern Ocean. ‘Our study provides another layer of information to bring about science-driven policies of ocean protection – there are other layers out there, and [our study] is not the only piece of the puzzle,’ says Ropert-Coudert. Nonetheless, the identification of AESs in the Southern Ocean highlights where protection efforts might best be directed. As these ecological hotspots shift around the Southern Ocean in response to climate change, marine protected areas must limber up if they are to match the dynamism of the species they serve to protect.