Ramírez F, Afán I, Davis LS, and Chiaradia A. Climate Impacts on global hot spots of marine biodiversity. Science Advances. 22 February 2017. DOI: 10.1126/sciadv.1601198.
You wake up on the weekend feeling pretty yucky. Maybe you have plague. Lol. Better get that checked out. When you arrive at the doctor’s office, the nurse assesses your condition to decide where you fall in line among the other patients—a medical triage. The system works well because the highest risk patients are seen first, thereby ensuring that their situation does not deteriorate in the waiting room.
Now take a planet faced with climate change. Ecosystems aren’t feeling so hot (because they are getting too hot). To add insult to injury, humans are fishing, hunting, mining, drilling, and otherwise exploiting these very same ecosystems. Like the nurse at urgent care, conservationists face the dilemma of triaging efforts to ameliorate the environmental one-two punch posed to ecosystems by climate change and direct human exploitation—but how? In one of the first studies of its kind, a multinational team of scientists hailing from institutions in Spain, New Zealand, and Australia, addresses the question of the dual impacts of climate change and overfishing. Their findings that provide a framework for prioritizing marine conservation efforts are reported in a recent issue of the journal Science Advances.
Thanks (or no thanks) to the efficiency of commercial fishing, fish populations are facing unprecedented pressures. Unfortunately, it is not all that feasible to place a hold on commercial fishing activities to clear the waters, so to speak, on the issue. A more practical approach would be for conservationists to focus their efforts on hot spots of biological diversity that are particularly susceptible to fishing (mal)practices. With this goal in mind, the team lead by ecologist Francisco Ramirez, set out to determine which marine habitats are most affected by global warming, and, in turn, how those line up with the geography of commercial fisheries.
To identify areas with the highest occurrence of the largest number of species (i.e. the greatest biodiversity), Ramírez and co-workers mapped the global distributions of over two-thousand marine species including mammals, birds, and (mostly) fish. Having identified these host spots of biodiversity, the team next sought to determine how these ecosystems have been effected by the dual impacts of climate change and commercial fishing.
Curating three decades of satellite records, Ramírez and colleagues constructed a stop-motion picture documenting changes in ocean currents, sea water temperatures, and levels of photosynthesis by tiny plankton that form the foundation of the marine food chain. They next overlaid their observations with fishing records collected since the 1950s, which provide a rough picture of changes in ecosystem composition over time.
Ramírez and colleagues observed an overall warming trend in the world’s oceans, resulting in reductions in primary production. Consistent with temperature changes, they further noted slowing in the massive current (a.k.a. the “thermohaline current”) that connects the world’s oceans, resulting in changes in transport of cooler waters and nutrients. In support of their initial hypothesis that some areas might be more vulnerable to climate change than others, Ramirez and colleagues observed patchiness in the distribution of the impacts of climate change. That is, some areas were deeply impacted, while others seemed to be going about their business as usual. Particularly troublesome was the fact that many of the most affected areas coincided with hot spots of marine biodiversity. Examination of over a half a century of fisheries data lead to the further heart-sinking conclusion that the areas most vulnerable to climate change are also some of the most overfished waters.
In light of their analyses, Ramírez and colleague propose the six most vulnerable marine ecosystems, which mostly fall in the southern hemisphere and include the areas in the Atlantic, Pacific, and Indian Oceans. As many of the tottering ecosystems exist in sovereign waters, the researchers note the importance of multi-national conservation efforts to reverse the trend of ecosystem destruction due exploitation of habitats already afflicted by climate change. Moreover, the authors emphasize the need for studies like theirs that are “spatially explicit,” not taking a single longitude and latitude for granted when considering the uneven effects of climate change. As bad as things look we can at least find comfort in the fact that scientists like Ramírez are able to pin-point where we should begin to direct our efforts to protect our global biodiversity. Let’s start at the very beginning. A very good place to start.
Abrahim is a PhD student at Scripps Institution of Oceanography in San Diego where he studies marine chemical biology.